Atlantic Tropical Action 2012 - Part II

[Mike.Ventrice]

what dates can we expect the activity to pick up again after the lull?

I'm projecting another period of increased activity beginning around September 17 and continuing through early October. You can see my forecasts with a brief scientific explanation at my forecast page.

[Mike.Ventrice]

^^ 12Z GFS has AEW that came off Africa in the Bahamas in 8 days...

I did see that... but I think that the GFS it is one of the only model guidances that keeps it around for as long as it does.

[Ed Lizard]

I did see that... but I think that the GFS it is one of the only model guidances that keeps it around for as long as it does.

Euro fishes it.

[Eyewall2005]

12z Canadian with its recurve nature takes it straight westward to just north of puerto Rico.

[Ed Lizard]

I like the cut of the 12Z and 18Z GFS's jib. I want a Florida chase...

[Ground Scouring]

Practically all of the GFS ensembles over the past few days have continued to develop the surface trough within two days that is currently a few hundred miles south of the Cape Verde islands. Recently, the ECMWF ensemble mean has also joined the chorus, although it is slower and shows recurvature, whereas the GFS guidance has been highly insistent upon a track N of Puerto Rico and has varied little in its projected position even eight days out. Certainly, the system, although weakly reflected at 850-1000 mb, is displaced far enough to the south that it would avoid the relatively minimal Saharan inversion over the next several days. Given climatology and the consistency of the global models, I would not dismiss the prospects of development even in the suppressed MJO regimen. Based upon the MJO signal and other factors, plus recent performance, I think the GFS call for a faster movement / stronger subtropical ridging seems reasonable, and that this system may well pose at least a shot at a threat to the U.S. Southeast in about a week.

[Ground Scouring]

An interesting note is that 1972 and 2004 featured a similar ENSO evolution and configuration to those of 2012, and each year featured similar mean formative locations for the first TC of the year--i.e., off NE FL. The evolution of the tracks in the deep tropics this year has generally been oriented westward toward FL and the Southeast. If I recall correctly, another such evolution occurred in 1928; did that year feature an ENSO progression reminiscent of that of 2012? I am just asking because a common theory is that the early track trends often tend to portend a general seasonal trend due to certain atmospheric teleconnections. If the theory holds merit, the upcoming few weeks could be strongly biased toward a threat from FL to the Carolinas, particularly S FL. Thoughts?

[phil882]

Practically all of the GFS ensembles over the past few days have continued to develop the surface trough within two days that is currently a few hundred miles south of the Cape Verde islands. Recently, the ECMWF ensemble mean has also joined the chorus, although it is slower and shows recurvature, whereas the GFS guidance has been highly insistent upon a track N of Puerto Rico and has varied little in its projected position even eight days out. Certainly, the system, although weakly reflected at 850-1000 mb, is displaced far enough to the south that it would avoid the relatively minimal Saharan inversion over the next several days. Given climatology and the consistency of the global models, I would not dismiss the prospects of development even in the suppressed MJO regimen. Based upon the MJO signal and other factors, plus recent performance, I think the GFS call for a faster movement / stronger subtropical ridging seems reasonable, and that this system may well pose at least a shot at a threat to the U.S. Southeast in about a week.

I'm more in support of a southern track for this feature given the strength of the mid-level high and the past track records of both the GFS and ECMWF poorly forecasting the track of Isaac. My biggest question is if it will even develop... it seems like the models have backed away from early development like they had a few days ago. I am skeptical this even becomes a TC given the unfavorable MJO state and suppressed Kelvin wave that still take up the vast majority of the basin.

[U_Thant]

High latitude low WSW of the Azores getting a little wannabe attitude according to satellite presentation.

Wickedly sheared, but persisting, central convective mass.

[thewxmann]

I'm more in support of a southern track for this feature given the strength of the mid-level high and the past track records of both the GFS and ECMWF poorly forecasting the track of Isaac. My biggest question is if it will even develop... it seems like the models have backed away from early development like they had a few days ago. I am skeptical this even becomes a TC given the unfavorable MJO state and suppressed Kelvin wave that still take up the vast majority of the basin.

Maybe it'll be another one of those systems that traverses most of the Atlantic as a weak TS and then reaches Cat 1 status hours before landfall.

[sugaree]

Maybe it'll be another one of those systems that traverses most of the Atlantic as a weak TS and then reaches Cat 1 status hours before landfall.

it seems to be the trend for quite a while now

[Hurriplane]

Would love to see a Florida-cane one of these days...sure miss them..

[Superstorm93]

Quality tropical cyclone coming up

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[wxmx]

Quality tropical cyclone coming up

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Shear is strong, but convection pulled in the small LLC that was trying to escape

[Superstorm93]

INIT  28/2100Z 23.8N  43.9W   30 KT  35 MPH
12H  29/0600Z 24.1N  45.3W   35 KT  40 MPH
24H  29/1800Z 24.3N  47.4W   35 KT  40 MPH
36H  30/0600Z 24.6N  49.6W   35 KT  40 MPH
48H  30/1800Z 25.3N  51.7W   35 KT  40 MPH
72H  31/1800Z 27.5N  55.5W   35 KT  40 MPH
96H  01/1800Z 32.5N  55.0W   35 KT  40 MPH
120H  02/1800Z 40.0N  48.0W   35 KT  40 MPH

[Ground Scouring]

I'm more in support of a southern track for this feature given the strength of the mid-level high and the past track records of both the GFS and ECMWF poorly forecasting the track of Isaac. My biggest question is if it will even develop... it seems like the models have backed away from early development like they had a few days ago. I am skeptical this even becomes a TC given the unfavorable MJO state and suppressed Kelvin wave that still take up the vast majority of the basin.

What is intriguing is the fact that the models over the past few days have been consistently developing this system by August 30. Normally, I would also dismiss the prospects of development, but the the consistency, and the fact that the time frame has not been demurred, gives me reason to hesitate. Further, the latest (12Z) GFS and its ensembles are the most aggressive yet in terms of intensity. I, too, think the models are developing the system too rapidly, particularly given its weak signature; however, given the relatively weak shear and minimal dry air, I am inclined to believe this system will develop eventually, just as TD 11 did in spite of the unfavorable MJO regimen. Another factor favoring development is that the years that featured more than five named storms by late August have strongly tended to be quite active during the peak; currently, we are near the pace of 2005, and TD 11 will likely become a weak Kirk, so the data in my view favor a continuation of relatively active conditions.

The main question regarding the African system, in my view, is the track. The GFS has recently shifted toward the ECMWF in favoring recurvature, but given the poor synoptic performance of the models of late, and the likelihood that the system will develop more gradually, I think the ultimate track at this stage is quite uncertain. I agree with the notion of a more southerly track in the short term, but in the long run, I think that the models are currently underestimating projected heights in the Western Atlantic. Keep in mind that the GFS was originally quite adamant in taking the system to near FL in about eight days or so, only to shift very recently. I would not keep the door to a U.S. threat closed just yet.

[phil882]

What is intriguing is the fact that the models over the past few days have been consistently developing this system by August 30. Normally, I would also dismiss the prospects of development, but the the consistency, and the fact that the time frame has not been demurred, gives me reason to hesitate. Further, the latest (12Z) GFS and its ensembles are the most aggressive yet in terms of intensity. I, too, think the models are developing the system too rapidly, particularly given its weak signature; however, given the relatively weak shear and minimal dry air, I am inclined to believe this system will develop eventually, just as TD 11 did in spite of the unfavorable MJO regimen. Another factor favoring development is that the years that featured more than five named storms by late August have strongly tended to be quite active during the peak; currently, we are near the pace of 2005, and TD 11 will likely become a weak Kirk, so the data in my view favor a continuation of relatively active conditions.

The main question regarding the African system, in my view, is the track. The GFS has recently shifted toward the ECMWF in favoring recurvature, but given the poor synoptic performance of the models of late, and the likelihood that the system will develop more gradually, I think the ultimate track at this stage is quite uncertain. I agree with the notion of a more southerly track in the short term, but in the long run, I think that the models are currently underestimating projected heights in the Western Atlantic. Keep in mind that the GFS was originally quite adamant in taking the system to near FL in about eight days or so, only to shift very recently. I would not keep the door to a U.S. threat closed just yet.

Of course the caveat to that is if TD #11 remains a significant system, it will help to create a weakness in the mid-level ridge. The GFS takes Invest 98L through this weakness.

TD#11 is actually looking pretty good tonight. The shear over it is not inhibiting development, and the system seems to have escaped the SAL environment it was embedded in. The GFS is predicting the upper level trough currently situated to its east will split, with a TUTT feature ducking southwestward out of TD#11's way. I'm thinking a weak to moderate tropical storm, with an outside shot at hurricane intensity if it survives beyond 48 hours.

[thewxmann]

Of course the caveat to that is if TD #11 remains a significant system, it will help to create a weakness in the mid-level ridge. The GFS takes Invest 98L through this weakness.

The 0Z and 12Z GFS's were pretty much out-of-phase with regards to trough/ridge positioning in the ATL at hr 120. The models seem to have a poor handle on the synoptic situation.

[Superstorm93]

No love for 98L?

SHOWER AND THUNDERSTORM ACTIVITY CONTINUES IN ASSOCIATION WITH A

BROAD AREA OF LOW PRESSURE ALONG A TROPICAL WAVE LOCATED ABOUT 900

MILES WEST OF THE CAPE VERDE ISLANDS. WHILE DEVELOPMENT IS NOT

IMMINENT...ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR A TROPICAL

DEPRESSION TO FORM IN THE NEXT DAY OR TWO. THIS SYSTEM HAS A HIGH

CHANCE...60 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE

NEXT 48 HOURS AS IT MOVES WESTWARD TO WEST-NORTHWESTWARD AT 15 TO

20 MPH.

[MJO812]

The models show Kirk and 98L not impacting the United States. 98L is way out there so the models should get a better handle of the wave once Isaac moves on.

[tmagan]

If we can go to the middle of September without a major hurricane, it will mark something only done once in the last decade.

[phil882]

If we can go to the middle of September without a major hurricane, it will mark something only done once in the last decade.

The GFS suggests that 98L will be the one to break that mark for this year... However, I would be cautious taking the GFS verbatim. In fact, the ECWMF has difficulty developing the system as the low-level vorticity has a difficult time congealing with multiple low level circulation centers. You can see that to some degree using a visible animation.

[Ed Lizard]

Posted this on Steve's KHOU-TV 11 forum.

Some will bring up a bad call I made in August 2008. This is different. More 'probabalistic'. The glass, normally half full, is 3/32nds optimistic

Speaking of optimism, maybe at full daytime heating, some loosely associated bands indirectly associated with Isaac will rotate through. 6Z GFS and 12Z NAM seem to suggest winds around 30 knots will be around 900 mb, not too far overhead (GFS even stronger, closer to 40 knots) and a nice semi-tropical shower might mix down TS or near TS force winds.

But we *probably* have survived another season w/o a hurricane w/ Isaac missing us. Kirk is a fish, Leslie *probably" will be a fish, (Ed- assuming 98L does develop) and then degreed mets on another forum, some from SUNY at Albany, suggesting pattern of favorable conditions for the Atlantic shut down for a while. Probably to about mid-September. I would have expected developing warm ENSO to kill second half of season, but after looking like SOI was finally going full bore Nino, it has backed off.

The Equinox is the unofficial end of the season locally. With exceptions, besides barely Cat 1 Jerry in 1979, a major hurricane hit near Freeport first week in October. October hits very rare, but not impossible.

Best shot for local TC activity, although not super likely, either an unforeseen festering polar system, like an ULL or decaying frontal trough, or a weak wave that makes it to the Caribbean before developing, right as the pattern shifts to being favorable again.

Not season cancel, but end of season probably approaching. If we do get 40 knot gusts and a solid rain shower this afternoon courtesy Isaac, I will count 2012 as a success

Now, IIRC, 1938 was on the Equinox, Opal and Wilma shows the action doesn't stop in Florida just because its October, and, for that matter, Kate shows Florida can still get almost a major the week before Thanksgiving. Not trying to predict the state of the NAO or anything, forecast what the 500 mb pattern will be in mid September when the tropics may get active again. Been a few days since anyone posted their teleconnection forecasts (I'm not good at that) for mid to lateSeptember, I'd be interested to see where the mean ridges and troughs are likely to be

[Srain]

Posted this on Steve's KHOU-TV 11 forum.

Ed, Jerry was in 1989...

[Ed Lizard]

Ed, Jerry was in 1989...

Yes, that was the weekend when Peter Gardere beat Oklahoma as a freshman. I was in the very last row in the Cotton Bowl.

The years run together.

Noticed I didn't conclusively say "season over". No tempting Hunraken, the Carib god of storms, such that I spend no Summer weekends on the beach in 2013. Although I am *not* superstitious.

[Macintosh]

The GFS suggests that 98L will be the one to break that mark for this year... However, I would be cautious taking the GFS verbatim. In fact, the ECWMF has difficulty developing the system as the low-level vorticity has a difficult time congealing with multiple low level circulation centers. You can see that to some degree using a visible animation.

Don't. Even. Start. I have had all I can take in the not-vertically-stacked-multiple-circulations department with Isaac.

[Hurriplane]

Don't. Even. Start. I have had all I can take in the not-vertically-stacked-multiple-circulations department with Isaac.

As long as it doesn't detect a weakness in the ridge before 70, I'm good, but if it doesn't get it's act together after that, I consider this storm a failure.

[MJO812]

Up 70 percent for 98L

http://www.nhc.noaa.gov/gtwo_atl.shtml

[Superstorm93]

Could see a tropical depression within 12 hours

[GaWx]

Could see a tropical depression within 12 hours

It is looking good. However, a development into a TD that quickly or soon thereafter would mean an extremely low chance to make it to the US based on model runs (there is no strong high to make it likely that a well developed system would get that far west) as well as climo for storms that form this far east (even lower chance during El Nino's).

El Nino seasons: 19 CV storms formed in August during 33 seasons or ~0.6/August. Out of these 19, only 3 later hit the U.S. (1900's Galveston storm, 1930's storm #2, and 2004's Frances), which equates to a mere 16% U.S. hit rate during Ninos for Aug. formations. Since 1960, there have been 0.8 CV formations/August (14 in 17 Aug.'s) and a mere 7% U.S. hit rate (1 of 14).

*My def. of a CV a storm: a storm that first becomes a TD east of 50W and south of 20N.

IF this does become a TD prior to 50W, I'd give it no more than a 5% chance to make it to the U.S.

For those wanting this to have at least a halfway decent chance of making it to the U.S. or at least pretty far west into the Atlantic basin, the best hope would be for very slow development.