Atlantic Tropical Action 2012 - Part II

[wxmx]

I'd love to hear this explanation

My guess is he was thinking atmospheric cooling temps in Fall, but that's not true for tropopause temps in the tropics, they are roughly the same...once in the subtropics and farther north, temps are much cooler at that level.

[Superstorm93]

ECM now develops something in the LR

[HurricaneJosh]

[Superstorm93]

18z GFS develops the ECM low into a decent system.

All fantasy LR...

[HurricaneJosh]

18z GFS develops the ECM low into a decent system.

All fantasy LR...

The Euro shows something in the 8-10-day range, and a little birdie tells me it might be strong and might move WNW, which would be beyond hawt.

[somethingfunny]

I'm having a tough time buying anything very organized below 25°N this season.

[Ed Lizard]

6 Z GFS still onboard, and after a pretty 'meh' year, even a non-major into Florida would be an improvement.

Yes, its fantasy range, but this season owes me.

[CoastalWx]

Would be nice to end the season with somewhat of a bang. At least some of the indices seem to support the potential.

[phil882]

As the MJO RMM phase rotates around to a favorable phase, there is some potential for a gyre like disturbance to evolve in the Caribbean or Central America in the long range (beyond day 5). The differences between the GFS and the ECMWF at this time are mainly based on where this disturbance will form, with the GFS further west in the East Pacific, with the ECMWF east in the Caribbean.

http://www.atmos.albany.edu/student/macritch/rmm.php

[Ground Scouring]

The Euro shows something in the 8-10-day range, and a little birdie tells me it might be strong and might move WNW, which would be beyond hawt.

Josh,

A couple of notes:

1. I have looked at the atmospheric wavelengths since August, and given the strong and persistent East-Coast trough (plus recent indicators that, as recent cooling has begun to be reversed, El Niño may be finally emerging in the Pacific), I think a prolonged WNW movement is unlikely--if the system does actually emerge. Also, years in which most Cape-Verde / MDR systems recurved east of 60°W, as in 2012, tended to display a strong meridional, S-N or SW-NE component in the tracks of late-season Caribbean developments. This fact makes a Central American or Mexican impact less likely in this case, despite recent history.
   
2. The time frame in which this system may develop--on or after October 21--does not favor a Floridian hurricane impact. Since 1851, only six hurricanes have hit South FL on or after October 20, in 1865, 1870, 1876, 1924, 1935 (the Yankee hurricane on November 4), and 2005 (Wilma). Wilma was obviously the second latest impact, on October 24. Of course, only one other major, the 1921 Tampa Bay hurricane on October 25, struck the United States later than Wilma did. All these systems, except the 1935 hurricane, developed before October 21. And after the Yankee hurricane, only Kate 1985 made a later hurricane impact in the U.S.--the latest on record.
   
3. Most of the impacts described, except perhaps the ones in 1876 and 1935, did not occur in developing Niño situations.
   

So unless Cuba becomes democratic overnight, unless Haiti becomes modernized, and unless Jamaica tests your fancy for a chase, I would not be too optimistic at this point--though I would love to be.

By the way, the 00Z GFS has shifted in line with the 00Z ECMWF and takes the system over E Cuba and the Bahamas in the long range (around November 1).

[wxmx]

Josh,

A couple of notes:

1. I have looked at the atmospheric wavelengths since August, and given the strong and persistent East-Coast trough (plus recent indicators that, as recent cooling has begun to be reversed, El Niño may be finally emerging in the Pacific), I think a prolonged WNW movement is unlikely--if the system does actually emerge. Also, years in which most Cape-Verde / MDR systems recurved east of 60°W, as in 2012, tended to display a strong meridional, S-N or SW-NE component in the tracks of late-season Caribbean developments. This fact makes a Central American or Mexican impact less likely in this case, despite recent history.
   
2. The time frame in which this system may develop--on or after October 21--does not favor a Floridian hurricane impact. Since 1851, only six hurricanes have hit South FL on or after October 20, in 1865, 1870, 1876, 1924, 1935 (the Yankee hurricane on November 4), and 2005 (Wilma). Wilma was obviously the second latest impact, on October 24. Of course, only one other major, the 1921 Tampa Bay hurricane on October 25, struck the United States later than Wilma did. All these systems, except the 1935 hurricane, developed before October 21. And after the Yankee hurricane, only Kate 1985 made a later hurricane impact in the U.S.--the latest on record.
   
3. Most of the impacts described, except perhaps the ones in 1876 and 1935, did not occur in developing Niño situations.
   

So unless Cuba becomes democratic overnight, unless Haiti becomes modernized, and unless Jamaica tests your fancy for a chase, I would not be too optimistic at this point--though I would love to be.

By the way, the 00Z GFS has shifted in line with the 00Z ECMWF and takes the system over E Cuba and the Bahamas in the long range (around November 1).

Climo wise, you're completely right, it's a lot more feasible a trajectory from 0-90 than from 270-320 for a TC in the W Carib. Synoptically, the period from days 8-12 most prominent hemispheric feature is the W AK /Alelutian high, shown in most GFS ensembles, as well as in the op Euro (and probably in it's ensembles as well). This will probably promote a W Coast trough, and above normal ridging east of the Rockies as far as the East coast. For this time of the year, above normal ridging for such an ample area doesn't equate to a 270-320 direction automatically underneath it...there might be anticyclonical steering currents, but they will probably be weak. Also, the weakest s/w can easily erode this kind of ridging and they are becoming more common and dig deeper. It's still way out there, but there's an enhanced chance, IMO, for anything developing in the W Caribbean in the mid range to mostly drift aimlessly or even W to NW...I don't expect this regime to last long, so after a few days it will eventually head towards 0-50...unless it crawls underneath a MX ridge.

[Ed Lizard]

Any potential tropical system can start turning Eastward once West of 85ºW and North of 25ºN and you won't hear me complain about it

[Ground Scouring]

Yes, indeed...and I suspect that the warming of the mid-troposphere during 2006-2012 may have played a significant role. For some reason, the Atlantic, in my experience, seems to be more sensitive to planetary factors than does either the East or West Pacific basins...perhaps, in the case of the Caribbean, because of the topographical influence of South America and its effect on the Walker circulation. (Note that the Atlantic is enclosed by large land masses and is therefore more readily influenced by synoptic and land-sea thermal differences/air masses than is the North Pacific, which is a much larger basin that is not so readily influenced by large land masses except north of 30-35°N or so.) Note also that the Caribbean has generally become more hostile for development in 2006-2012 as the South American heat low has become more dominant.

Another interesting detail is that, relative to historical patterns, including inactive cycles, while the average number of landfalling U.S. majors does not seem to have changed significantly, the intensity of U.S. major hurricanes, as well as the frequency of Category-4/5 hits, appears to have declined during 1995-2012. While data on active and inactive Atlantic cycles is somewhat unreliable before 1926--and while more reliable intensity data on storms begins from 1900 onward--the numbers from 1851-1900 are still reasonably consistent with data from similar periods after 1900. Of course, some storms may have also been underestimated in intensity as most coastal areas were sparsely populated before 1900. Obviously, most major strikes, and most Category-4/5 hits, tended to come in concentrated spurts or clusters, so I included the median clusters or intervals in which the Cat.-4/5 hits tended to arrive.

1851-1900: 26 major strikes,* avg. intensity 108 kt, Cat. 4/5 once every 9.8 yrs. (median cluster w/in 5 yrs.)

1901-1950: 31 major strikes (19 during active cycle 1926-1950),* avg. intensity 111 kt (avg. intensity 113 kt during active cycle 1926-1950), Cat. 4/5 once every 4.4 yrs. (median cluster w/in 3 yrs.)

1951-1994: 24 major strikes (11 during inactive cycle 1969-1994),* avg. intensity 112 kt (avg. intensity 115 kt during inactive cycle 1969-1994), Cat. 4/5 once every 5.1 yrs. (median cluster w/in 3 yrs.)

1995-2012: 10 major strikes,* avg. intensity 106 kt, Cat. 4/5 once every 9 yrs. (median cluster w/in >9 yrs.)

*Includes major hurricanes that did not make landfall in the United States but produced major-hurricane conditions on a section of the U.S. coastline.

Note: After 1935--the latest year reanalyzed by the Best Track Committee--I usually used the official U.S. hurricane designations and took the lowest possible major (>100 kt) wind speed supportable if HURDAT listed a lower value than 100 kt. If a reanalyzed value was available--i.e., the 105 kt (Strahan et al., 2010) for the 1938 Long Island Express / Great New England hurricane--I used that value instead. After 1943, I utilized the intensities from the 1944-1953 reanalysis of Hagen et al. (2012). Obviously, such values are preliminary and my list will not be exact, but it should give a rough idea as to long-term trends.

Some noted highlights from the findings I made:

• The intensity of major hurricanes and the frequency Cat.-4/5 strikes were actually about the same as in previous periods during the last reliably documented inactive cycle (1969-1994), but the active cycle since 1995 has featured a decline in both the intensity of majors and the frequency of Cat.-4/5 hits relative to those which occurred in previously documented active cycles/periods (1926-1950, 1950-1968).
  
• Gulf Coast Cat.-4/5 hits were much more frequent historically: 5 in 1851-1900, 4 in 1901-1950 (at least 1 in 1926-1950), and at least 3 (perhaps higher if Celia 1970 and Frederic 1979 are reanalyzed as Cat. 4) in 1951-1994 (all in 1951-1969; this may be higher or stay the same if Betsy 1965 is reanalyzed as Cat. 4 in LA). None has occurred in 1995-2012, even though the average return rate in previous active cycles was once per 8.4 yrs. (with a median cluster w/in 6 yrs.).
  

As the potential upcoming system is highly unlikely to impact the U.S. (as per Jorge and the latest 12Z GFS, which concurs with the 00Z GFS and the 00Z ECMWF), does anyone care to comment re: this assessment? The no-major streak seems destined to continue this year and the long-range planetary trends seem to favor another W-Coast ridge / E-Coast trough scenario next season, meaning more recurvatures and a suppressed risk of major landfalls in the U.S. Also, I have hinted that we may be entering a cycle in which Atlantic landfalls will be less intense intense and less frequent in the U.S., while the larger Pacific basin may not be substantially affected due to its size.

[HurricaneJosh]

Josh,

A couple of notes:

1. I have looked at the atmospheric wavelengths since August, and given the strong and persistent East-Coast trough (plus recent indicators that, as recent cooling has begun to be reversed, El Niño may be finally emerging in the Pacific), I think a prolonged WNW movement is unlikely--if the system does actually emerge. Also, years in which most Cape-Verde / MDR systems recurved east of 60°W, as in 2012, tended to display a strong meridional, S-N or SW-NE component in the tracks of late-season Caribbean developments. This fact makes a Central American or Mexican impact less likely in this case, despite recent history.
   
2. The time frame in which this system may develop--on or after October 21--does not favor a Floridian hurricane impact. Since 1851, only six hurricanes have hit South FL on or after October 20, in 1865, 1870, 1876, 1924, 1935 (the Yankee hurricane on November 4), and 2005 (Wilma). Wilma was obviously the second latest impact, on October 24. Of course, only one other major, the 1921 Tampa Bay hurricane on October 25, struck the United States later than Wilma did. All these systems, except the 1935 hurricane, developed before October 21. And after the Yankee hurricane, only Kate 1985 made a later hurricane impact in the U.S.--the latest on record.
   
3. Most of the impacts described, except perhaps the ones in 1876 and 1935, did not occur in developing Niño situations.
   

So unless Cuba becomes democratic overnight, unless Haiti becomes modernized, and unless Jamaica tests your fancy for a chase, I would not be too optimistic at this point--though I would love to be.

By the way, the 00Z GFS has shifted in line with the 00Z ECMWF and takes the system over E Cuba and the Bahamas in the long range (around November 1).

My hope is actually for late-October action in Mexico or Belize. I have no further interest in the USA this year-- nothing decent can get up there.

[wxmx]

A US hit is very low, but the highest probabilities are for SW FL.

Being said that, the Carib development is severely hindered by outflow induced shear from a developing cyclone near Central Am in the EPac side in the GFS. Euro has been a lot weaker with the EPac disturbance, with the NW Carib becoming the dominant one.

[Ground Scouring]

My hope is actually for late-October action in Mexico or Belize. I have no further interest in the USA this year-- nothing decent can get up there.

Yes...climatology is different for MX and Belize. Since 1851, there have been at least three Category-2+ strikes after October 20 in those areas: a 1942 hurricane (09 November), Hattie 1961 (31 October), and Wilma 2005 (22 October). There may have been more, but I could not locate any. (The reanalysis will offer a final count in the end.) In any event, your chances decrease after Halloween.

[HurricaneJosh]

Yes...climatology is different for MX and Belize. Since 1851, there have been at least three Category-2+ strikes after October 20 in those areas: a 1942 hurricane (09 November), Hattie 1961 (31 October), and Wilma 2005 (22 October). (There may have been more, but I could not locate any. (The reanalysis will offer a final count in the end.) In any event, your chances decrease after Halloween.

Off the top of my head, there's also Richard 2010.

As far as I'm concerned, the chase season ends with Halloween. There's a huge Halloween festival in my city, and I consider it sort of the End of Chase Season party. I don't even really follow the tropics in November.

[Superstorm93]

I agree that anything that does develop in the Caribbean will most likely visit the Cuba/Haiti area as opposed to the GOM.

Always nice to see the ensembles picking up on this.

[CoastalWx]

I like the dual cyclone action on the 06z GFS.

[icebreaker5221]

Looks like there will be a relatively favorable region for genesis in the W Caribbean next week. That we can all agree on.

The genesis event itself, however, is still somewhat uncertain. There is a pre-existing broad cyclonic circulation extending from Nicaragua to Colombia. Various definitions of monsoon troughs / gyres exist. I personally wouldn't call this one due to the fact that it's still a bit on the small side and winds at high radii are quite weak. (Many W. Pac monsoon troughs have 30+ kt winds at 850 mb extending out ~1000 km.) Most of the models agree that persistent convection will develop, associated with significant LL convergence, and LL vorticity within the broad low pressure will consolidate.

There is also a very weak tropical wave currently located over the Lesser Antilles that is expected to slowly push westward and interact / contribute to W Caribbean genesis. Lastly, the ITCZ is convectively active in the E Pac at this time in a region generally characterized by weak westerlies at the moment. It is likely that some vorticity will cross basins and be ingested by the broad W Caribbean low.

So we have 3 weak genesis mechanisms - broad W Caribbean low, tropical wave near Lesser Antilles, and ITCZ breakoff - all trying to work together next week to give us a genesis event. The extent to which each mechanism is dominant really depends on which run of whatever model you're looking at.

[Srain]

Monsoonal trough ftl... Probably a rainer for Florida and the Bahamas before becoming frontal and swept out to the NE with the next trough.

[am19psu]

Monsoonal trough ftl... Probably a rainer for Florida and the Bahamas before becoming frontal and swept out to the NE with the next trough.

Yup. And Cuba and Jamaica.

[phil882]

Yup. And Cuba and Jamaica.

The ECMWF wants to spin the monsoon gyre/trough into a very large TC. Could be a very interesting gyre case. From wind impact perspective though, this system is unlikely to become anything of substancial consequence From a flooding perspective, there is a larger than normal threat for flooding rainfall across a large chunk of the caribbean and eastern seaboard were this to interact with the mid-latitudes beyond 240 hours as the ECMWF alludes to.

[am19psu]

Yep, agree with that idea, Phil

[Ed Lizard]

Be nice if the 12Z Euro verified.

[icebreaker5221]

Be nice if the 12Z Euro verified.

What an absolute mess. Probably the ugliest genesis scenario I've ever seen.

Sadly, I'd still take it...

[icebreaker5221]

Just as things are about to get cranking, this happens:

[somethingfunny]

The model depiction kinda reminds me of Nicole from 2010:

[wxmx]

Just as things are about to get cranking, this happens:

Hey, Tony, Valerie, William and Alpha could get out of it (Sandy taken by yet another mid latitude TC a few days before)

[wxmx]

W AK super ridge -> NW coast low on 'roids -> Ridging in the mid section to east coast...plus a strong -NAO...that's a map of extremes. The weak link is the trough offshore of the E coast and how much it can erode the eastern end of the 2/3s CONUS ridge before it gets reinforced.