Atlantic Tropical Action 2012 - Part I

[Srain]

From one of our 'local' Pro Mets (Jeff) in a morning e-mail I post regularly in the Central/Western sub Texas/Mexico/New Mexico/Louisiana thread...

Atlantic basin tropical activity appears to be entering into a more active period over the next several week.

As is normal for this time of year, the Atlantic basin tropical activity usually shows an upswing in activity starting in early August. Factors over the Atlantic basin do suggest that the potential for tropical cyclone formation will be increasing over the next several weeks in part due to climatology and in part due to increasingly favorable atmospheric factors within the basin. Tropical waves leaving Africa are slightly more well defined and robust, stable and dry African air moving westward off Africa is slowly subsiding, a fairly favorable MJO pulse will be moving into the basin over the next 2 weeks. Forecast models are resolving these increasingly favorable factors with increasing tropical activity. However one must remember that we are borderline ENSO warm (El Nino) in the Pacific and this can negate development in the Atlantic basin with increased wind shear even when all other factors are favorable.

99L:

A weak surface low pressure system located 1100 miles WSW of the Cape Verde Islands in remains embedded within the monsoon tropical across the central Atlantic basin. A review of water vapor images and Total PW images show a large envelop of deep tropical moisture with this feature and the surface trough protecting the surface low with dry air well to the north. Convection is overall disorganized and scattered near the feature and not centered or concentrated near the weak surface low, but off it its north and northwest. As is usual with systems tangled with the monsoon trough, slow development is possible, but the key word is slow!

Global forecast model support for this system is fairly good with nearly every model making it into a closed storm (exception the NOGAPS model which keeps it an open wave). Most of the guidance shows fairly quick development east of the Windward Islands, except the EURO which races the system westward barely keeping it a defined system. Nearly all of the guidance shows the system struggling after making it near/into the Caribbean and this is likely a factor of increased wind shear (either due to a possible fast forward motion or increasing upper level winds aloft). Feel the EURO is too fast on the westward motion and the CMC too far to the north and too strong. The system will likely continue a W to even WSW track for the next 2-3 days and gradually organize possibly into a tropical depression or even a tropical storm as it nears/approaches the Windward and Leeward Islands. After that there is much spread in the track and intensity guidance.

Does a Wet July suggest an increased threat of Texas tropical activity in August and September?

Chris Hebert of Impact Weather recently completed a study looking at the effects of the top 20 wettest and top 20 driest July’s and the impacts of tropical activity on the upper TX coast in August-November of that year. The results are seen in the graphic below and are fairly dramatic. For the 20 wettest July’s, 13 tropical storms impacted the NW Gulf following that wet July versus 9 in the top 20 dry years. Even more astounding is that 11 hurricanes impacted following a wet July with only 4 in the dry years and 8 major hurricanes impacted the NW Gulf versus none following a dry July. To sum up the data following a wet July, there is a greater than 50% chance a hurricane will strike the TX/LA coast.

The reasoning of this makes sense, as a wet July strongly indicates a lack of strong high pressure over TX (much like this summer) usually with a weakness or trough in the height field aloft in this region. Tropical systems approaching from the south and east will flow toward this weakness in the ridge…hence unlike in 2011 when Texas was strongly protected by strong high pressure, this year we are not and we will need to keep a very close eye on developments over the next 2 months.

[Superstorm93]

^^ Excellent info! Thanks for posting that. I really enjoy Impact Weather.

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

0915 AM EDT TUE JULY 31 2012

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 01/1100Z TO 02/1100Z AUGUST 2012

TCPOD NUMBER.....12-074

I. ATLANTIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

3. ADDITIONAL DAY OUT LOOK: PROBABLE LOW LEVEL

INVEST AT 03/1800Z NEAR 12.5N 57.5W

[jconsor]

99L is finally developing a decent ball of deep convection and, not surprisingly, has been given a Dvorak T-number of 1.0 this morning. Nice outflow pattern too. However, I think any development will still be gradual given that it's still attached to the monsoon trough, there is dry air just to the north, and the main vorticity and best convergence is a bit far south - 8-9N latitude.

If this doesn't develop before about 60W, I'd say it almost certainly waits till reaching the Caribbean before any development would occur. It has about 3 days to develop before reaching much more hostile conditions in the E. Caribbean. GFS appears to be much too slow.

[Superstorm93]

00z EPS control of the ECMWF has 99L making it into the Gulf after 10 days as a semi-defined wave. I'm less than excited about the enviormental conditions ahead of it, but maybe that CCKW (in addition to a miracle) can get Josh a decent system.

Light at the end of the tunnel?

[bluewave]

It may be as we go through August, that the tropical waves coming in behind this one will

encounter slowly improving conditions for development.

[wxmx]

There's definitely some improvement in organization and convection with 99L... could be upgraded a bit in the next TWO

[Superstorm93]

There's definitely some improvement in organization and convection with 99L... could be upgraded a bit in the next TWO

Only up to 30% now.

OSCAT has a disorganized low.

[Floydbuster]

Video Update on 99L

[Superstorm93]

Still looks to be getting together on visible. SHIPS prints a rough future for this one while in the Caribbean.

* ATLANTIC SHIPS INTENSITY FORECAST	 *
			 * GOES AVAILABLE,	 OHC AVAILABLE	 *
			 *	 INVEST AL992012 07/31/12 18 UTC *
TIME (HR)		 0	 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 25 28 32 37 41 47 52 56 57 57 58 58 58
V (KT) LAND	 25 28 32 37 41 47 52 56 57 57 58 58 58
V (KT) LGE mod 25 28 30 33 35 41 46 51 55 57 57 56 55
Storm Type	 TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP
SHEAR (KT)		 6	 3	 6	 9	 6 10	 8 13 14 21 16 28 21
SHEAR ADJ (KT)	 6 11	 7	 4	 8	 7	 7	 3	 2	 1	 1	 0	 1
SHEAR DIR	 322	 4 332 353 329 325 305 290 260 257 268 268 261
SST (C)		 27.8 27.9 28.0 28.0 28.0 28.0 28.0 28.1 28.2 28.1 28.1 28.2 28.5
POT. INT. (KT) 136 136 137 137 137 137 137 139 141 140 140 142 146
ADJ. POT. INT. 140 139 139 138 138 137 136 139 142 141 142 143 147
200 MB T (C) -53.2 -53.6 -54.0 -54.0 -53.3 -53.9 -53.3 -53.4 -53.2 -53.7 -53.1 -53.5 -53.2
TH_E DEV (C)	 6	 6	 6	 6	 6	 7	 7	 8	 8	 9 10	 9 10
700-500 MB RH	 61 64 65 64 62 62 63 64 61 62 60 62 63
GFS VTEX (KT)	 9 10 11 12 11 11 11 11 11 12 12 12 11
850 MB ENV VOR	 8 18 16 14 10 12 17 23 25 30 30 19 14
200 MB DIV		 7 20 35 48 40 40	 7 14 14 35 44 31 44
700-850 TADV	 -10 -13 -12 -12 -10 -8 -1 -2	 0	 3	 7	 6	 9
LAND (KM)	 1249 1149 1058 991 935 821 746 686 656 425 356 395 191
LAT (DEG N)	 9.6 9.9 10.1 10.4 10.6 11.0 11.4 11.7 12.4 13.0 14.0 15.0 16.2
LONG(DEG W)	 41.3 42.6 43.8 44.9 46.0 48.2 50.3 52.5 55.1 57.8 60.8 63.9 67.1
STM SPEED (KT) 15 13 12 11 11 11 10 12 14 14 16 16 17
HEAT CONTENT	 20 19 22 28 37 24 18 39 50 66 57 50 54

[phil882]

Only up to 30% now.

OSCAT has a disorganized low.

Looks like its still attached to the ITCZ to some degree. However, both the GFS and ECMWF show the system breaking away from the ITCZ and become much more symmetrical in the low levels. Tonight we will probably see a large convective burst given the assistant of the overhead convectively coupled kelvin wave and that could be the burst that brings this system to tropical cyclone status. The big question remains how the upper level trough located north of the system modifies the upper level flow over 99L. It will be an interesting battle between TUTT influences vs. CCKW influences in the upper level pattern. Which one comes out on top will ultimately determine the fate of 99L.

[am19psu]

Short term fate. Medium term fate is to get sheared apart in the E Caribbean, regardless if it reaches TC status or not this week.

[Superstorm93]

Short term fate. Medium term fate is to get sheared apart in the E Caribbean, regardless if it reaches TC status or not this week.

Completely agree. Might become a cyclone within the next few days before reaching the islands, but conditions just are not favorable for anything other than a complete degeneration into an open-wave.

After that, the question is if this runs into CA or gets a second chance in the WCARB/GOM.

[HurricaneJosh]

From one of our 'local' Pro Mets (Jeff) in a morning e-mail I post regularly in the Central/Western sub Texas/Mexico/New Mexico/Louisiana thread...

Thanks, Steve. The correlation between a wet July in TX and hurricane landfalls in TX/LA is pretty cool. Fingers crossed on that.

00z EPS control of the ECMWF has 99L making it into the Gulf after 10 days as a semi-defined wave. I'm less than excited about the enviormental conditions ahead of it, but maybe that CCKW (in addition to a miracle) can get Josh a decent system.

Light at the end of the tunnel?

It may be as we go through August, that the tropical waves coming in behind this one will

encounter slowly improving conditions for development.

Yep-- it seems the MJO transition is coinciding nicely with climo.

Short term fate. Medium term fate is to get sheared apart in the E Caribbean, regardless if it reaches TC status or not this week.

I've had enough o' you with regard to this system.

[wxmeddler]

<3 CV Waves... I love how they pull themselves together.

[phil882]

Short term fate. Medium term fate is to get sheared apart in the E Caribbean, regardless if it reaches TC status or not this week.

I tend to agree with you given the weak upper level flow vs. strong mid/low-level easterly flow expected in the Caribbean. There is an small outside chance that 99L intensifies much more rapidly than expected (unlikely), and generates a decent upper level anticyclone that could persist over the cyclone. I am in support of the more agressive GFS solution, because given the CCKW passage, there should be some anomalous low-level westerly flow (it could still be net easterly, but less than climo) that slows down the TC that allows it to be better aligned with the mid-level circulation center. The ECMWF is racing the circulation ahead over the next 48 hours, and that seems more unlikely given the equatorial wave passage.

On the other hand, the GFS also weakens 99L in the medium range in the Caribbean... so eventually the prevailing climo flow will take back over.

[wxmx]

Very short term...it's getting that look....

[wxmx]

As long as the inflow from the SSE and especially WSW is unimpeded, development should continue....upper levels are ok.

[HurricaneJosh]

I just wanna see a closed low make it into the BoC next week-- then let's see some magic.

[jconsor]

The upper level pattern on most of the models is actually better in the central Caribbean (between 65 and 80W) than further west into the Gulf of Mexico. A lot depends on how fast 99L moves in relation to the 200 mb high and trough over the Gulf of Mexico.

Completely agree. Might become a cyclone within the next few days before reaching the islands, but conditions just are not favorable for anything other than a complete degeneration into an open-wave.

After that, the question is if this runs into CA or gets a second chance in the WCARB/GOM.

[Mencken_Fan]

I just wanna see a closed low make it into the BoC Bahamas next week-- then let's see some magic.

Fixed.

[wxmx]

Competing low and mid level energy, no model support, Hispaniola and everything, but that lemon deserves something better than ~0%...CCKW is working it's magic, and convection is a bit close to the low level turning....

[wxmeddler]

50% for 99L on the 8pm TWO

1. SHOWERS AND THUNDERSTORMS HAVE BECOME A LITTLE MORE CONCENTRATED

NEAR THE CENTER OF A LOW PRESSURE SYSTEM LOCATED ABOUT 1150 MILES

EAST-SOUTHEAST OF THE WINDWARD ISLANDS. ENVIRONMENTAL CONDITIONS

ARE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF

THIS DISTURBANCE OVER THE NEXT FEW DAYS AS IT MOVES WESTWARD AT

15 TO 20 MPH. THIS SYSTEM HAS A MEDIUM CHANCE...50 PERCENT...OF

BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS

[wxmx]

Not sure I agree with the lemon not having a sign of a surface circulation...there's a weak one S of Haiti...or at least it looks like one in the last vis images available...but it probably won't ammount to much either way.

[Superstorm93]

Phils Kelvin wave might just do the trick for 99L in the next 18 hours. Expecting to see a nice Cherry by 8am tomorrow.

Could become a decent 50-60 knot cyclone before reaching the islands if everything works out nicely.

Extended range: Off with its head!

[HurricaneJosh]

Extended range: Off with its head!

I won't tolerate such violent talk in this thread.

[Superstorm93]

I won't tolerate such violent talk in this thread.

There's a fairly good chance that you'll see this open up and have the possibility to wind up in a more favorable location within the next 7-10 days.

Whether it's the EPAC or WATL remains to be seen.

EDIT: 18z HWRF holds out hope that this could survive a bit in the Caribbean.

[Riptide]

It's always a good idea to be skeptical of intensity forecasts, if the system is more developed than expected then it will most likely survive the trip through the "Caribbean graveyard", which apparently has been a inherently unfavorable area for some time. 99L is a legit player that will be in a position of concern later in the period, in my opinion.

[HurricaneJosh]

There's a fairly good chance that you'll see this open up and have the possibility to wind up in a more favorable location within the next 7-10 days.

Whether it's the EPAC or WATL remains to be seen.

EDIT: 18z HWRF holds out hope that this could survive a bit in the Caribbean.

A close low S of Shredderola. Me likey.

[HurricaneJosh]

The Mandarin's up to 50% as of 8 pm EDT. Gonna be cherrytime soon.

[Derecho!]

It's always a good idea to be skeptical of intensity forecasts, if the system is more developed than expected then it will most likely survive the trip through the "Caribbean graveyard", which apparently has been a inherently unfavorable area for some time. 99L is a legit player that will be in a position of concern later in the period, in my opinion.

I think there's such an astounding level of data available now it's become almost too easy to find some sort of index or data point or model or oscillation that isn't absolutely ideal for development and be too pessimistic.