Historical Tropical Cyclones, Reanalysis and Climatology Discussion

[Windspeed]

Often times posters will discuss, compare and contrast historical tropical cyclones and their climatology during an active event thread, but these posts end up buried amongst the overall meteorological storm discussion for obvious reasons. I am opening this thread for current and future discussion as it relates to past tropical cyclone events and their peer-reviewed reanalysis projects.

If any person wishes to post about, reminisce or debate past tropical cyclones, regardless of oceanic basin or sea, perhaps they carry that on in this thread so we may have an easier flow of information and archive of such discussion.

I have quite a few cyclones to discuss myself and existing preconceptions / misconceptions about a particular region of the Atlantic to flesh out. My first post will be later this evening. But don't wait on me.

 

[gymengineer]

Here's one: Hugo was clearly a Category 4 in its SC landfall based on recon data. The wind map of peak gusts created by Fujita himself was strangely tepid in the eyewall zone. It's even more curious since the Fujita scale wind increments would later be *lowered* after his death, meaning his own estimates of wind speeds corresponding to levels of damage were deemed as over-estimates. 

[the ghost of leroy]

^A vessel docked inland on one of the rivers recorded 120 sustained but it was a bit above 10m if I remember correctly. I think the areas that received the highest winds weren't sampled, and even if they were I am not sure how Fujita would have distinguised between wind and surge damage since the worst of both were likely collocated. 

[gymengineer]

1 hour ago, cmasty1978 said:

^A vessel docked inland on one of the rivers recorded 120 sustained but it was a bit above 10m if I remember correctly. I think the areas that received the highest winds weren't sampled, and even if they were I am not sure how Fujita would have distinguised between wind and surge damage since the worst of both were likely collocated. 

That Sampit River boat reading of 120 mph (~60 ft elevation) would again support a higher maximum gust estimate in the RMW zone. Since I support the NHC's assigned landfall intensity, the other data indicating Category 4 is what made his wind map based on damage to trees and structures stand out as an outlier. 

Hmm, to add some more confusion, this other map does not match the original one I imbedded. It's somehow tied to Fujita as well, but has a zone of 145 mph+ gusts:

 

[the ghost of leroy]

26 minutes ago, gymengineer said:

That Sampit River boat reading of 120 mph (~60 ft elevation) would again support a higher maximum gust estimate in the RMW zone. Since I support the NHC's assigned landfall intensity, the other data indicating Category 4 is what made his wind map based on damage to trees and structures stand out as an outlier. 

Hmm, to add some more confusion, this other map does not match the original one I imbedded. It's somehow tied to Fujita as well, but has a zone of 145 mph+ gusts:

 

It could just be different gust methodology. Like 3sec vs 10sec or something. 

Fujita did make the best maps, though. I'd love to get my hands on some of his stuff for framing purposes. They are flat out art. 

[LongBeachSurfFreak]

I would do anything for a satalite loop of the hurricane of 1938. I would love to know what it's actual structure was at time of landfall in NY

[gymengineer]

34 minutes ago, LongBeachSurfFreak said:

I would do anything for a satalite loop of the hurricane of 1938. I would love to know what it's actual structure was at time of landfall in NY

For me, it would be a radar loop of Carol making landfall. Perhaps the most purely tropical hit of the famous New England storms? 

[Roger Smith]

Ranking seasons 1851 to 2017

167 North Atlantic tropical storm (or hurricane) seasons are ranked below by number of storms, then by hurricanes, and finally by major hurricanes. (original post) The assumption is made that 2017 will finish 17/10/5 and this assumption will be edited at the end of the season. 2017* may change ranks. It currently stands 9th and would stay there at 18/10/5 or 18/11/5.

(edit October 14 at 15z -- NHC upgraded Ophelia to cat-3 which means the assumption has now changed to a finish of 17/10/6 but it will remain 9th at 18/10/6 or 18/11/6.)

(update Nov 9th -- With Philippe and Rina in the books now, 2017 has made my guesstimate of 17/10/6. Any further increases will be noted but 2017 remains 9th if it adds one more storm even if that becomes a hurricane.)

(update Jan 2018 ... final count confirmed as 17 10 6 for 2017)

 

RANK _ YEAR ___ S __ H __ M _____ RANK __ YEAR ____ S __ H __ M _____ RANK __ YEAR ___ S _ M _ H

_ 1 ___ 2005 ___ 28 _ 15 __ 7 ______ 61 ___ 1898 ____ 11 __ 5 __ 1 _____ 119t___ 1972 _____7 _ 3 _ 0

_ 2 ___ 1933 ___ 20 _ 11 __ 6 ______ 62t___ 1974 ____ 11 __ 4 __ 2 _____ 119t___ 1994 _____7 _ 3 _ 0

_ 3 ___ 2010 ___ 19 _ 12 __ 5 ______ 62t___ 2015 ____ 11 __ 4 __ 2 _____ 123 ___ 1858 _____6 _ 6 _ 0

_ 4 ___ 1995 ___ 19 _ 11 __ 5 ______ 64t___ 1937 ____ 11 __ 4 __ 1 _____ 124 ___ 1915 _____6 _ 5 _ 3

_ 5 ___ 1887 ___ 19 _ 11 __ 2 ______ 64t___ 1942 ____ 11 __ 4 __ 1 _____ 125t___ 1875 _____6 _ 5 _ 1

_ 6 ___ 2012 ___ 19 _ 10 __ 2 ______ 66t___ 1869 ____ 10 __ 7 __ 1 _____ 125t___ 1977 _____6 _ 5 _ 1

_ 7 ___ 2011 ___ 19 __ 7 __ 4 ______ 66t___ 1891 ____ 10 __ 7 __ 1 _____ 127 ___ 1941 _____6 _ 4 _ 3

_ 8 ___ 1969 ___ 18 _ 12 __ 5 ______ 66t___ 1903 ____ 10 __ 7 __ 1 _____ 128t___ 1856 _____6 _ 4 _ 2

_ 9 ___ 2017*___ 17 _ 10 __ 6 ______ 69 ___ 1948 ____ 10 __ 6 __ 4 _____ 128t___ 1882 ____ 6 _ 4 _ 2

_10 ___ 1936 ___ 17 __ 7 __ 1 ______ 70 ___ 1976 ____ 10 __ 6 __ 2 _____ 130t___ 1918 _____6 _ 4 _ 1

_11 ___ 1950 ___ 16 _ 11 __ 6 ______ 71 ___ 1908 ____ 10 __ 6 __ 1 _____ 130t___ 1965 _____6 _ 4 _ 1

_12 ___ 2008 ___ 16 __ 8 __ 5 ______ 72t___ 1943 ____ 10 __ 5 __ 2 _____ 132t___ 1904 _____6 _ 4 _ 0

_13t___ 1954 ___ 16 __ 7 __ 3 ______ 72t___ 1947 ____ 10 __ 5 __ 2 _____ 132t___ 1913 _____6 _ 4 _ 0

_13t___ 2003 ___ 16 __ 7 __ 3 ______ 72t___ 1970 ____ 10 __ 5 __ 2 _____ 132t___ 1986 _____6 _ 4 _ 0

_15 ___ 1949 ___ 16 __ 7 __ 2 ______ 72t___ 2006 ____ 10 __ 5 __ 2 _____ 135t___ 1851 _____6 _ 3 _ 1

_16 ___ 1916 ___ 15 _ 10 __ 5 ______ 76 ___ 1899 ____ 10 __ 3 __ 2 _____ 135t___ 1939 _____6 _ 3 _ 1

_17 ___ 2004 ___ 15 __ 9 __ 6 ______ 77 ___ 1963 _____ 9 __ 7 __ 2 _____ 137t___ 1862 _____6 _ 3 _ 0

_18 ___ 2001 ___ 15 __ 9 __ 4 ______ 78 ___ 1975 _____ 9 __ 6 __ 3 _____ 137t___ 1897 _____6 _ 3 _ 0

_19 ___ 2000 ___ 15 __ 8 __ 3 ______ 79 ___ 1888 _____ 9 __ 6 __ 2 _____ 137t___ 1911 _____6 _ 3 _ 0

_20 ___ 1932 ___ 15 __ 6 __ 4 ______ 80 ___ 1867 _____ 9 __ 6 __ 1 _____ 140 ___ 1982 _____6 _ 2 _ 1

_21 ___ 2007 ___ 15 __ 6 __ 2 ______ 81t___ 1889 _____ 9 __ 6 __ 0 _____ 141 ___ 1895 _____6 _ 2 _ 0

_22 ___ 1998 ___ 14 _ 10 __ 3 ______ 81t___ 1940 _____ 9 __ 6 __ 0 _____ 142 ___ 1852 _____5 _ 5 _ 1

_23 ___ 1944 ___ 14 __ 8 __ 3 ______ 83 ___ 1979 _____ 9 __ 5 __ 2 _____ 143 ___ 1876 _____5 _ 4 _ 2

_24 ___ 1990 ___ 14 __ 8 __ 1 ______ 84t___ 1863 _____ 9 __ 5 __ 0 _____ 144 ___ 1855 _____5 _ 4 _ 1

_25 ___ 1953 ___ 14 __ 7 __ 3 ______ 84t___ 1892 _____ 9 __ 5 __ 0 _____ 145t___ 1872 _____5 _ 4 _ 0

_26 ___ 1959 ___ 14 __ 7 __ 2 ______ 86 ___ 1938 _____ 9 __ 4 __ 2 _____ 145t___ 1920 _____5 _ 4 _ 0

_27 ___ 2016 ___ 14 __ 6 __ 2 ______ 87 ___ 1923 _____ 9 __ 4 __ 1 _____ 147 ___ 1873 _____5 _ 3 _ 2

_28 ___ 2013 ___ 14 __ 2 __ 0 ______ 88 ___ 2009 _____ 9 __ 3 __ 2 _____ 148t___ 1854 _____5 _ 3 _ 1

_29 ___ 1955 ___ 13 _ 10 __ 5 ______ 89 ___ 1859 _____ 8 __ 7 __ 1 _____ 148t___ 1910 _____5 _ 3 _ 1

_30 ___ 1996 ___ 13 __ 9 __ 6 ______ 90t___ 1871 _____ 8 __ 6 __ 2 _____ 148t___ 1922 _____5 _ 3 _ 1

_31 ___ 1934 ___ 13 __ 7 __ 1 ______ 90t___ 1879 _____ 8 __ 6 __ 2 _____ 148t___ 1929 _____5 _ 3 _ 1

_32t___ 1901 ___ 13 __ 6 __ 1 ______ 90t___ 2014 _____ 8 __ 6 __ 2 _____ 148t___ 1962 _____5 _ 3 _ 1

_32t___ 1971 ___ 13 __ 6 __ 1 ______ 93t___ 1861 _____ 8 __ 6 __ 0 _____ 153t___ 1864 _____5 _ 3 _ 0

_34 ___ 1984 ___ 13 __ 5 __ 1 ______ 93t___ 1885 _____ 8 __ 6 __ 0 _____ 153t___ 1902 _____5 _ 3 _ 0

_35 ___ 1931 ___ 13 __ 3 __ 1 ______ 95 ___ 1935 _____ 8 __ 5 __ 3 _____ 155 ___ 1919 _____5 _ 2 _ 1

_36 ___ 1893 ___ 12 _ 10 __ 5 ______ 96 ___ 1967 _____ 8 __ 5 __ 1 _____ 156 ___ 1905 _____5 _ 1 _ 1

_37 ___ 1886 ___ 12 _ 10 __ 4 ______ 97t___ 1853 _____ 8 __ 4 __ 2 _____ 157 ___ 1907 _____5 _ 0 _ 0

_38 ___ 1878 ___ 12 _ 10 __ 2 ______ 97t___ 1960 _____ 8 __ 4 __ 2 _____ 158 ___ 1884 _____4 _ 4 _ 1

_39 ___ 1999 ___ 12 __ 8 __ 5 ______ 97t___ 1991 _____ 8 __ 4 __ 2 _____ 159 ___ 1883 _____4 _ 3 _ 2

_40 ___ 1951 ___ 12 __ 8 __ 3 ______100t___ 1927 _____ 8 __ 4 __ 1 _____ 160 ___ 1983 ____ 4 _ 3 _ 1

_41t___ 1958 ___ 12 __ 7 __ 3 ______100t___ 1973 _____ 8 __ 4 __ 1 _____ 161t___ 1857 _____4 _ 3 _ 0

_41t___ 1981 ___ 12 __ 7 __ 3 ______100t___ 1993 _____ 8 __ 4 __ 1 _____ 161t___ 1868 _____4 _ 3 _ 0

_43 ___ 1964 ___ 12 __ 6 __ 6 ______103 ___ 1968 _____ 8 __ 4 __ 0 _____ 163 ___ 1917 _____4 _ 2 _ 2

_44 ___ 1909 ___ 12 __ 6 __ 4 ______104 ___ 1957 _____ 8 __ 3 __ 2 _____ 164 ___ 1890 _____4 _ 2 _ 1

_45 ___ 1988 ___ 12 __ 5 __ 3 ______105t___ 1877 _____ 8 __ 3 __ 1 _____ 165 ___ 1925 _____4 _ 1 _ 0

_46 ___ 1978 ___ 12 __ 5 __ 2 ______105t___ 1997 _____ 8 __ 3 __ 1 _____ 166 ___ 1930 _____3 _ 2 _ 2

_47 ___ 2002 ___ 12 __ 4 __ 2 ______107 ___ 1896 _____ 7 __ 6 __ 2 _____ 167 ___ 1914 _____1 _ 0 _ 0

_48 ___ 1956 ___ 12 __ 4 __ 1 ______108t___ 1860 _____ 7 __ 6 __ 1 _______ 

_49 ___ 1870 ___ 11 _ 10 __ 2 ______108t___ 1866 _____ 7 __ 6 __ 1 _______ 

_50t___ 1880 ___ 11 __ 9 __ 2 ______110 ___ 1894 _____ 7 __ 5 __ 4 _______ 

_50t___ 1980 ___ 11 __ 9 __ 2 ______111 ___ 1921 _____ 7 __ 5 __ 2 _______ 

_52 ___ 1961 ___ 11 __ 8 __ 7 ______112t___ 1912 _____ 7 __ 4 __ 1 _______ 

_53 ___ 1926 ___ 11 __ 8 __ 6 ______112t___ 1928 _____ 7 __ 4 __ 1 _______

_54t___ 1966 ___ 11 __ 7 __ 3 ______112t___ 1992 _____ 7 __ 4 __ 1 _______ 

_54t___ 1985 ___ 11 __ 7 __ 3 ______115t___ 1874 _____ 7 __ 4 __ 0 _______ 

_56 ___ 1989 ___ 11 __ 7 __ 2 ______115t___ 1881 _____ 7 __ 4 __ 0 _______ 

_57 ___ 1906 ___ 11 __ 6 __ 3 ______117 ___ 1900 _____ 7 __ 3 __ 2 _______ 

_58t___ 1924 ___ 11 __ 5 __ 2 ______118 ___ 1987 _____ 7 __ 3 __ 1 _______ 

_58t___ 1945 ___ 11 __ 5 __ 2 ______119t___ 1865 _____ 7 __ 3 __ 0 _______ 

_58t___ 1952 ___ 11 __ 5 __ 2 ______119t___ 1946 _____ 7 __ 3 __ 0 _______ 

_____________________________________________________________________

RANKS by Hurricanes only

Rank __YEAR __________________________ H (M) ______ rank of majors

__ 1 __ 2005 _________________________ 15 _ 7 _______ 1 (2 tied)  

__ 2t__ 1969, 2010 ____________________ 12 _ 5 _______ 9 (9 tied)  

__ 4t__ 1933, 1950 ____________________ 11 _ 6 _______ 3 (7 tied)

__ 6 __ 1995 _________________________ 11 _ 5 _______10 (8 tied)

__ 7 __ 1887 _________________________ 11 _ 2 _______42 (46 tied) 

__ 8 __ 2017 _________________________ 10 _ 6 _______ 3 (7 tied)

__ 9t __ 1893, 1916, 1955 ______________ 10 _ 5 _______10 (8 tied)

_ 12 __ 1886 _________________________ 10 _ 4 _______18 (7 tied)

_ 13 __ 1998 _________________________ 10 _ 3 _______25 (17 tied)

_ 14t _ 1870, 1878, 2012 _______________ 10 _ 2 _______42 (46 tied)

_ 17t__ 1996, 2004 ____________________ 9 _ 6 _______ 3 (7 tied)

_ 19 __ 2001 _________________________ 9 _ 4 _______18 (7 tied)

_ 20t__ 1880, 1980 ____________________ 9 _ 2 _______42 (46 tied)

_ 22 __ 1961 _________________________ 8 _ 7 _______ 1 (2 tied)

_ 23 __ 1926 _________________________ 8 _ 6 _______ 3 (7 tied)

_ 24t__ 1999, 2008 ____________________ 8 _ 5 _______10 (8 tied)

_ 26t__ 1944, 1951, 2000 _______________ 8 _ 3 _______25 (17 tied)  

_ 29 __ 1990 _________________________ 8 _ 1 _______ 88 (49 tied)

_ 30 __ 2011 _________________________ 7 _ 4 _______ 18 (7 tied)

_ 31t__ 1953,54,58, 1966, 1981,85, 2003 __ 7 _ 3 _______ 25 (17 tied) 

_ 38t__ 1949, 1959, 1963, 1989 __________7 _ 2 _______ 42 (46 tied)

_ 42t__ 1859,1869,1891,1903,1934,1936___7 _ 1 ________88 (49 tied)

_ 48 __ 1964 _________________________6 _ 6 ________ 3 (7 tied)

_ 49t__ 1909, 1932, 1948 ______________ 6 _ 4 _______ 18 (7 tied)

_ 52 __ 1906, 1975 ____________________6 _ 3 _______ 25 (17 tied)

_ 54t__ 1871,79,88,96, 1976, 2007,14,16 __6 _ 2 _______ 42 (46 tied)

_ 62t__ 1860,66,67 1901,08, 1971 _______ 6 _ 1 _______ 88 (49 tied)

_ 68t__ 1858, 1861, 1885, 1889, 1940 ____6 _ 0 ______ 137 (31 tied)

_ 73 __ 1894 ________________________ 5 _ 4 ______ 18 (7 tied)

_ 74t__ 1915, 1935, 1988 ______________ 5 _ 3 ______ 25 (17 tied)

_ 77t__1921,24,43,45,47,52,70,78,79,2006_5 _ 2 ______ 42 (46 tied)

_ 87t__1852,1875,1898, 1967,1977,1984 __5 _ 1 ______ 88 (49 tied)

_ 93t__ 1863, 1892 ___________________ 5 _ 0 ______ 137 (31 tied)

_ 95 __ 1941 ________________________ 4 _ 3 ______ 25 (17 tied)

_ 96t __1853,56,76,82,

_________ 1938,60,74,91, 2002, 2015 ___ 4 _ 2 ______ 42 (46 tied)

_106t __1855,84, 1912,18,23,27,28,

________1937,42,56,65,73,92,93 _______ 4 _ 1 _______ 88 (49 tied)

_120t __1872,74,81, 1904,13,20,68,86 ___ 4 _ 0 ______ 137 (31 tied)

_128t __1873,83,99, 1900, 1957, 2009 ___ 3 _ 2 _______ 42 (46 tied)

_134t __1851,54,77, 1910,22,29,

________ 1931,39,62,83,87,97 _________ 3 _ 1 ________ 88 (49 tied)

_146t __1857,62,64,65,68, 1897,

________ 1902, 1911, 1946, 1972, 1994__3 _ 0 ________137 (31 tied)

_157t __ 1917, 1930 _________________ 2 _ 2 ________ 42 (46 tied)

_159t __ 1890, 1919, 1982 ____________ 2 _ 1 ________ 88 (49 tied)

_162t __ 1895, 2013 _________________ 2 _ 0 ________ 137 (31 tied)

_164 ___ 1905 ______________________ 1 _ 1 ________ 88 (49 tied)

_165 ___ 1925 ______________________ 1 _ 0 ________ 137 (31 tied)

_166t __ 1907, 1914 _________________ 0 _ 0 ________ 137 (31 tied)

____________________________________________________

seasons with this many majors:

7 _ 2

6 _ 7

5 _ 8

4 _ 7

3 _17

2 _46

1 _49

0 _31

[Windspeed]

Much has been discussed in various tropical cyclone threads on this forum and the old predecessor Eastern Wx forums over the past 17 years about the northern Gulf of Mexico and its unfavorability in sustaining major hurricane landfalls. Even as recently a Hurricane Nate, the discussion was brought up again. Though Nate was not a major hurricane, nor was it forecast to be, it was forecast by the NHC to reach 90 kts / 105 mph by landfall. Nate did not reach Category 2 intensity however, and even appeared to weaken more significantly than the official advisory prior to landfall; though we will need reanalysis to perhaps know for certain just how much weakening occurred. Either way, it is clear Nate did not strengthen or maintain its structure into landfall. Convection waned, the core appeared to collapse and the NE eyewall barely held its curved banding into the MS coastline. As such, discussion linked Nate to the unfavorability that exists there. I disagree with this conception, however. Hurricane Nate is not a good example of a cyclone sustaining intensity due to SST environmental conditions.

Nate was a hurricane with a small core that was under a extremely fast steering regime. Convective mesos would form, rotate to the western half of the circulation and collapse. This happened at a near constant rate as its forward motion increased until it couldn't manage to close off its eyewall vortex. At multiple points on track, an eyewall would develop only to pivot around into a new intensifying meso. I think recon may have measured hurricane force winds within the stronger east side of these mesos, but I am not so sure Nate ever held a steady state intensity for prolonged periods. It's quite possible the core would reattain hurricane force during each meso, but an eyewall band had trouble establishing overall dominance as the core vortex feature.

Whether the shallower heat content had an effect I believe is insignificant compared to the unfavorable flow against the western half of the hurricane. Perhaps radial convergence and evaporation feed of heat flux really was suffered by Nate. The storm was just moving way too fast for it to take advantage of any immediate sea surface heat layer, much less heat content at depth (regardless of its presence). Understand that I have been skeptical of forward motion, low-level convergence and heat flux being a significant factor, but I am now wondering if this is a critical to sustainment of eyewall convective banding as upper-level divergence over LLC core may be overwhelmed or disrupted with meso scale vortices updrafts within the inner periphery of the low-level vortex in rapidly moving systems such as Nate. This may not have been as much a negative factor for an already well-organized surface vortex, but Nate seemed to be struggling with this process even as a hurricane.

We also have plenty of examples of hurricanes intensifying at landfall in the northern Gulf over the shallow surface layer to contend with the hurricanes that weakened. Alicia, Fredrick and Camille (after completing an ERC) are some of the more notable cyclones. The most intense major hurricane to be shown to have reintensified by landfall in reanalysis is Camille. Though it weakened during an ERC SSE of the mouth of the Mississippi River when the tiny inner eyewall finally collapsed, a bright outter ring representing the outter eyewall contracted quite rapidly. It did not lose its structure and in fact appears to have sustained nearly a 360° 12 nm closed band right at landfall at Waveland, MS. See linked animation .gif of landfall and PDF of reanalysis.

Now clearly, shallow surface layer SSTs in August near the northern Gulf coastline are warmer than in October. We typically observe 29-31° C shallow surface water by late August without any significant frontal interaction. By October, the shelf typically drops a few degrees. But 28° were still being observed in Nate's track. That would have been sufficient to support a major hurricane, especially a fast mover. Unfortunately, Nate was moving so fast, it began to collapse before the shallow layer even mattered.

We have seen rapid motion in major hurricanes before. Charley was moving around 20 mph when it underwent rapid intensification from 95 to 125 kts and a 27 mb pressure drop in less than 8 hours. But when Charley's core gained faster forward motion, it already had a well organized and symmetrical core. Interestingly, though it did not cross over the northern Gulf shallow shelf, it was crossing the shallow shelf off of SW Florida, north of the Keys. Wilma also intensified crossing this shallow shelf. OTOH, Nate was in the process of developing its core vortex the entirety of its track across the W. Caribbean and GOM between 22 and 26 mph. These are purely tropical cyclone examples. We can also cite the rapid motion of the 1938 Long Island Hurricane; however, this storm was likely undergoing rapid baroclinic forcing as well, which likely sustained intense convection and major hurricane force winds/surge straight inland.

Some majors that weakened at landfall are obviously noteworthy. Katrina, Rita and Ivan are mentioned frequently. But every one of these systems were battling significant shear as well. Ivan is an interesting case as it managed to remain 105 kts Category 3 even with 30 kts of mid-level shear advecting dry stable air into its core. The northern and eastern eyewall band held together quite well.

With past hurricane examples of intensifying storms into the northern Gulf coast, these systems were all in a more favorable upper-level environment. Even though Nate was in a low shear environment, the western circulation northerly flow was hampered by such strong opposing directional mid-level flow. I think if Nate had been a slower moving storm, being a purely tropical entity, it would have been able to reach Category 2 intensity at landfall. Perhaps even strengthen all the way into landfall. But this is speculative. I'm only wanting to point out that the sea surface environmental aspects were not its doom.

Edit: I initially intended to preview and correct typos, but I accidentally submitted the entire post prematurely. If you read this post within the first hour of submission, you may want to reread before commenting. Thanks!

[the ghost of leroy]

2 hours ago, Windspeed said:

Much has been discussed in various tropical cyclone threads on this and the old predecessor Eastern Wx forums over the past 17 years about the northern Gulf of Mexico and its unfavorability in sustaining major hurricane landfalls. Even as recently a Hurricane Nate, the discussion was brought up again. Though Nate was not a major hurricane, nor was it forecast to be, it was forecast by the NHC to reach 90 kts / 105 mph by landfall. Nate did not reach Category 2 intensity however, and even appeared to weaken more significantly than the official advisory prior to landfall; though we will need reanalysis to perhaps know for certain just how much weakening occurred. Either way, it is clear Nate did not strengthen or maintain its structure into landfall. Convection waned, the core appeared to collapse and the NE eyewall barely held its curved banding into the MS coastline. As such, discussion linked Nate to the unfavorability that exists there. I disagree with this conception, however. Hurricane Nate is not a good example of a cyclone sustaining intensity due to SST environmental conditions.

Nate was a hurricane with a small core that was under a extremely fast steering regime. Convective mesos would form, rotate to the western half of the circulation and collapse. This happened at a near constant rate as its forward motion increased until it couldn't manage to close off its eyewall vortex. At multiple points on track, an eyewall would develop only to pivot around into a new intensifying meso. I think recon may have measured hurricane force winds within the stronger east side of these mesos, but I am not so sure Nate ever held a steady state intensity for prolonged periods. It's quite possible the core would reattain hurricane force during each meso, but an eyewall band had trouble establishing overall dominance as the core vortex feature.

Whether the shallower heat content had an effect I believe is insignificant compared to the unfavorable flow against the western half of the hurricane. Perhaps radial convergence and evaporation feed of heat flux really was suffered by Nate. The storm was just moving way too fast for it to take advatage of any immediate sea surface heat layer, much less heat content at depth (regardless of its presence). Understand that I have been skeptical of forward motion, low-level convergence and heat flux being a significant factor, but I am now wondering if this is a critical to sustainment of eyewall convective banding as upper-level divergence over LLC core may be overwhelmed or disrupted with meso scale vortices updrafts within the inner periphery of the low level vortex in rapidly moving systems such as Nate. This may have not been as much a negative factor for an already well-organized surface vortex, but Nate seemed to be struggling with this process even as a hurricane.

We also have plenty of examples of hurricanes intensifying at landfall in the northern Gulf over the shallow surface layer to contend with the hurricanes that weakened. Alicia, Fredrick and Camille (after completing an ERC) are some of the more notable cyclones. The most intense major hurricane to be shown to have reintensified by landfall in reanalysis is Camille. Though it weakened during an ERC SSE of the mouth of the Mississippi River when the tiny inner eyewall finally collapsed, a bright outter ring representing the outter eyewall contracted quite rapidly. It did not lose its structure and in fact appears to have sustained nearly a 360° 12 nm closed band right at landfall at Waveland, MS. See linked animation .gif of landfall and PDF of reanalysis.

Now clearly, shallow surface layer SSTs in August near the northern Gulf coastline are warmer than in October. We typically observe 29-31° C shallow surface water by late August without any significant frontal interaction. By October, the shelf typically drops a few degrees. But 28° were still being observed in Nate's track. That would have been sufficient to support a major hurricane, especially a fast mover. Unfortunately, Nate was moving so fast, it began to collapse before the shallow layer even mattered.

We have seen rapid motion in major hurricanes before. Charley was moving around 20 mph when it underwent rapid intensification from 95 to 125 kts and a 27 mb pressure drop in less than 8 hours. But when Charley's core gained faster forward motion, it already had a well organized and symmetrical core. Interestingly, though it did not cross over the northern Gulf shallow shelf, it was crossing the shallow shelf off of SW Florida, north of the Keys. Wilma also intensified crossing this shallow shelf. OTOH, Nate was in the process of developing its core vortex the entirety of its track across the W. Caribbean and GOM between 22 and 26 mph. These are purely tropical cyclone examples. We can also cite the rapid motion of the 1938 Long Island Hurricane; however, this storm was likely undergoing rapid baroclinic forcing as well, which likely sustained intense convection and major hurricane force winds/surge straight inland.

Some majors that weakened at landfall are obviously noteworthy. Katrina, Rita and Ivan are mentioned frequently. But every one of these systems were battling significant shear as well. Ivan is an interesting case as it managed to remain 105 kts Category 3 even with 30 kts of mid-level shear advecting dry stable air into its core. The northern and eastern eyewall band held together quite well.

With past hurricane examples of intensifying storms into the northern Gulf coast, these systems were all in a more favorable upper-level environment. Even though Nate was in a low shear environment, the western circulation northerly flow was hampered by such strong opposing directional mid-level flow. I think if Nate had been a slower moving storm, being a purely tropical entity, it would have been able to reach Category 2 intensity at landfall. Perhaps even strengthen all the way into landfall. But this is speculative. I'm only wanting to point out that the sea surface environmental aspects were not its doom.

Edit: I initially intended to preview and correct typos, but I accidentally submitted the entire post prematurely. If you read this post within the first hour of submission, you may want to reread before commenting. Thanks!

Good post. I agree that speed was perhaps the biggest detriment. It maybe could have gotten to 100kts or so had it just been moving at a more routine pace. 

[Windspeed]

Good post. I agree that speed was perhaps the biggest detriment. It maybe could have gotten to 100kts or so had it just been moving at a more routine pace.

My main point was to show that you do not need deep oceanic heat content for a fast moving cyclone. Often times people post these OHC images as evidence for rapid intensification, but in my opinion, it is of far less importance for fast moving hurricanes versus the overall upper-level atmospheric environment. These NOAA maps that show depth of the 26° isotherm and also TCHP in the Gulf of Mexico are far more critical in slow to moderate motion in cyclones where their own upwelling below the shallow surface layer can affect intensity.

 

Another hurricane I completely forgot to mention is Harvey. Here is another example of a hurricane that rapidly intensified over a shallow shelf just off the SE Texas coast. The immediate surface layer was around 30-31° C at the time. But Harvey's core had already moved away from deeper oceanic heat content and a deep warm eddy. See the CIMSS image: http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2017/08/Harvey_track_OHC.jpg

 

The shallow surface layer was essentially overkill to support rapid intensification. The improving upper-level environment became spectacular near the coast however, and the models had been hinting at a favorable 200 mb pattern in the days proceeding Harvey's rapid intensification.

 

The reason I cited Camille in the post above is that it is an example of a Category 5 that actually reintensified over the shallow shelf just east of Louisiana. In late August, the shallow surface layer near eastern Louisiana / southern MS-AL coast would have been around 30-31° C, similar to what we observed under Harvey just off Texas coast.

 

I worry that we will see another Camille again. Granted, October the SSTs have dropped enough. But in the prime GOM months of July and August, I have little doubt a Category 5 can make landfall along the northern Gulf coast. We have developed a preconception of that region of the GOM due to recent examples of major hurricane landfalls. But it just takes the right upper-level environment and storm motion to change or erase that conception.

[wxmx]

Not just forward speed, but also size is a factor on whether OHC is important or not. Big cyclones will tend to churn water ahead of it, cooling SSTs.

 

Also, another example of an intense cyclone strengthening up to landfall in a very shallow shelf was Felix. Does it matter much that you upwell water from 15-20 mts below sea surface when the whole column is 30C?

[the ghost of leroy]

On 10/11/2017 at 2:47 PM, wxmx said:

Also, another example of an intense cyclone strengthening up to landfall in a very shallow shelf was Felix. Does it matter much that you upwell water from 15-20 mts below sea surface when the whole column is 30C?

felix is the best example for sure.  for those that don't remember, look at the TCHP off the landfall zone in nicaragua prior to the storm...

[Windspeed]

Here's a blast from the past: Anyone remember Major Hurricane Elena? It is another example of a hurricane that intensified significantly while over the shallow shelf waters of the northern Gulf. Elena reached upper Category 3 intensity with maximum estimated winds of 110 kts, but did weaken slightly to 100 kts in the hours just before landfall near Biloxi, Mississippi. I think we should realize, however, that Elena was its own worst enemy. It spent nearly four days in the same general region of the Gulf. The circulation took on slow and erratic movement ENE before looping sharply back to the WNW. This motion was due to interaction with a fast moving weak upper level shortwave trough that lifted and left Elena behind. The 500 mb weakness filled and allowed a ridge to take the wheel. Prolonged meandering and drift of the circulation likely did upwell cooler water from the previous days. This combined with the core's close proximity to the coast on its WNW track prior to landfall perhaps did prevent Elena from becoming a Category 4. The highest official coastal measurements were 92 kts sustained with 118 kts gust on Dauphin Is., Alabama, and gusts of 105 kts in Gulfport, Miss.

Elena is also one of the few early and rare moments where a successful storm chaser was lucky enough to have a quality camera on the ground inside the eye at landfall. The chaser filmed the clear blue sky overhead and the beautiful concave eyewall seen @ 1m 20s. A stunning shot made even more impressive that this was captured in 1985.

[the ghost of leroy]

My grandparents lived in Bay St Louis at the time.  They evacuated at first towards my aunt in Tampa, then the hurricane turned so they went home, then it turned back and they said screw it and rode it out.  I remember thumbing through an album that had their hurricane party pics in it.  Total rager.

That eye video is still amongst the best ever.

Another thing I remember is this photo, which is one of the iconic hurricane pics of the 80's.  I used to have a book with it on the cover.

[Windspeed]

2 hours ago, cmasty1978 said:

That eye video is still amongst the best video ever.

Here is a longer version with footage from the eyewall.

 

[Windspeed]

With respect to the recent impacts on the Lesser & Greater Antilles and US territories, PBS NOVA is airing a new documentary that focuses on the deadliest Altantic major hurricane in the historical record, The Great Hurricane of 1780.

Quote

Killer Hurricanes

Experts reconstruct the Great Hurricane of 1780 to help predict the risk of future storms. Airing November 1, 2017 at 9 pm on PBS:

Devastating hurricanes struck the U.S. mainland and Caribbean islands in 2017. But they weren’t the first. The Great Hurricane of 1780 took nine days to blast its way across the Caribbean, killing at least 20,000—the highest known death toll of any single weather event in history. What made this superstorm so deadly? To reconstruct its epic scale and investigate what made it so devastating, NOVA joins historians and storm sleuths as they track down clues in eyewitness chronicles, old ruins, and computer simulations. Their evidence points to a truly terrifying, 300-mile-wide storm—with wind speeds probably exceeding 230 miles an hour and 25-feet storm surges that demolished everything in their path. But just how unusual was the Great Hurricane? Diving into sinkholes off Barbados and squirming into caves in the Yucatan, NOVA’s experts recover traces of tempests stretching back over more than 1,000 years. The picture they paint is disturbing: mega-hurricanes were not only more frequent in the past but are likely to strike again in our near future, as climate change warms the oceans and fuels more intense hurricanes.

http://player.pbs.org/viralplayer/3005566471/

[the ghost of leroy]

Quote

 Their evidence points to a truly terrifying, 300-mile-wide storm—with wind speeds probably exceeding 230 miles an hour and 25-feet storm surges that demolished everything in their path. 

something tells me this is going to be presented in a way that is sensationalized...

[Windspeed]

 something tells me this is going to be presented in a way that is sensationalized...

^Likely. But the cyclone did inflict some horrific devestation and loss of life. It hit two major fleets and several large ports so fortunately plenty of details were logged that can be ironed out from a meteorological standpoint. Hopefully they don't spend the entire episode in Weenieville.

[Windspeed]

A new peer-reviewed study in the British Royal Meteorological Society journal Weather is proposing that Super Typhoon Haiyan is likely the most intense cyclone ever observed in the Satellite Era. They believe the center eye pressure peaked near 860 mb.
http://onlinelibrary.wiley.com/doi/10.1002/wea.3045/full

Quote

Since 12 October 1979, Typhoon Tip has officially remained the tropical cyclone associated with the lowest atmospheric pressure measured at sea level: 870hPa. The average winds over 1min were estimated at 165kn. On 7 November 2013, Typhoon Haiyanwas the first cyclone to have been estimated at 170kn from satellite imagery. In the absence of aircraft reconnaissance, the minimum pressure has been estimated at 895hPa using the wind–pressure relationship. Using data observed at Guiuan meteorological station in the Philippines, we have estimated the minimum surface pressure in the eye of Haiyan. On the basis of the last pressure measurement of 910hPa at Guiuan, which was located at the outer edge of the eyewall, we estimated the pressure gradient for the 11km of the eyewall. This estimation was made using a comparison with the pressure gradient of the eyewall of two of the most intense tropical cyclones for which the pressures were precisely measured by aerial reconnaissance. During these airborne missions, Hurricane Patricia (23 October 2015), which formed in the eastern North Pacific, had a pressure of 879hPa, and Typhoon Megi (17 October 2010), which formed in the western North Pacific, had a pressure of 890hPa. At the time of the aircraft reconnaissance, the sustained winds of 180kn for Patricia (6h before the maximum wind of 185kn) and 160kn for Megi were comparable to the 170kn of Haiyan. Based on the pressure gradient calculated inside the eyewall of Patricia and Megi, we distinguished three scenarios for Haiyan. Each of them gives a minimum pressure at sea level below the 870hPa of Typhoon Tip, which was the world record holder.

I have always argued that Haiyan remains the most intense cyclone we have witnessed in modern times. Had there been reconnaissance, no other cyclone's intensity data sets would top it. This paper puts that in perspective for me. I had no idea the station reading at Guiuan existed. Recorded 18 miles from center fix and measured to 910 mb, that observation is bloody insane! Even loosely estimating gradient, a center pressure of 866 mb is calculated. The authors settled on 861 mb and rounded to 860 mb based on a few variables. The eyewall had held a steady state in the 30 hrs following the last visible completion of an ERC. The coldest tower tops around the immediate wall were not warming at the recording of that surface pressure. The diameter of the eye had actually decreased slightly. Given Haiyan was positioned against the southern periphery of an amplified subtropical ridge (STR) at the time, imbedded in an above mean surface pressure regime, the pressure gradient most likely was not loose at that obs timestamp. They still did not go with the tightest gradient scenario however.

The following is an excellent write-up by Bob Henson discussing the paper over at underground:

Quote

The authors used three possible scenarios to determine Haiyan’s minimum central pressure based upon the time of the 910 mb measurement from Guiuan when the eye was 28km distant. One scenario employed an average gradient of 3.5 mb/km, another 4.0 mb/km, and another 4.5 mb/km. In the low-gradient scenario, the central pressure of Haiyan was estimated at 866.5 mb; the median scenario resulted in a 861-mb central pressure, and the steep gradient scenario an 855.5-mb central pressure. The authors settled on the 861-mb figure, rounded off to 860 mb.

As for the wind-pressure relationship, Patricia officially holds the record for the strongest winds attributed to a tropical cyclone with 185 knots (213 mph) sustained at its peak strength (central pressure 872 mb). This compares to Typhoon Tip’s 165 kts (190 mph) with 870 mb, and Haiyan’s 170kn (195 mph) with a minimum ‘official’ pressure of 895 mb. From these facts alone, we may surmise that the pressure of Haiyan was almost certainly lower than 895 mb, since we know Haiyan was a large typhoon. Using the Dvorak technique, Haiyan was a perfect 8.0 (on a scale of 1 to 8). That being said, several other tropical cyclones have attained that exalted status aside from Haiyan, Tip, and Patricia.

This may all be semantics and the WMO may or may not take this new research into consideration for crowning Haiyan the most intense on record. But at least from a meteorological standpoint, that surface pressure ob is great evidence to support just why Haiyan's satellite presentation at that timestamp has no equal. Had there been a recon flight around that time, in my mind, the windspeeds would have no doubt been the strongest ever recorded in a tropical cyclone. Obviously, this is still speculation, but I believe it was at least 185 kts or equal to Major Hurricane Patricia. But given the surface pressure obs 18 miles from center fix and given the pressure environment, Haiyan may very well have had higher sustained winds. I realize It is difficult to fathom a 190-200 kts cyclone. But keep in mind, even though Patricia had a tiny core, it was imbedded in a surface trough. The hurricane was moving into a weakness by means of an advancing mid-to-upper trough and southwesterly steering regime. Haiyan's synoptic pattern contrasts significantly as the cyclone was imbedded within a moderate easterly steering flow against a strong mid-level ridge and higher surface pressures.

Obviously, we will never know for certain Haiyan's peak windspeeds with the absence of reconnaissance. After considering all these factors and the new paper, however, I am confident Haiyan is the most intense system even if unofficial. To me it remains the Godzilla of tropical cyclones.

[LongBeachSurfFreak]

On 11/3/2017 at 1:16 AM, Windspeed said:

A new peer-reviewed study in the British Royal Meteorological Society journal Weather is proposing that Super Typhoon Haiyan is likely the most intense cyclone ever observed in the Satellite Era. They believe the center eye pressure peaked near 860 mb.
http://onlinelibrary.wiley.com/doi/10.1002/wea.3045/full

I have always argued that Haiyan remains the most intense cyclone we have witnessed in modern times. Had there been reconnaissance, no other cyclone's intensity data sets would top it. This paper puts that in perspective for me. I had no idea the station reading at Guiuan existed. Recorded 18 miles from center fix and measured to 910 mb, that observation is bloody insane! Even loosely estimating gradient, a center pressure of 866 mb is calculated. The authors settled on 861 mb and rounded to 860 mb based on a few variables. The eyewall had held a steady state in the 30 hrs following the last visible completion of an ERC. The coldest tower tops around the immediate wall were not warming at the recording of that surface pressure. The diameter of the eye had actually decreased slightly. Given Haiyan was positioned against the southern periphery of an amplified subtropical ridge (STR) at the time, imbedded in an above mean surface pressure regime, the pressure gradient most likely was not loose at that obs timestamp. They still did not go with the tightest gradient scenario however.

The following is an excellent write-up by Bob Henson discussing the paper over at underground:

This may all be semantics and the WMO may or may not take this new research into consideration for crowning Haiyan the most intense on record. But at least from a meteorological standpoint, that surface pressure ob is great evidence to support just why Haiyan's satellite presentation at that timestamp has no equal. Had there been a recon flight around that time, in my mind, the windspeeds would have no doubt been the strongest ever recorded in a tropical cyclone. Obviously, this is still speculation, but I believe it was at least 185 kts or equal to Major Hurricane Patricia. But given the surface pressure obs 18 miles from center fix and given the pressure environment, Haiyan may very well have had higher sustained winds. I realize It is difficult to fathom a 190-200 kts cyclone. But keep in mind, even though Patricia had a tiny core, it was imbedded in a surface trough. The hurricane was moving into a weakness by means of an advancing mid-to-upper trough and southwesterly steering regime. Haiyan's synoptic pattern contrasts significantly as the cyclone was imbedded within a moderate easterly steering flow against a strong mid-level ridge and higher surface pressures.

Obviously, we will never know for certain Haiyan's peak windspeeds with the absence of reconnaissance. After considering all these factors and the new paper, however, I am confident Haiyan is the most intense system even if unofficial. To me it remains the Godzilla of tropical cyclones.

I just saw these posts for the first time. I too have been a big proponent Hiayan being the most intense TC ever observed. If Dvorak went to a 10 it would be a 10. We just haven’t seen another storm with a ring of cloud tops that perfectly cold. Colors usually only seen in hot towers encircled the entire eye.

That and the tsunami like surge just put it in its own league. 

 

https://www.google.com/search?tbm=isch&source=hp&ei=j-D_WeHNB8WXmwHt1YXADw&sjs=3&q=typhoon+haiyan&oq=typhoon+&gs_l=mobile-gws-img.1.2.0l5.1533.8985.0.10484.9.8.0.1.1.0.210.999.2j5j1.8.0....0...1.1.64.mobile-gws-img..0.9.1043.3..41.0.a1Zq05MCH5g#imgrc=dwgv1-ElXb7lRM:

[ncforecaster89]

Listed below are a few NATL basin hurricanes whose current HURDAT2 intensity estimates merits a revision.             

1) Hurricane Charley (2004):

Suggest a 135 kt MAX intensity for first SW FL landfall.  

Based on a 148 kt 700 mb FLW measured by RECON, its rapid intensification, small contracting eye, and tiny RMW (at the time of landfall at Cayo Costa, FL)...a revised intensity of 135 kt (up from 130 kt) is most applicable.

2) Hurricane OPAL (1995):

Suggest a 140 kt MAX intensity in N central GOM (1000z/4th).     

Based on a 152 kt 700 mb FLW measured by RECON, its rapid intensification to 916 mb, small contracting eye, and compact RMW (about 12 hours prior to landfall in the NW FL Panhandle), it's highly likely Opal achieved a peak intensity of 140 kt and category-five on the SSHWS (up from 130 kt). 

3) Hurricane Marilyn (1995):

Suggest a 100 kt/CAT 3 intensity for St. Thomas, USVI.   

It's highly likely that Marilyn was a 100 kt category-three hurricane (up from 95 kt) when it blasted St. Thomas, USVI with its NE eyewall.  At the time, RECON measured 700 mb FLWs between 105-110 knots, while the hurricane was undergoing a period of rapid intensification. 

Moreover, the official ASOS at the airport in St. Thomas recorded two-minute sustained winds of 90 kts.  

Given these data, it's most probable that even stronger winds impacted the immediate shoreline at that time of Marilyn's closest approach and greatest impact (0430z/16th).   

References:  NHC Tropical Cyclone Reports for each respective hurricane shown above.   

https://www.nhc.noaa.gov/data/tcr/index.php?season=1995&basin=atl

[Floydbuster]

I suspect Hurricane Isidore (2002) peaked as a 115 kt Category 4 hurricane. Operationally, it never got higher than 110 kt, despite an astounding satellite appearance, high dvorak numbers, and a pressure of 934 mb. But I suspect it reached Category 4 strength prior to landfall in the Yucatan.

 

[ncforecaster89]

5 hours ago, Floydbuster said:

I suspect Hurricane Isidore (2002) peaked as a 115 kt Category 4 hurricane. Operationally, it never got higher than 110 kt, despite an astounding satellite appearance, high dvorak numbers, and a pressure of 934 mb. But I suspect it reached Category 4 strength prior to landfall in the Yucatan.

 

That's definitely a borderline case as the max FLWs were 117 kt, which corresponds to 105 kt at the surface.  The satellite intensity estimates were the equivalent of 115 kt...so they went with a compromise between the two.   Given the continued drop of the central pressure from 936 to 934 mb following the aforementioned RECON ob, it's certainly possible...if not likely, it achieved Cat 4 right before landfall.  

[Windspeed]

I worry that we will see another Camille again. Granted, October the SSTs have dropped enough. But in the prime GOM months of July and August, I have little doubt a Category 5 can make landfall along the northern gulf coast. We have developed a preconception of that region of the GOM due to recent examples of major hurricane landfalls. But it just takes the right upper-level environment and storm motion to change or erase that conception.

Reading back through this thread, I was dead wrong in one point while trying to discredit preconceptons or misconceptions about landfalling Cat 5s along the N. GOM coast, including rapid intensification over its shallow shelf. I never once imagined that scenario being possible in the month of October. Then having that play out approximately one year later? Crazy!

[LibertyBell]

4 hours ago, Windspeed said:

On 10/11/2017 at 1:58 PM, Windspeed said:

I worry that we will see another Camille again. Granted, October the SSTs have dropped enough. But in the prime GOM months of July and August, I have little doubt a Category 5 can make landfall along the northern gulf coast. We have developed a preconception of that region of the GOM due to recent examples of major hurricane landfalls. But it just takes the right upper-level environment and storm motion to change or erase that conception.

Reading back through this thread, I was dead wrong in one point while trying to discredit preconceptons or misconceptions about landfalling Cat 5s along the N. GOM coast, including rapid intensification over its shallow shelf. I never once imagined that scenario being possible in the month of October. Then having that play out approximately one year later? Crazy!

Some of the strongest 'canes have occurred in October though- it seems to be the new peak month for the strongest 'canes.

 

[Windspeed]

Some of the strongest 'canes have occurred in October though- it seems to be the new peak month for the strongest 'canes.

Right. But from a climatological and historical perspective, the SSTs of the northern gulf shelf by Sept-Oct have generally cooled below what is required to support a rapidly deepening Cat 5. Sure, the central, southern GOM and Bay of Campeche would continue supporting Cat 5 intensity through October, but those storms tend to weaken drastically if steered into the N. GOM. Major hurricane Opal being a prime example. October of 2018 hopefully remains anomalous in its mutliple contributing factors that lead to Michael, as generally multiple cold fronts have swept through the northern gulf by mid-to-late September and subsequent dry continental air plus radiational cooling has brought down mean heat content by 3-4°C. Again, it's one thing to consider a rare Category 5 threat in July, August, perhaps still even September, but October? Michael is hopefully the rarest of generational occurrences.

[Floydbuster]

On 4/30/2019 at 8:04 PM, Windspeed said:

Right. But from a climatological and historical perspective, the SSTs of the northern gulf shelf by Sept-Oct have generally cooled below what is required to support a rapidly deepening Cat 5. Sure, the central, southern GOM and Bay of Campeche would continue supporting Cat 5 intensity through October, but those storms tend to weaken drastically if steered into the N. GOM. Major hurricane Opal being a prime example. October of 2018 hopefully remains anomalous in its mutliple contributing factors that lead to Michael, as generally multiple cold fronts have swept through the northern gulf by mid-to-late September and subsequent dry continental air plus radiational cooling has brought down mean heat content by 3-4°C. Again, it's one thing to consider a rare Category 5 threat in July, August, perhaps still even September, but October? Michael is hopefully the rarest of generational occurrences.

 

I have to agree. The lack of cold fronts and troughs also contributed to Hurricane Florence's unlikely westward progression from Africa northwest into the middle of the Atlantic Ocean, to an eventual landfall in North Carolina. 

[LibertyBell]

On 4/30/2019 at 8:04 PM, Windspeed said:

On 4/30/2019 at 6:56 PM, LibertyBell said:

Some of the strongest 'canes have occurred in October though- it seems to be the new peak month for the strongest 'canes.

Right. But from a climatological and historical perspective, the SSTs of the northern gulf shelf by Sept-Oct have generally cooled below what is required to support a rapidly deepening Cat 5. Sure, the central, southern GOM and Bay of Campeche would continue supporting Cat 5 intensity through October, but those storms tend to weaken drastically if steered into the N. GOM. Major hurricane Opal being a prime example. October of 2018 hopefully remains anomalous in its mutliple contributing factors that lead to Michael, as generally multiple cold fronts have swept through the northern gulf by mid-to-late September and subsequent dry continental air plus radiational cooling has brought down mean heat content by 3-4°C. Again, it's one thing to consider a rare Category 5 threat in July, August, perhaps still even September, but October? Michael is hopefully the rarest of generational occurrences.

Yes, we dont need to have another one of these supercanes.  Going by purely statistical records, we seem to get a Cat 5 landfalling cane in the US about every 30 years or so and this is the first one that's happened in October.  August into early September is when the others have occurred.

The question I have besides this is a general one about the Atlantic basin- has there been some change in the general circulation pattern to increase the number of high intensity hurricanes in October across the totality of the Atlantic basin?  I know we have a secondary peak in average activity in October, but it seems like over the past number of years we've seen more major hurricanes in October.

 

[ncforecaster89]

On 5/2/2019 at 6:39 PM, LibertyBell said:

Yes, we dont need to have another one of these supercanes.  Going by purely statistical records, we seem to get a Cat 5 landfalling cane in the US about every 30 years or so and this is the first one that's happened in October.  August into early September is when the others have occurred.

The question I have besides this is a general one about the Atlantic basin- has there been some change in the general circulation pattern to increase the number of high intensity hurricanes in October across the totality of the Atlantic basin?  I know we have a secondary peak in average activity in October, but it seems like over the past number of years we've seen more major hurricanes in October.

 

Hi Liberty!  I’ve done a lot of statistical research into NATL basin activity via HURDAT2 and other historical sources.  These records seem to indicate that the recent apparent increase of major hurricanes (MH) during the month of October isn’t that unusual or even anomalous.  

Here’s an overview of the known October MH activity in the NATL basin since 1851.  It’s important to note that it’s highly likely...more like a certainty...that many other MHs are unaccounted for in the historical record prior to the satellite era, beginning in 1966. Moreover, it’s also most probable that a large number of the known hurricanes and major hurricanes likely had a higher peak intensity than presently listed in HURDAT2; especially the further it goes back in time.  With that in mind, I’m also listing all the conservatively estimated 90 kt hurricanes from 1851-1910 and the 95 kt hurricanes from 1911-2000.  The years highlighted in bold correspond to the seasons in which the strongest hurricane of that year occurred in either October or November (48 out of the 168 seasons since 1851). 

1852 = 90 kt; 1853 = 90 kt; 1858 = 90 kt; 1859 = 110 kt; 1860 = 90 kt, 90 kt 1865 = 90 kt; 1866 = 120 kt; 1867 = 110 kt; 1868 = 90 kt, 90 kt; 1869 = 90 kt; 1870 = 100 kt, 90 kt, 90 kt; 1873 = 100 kt; 1874 = 90 kt (NOV); 1875 = 90 kt; 1876 = 90 kt, 100 kt; 1877 = 100 kt; 1878 = 120 kt, 100 kt, 90 kt; 1879 = 90 kt (NOV); 1880 = 120 kt; 1882 = 120 kt; 1884 = 90 kt; 1886 = 105 kt; 1887 = 90 kt; 1888 = 95 kt; 1893 = 105 kt, 115 kt; 1894 = 105 kt, 115 kt, 95 kt; 1895 = 90 kt; 1898 = 115 kt; 1899 = 95 kt; 1902 = 90 kt; 1905 = 105 kt; 1906 = 105 kt; 1908 = 95 kt, 90 kt; 1909 = 105 kt, 90 kt (NOV); 1910 = 130 kt;  1912 = 100 kt (NOV); 1916 = 105 kt, 95 kt; 

1921 = 120 kt; 1922 = 95 kt; 1924 = 145 kt; 1926 = 130 kt; 1932 = 150 kt; 1933 = 110 kt; 1934 = 100 kt (NOV); 1939 = 120 kt;  1941 = 105 kt; 1942 = 95 kt (NOV); 1943 = 95 kt; 1944 = 125 kt; 1947 = 105 kt;  1948 = 110 kt; 1949 = 95 kt; 1950 = 95 kt, 100 kt, 115 kt; 1952 = 125 kt; 1954 = 115 kt; 1955 = 95 kt; 1959 = 105 kt; 1961 = 110 kt, 140 kt; 1962 = 95 kt, 100 kt; 1963 = 125, 95 kt;  1964 = 130 kt, 110 kt; 1966 = 130 kt; 1975 = 120 kt; 1985 = 105 kt (NOV); 1988 = 125 kt; 

1994 = 95 kt (NOV); 1995 = 130 kt, 110 kt; 1996 = 100 kt; 1998 = 155 kt (NOV); 1999 = 95 kt, 135 kt (NOV);  2000 = 120 kt; 2001 = 125 kt, 120 kt (NOV); 2002 = 125 kt; 2003 = 110 kt; 2005 = 160 kt, 100 kt; 2008 = 115 kt, 125 kt (NOV); 2011 = 120 kt, 100 kt; 2012 = 100 kt; 2014 = 125 kt; 2015 = 135 kt; 2016 = 145 kt, 120 kt, 100 kt; 2017 = 100 kt; 2018 = 140 kt.

As can be ascertained from these data, the seemingly increases in late-season/October MH frequency is more the result of much improved detection and verification of such storms, as well as a recency bias.  The biggest takeaway for me is the realization that a very significant number of NATL basin major hurricanes occur after 9/30.