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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Quoting flsky:
canesrule1 please post a link for the dropsonde info instead of the entire listing. Thank you.
ok no prob
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Thanks for your take,Kman. It is a bit chancy going over with all the activity in the ATL. May organize everything here just in case with our house, office, boats etc... before we go. Miss Universe is there this week, so you know things will be crazy over there. I wonder what their back-up plan would be in the case of a storm during the pageant's week of activities? Anyway, I'll leave you to the discussion of the weather. Keep your points/observations coming.
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Quoting jdjnola:
Is it just me or did Ana cover herself up?... with convection that is.

half way
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Quoting weathersp:


LOL Winds don't get that strong at that level in the tropics...

That sonde must of been going reeally fast when it ejected from the plane...
LOL, i know, looks like a MLB picher threw it at full speed, lol.
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1659. flsky
canesrule1 please post a link for the dropsonde info instead of the entire listing. Thank you.
Member Since: October 24, 2006 Posts: 0 Comments: 2111
this is weird i just read a list and it said TS bill and Hurricane Claudette hit Texas in the same year. Not saying this means anything but its just weird
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Storms often survive a cuban landfall with little or no effect.... Hispaniola, however, is another story. I think Ana is going south of PR, but hispaniola is just too large and situated that it may just crash into it. And teh eastern caribbean is a graveyard... for some reason storms simply dont develop much in this area. Ana will ahve to get her act together before her confrontation with the islands. This is a wait and see game, we'll have to just be patient.
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Quoting gtownTX:
Just one of the millions of earthlings who pay attention to weather and learning what I can. Storm tracking seems a lot like trying to nail Jello to the wall.....

Anyway I was wondering...why so many different models with different conclusions? Is one more reliable than another?
While not worthless, computer models are notoriously incorrect, and all disagree with each other. Some I hear are more reliable than others, although I do not specifically know the best. It seems that GFS is quoted a lot, but there are probably others mets who think another is far better. They are tools but not crystal balls. The computers take in information, and try to make sense out of it by way of an educated guess. There are other factors the NHC takes into consideration when predicting projected path. It's an evolving science, better all the time, but not flawless, thus the huge disclaimers on them stating to heed official warnings in your area, and not to use the model as gospel. That's my best understanding and theory of how they work: a complete layman's perspective
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1653. jdjnola
Is it just me or did Ana cover herself up?... with convection that is.
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Quoting mobilegirl81:

It has happened numerous times.
from the looks of post 1626 taking us through Tuesday, looks like it's gonna be really wet here for the next three days or so...stay safe..
Member Since: July 31, 2009 Posts: 0 Comments: 324
Quoting canesrule1:
162mb 285° (from the WNW) 98 knots (113 mph) but in the upper levels.



LOL Winds don't get that strong at that level in the tropics...

That sonde must of been going reeally fast when it ejected from the plane...
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everything has to be in the right place for a tc to impact the southeast coast were TS ana currently is.
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Quoting Weather456:
WOW! what a burst of convection around the COC
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Bill is gaining covection near the center.
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Quoting FloridaTigers:


Will this be the 18z or 00z models?


The 00Z and 12Z models use the upper-air data.
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Quoting FloridaTigers:


Will this be the 18z or 00z models?


18Z already running
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Quoting KATRINABILOXIGIRL:
Hey Mobilegirl...whoever made that comment about why are people so worried about the BLOB in the gulf must not live on th gulf coast like we do....it's waaaaayyyyy too hot in the gulf right now...could sneak up on us...

It has happened numerous times.
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Quoting TampaMishy:
So everyone thinks that Bill will stay away from the gulf side?


Most likely yes, ana is the one that bears watching for the Gulf coast.
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Quoting InTheCone:
Just a quick reminder that the models now have the Gulfstreaam data to use and they will be far more accurate than they were a few days ago if the storms strenghten according to the forcasts.



Will this be the 18z or 00z models?
Member Since: May 17, 2009 Posts: 0 Comments: 559
Observation #5:
Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 15th day of the month at 22:42Z
Aircraft: Gulfstream IV-SP (G-IV) (Reg. Num. N49RF)
Storm Number: 02
Storm Name: Ana (originating in the North Atlantic basin)
Mission: Non-Tasked Mission
Observation Number: 05

Part A...

Date: Near the closest hour of 22Z on the 15th day of the month
Highest Mandatory Level For Which Wind Was Reported: 200mb
Coordinates: 17.4N 52.1W (View map)
Location: 583 miles (938 km) to the ENE (59°) from Bridgetown, Barbados.
Marsden Square: 042 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1012mb (29.88 inHg) Sea Level (Surface) 27.6°C (81.7°F) 24.5°C (76.1°F) 85° (from the E) 28 knots (32 mph)
1000mb 106m (348 ft) 26.6°C (79.9°F) 24.1°C (75.4°F) 80° (from the E) 26 knots (30 mph)
925mb 791m (2,595 ft) 21.6°C (70.9°F) 20.3°C (68.5°F) 85° (from the E) 34 knots (39 mph)
850mb 1,522m (4,993 ft) 18.0°C (64.4°F) 16.7°C (62.1°F) 95° (from the E) 32 knots (37 mph)
700mb 3,166m (10,387 ft) 9.8°C (49.6°F) Approximately 3°C (37°F) 110° (from the ESE) 30 knots (35 mph)
500mb 5,890m (19,324 ft) -5.3°C (22.5°F) Approximately -14°C (7°F) 75° (from the ENE) 12 knots (14 mph)
400mb 7,600m (24,934 ft) -16.5°C (2.3°F) Approximately -26°C (-15°F) 75° (from the ENE) 10 knots (12 mph)
300mb 9,700m (31,824 ft) -31.7°C (-25.1°F) -36.5°C (-33.7°F) 280° (from the W) 4 knots (5 mph)
250mb 10,970m (35,991 ft) -41.5°C (-42.7°F) Approximately -54°C (-65°F) 210° (from the SSW) 11 knots (13 mph)
200mb 12,440m (40,814 ft) -53.7°C (-64.7°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 170° (from the S) 20 knots (23 mph)
150mb 14,240m (46,719 ft) Height extrapolated since sonde was released within 25mbs below this level.

Maximum Wind Level (maximum wind did not coincide with flight level):
- Pressure at maximum wind level: 162 mb
- Wind Direction: 285° (from the WNW)
- Wind Speed: 98 knots (113 mph)
- Vertical Wind Shear: Absolute value of vector difference between this level and 3,000 feet below: Greater than 99 knots
- Vertical Wind Shear: Absolute value of vector difference between this level and 3,000 feet above: Not Available

Information About Radiosonde:
- Launch Time: 22:05Z
- About Sonde: A descending radiosonde tracked automatically by satellite navigation with no solar or infrared correction.

Remarks Section...

Splash Location: 17.37N 52.2W
Splash Time: 22:19Z

Release Location: 17.35N 52.13W (View map)
Release Time: 22:04:59Z

Splash Location: 17.37N 52.2W (View map)
Splash Time: 22:19:35Z

Mean Boundary Level Wind (mean wind in the lowest 500 geopotential meters of the sounding):
- Wind Direction: 80° (from the E)
- Wind Speed: 29 knots (33 mph)

Deep Layer Mean Wind (average wind over the depth of the sounding):
- Wind Direction: 110° (from the ESE)
- Wind Speed: 11 knots (13 mph)
- Depth of Sounding: From 152mb to 1011mb

Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 159 gpm - 9 gpm (522 geo. feet - 30 geo. feet)
- Wind Direction: 80° (from the E)
- Wind Speed: 26 knots (30 mph)

Sounding Software Version: AEV 20801

Part B: Data For Significant Levels...

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point
1012mb (Surface) 27.6°C (81.7°F) 24.5°C (76.1°F)
939mb 22.0°C (71.6°F) 21.2°C (70.2°F)
850mb 18.0°C (64.4°F) 16.7°C (62.1°F)
762mb 13.6°C (56.5°F) 11.3°C (52.3°F)
730mb 12.0°C (53.6°F) Approximately 6°C (43°F)
673mb 7.8°C (46.0°F) Approximately 3°C (37°F)
661mb 7.6°C (45.7°F) Approximately -4°C (25°F)
648mb 6.4°C (43.5°F) Approximately 0°C (32°F)
620mb 4.2°C (39.6°F) Approximately -3°C (27°F)
592mb 1.8°C (35.2°F) -1.7°C (28.9°F)
581mb 1.2°C (34.2°F) Approximately -6°C (21°F)
561mb -0.5°C (31.1°F) -4.2°C (24.4°F)
527mb -2.5°C (27.5°F) -7.1°C (19.2°F)
507mb -4.9°C (23.2°F) -8.7°C (16.3°F)
497mb -5.7°C (21.7°F) Approximately -17°C (1°F)
482mb -7.1°C (19.2°F) Approximately -18°C (-0°F)
475mb -7.7°C (18.1°F) Approximately -34°C (-29°F)
456mb -10.1°C (13.8°F) Approximately -17°C (1°F)
437mb -11.7°C (10.9°F) Approximately -40°C (-40°F)
407mb -15.5°C (4.1°F) Approximately -42°C (-44°F)
399mb -16.5°C (2.3°F) Approximately -26°C (-15°F)
393mb -16.9°C (1.6°F) Approximately -42°C (-44°F)
388mb -17.5°C (0.5°F) Approximately -40°C (-40°F)
371mb -19.9°C (-3.8°F) Approximately -38°C (-36°F)
364mb -20.9°C (-5.6°F) Approximately -49°C (-56°F)
356mb -21.9°C (-7.4°F) Approximately -32°C (-26°F)
347mb -23.1°C (-9.6°F) Approximately -50°C (-58°F)
337mb -24.5°C (-12.1°F) Approximately -40°C (-40°F)
331mb -25.5°C (-13.9°F) Approximately -46°C (-51°F)
325mb -26.5°C (-15.7°F) Approximately -48°C (-54°F)
291mb -33.5°C (-28.3°F) -35.9°C (-32.6°F)
269mb -37.3°C (-35.1°F) Approximately -43°C (-45°F)
246mb -42.3°C (-44.1°F) Approximately -56°C (-69°F)
222mb -48.7°C (-55.7°F) Approximately -59°C (-74°F)
203mb -52.9°C (-63.2°F) Approximately -69°C (-92°F)
179mb -59.7°C (-75.5°F) Reading usually unavailable when air temperature is below -40°C (-40°F)
152mb -63.9°C (-83.0°F) -68.3°C (-90.9°F)

Significant Wind Levels...
Level Wind Direction Wind Speed
1012mb (Surface) 85° (from the E) 28 knots (32 mph)

1002mb 80° (from the E) 26 knots (30 mph)
990mb 85° (from the E) 31 knots (36 mph)
938mb 80° (from the E) 35 knots (40 mph)
899mb 95° (from the E) 32 knots (37 mph)
880mb 95° (from the E) 35 knots (40 mph)
850mb 95° (from the E) 32 knots (37 mph)
706mb 110° (from the ESE) 31 knots (36 mph)
601mb 100° (from the E) 32 knots (37 mph)
546mb 115° (from the ESE) 20 knots (23 mph)
487mb 70° (from the ENE) 9 knots (10 mph)
471mb 55° (from the NE) 11 knots (13 mph)
456mb 70° (from the ENE) 11 knots (13 mph)
418mb 60° (from the ENE) 11 knots (13 mph)
401mb 75° (from the ENE) 10 knots (12 mph)
385mb 65° (from the ENE) 10 knots (12 mph)
280mb 190° (from the S) 3 knots (3 mph)
251mb 210° (from the SSW) 10 knots (12 mph)
238mb 190° (from the S) 16 knots (18 mph)
224mb 190° (from the S) 15 knots (17 mph)
211mb 155° (from the SSE) 15 knots (17 mph)
190mb 180° (from the S) 23 knots (26 mph)
174mb 170° (from the S) 31 knots (36 mph)
170mb 200° (from the SSW) 22 knots (25 mph)
167mb 255° (from the WSW) 39 knots (45 mph)
162mb 285° (from the WNW) 98 knots (113 mph) but in the upper levels.

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LOL looks like the sonde still had some speed from being ejected from that plane...

98 kts at 162mb...
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1637. java162
did the models pick up this southerly movement during their runs? if not then i guess they can't be trusted at this point
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1636. jdjnola
Quoting TexasHurricane:


I would have to agree.


I would have to agree to agree.
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So everyone thinks that Bill will stay away from the gulf side?
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Quoting stormwatcherCI:
I grew up in Miamai so I had been through hurricnaes before but that was the first one my kids experienced and I thouroughly enjoyed letting them watch what was going on. Thank God it wasn't any closer.

which hurricanes have you been through?
Member Since: July 7, 2008 Posts: 0 Comments: 473
1632. Dakster
Quoting canesrule1:
So long story short me and all of SFLA are f***ed


I hope not!

BTW, the person that kept saying this was going to be a 0,0,0 year can shove it now... (Unfortunately)
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Hey Mobilegirl...whoever made that comment about why are people so worried about the BLOB in the gulf must not live on th gulf coast like we do....it's waaaaayyyyy too hot in the gulf right now...could sneak up on us...
Member Since: July 31, 2009 Posts: 0 Comments: 324
Just a quick reminder that the models now have the Gulfstreaam data to use and they will be far more accurate than they were a few days ago if the storms strenghten according to the forcasts.

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1629. jdjnola
Quoting Wariac:
I don't get why people are obsess with the blob near Florida when we have to real systems in the Atlantic and one of them nearing the islands.


Because as someone mentioned earlier, remember Humberto.
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Quoting Halon056:
Here's an interesting question. The low off of swfl obviously has the SST working for it, how's the shear? Could the conditions be right for "rapid intensification"?



Well first of all, I'll tell you what, the GOM SST's are HOT!
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Bill might earn a retired name i am afraid.
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even though Ana is much much smaller than Bill, Ana's TS force wind radius is almost triple the size of Bill's radius.
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Quoting Weather456:
Orca thanks


according to reccon, Ana is maintaining TS status


I read the dropsondes... two were not reporting winds.. only one close in is working.
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting Weather456:
Bill is getting ready to intensify



I would have to agree.
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Here's an interesting question. The low off of swfl obviously has the SST working for it, how's the shear? Could the conditions be right for "rapid intensification"?
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Quoting Weather456:
Bill is getting ready to intensified

yup, i think 50MPH at 11 could be possible
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1620. hahaguy
Quoting Weather456:
Bill is getting ready to intensified



Looking good.
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Bill keep diving a bit south, while Ana keep trucking west.
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Bill is getting ready to intensify

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Quoting Kmanwoodie:

Our little Cayman chapter is expanding. THanks for the comment on the kids. Two are mine and the others are cousins. My little trouble makers.
Always look for your comments on here during this time of year. I have been lurking since 2007/08. You are always very informative & seem to always know your stuff. I have a family vacation planned for Nassau this Tuesday. What's your advice?


Ana would be about 5 days away from Nassau at its present speed taking into account the fact that these systems do not travel in a straight line. As always this time of year if you plan to travel to a place that might be impacted by a storm have a plan for where you would go if it threatened that location. Bear in mind that it may prove difficult to get a flight out if there are mass evacuations from where you are and that you could get stranded there.

For now Ana does not look like a threat to Nassau but so much can change over time. If your tickets are paid for you will certainly have a very good idea by departure time around 6 pm Tuesday whether Nassau is at risk or not.
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Quoting WeatherMSK:
Well my early prediction is for an East Coast toward the Carolina's. I was thinking Florida but i think this may go further north but not out to sea.
it is too early in the game.
Member Since: July 7, 2008 Posts: 0 Comments: 473

Your picture is disturbing
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Quoting Funkadelic:
I remember StormW making a good point about Bill's potential track. He of course said that it is to far out to Really predict what the trough is going to do and everything. But he said Bill could feel a weakness and move WNW like models are thinking, but then th high could move back in and then steer Bill off to the west.

So a recurveature is certaintly not a given at this point in time.

And Anna right now if she keeps moving lke she has, will miss her next forcasted point to the north by a little.



Link
thats bring everything in focus
Member Since: July 7, 2008 Posts: 0 Comments: 473

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