Tropical Atlantic 2015 speculation/action

[GaWx]

ENSO is typically a very important factor as regards the Atlantic tropical season. It looks like 2015 will be a 2nd year El Niño. These are the years that I have in the 2nd year El Niño category: 1987, 1977 (quiet overall but had Anita), 1969 (this one very active in addition to Camille ), 1958, 1953, 1940, 1919 (cat 3 S TX hit), 1914, 1905, 1900 (big Galveston hit), 1896 (big FL Big Bend hit), and 1885. One could make a case to also count 1877 and 1930. Note that the five 2nd year Niño's with the noted big GOM hits were all weak El Nino's except for 1896. The strongest El Nino's of the 2nd year bunch were 1987, 1930, 1905, 1896, and 1877. The most recent model trends as well as warming/very warm subsurface suggest we may very well be headed for an El Niño on the stronger side, but that remains to be seen. If so, then I'd think that 1987, 1930, 1905, 1896, and 1877 would be the closest ENSO analogs to use from this 2nd year bunch.

Anyone else have any feel for the 2015 season? What are the most important factors to consider?

**Edited

[Srain]

For those interested, myself, Josh and wxman57 will be attending the National Tropical Weather Conference on South Padre Island tomorrow thru Sunday. Dr. Philip Klotzbach will have a press conference beginning at 9:00 AM CDT Thursday (April 9th) and it will be carried 'live' via twitter Periscope Broadcast as well as several other presentations @HurricaneCon. Some early indications suggest the Gulf may be closer to normal regarding tropical development this season while the MDR will be hostile. If the Gulf of Mexico is a bit active, that could suggest Mexico, across the Gulf Coast including Florida into the Bahamas may be the areas to monitor this season.

 

[Ginx snewx]

Josh is on the speakers list I see, have fun 

[icebreaker5221]

The eastern MDR, which correlates quite well with overall activity, is quite cooler than average.  This fact, coupled with a likely moderate-end ENSO leads me to believe the numbers will be below average again this year. 

 

However, the Gulf and Western Caribbean are both quite warm.  It remains to be seen whether or not this will carry into hurricane season, but as GaWx and Srain have mentioned you can still get decent homebrew action in a 2nd year Nino with a warm Gulf. 

[DopplerWx]

Been waiting for the first tropical thread of the year.  Looks like all signs point to another dud but lets hope we have at least something to watch.  

[wxmx]

The EPac looks fertile for an above average season. Most probably the mean anticyclone will favor the easternmost EPac vs the GoM and W Carib, with higher shear profiles on the latter two sub-basins.

 

I also envision strong MJO waves during phases 7 & 8, dampening during phases 1 & 2. If we can get strongish phases 1 & 2, maybe aided by atmospheric KWs as well, then that's when I would favor cyclogenesis around the W Atl, W Caribbean and GoM. Overall, I think, the windows for such potential will be rather narrow, but that's how I imagine a strong hurricane that threaten land could form.

[GaWx]

The ECMWF and CFS are both going for the 5th consecutive Atlantic hurricane season

where the strongest activity is focused north of 20N.

 

 

Bluewave,

 Thanks. By the way I have noticed that in addition to the correlation of El Nino and increased MDR shear, there seems to be a correlation between El Nino and MDR dryness/SAL. So, imo it very likely isn't just about the often mentioned shear as regards El Nino's slowing down the MDR activity. Do you agree/have an opinion about the correlation to MDR dryness?

[Ground Scouring]

Bluewave,

 Thanks. By the way I have noticed that in addition to the correlation of El Nino and increased MDR shear, there seems to be a correlation between El Nino and MDR dryness/SAL. So, imo it very likely isn't just about the often mentioned shear as regards El Nino's slowing down the MDR activity. Do you agree/have an opinion about the correlation to MDR dryness?

Since 2010, we have only seen one official Niño, that of this year (2014-5), and yet we have seen the same pattern--lower-than-normal (for an +AMO cycle) instability basin-wide, higher-than-average vertical shear in the Central Atlantic, W Caribbean, and Gulf--in practically every season, with the possible exception of 2011, which still featured less favorable values than in other years prior. In fact, most or all of the usual indicators favored an active season (with a strong, west-based Bermuda high in at least a few of the peak periods) in several of these seasons (2012 and 2013), yet expectations simply did not pan out. No one has really come up with a convincing explanation as to why. Drs. Gray and Klotzbach, despite their (deserved) reputations in some areas of seasonal forecasting, did not offer a tested hypothesis to account for the reduced activity; their NAO/AO explanation (that the NAO/AO somehow contributed to reduced instability) is, to me, insufficient without taking into account other factors. Otherwise, it is simply not supported by history or their past studies' criteria. In my opinion, instability and shear are both equally important, but may affect different aspects and areas depending on their location. Experience, to me, has shown that these factors can easily nullify higher-than-normal heat content. Unfavorable conditions in the Central Atlantic shut down the MDR; similar conditions in the W Caribbean/Gulf shut down homegrown threats. Result: higher-latitude fish activity. Having looked at available evidence, I think we may well see record-low activity this season with only a tenuous land threat to Bermuda and E Canada (another Fay or Gonzalo, perhaps).

[AvantHiatus]

Would be nice to have last year's forecast posted as a comparison. It looks more tame over the MDR (wetter) this go around. Small region of normal precip along the ITCZ on the Atlantic side, that's new.

[icebreaker5221]

Since 2010, we have only seen one official Niño, that of this year (2014-5), and yet we have seen the same pattern--lower-than-normal (for an +AMO cycle) instability basin-wide, higher-than-average vertical shear in the Central Atlantic, W Caribbean, and Gulf--in practically every season, with the possible exception of 2011, which still featured less favorable values than in other years prior. In fact, most or all of the usual indicators favored an active season (with a strong, west-based Bermuda high in at least a few of the peak periods) in several of these seasons (2012 and 2013), yet expectations simply did not pan out. No one has really come up with a convincing explanation as to why. Drs. Gray and Klotzbach, despite their (deserved) reputations in some areas of seasonal forecasting, did not offer a tested hypothesis to account for the reduced activity; their NAO/AO explanation (that the NAO/AO somehow contributed to reduced instability) is, to me, insufficient without taking into account other factors. Otherwise, it is simply not supported by history or their past studies' criteria. In my opinion, instability and shear are both equally important, but may affect different aspects and areas depending on their location. Experience, to me, has shown that these factors can easily nullify higher-than-normal heat content. Unfavorable conditions in the Central Atlantic shut down the MDR; similar conditions in the W Caribbean/Gulf shut down homegrown threats. Result: higher-latitude fish activity. Having looked at available evidence, I think we may well see record-low activity this season with only a tenuous land threat to Bermuda and E Canada (another Fay or Gonzalo, perhaps).

 

They also put significant blame on the quiet 2013 season on the big drop in their thermohaline circulation index (THC) index (somewhat analogous to their AMO index but includes a combination of SSTs, MSLP and V) during May that year:

http://hurricane.atmos.colostate.edu/forecasts/2013/nov2013/nov2013.pdf

begins on pg 54.

 

Not sure if you saw Klotzbach's tweet about March AMO but we're currently running near record-low values tied with 1990:

https://twitter.com/philklotzbach/status/583846874483924994

Also note that the index was below normal last year but not quite as low.  Their AMO index was actually above average for Mar 2013 but then fell rapidly during April and May. 

[The_Global_Warmer]

Looks like a lot of heat the SW N ATL and GOM.

[Srain]

I was on the same flight with Phil Klotzbach, Rick Knabb, and Jason Samenow yesterday afternoon from Houston to Harlingen and we had an interesting discussion concerning this season. While it is true the MDR appears very hostile this year, there were concerns expressed for a potentially near average development particularly across the far Western Basin as well as the EPAC where once again above normal tropical activity could present problems. Phil will offer his first seasonal outlook this morning at National Tropical Weather Conference around 9:00AM via the live periscope Twitter feed provided above.

[Juliancolton]

Klotzbach going 7/3/1 per twitter.

[calm_days]

 

Here is a simple graphic showing the cyclone tracks from 2008-2014. 

I am very amateur level when it comes to tropical cyclones and cyclogenesis so sharing this image will be my contribution to help augment others' insights!

2014 was very intriguing and it would be helpful if it did actually represent a threshhold passed in terms of Atlantic cyclone paths becoming less complex.

 

[PSUBlizzicane2007]

I don't see why people are thinking development in the GOM should likely be more than the tropical Atlantic. Sure the SST anomalies are going to be much better, but that's going to mean crap if we have a strong El Nino by August which is what most ECMWF members are predicting. Shear over the Gulf will be howling.

[Amped]

I don't see why people are thinking development in the GOM should likely be more than the tropical Atlantic. Sure the SST anomalies are going to be much better, but that's going to mean crap if we have a strong El Nino by August which is what most ECMWF members are predicting. Shear over the Gulf will be howling.

Gom and Carribien was crap last year with similar SST anomolies.

[GaWx]

 Regarding H hits on the US gulf coast, there clearly has been a quieting effect from El Nino. Since 1950, there have been only 14 US gulf H hits out of 22 seasons with El Nino (and that's counting Bonnie of June of 1986, which technically hit before El Nino had actually started that season). So, that gives us 0.64/season. OTOH, for the other 43 seasons, there were 41 gulf hits or 0.95/season.

El Nino US Gulf H hits since 1950

1953 Florence
1957 Audrey
1963 Cindy
1965 Betsy
1968 Gladys
1969 Camille
1972 Agnes
1977 Babe
1986 Bonnie
1987 Floyd
1997 Danny

2002 Lili
2004 Charley
2004 Ivan

Sources:

ENSO (ONI):

http://www.cpc.ncep.noaa.gov/products/a ... ears.shtml


Hurricane tracks:

http://weather.unisys.com/hurricane/atlantic/

 

*Edited for two corrections: 1) I inadvertently had counted Lili of 2002 as non-Nino. It clearly is Nino.  2) 41 hits rather than 43 hits for non-Nino

[GaWx]

1) The quieting effect of El Nino vs. non-Nino is more evident when one just looks at either only seasons with multiple US Gulf H hits or just major US Gulf H hits:

a. Multiple US Gulf H hit seasons, alone:
- Non-Nino: 9 seasons of 43 (21%) with 2+ US Gulf H hits: 1950, 1964, 1979, 1985, 1989, 1995, 1998, 2005, and 2008; 3 seasons with 3+

- Nino: only 1 season out of 22 (5%) with 2+ US Gulf H hits: 2004; no seasons with 3+ hits


b. Major H US Gulf hits, alone:

- non-Nino: 19 hits in 43 seasons (0.44 per season)
- El Nino: 5 hits in 22 seasons (only 0.23 per season or about half the non-Nino rate)

2) When looking at the % of seasons with 1+ US GOM H hits, the difference is very small: 27 of 43 (63%) non-Nino v. 13 of 22 (59%) Nino. So, much of the difference is due to seasons with multiple hits, alone.

[Amped]

So we are all pretty much in agreement of a below average or well below average season unless something drastic changes?

[AvantHiatus]

So we are all pretty much in agreement of a below average or well below average season unless something drastic changes?

I could envision an active West Atlantic basin again, similar to last year. Homebrew systems have their own unique caveats. Not sure about Florida and GOM tho.

[Amped]

I could envision an active West Atlantic basin again, similar to last year. Homebrew systems have their own unique caveats. Not sure about Florida and GOM tho.

 

Based on the Eurosip it looks doubtful the Gulf and Caribbean or Cape Verde will produce much significant activity. If those areas can sneak in a few storms while we get a lot of home brew systems than it will be an active season. However I doubt that's a long shot and most likely the entire basin will be a dry sheared disaster.

[wxmx]

MJO waves on phases 8 and 1 could be stronger than average, that means added instability. Even the strongest Niños have their small windows of opportunity. Just look at the parade of MCVs/instability we have had in NE MX and S TX...plus the N GoM and W Atl isn't affected as much as the MDR by shear.

Not really expecting above average activity in those regions, but I could see how the pattern could be more conducive than years past.

I don't see why people are thinking development in the GOM should likely be more than the tropical Atlantic. Sure the SST anomalies are going to be much better, but that's going to mean crap if we have a strong El Nino by August which is what most ECMWF members are predicting. Shear over the Gulf will be howling.

[icebreaker5221]

I don't see why people are thinking development in the GOM should likely be more than the tropical Atlantic. Sure the SST anomalies are going to be much better, but that's going to mean crap if we have a strong El Nino by August which is what most ECMWF members are predicting. Shear over the Gulf will be howling.

 

This is the latest shear anomaly forecast from CFS v2, which has a robust El Nino with a mean ASO temp in region 3.4 of about 2C.  Note that while shear is very harsh south of 20N, it's actually quite favorable north of 20N in the Gulf and NW Caribbean especially early in the season.  Nino climo actually isn't too horrible north and west of the MDR either.  I wouldn't expect a particularly active season, but I wouldn't call it a total bust already either.

 

[jshetley]

Maybe we had better hope it busts with the models like they are now. I could see us easily missing a landfall forecast by hundreds of miles at 24-48 out.

[ineedsnow]

What? Not a chance 5 days out yes 1 to 2 no way!

Maybe we had better hope it busts with the models like they are now. I could see us easily missing a landfall forecast by hundreds of miles at 24-48 out.

[cbmclean]

 

Interesting new paper:

 

http://onlinelibrary.wiley.com/doi/10.1002/2015GL063652/full

 

 

The Frequency and Duration of US Hurricane Droughts^†

 

Abstract

As of the end of the 2014 hurricane season, the US has experienced no major hurricane landfall since Hurricane Wilma in 2005, a drought that currently stands at nine years. Here, we use a stochastic tropical-cyclone model to calculate the mean waiting time for multi-year landfall droughts. We estimate that the mean time to wait for a nine-year drought is 177 years. We also find that the average probability of ending the drought with a major landfall in the next year is 0.39, and is independent of the drought duration, as one would expect for a Bernoulli process.

 

Hello.  I am just an amateur who usually lurks quietly soaking up knowledge, but I was just reading about the current hurricane drought on another site and it got me thinking.  On these forums I have seen various discussions of reanalysis of past storms' strength.  It seems to me that the general trend is for reanalysis is to downgrade the estimated strength of the past storm.

 

Is it generally true that the strength of storms was overestimated in the past?  If so, would that not skew the above quoted analysis by making past activity seem erroneously strong? 

[Amped]

Maybe we had better hope it busts with the models like they are now. I could see us easily missing a landfall forecast by hundreds of miles at 24-48 out.

A lot of storms don't even travel hundreds of miles in 24-48hrs. Odile was a pretty big bust and that was only about 50 miles.   I don't even know what your post is in reference too, but since I think this season will involve a lot of discussions about hypothetical storms I figured I might as well start practicing.

[klw]

Almost hate to ask as it is in fantasy land, but is the storm GFS is showing east of the Bahamas on May 8 tropical?  Is this the first fantasy storm of the season?

It seems to come north of Hispanola and then comes north along the east coast.

http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=namer&pkg=mslp_pcpn_frzn&runtime=2015042306&fh=360&xpos=0&ypos=500

[Ground Scouring]

This is the latest shear anomaly forecast from CFS v2, which has a robust El Nino with a mean ASO temp in region 3.4 of about 2C.  Note that while shear is very harsh south of 20N, it's actually quite favorable north of 20N in the Gulf and NW Caribbean especially early in the season.  Nino climo actually isn't too horrible north and west of the MDR either.  I wouldn't expect a particularly active season, but I wouldn't call it a total bust already either.

 

AtludifSea.gif

I really doubt that climatology is as useful as people make it to be in the new normal as the overall global circulation has changed due to large-scale issues that aren't really being addressed. What about the shift in the South American heat low? Why has that happened? Has seasonal variability decreased in some time scales due to more persistent mid- to upper-level patterns (i.e., a wavier flow)? Why has the THC decreased? Should such an index really take into account a bunch of variables that are unrelated to each other, thereby masking some unknown influence's effect(s) on factors that directly affect each other? The only really compelling reason, in part, for the slowdown in MDR development is a long-term drought in West Africa, but even that doesn't explain everything.

[Ground Scouring]

Hello.  I am just an amateur who usually lurks quietly soaking up knowledge, but I was just reading about the current hurricane drought on another site and it got me thinking.  On these forums I have seen various discussions of reanalysis of past storms' strength.  It seems to me that the general trend is for reanalysis is to downgrade the estimated strength of the past storm.

 

Is it generally true that the strength of storms was overestimated in the past?  If so, would that not skew the above quoted analysis by making past activity seem erroneously strong? 

No, or at least not necessarily. Land and even marine data coverage after 1900 is actually pretty decent in the U.S., especially from the 1920s onward. We have pretty good evidence with which to determine the size and intensity of landfalls in the same period. For instance, we have good data to show that 1900 Galveston, 1926 Miami, 1928 Okeechobee, 1935 Labor Day, and the 1932 TX hurricanes were at least 120 kt at landfall (with the latter three 125-130 kt, if not a bit higher). Based on data from the last active cycle (1926-1969) compared to those for 1995-present, the recent cycle, even when compared to a similar 15-year period in 1926-1969, has seen a noted decrease in the frequency of upper-end majors (Cat. 4/5) making landfall. Also, there has been a significant net decrease in the frequency of major landfalls; note that practically all the major U.S. strikes since 1995 occurred in just two seasons, 2004 and 2005. While major hits have tended to frequently cluster in other cycles, the major hits in 1926-1969 were more frequent and the clusters more closely spaced. The late 19th century lacks significant data, but when this is taken into account, some evidence indicates that 1851-1894 may have featured at least as high a frequency of major landfalls as did 1926-1969. Basically, the latest active cycle has for the most part underperformed relative to the past. We haven't seen a reasonably large-sized, high-end major event (Charley was tiny, while the other Gulf majors were all Cat. 3, not Cat. 4/5). Also, SSTA data seem to indicate that the latest active cycle may already be ending prematurely, though that remains to be seen.