Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 16:17 GMT le 15 août 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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Quoting Ldog74:


Well, it could. Other requirements besides 39mph winds can prohibit a tropical cyclone from forming. So there could be a storm that was a TS the second it gained tropical cyclone status. Ie. Vince, Tammy 2005.


well stated.
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BROAD area of 26 to 34 KT winds... in all sectors..

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RE:3906

and they had that as a yellow scribble in the earlier (way less than 48hours ago) advisory
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Quoting Stormchaser2007:


Whatever...I didnt look.

I just posted the model data that says it up to 45.


how old are you?
Member Since: 22 août 2006 Posts: 2 Comments: 1988
can someone please post a link to the long loop nexrad radar on 91L thank you
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3909. jpsb
Quoting STORMT0P:
this gom storm could mean severe inland flooding after landfall...if no boundries come in to pick it up it could stall out bringing core rains to the region during nightfall resulting in 14 to 28 inches of rain easily...st
1978 T.S. Cluadette(sp) dumped 28 inches of rain in 12 hours in the NASA area of Texas. What a mess that was!
Member Since: 30 juin 2009 Posts: 0 Comments: 1197
3908. Ldog74
Quoting ncwxman68:


actually, it doesn't "skip" TD status, it just happens to develop so fast that it beats the forecasters to the punch. I've seen it happen a few times with these close-in systems and with hybrids.


Well, it could. Other requirements besides 39mph winds can prohibit a tropical cyclone from forming. So there could be a storm that was a TS the second it gained tropical cyclone status. Ie. Vince, Tammy 2005.
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Quoting serialteg:


i dont get it, it says 6:45 UTC which would be 30 mins behind from my current hour?



Whatever...I didnt look.

I just posted the model data that says it up to 45.
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3906. Patrap
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MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN AUG 16 2009

MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA
AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W.

AN AREA OF LOW PRES HAS DEVELOPED OVER THE EASTERN GULF OF MEXICO
ABOUT 80 MILES SW OF TAMPA. THE LATEST NHC TROPICAL OUTLOOK SAYS
THERE IS A GOOD CHANCE THAT THIS LOW COULD DEVELOP INTO A
TROPICAL CYCLONE LATER TODAY. THE LOW IS MOVING NW 15 KT. WILL
UP THE WINDS IN THE EASTERN GULF WITH THE LOW FROM 15-20 TO
20-25 KT. WINDS INCREASE OVER THE SW GULF LATE MON AND MON NIGHT
AS THE N PORTION OF A TROPICAL WAVE MOVES ACROSS THE SOUTHERN
BAY OF CAMPECHE. WILL WAIT FOR LATEST ADVISORY ON TROPICAL
STORM ANA...AS THE PREVIOUS ADVISORY BROUGHT ANA INTO THE
STRAITS OF FLORIDA ON THU EVENING. MAY HAVE TO HEADLINE
E GULF ZONE FOR TROPICAL CONDITIONS EXPECTED.
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Special marine warning.

SPECIAL MARINE WARNING
GMZ853-873-160900-
/O.NEW.KTBW.MA.W.0114.090816T0711Z-090816T0900Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
311 AM EDT SUN AUG 16 2009

THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* SPECIAL MARINE WARNING FOR...
WATERS FROM ENGLEWOOD TO TARPON SPRINGS FL OUT 20 TO 60 NM OVER
GULF OF MEXICO WATERS...
COASTAL WATERS FROM ENGLEWOOD TO TARPON SPRINGS FL OUT 20 NM OVER
GULF OF MEXICO WATERS...

* UNTIL 500 AM EDT

* AT 306 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS...PRODUCING STRONG WINDS 34 KNOTS OR GREATER...
COVERING MOST OF THE GULF WATERS BETWEEN 15 AND 60 NM OFFSHORE
FROM ENGLEWOOD NORTH TO CLEARWATER BEACH. THESE STORMS ARE
ASSOCIATED WITH AN AREA OF LOW PRESSURE MOVING NORTHWEST THROUGH
THE EASTERN GULF. THE STORMS ARE MOVING NORTH AT 25 TO 30 KNOTS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MARINERS CAN EXPECT STRONG WINDS...HIGH WAVES...DANGEROUS
LIGHTNING...AND HEAVY RAINS. WATERSPOUTS WILL ALSO BE POSSIBLE IN
SOME OF THE HEAVIER RAIN BANDS. BOATERS SHOULD SEEK SAFE HARBOR
IMMEDIATELY.

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Quoting ST6CaptChaos:
After Ike us Houstonians dont need or want another one tyvm...lol



Amen. We haven't been the same since, nobody around this part of Texas wants anything to do with anything over 20 mph. Kids still get spooked during a regular thunderstorm.

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Quoting stormno:
yes i certainly agree we have a depression now and by 5am we will probably have a strong tropical storm approaching hurricane force...i just looked at the latest satellite pics and radar from tampa and it is definitely moving nw maybe even a little wnw..i would say about 6-8 mph..this is certainly not goog for new orleans if it goes more wnw we will get the brunt of claudette and she will be over the water a lot longer...i agree a watch should come out at 5am or by 8am....the way its moving now i would think the watch would be as far west as lafayette and as far east as pensecola...this storm is growing rapidly in size also..not a good scenario...Stormno


Wow.. Seriously? It's not even close to Hurricane strength, and it is definitely not a Tropical Storm at the moment. It would be lucky to be named a Depression as of now, given the lack of outflow and the latest QuikSCAT which shows no closed surface circulation, or any lower level circulation for that matter. This is still a wave interactive with a middle and upper-level trough. However, with that said, it is in a steamy Gulf of Mexico where any tropical system can intensify quite rapidly, and it does look likely (Given 10kt shear, 86 degree SST's, decent OHC nearby) that this will intensify today and become a Depression at some point today, and possibly a Storm.
I see a storm soon, but not a Hurricane. We need to temper those forecasts a bit :)

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Quoting TexasHurricane:


Yeah, this one definitely developed quickly...

I hate to say it...but this is why they always say - be prepared by June 1 - you NEVER know what will happen. I'm just afraid too many don't heed the warning
Member Since: 5 septembre 2007 Posts: 0 Comments: 3488
3900. jipmg
Quoting Drakoen:


can I get the loop of Bill with that satellite imagiry
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3899. Fshhead
Quoting serialteg:


maybe this will help


Mmmmm THANX for popping in that link. Like I said before with the water vapor loop link, Anna looks like she is feeling the ULL. That visible defintely shows it..
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Quoting Weather456:
but i guess its been preached in June and July that untapped waters in the GOM can easily spin up a system under the right conditions.


No kiddin

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000
WHXX01 KWBC 160715
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0715 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

TROPICAL CYCLONE ANA (AL022009) 20090816 0600 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090816 0600 090816 1800 090817 0600 090817 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 14.5N 52.9W 15.8N 57.2W 17.1N 61.7W 19.2N 66.2W
BAMD 14.5N 52.9W 15.2N 56.0W 15.8N 59.6W 16.5N 63.3W
BAMM 14.5N 52.9W 15.2N 56.5W 15.8N 60.4W 16.7N 64.5W
LBAR 14.5N 52.9W 15.0N 56.1W 15.8N 59.8W 16.7N 63.7W
SHIP 35KTS 36KTS 39KTS 45KTS
DSHP 35KTS 36KTS 39KTS 45KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090818 0600 090819 0600 090820 0600 090821 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 20.8N 70.3W 23.9N 76.7W 26.2N 80.4W 27.6N 82.6W
BAMD 17.3N 67.0W 18.8N 74.1W 20.0N 79.8W 21.2N 85.1W
BAMM 17.5N 68.5W 18.8N 76.2W 20.1N 83.0W 21.6N 88.9W
LBAR 17.3N 67.5W 18.8N 74.7W .0N .0W .0N .0W
SHIP 49KTS 56KTS 63KTS 72KTS
DSHP 49KTS 36KTS 37KTS 45KTS

...INITIAL CONDITIONS...
LATCUR = 14.5N LONCUR = 52.9W DIRCUR = 270DEG SPDCUR = 17KT
LATM12 = 14.4N LONM12 = 49.2W DIRM12 = 272DEG SPDM12 = 15KT
LATM24 = 14.5N LONM24 = 46.1W
WNDCUR = 35KT RMAXWD = 40NM WNDM12 = 35KT
CENPRS = 1005MB OUTPRS = 1010MB OUTRAD = 150NM SDEPTH = M
RD34NE = 60NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$
NNNN
Member Since: 23 août 2008 Posts: 7 Comments: 5300
Quoting Weather456:


those are the winds and direction reported by buoys, ships and coastal stations in the last hour. The arrows are wind direction while the numbers below the arrows are the speed of the wind.

If you look closel, you see that arrows curve or veer around the area of low pressure.


Thanks! I don't know why they didn't teach me this stuff when I was studying accounting & taxes!
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Quoting Patrap:



more W i see
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3893. Drakoen
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but i guess its been preached in June and July that untapped waters in the GOM can easily spin up a system under the right conditions.
Member Since: 24 juillet 2005 Posts: 407 Comments: 19076
Tampa has issued a Special marine warning for the area around 91L

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
311 AM EDT SUN AUG 16 2009

THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* SPECIAL MARINE WARNING FOR...
WATERS FROM ENGLEWOOD TO TARPON SPRINGS FL OUT 20 TO 60 NM OVER
GULF OF MEXICO WATERS...
COASTAL WATERS FROM ENGLEWOOD TO TARPON SPRINGS FL OUT 20 NM OVER
GULF OF MEXICO WATERS...

* UNTIL 500 AM EDT

* AT 306 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS...PRODUCING STRONG WINDS 34 KNOTS OR GREATER...
COVERING MOST OF THE GULF WATERS BETWEEN 15 AND 60 NM OFFSHORE
FROM ENGLEWOOD NORTH TO CLEARWATER BEACH. THESE STORMS ARE
ASSOCIATED WITH AN AREA OF LOW PRESSURE MOVING NORTHWEST THROUGH
THE EASTERN GULF. THE STORMS ARE MOVING NORTH AT 25 TO 30 KNOTS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MARINERS CAN EXPECT STRONG WINDS...HIGH WAVES...DANGEROUS
LIGHTNING...AND HEAVY RAINS. WATERSPOUTS WILL ALSO BE POSSIBLE IN
SOME OF THE HEAVIER RAIN BANDS. BOATERS SHOULD SEEK SAFE HARBOR
IMMEDIATELY.

&&

LAT...LON 2805 8385 2811 8309 2690 8262 2670 8340
2707 8364 2752 8381 2790 8387
TIME...MOT...LOC 0706Z 176DEG 27KT 2721 8339
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Quoting Stormchaser2007:


Thats old. lol

The models were run with the data of Bill up to 45mph. Look back a few pages.


i dont get it, it says 6:45 UTC which would be 30 mins behind from my current hour?

Member Since: 22 août 2006 Posts: 2 Comments: 1988
Quoting extreme236:


Uh the NHC says so! Dvorak estimates of 2.5 and 3.0 blend to make 40knots.


Ok we shall see! :) That's what Im going to say! :)
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Quoting Weather456:
91L surprised me though.


How? Look at those SSTs
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this gom storm could mean severe inland flooding after landfall...if no boundries come in to pick it up it could stall out bringing core rains to the region during nightfall resulting in 14 to 28 inches of rain easily...st
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CMC model has been picking up on 91L for about a week...
Member Since: 5 septembre 2007 Posts: 0 Comments: 3488
Quoting Giga2001:
456 Any chance you can give me the "for dummies" version explanation of that graphic you posted?
Thanks


those are the winds and direction reported by buoys, ships and coastal stations in the last hour. The arrows are wind direction while the numbers below the arrows are the speed of the wind.

If you look closel, you see that arrows curve or veer around the area of low pressure.
Member Since: 24 juillet 2005 Posts: 407 Comments: 19076
3884. Ldog74
http://www.ssd.noaa.gov/goes/flt/t1/loop-rgb.html
It best shows how rapidly the LLC of Ana is running away from...well, theres not much convection to speak of at this point.
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3883. Patrap
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Quoting weathersp:
This.... is... scary...



Yeah, this one definitely developed quickly...
Member Since: 2 juillet 2009 Posts: 0 Comments: 2811
Quoting ncwxman68:


Yes, it can happen...has many times in the past.


actually, it doesn't "skip" TD status, it just happens to develop so fast that it beats the forecasters to the punch. I've seen it happen a few times with these close-in systems and with hybrids.
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Quoting weathersp:
This.... is... scary...



rapid intensification poster boy, indeed
Member Since: 22 août 2006 Posts: 2 Comments: 1988
can someone please post a link to the long loop nexrad radar on 91L thank you
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As of now Bills up to 45mph.

AL, 03, 2009081606, , BEST, 0, 114N, 374W, 40, 1002, TS,
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Quoting taco2me61:
Well just getting back from the Miss Gulf Coast and I have to tell you there are a lot of people upset that there is not much of a warning out yet and tomorrow will be to late....
Also the gas prices has gone up almost 10 cents from yesterday....

Taco :0)


? I just bought gas today and yesterday, same price, and no one I've talked has even mentioned the storm or lack of warnings.
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Quoting Weather456:
91L surprised me though.


i was here when we started talkin bout it at about 1pm edt? i get confused about my time zone lol
Member Since: 22 août 2006 Posts: 2 Comments: 1988
This.... is... scary...

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Quoting WeafhermanNimmy:


We'll see....but I dont think so! :)


Uh the NHC says so! Dvorak estimates of 2.5 and 3.0 blend to make 40knots.
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Quoting Stormchaser2007:


Unrecognizable.




maybe this will help
Member Since: 22 août 2006 Posts: 2 Comments: 1988
3872. Patrap
Tropical Storm Watches and warnings may go up as early as Noon I would think.
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91L surprised me though.
Member Since: 24 juillet 2005 Posts: 407 Comments: 19076
Quoting Stormchaser2007:


Bill is up to 45mph.


We'll see....but I dont think so! :)
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Quoting serialteg:


dont see that here...



Thats old. lol

The models were run with the data of Bill up to 45mph. Look back a few pages.
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Quoting stormsurge39:
Tennisgirl, Stormno said to keep an eye on this in the GOM days ago, so i wouldnt be so quick to LOL.


you can bash him all you want, but thats true
Member Since: 22 août 2006 Posts: 2 Comments: 1988
3867. stormno
well tennisgirl all you have to do is look at the radar and satellite to see its a depression and its growing in size rapidly...feeder bands continue to develop around the storm it has good outflow around it ..this is getting to be a picture perfect storm and it will be one to remember if it happens to slow down...it will definitely be named by 8am sunday...it will be a strong tropical storm...be aware of this one tennisgirl..Stormno
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456 Any chance you can give me the "for dummies" version explanation of that graphic you posted?
Thanks
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Quoting victoriahurricane:
Is there any chance that Invest 91L skips TD status and goes straight to TS. It looks damn impressive on radar.

Does anyone know? I wasn't here for Humberto.


Yes, it can happen...has many times in the past.
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Quoting serialteg:


i know but the system has been going on since the cape verdes and it regenerates. so

thats a fact too.



Unrecognizable.


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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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