Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 4:17 PM GMT on August 15, 2009

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Tropical Storm Ana was born this morning, when the remnants of Tropical Depression Two made a comeback and organized into the first tropical storm of the 2009 Atlantic hurricane season. Ana is the latest first named storm of the season since Hurricane Andrew got its name on August 17, 1992. The two storms have some similarities, as Andrew formed in the same part of the ocean, and also struggled in its early days with high wind shear and dry air. Let's hope the similarities end there.

Ana is struggling this afternoon. After an modest burst of heavy thunderstorm activity prompted NHC to upgrade Ana to a tropical storm early this morning, Ana has run into strong upper-level winds from the west that are creating high wind shear. This shear was not forecast, and it is not clear how long it will last. The shear has acted to drive dry air into the core of Ana, destroying almost all of Ana's heavy thunderstorms. The low-level center of the storm is now exposed to view, something that often foreshadows the death of a storm. It is possible the shear will destroy Ana, and several models (the GFS and ECMWF) forecast this may be the case. However, the shear forecast calls for shear to drop into the low range, 5 - 10 knots, tonight through Tuesday. If the shear does drop as forecast, Ana should be able to moisten the atmosphere around it sufficiently to protest itself from the dry Saharan air that surrounds it (Figure 1). SSTs are 27°C today, and will increase to 28°C by Sunday. By the time Ana moves into the Bahamas, total ocean heat content rises steeply (Figure 2), and rapid intensification of Ana is possible, if the shear and dry air haven't disrupted the storm. The intensity forecast models, for the most part, predict a steady intensification of Ana to the threshold of hurricane strength five days from now. The HWRF model is on the strong side, predicting a Category 2 hurricane. The GFDL predicts a weak tropical storm five days from now, but that is because the model has Ana passing over the rugged terrain of Hispaniola, something the other models do not predict. In summary, the intensity forecast for Ana has higher than usual uncertainty, and I give equal chances that the storm will be a hurricane--or non-existent--four days from now.


Figure 1. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the north of Tropical Depression Three. Image credit: NOAA/SSD

Tropical Depression Three forms, could be Bill later today
QuikSCAT data from this morning and satellite loops revealed that the tropical wave (90L) in the middle Atlantic has finally developed a well developed surface circulation and can be classified as Tropical Depression Three. Recent satellite imagery suggests that TD 3 may already be Tropical Storm Bill. Water vapor imagery (Figure 1) shows that TD 3's center consolidated a few hundred miles south of the dry air of the Saharan Air Layer (SAL). Thus, the storm should not be affected by dry air and dust as much as Ana has been. Ana may also act to moisten the atmosphere in front of TD 3, helping protect the storm from the SAL as it edges farther north over the the three days.



Figure 2. Heat content of the ocean, in kJ per square cm. Oceanic heat content steadily increases for Ana and TD 3 as they approach the Lesser Antilles Islands. Oceanic heat content levels of 90 kJ per square cm are frequently associated with rapid intensification of hurricanes. Image credit: University of Miami.

Wind shear is moderate, 15 knots, but is forecast to fall to 10 - 15 knots on days 2 - 5. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow TD 3 to intensify steadily, and I expect the storm will be at hurricane strength by Wednesday, when it will be near the northern Lesser Antilles Islands. Most of our reliable intensity models strengthen TD 3 into a hurricane by Wednesday. Oceanic heat content (Figure 2) increases sharply just before the islands, so TD 3 could be intensifying rapidly as it moves through or just north of the Lesser Antilles on Thursday. TD 3 consolidated farther south than expected, so the track models calling for a more northerly path were probably incorrect. In particular, the ECMWF model, which had TD 3 turning sharply northwestward and missing the Lesser Antilles Islands, was probably much too far to the north in this morning's 00Z run. TD 3 will probably pass very close to the northern Lesser Antilles islands on Wednesday and Thursday.

I'll have an update Sunday.

Jeff Masters

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000
WHXX01 KWBC 160102
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0102 UTC SUN AUG 16 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL912009) 20090816 0000 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090816 0000 090816 1200 090817 0000 090817 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 25.9N 83.1W 27.2N 85.4W 28.4N 87.2W 29.4N 89.1W
BAMD 25.9N 83.1W 27.1N 85.1W 28.1N 87.0W 29.0N 88.9W
BAMM 25.9N 83.1W 27.1N 85.1W 28.1N 87.0W 29.0N 88.8W
LBAR 25.9N 83.1W 27.3N 85.2W 29.0N 87.3W 30.7N 89.0W
SHIP 25KTS 28KTS 35KTS 40KTS
DSHP 25KTS 28KTS 35KTS 40KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090818 0000 090819 0000 090820 0000 090821 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 30.3N 90.7W 31.9N 93.6W 34.5N 95.6W 37.9N 85.6W
BAMD 30.0N 90.7W 32.3N 93.4W 36.6N 91.0W 41.9N 72.1W
BAMM 29.9N 90.6W 31.6N 93.5W 34.5N 94.9W 39.2N 80.9W
LBAR 32.8N 90.0W 36.4N 87.4W 38.1N 78.1W 34.1N 75.3W
SHIP 49KTS 63KTS 70KTS 76KTS
DSHP 34KTS 28KTS 27KTS 28KTS

...INITIAL CONDITIONS...
LATCUR = 25.9N LONCUR = 83.1W DIRCUR = 300DEG SPDCUR = 14KT
LATM12 = 24.2N LONM12 = 80.2W DIRM12 = 295DEG SPDM12 = 13KT
LATM24 = 23.5N LONM24 = 78.0W
WNDCUR = 25KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1013MB OUTPRS = 1014MB OUTRAD = 125NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$
NNNN


Member Since: Posts: Comments:
Quoting JLPR:


xD Im going to pull a chair and sit inside a supermarket on Monday morning xD


lol...monday morning...caos!
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2262. 996tt
Quoting DestinJeff:


Ana doing ok with the dry air to her west still. doesn't look to be sucking too much of it in, while also some moisture increase is evident on the western flank of the broader circulation.

dry air getting squeezed


Yes it.
Member Since: Posts: Comments:
I guess we can have two 91Ls rofl.
91L could become Claudette. African wave could become Danny. Or vice versa.
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2260. jdjnola
Quoting DestinJeff:


Ana doing ok with the dry air to her west still. doesn't look to be sucking too much of it in, while also some moisture increase is evident on the western flank of the broader circulation.

dry air getting squeezed


Yeah the dry air is shrinking quickly over the last 24hrs.
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2259. A4Guy
Quoting TexasHurricane:
Regarding Bill....Seems they went up a little north this time. Goes south then goes north and visa versa...Those who were thinking that this will end up going more south - Do you still feel this way?


First - the NHC indicated that motion would be erratic since the COC was consolidating

Second...best not to watch wobbles from frame to frame....need to look at the trend over several hours.

JMHO
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2258. Grothar
Quoting WeafhermanNimmy:


No I dont think so! It will be the same!

Thank you.
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It's kind of breezy here tonight, but who knows about tomorrow.
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2256. jdjnola
Quoting MississippiWx:


Wow, looks can be deceiving. Looks very much like a Tropical Storm!


Methinks it is a TS.
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2255. Patrap
GOM Rainbow Image,INVEST

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Quoting DestinJeff:
invest looks on a beline away from coast ... out to the open waters.
Local Klystron 9 animation (Bay News 9) takes it north into P-cola bay over next 24 hrs and doesn't develop it into any more than a wave.
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Quoting jipmg:
I am so confused right now..


welcome to the F5 session. its taken me oh, years to get used to. (i was a lurker - reluctant poster until now, wunderground frequenter since 1996 or something like that)
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2251. ssmate
Quoting Ameister12:
Look how happy TS Bill is.



I'm glad you put a mouth on that image.
Member Since: July 17, 2008 Posts: 0 Comments: 347
i think bill has reached cat 1 satus look at burst of convection at the coc.
Member Since: August 14, 2008 Posts: 0 Comments: 1002
Quoting IKE:


I figured it might get an invest.


I guess Bastardi called and bished at the NHC! LOL
Member Since: September 8, 2005 Posts: 0 Comments: 3805
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Quoting jdjnola:


Give Ana a break, she's been dealing with a lot of dry air. It's impressive that she has managed to survive, dmax or dmin aside.


Leave Ana Alone link
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2246. jipmg
I am so confused right now..
I can't help to say that 91L reminds me of Humberto (2007).. Conditions are *ripe* for development, plus it has an anticyclone over it.. I have a feeling I will wake up to a TD or even a Storm in the GOM in the morning. I don't say this with every storm.. Banding features are now starting to get more evident on the IR

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Paths for all these storms will be interesting to track to say the least. Still a good way out at sea; a lot can happen in very little time.
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2242. jpsb
Quoting Drakoen:
Deadly Catastrophic 20mph winds racing through the Keys.
Yea, right.
Member Since: June 30, 2009 Posts: 0 Comments: 1197
2241. jdjnola
Quoting Patrap:
JSL Image,GOM INVEST



Why u gotta scare me like that?
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Looks like Ana is wining the dry air battle so far.
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So I hate to be the stupid one, but is 91L the blob off of Florida? I can't find it anywhere so I have to ask.
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Look how happy TS Bill is.

Member Since: August 9, 2009 Posts: 10 Comments: 5070
Quoting Patrap:
JSL Image,GOM INVEST



Wow, looks can be deceiving. Looks very much like a Tropical Storm!
Member Since: Posts: Comments:
Regarding Bill....Seems they went up a little north this time. Goes south then goes north and visa versa...Those who were thinking that this will end up going more south - Do you still feel this way?
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Quoting Hurricanejer95:

Whats this? Is Bill happy? LOL!


Bill looks like the Joker in that picture. Evil and no knowing what he's up to!
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2233. jdjnola
Quoting Weather456:
My 11PM predictions:

Ana 40mph

Bill 45mph

Ana is being influence too much by dirunal cycles. it needs to maintain convection both during dmax and dmin

Bill T numbers continue to rise, quikscat showed some 40 knot winds. organization continue to greatly improve


Give Ana a break, she's been dealing with a lot of dry air. It's impressive that she has managed to survive, dmax or dmin aside.
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It's just annoying when high school is out...
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Quoting Grothar:
Here is my question. I looked at the NOAA vapor map and only see a large Low NE of the Bahamas. Can someone tell me what would cause the turn of Bill so rapidly to the North as is being displayed in the Ensemble models?

P.S. Hi Taz
In my limited Knowledge, the stronger it gets the more poleward it will try to go. It will find a weakspot in the Ridge find its way through.
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Quoting Weather456:
My 11PM predictions:

Ana 40mph

Bill 45mph

Ana is being influence too much by dirunal cycles. it needs to maintain convection both during dmax and dmin

Bill T numbers continue to rise, quikscat showed some 40 knot winds. organization continue to greatly improve


No I dont think so! It will be the same!
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2229. Patrap
JSL Image,GOM INVEST

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2228. jdjnola
Quoting Weather456:
Back to matters



Hear hear. I'd rather discuss Ana and Bill than who is/isn't a met or who is/isn't using English correctly, any day.
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Quoting Grothar:
Thank you Weather456 & bajelayman2. I hope I do not become a troll. Can you tell me where the information was posted for the new invest?


I am sure that you are not a troll and will never be.

As I said, that is for those who seek to make trouble, which I know you are not one.

Bye.
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there is no jog every one is still going due west common guys !!
Member Since: August 14, 2008 Posts: 0 Comments: 1002
My 11PM predictions:

Ana 40mph

Bill 45mph

Ana is being influence too much by dirunal cycles. it needs to maintain convection both during dmax and dmin

Bill T numbers continue to rise, quikscat showed some 40 knot winds. organization continue to greatly improve
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
Back to matters

Both looking impressive, my expectation:

Ana: 45MPH

Bill: 50MPH
In my opinion both of these verde syetems are at a crucial stage the next few days as the big question will be if the northward turns takes place and when?. Even more crucial than once these type storms when they get in the gulf. It will be very interesting to see what models and mets are able to forecast the steering directionof the #2 storms
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Later bajelayman
2221. Drakoen
Quoting 996tt:


This really isn't the place for English lessons . . . Kind of like me acting like a met too . . . Let it go and enjoy life. Have a great evening you guys.


It's just annoying with the involved syntactical structure and not structure it properly.
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All 00z gfs ensemble models curve it, all other models stop around P.R pointing to SFLA.
2219. Grothar
Thank you Weather456 & bajelayman2. I hope I do not become a troll. Can you tell me where the information was posted for the new invest?
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91L IS GOING TO BE A RAIN STORM FOR FL.
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Quoting Drakoen:
\

The way you use your commas. When and when not to.


You're saying the placement of them are incorrect?
2216. auburn (Mod)
152. Blogger 7:52 PM CDT on August 15, 2009 comment.
Skye... are they still flying??? navy just called the blob off Florida an invest 91L..
Member Since: Posts: Comments:
Nice outflow with 91L. If it hits the Panhandle, I say nothing stronger than TD. If it comes ashore further west around MS/AL, I'd say a weak TS isn't out of the question. Check out the JSL loop to see the respectable outflow.

91L JSL Loop
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Go outside to walk the dog and come back in to a new invest, what's next.... Oh, yeah - African wave!!!
Member Since: September 1, 2007 Posts: 0 Comments: 1990

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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