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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Blah, I think we could be in for a show tonight from 91L. BTW, Ike...You called this one yesterday. I know it hasn't formed yet, but you certainly warned everyone of the possibility. Nice pick up!
Member Since: July 15, 2006 Posts: 17 Comments: 10159
91L may be the best thing that could happen for the gulf coast right now, maybe it can reduce the water temps in case Ana or Bill come a calling.
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ok, by this picture looks like Bill took a little dip south....

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2311. Skyepony (Mod)
Quoting thelmores:


You have to look at it in relation to its surrounding pressure as well...... pressure gradient. Not just the actual pressure.

So while 1013mb may not be impressive, it may be a little more quantitatively than normal.

I bet Drak will be impressed! quantitatively! LOL


thelmores is right. It's imbeded in an area of 1017+ mb...pressure gradient makes the wind.
Member Since: August 10, 2005 Posts: 161 Comments: 37327
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?

Yes, these models will flip back and forth many more times. I always believe that until a storm passes your latitude anything can happen and you need to pay attention if it is coming in your direction.
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Quoting WeatherStudent:


Excuse me, Drakoen? Here you find yourself complaining and whining about my grammatical punctuations; yet, ironically speaking, regarding you, it is actually lack thereof, so ain't that something, right? Interesting how life operates. :)


Give it a rest already.
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Quoting Beta:
Hey Weather456 which website did you get the satellite loop of Ana & Bill
Sat


here

Member Since: July 24, 2005 Posts: 407 Comments: 19076
2306. IKE
Quoting tennisgirl08:


What's your take on the invest, Ike? steering and strength?


Moving at 300 degrees is WNW...moving at near 16 mph...looks like it's got 36 hours +/- before landfall.

Could have Claudette in the GOM....a little wearing and tearing on GOM folks...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Trying to guess where the center is/was is a fools game until the storms get closer to the CONUS. So many factors can influence the eventual track.
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Quoting WeatherStudent:


Excuse me, Drakoen? Here you find yourself complaining and whining about my grammatical punctuations; yet, ironically speaking, regarding you, it is actually lack thereof, so ain't that something, right? Interesting how life operates. :)


lol
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2302. Beta
Hey Weather456 which website did you get the satellite loop of Ana & Bill
Quoting Weather456:
Back to matters

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Quoting Patrap:
Atlantic Basin 2 Sept 2008



that was last year? i totally dont remember that... :( i have the memory of Dory, for sure
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Now we see why this is the beginning of peak season. You can put a lid on the tropics for a while, but you can't put a lid for the whole season. El Nino might still knock down Ana and Bill a bit before they hit anything, although it seems the big trough pattern in the Eastern US that has been so dominant this summer has finally broken down a bit -- soon as it did, the Atlantic and GOM fired up.
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2298. Skyepony (Mod)
That deep loud lightning going on in FL is the sounds of intensification.
Member Since: August 10, 2005 Posts: 161 Comments: 37327
91L.
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2296. cg2916
Hey, guys. I was gone for a while. I saw we have Bill, and Weather456 has a tropical storm watch and Ana may go into the Gulf. I g2g again. See you tommorow.
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amazing how that Ana still exceeds the unfavorable conditions..
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Quoting HurricaneKyle:
1013 MB is very high. This thing has a while to go.


You have to look at it in relation to its surrounding pressure as well...... pressure gradient. Not just the actual pressure.

So while 1013mb may not be impressive, it may be a little more quantitatively than normal.

I bet Drak will be impressed! quantitatively! LOL
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2292. jipmg
Quoting Grothar:
I was just informed by a friend who is a meterologist (yes!! she has a degree!) that the center of Bill may be relocated slightly more to the south than had been predicted. If this were to be true, does anyone wish to share an opinion of how this may effect the future track. Personally, I like the current track the way it is since I live in SE Fla and have no wish to be in the Cone of Uncertainty. (Is this the correct phrase?)


guess I was correct about the center being a bit south than originally estimated, and yes it will affect the track
Quoting Patrap:
GOM Rainbow Image,INVEST


I can't seem to find any buoy pressures under 1013.6 around there. Also no marine warnings. Maybe nothing still at the surface.
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2290. jipmg
so guys any new model runs that have come in? If not when can we expect them..
2288. Grothar
I was just informed by a friend who is a meterologist (yes!! she has a degree!) that the center of Bill may be relocated slightly more to the south than had been predicted. If this were to be true, does anyone wish to share an opinion of how this may effect the future track. Personally, I like the current track the way it is since I live in SE Fla and have no wish to be in the Cone of Uncertainty. (Is this the correct phrase?)
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Though the SSTs where 91L is some of the highest on Earth. Hotter than 2005 even.
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2286. jpsb
Quoting Tazmanian:
i think 91L will make land fall somm where in TX
456 had a model run earlier today that had it going to the Tx/La border. We sure could use the rain here in Texas, but not a strong hurricane!
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2285. Drakoen
SHIPS are generous giving this thing almost 2 days to intensify.
Member Since: October 28, 2006 Posts: 57 Comments: 29886
So should I put a turtle neck on and take a "model shot"? Seriously though, how do I upload an avatar. I promise, no head shots.
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Quoting IKE:


I figured it might get an invest.


What's your take on the invest, Ike? steering and strength?
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anyone call tell us up here in new england how much we should keep bill in the backs of our minds for later next week
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Any model tracks on the new invest? What kind of hook-path will this take (if any)?
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2279. Skyepony (Mod)
Quoting auburn:
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..


They just flew down the east side right outside the lower the storm, threw a few dropsondes ~20kts at the surface.

Sounds like I got bad ground to cloud lightning coming out there.
Member Since: August 10, 2005 Posts: 161 Comments: 37327
2278. KEEPEROFTHEGATE (Mod)
2009 Storms
All Active Year


Atlantic
91L.INVEST POSS T.C.F.A
03L.BILL T.S
02L.ANA T.S

East Pacific
10E.GUILLERMO HURR
09E.NINE

Central Pacific

West Pacific
94W.INVEST
01C.MAKA

Indian Ocean

Southern Hemisphere
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Can someone post a link to the models for the new invest please?
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting jipmg:


that would be crazy to have 4 named storms develope in less than a week's time


Can't remember who, but someone on the blog about 3 weeks ago predicted that during this time period. Wasn't a troll either
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2274. Patrap
Atlantic Basin 2 Sept 2008

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Quoting jipmg:


that would be crazy to have 4 named storms develope in less than a week's time


Hey we were all begging for action on here...guess we got all we can handle at the moment :)
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Quoting A4Guy:


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


Which is??
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1013 MB is very high. This thing has a while to go.
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2268. jipmg
Quoting HurricaneKyle:
I guess we can have two 91Ls rofl.
91L could become Claudette. African wave could become Danny. Or vice versa.


that would be crazy to have 4 named storms develope in less than a week's time
2267. 996tt
Look at difference between dry air field on Dr. Matthew's report and the dry air field as it exists now.
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I find it remarkable that we can see outburst nearly everywhere happening at the same time.
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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


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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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