Ana and TD 3 take aim at the Lesser Antilles
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
Reader Comments
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Quoting clwstmchasr:
StormW may not technically be a met but he is #2 on my list behind Dr. Masters. I also very much resect the work of weather456 and scottsvb.
Adrian (hurricane23) and CCHSweatherman are very good too. Also, you can't forget our IKE, and StormJunkie. Lots of very respectable Wunderground mets on here :)
I agree with you. I just thought I'd name the top of the class.
Good evening!
Zoo, did you water the lawn yet??
In the context of his post, I think that is an accurate statement. Of course, that same arrogance he speaks of can be applied to all ages.
The ones that said bill was an instant fish because of one model run rofl.
the ECMWF also develops it
Exactly! StormW has been around the block quite a few times. He knows his stuff,he knows the seas(he's been there). Presently training mets have the newer skill sets. Take it all with a grain of salt. Personally I go with
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1. NHC first(mostly StormW follows their reasonings, which is a wise thing to do, imo)
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2. Dr. Masters
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3-4. The couple of trained mets who have gone off to higher waters and prefer to stay away from this zoo.
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3-4. Weather456
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2km Storm Relative IR Imagery with BD Enhancement Curve
Time of Latest Image: 20090815 2200 UTC
Looks like we have a bit of a worry with Bill.
Each time I look at the loop and his size, it comes home that he is only two days away (Sunday, Monday) then Tuesday and Bill in our area.
I am most horrified at his size, impressive looking monster.
We need to be prepared to get anything we do not have Monday am, if necessary.
I did some supply shopping this morning, food, batteries.
It would be nice if the GFS, as Futuremet notes, is right, but I doubt it.
Even though I am an amateur, I have seen some of these things pass and my humble opinion is that some of the islands are going to get it.
My gut tells me to be prepared.
We shall see.
Keep safe.
Textbook banding, might need to work on the North a little bit but it looks like very healthy outflow. Anti-Cyclone is helping out here, fanning out the system.
Haha - we are quacking around here!
Good to see you.
Ana IR Shortwave Loop
UZNT13 KWBC 160004
XXAA 66001 99167 70468 04166 99015 26630 07521 00129 25427 07524
92811 20817 09022 85541 18834 09019 70189 10661 10543 50590 06168
08017 40761 15963 09517 30972 29970 15524 25099 40761 14529 20247
53361 15510 15427 657// 15025 88999 77999
31313 09608 82332
61616 NOAA9 WX02A ANA OB 11
62626 SPL 1677N04687W 2347 MBL WND 08025 AEV 20801 DLM WND 11521
013145 WL150 07524 083 REL 1674N04678W 233242 SPG 1677N04686W 234
724 =
XXBB 66008 99167 70468 04166 00015 26630 11891 18605 22860 19224
33850 18834 44830 18860 55798 17662 66734 13666 77583 01329 88517
05358 99503 06171 11489 07557 22464 08764 33448 10761 44429 12567
55413 14960 66404 15764 77299 30170 88258 38764 99230 45156 11196
54362 22167 629// 33145 66537
21212 00015 07521 11009 08025 22957 08026 33880 09516 44850 09019
55790 10525 66672 10545 77562 10540 88527 11023 99502 08018 11491
09015 22467 06018 33431 08514 44409 07517 55392 10518 66359 13020
77319 13023 88301 15524 99264 15035 11232 13020 22208 15008 33185
18014 44171 14510 55166 15508 66160 13517
31313 09608 82332
61616 NOAA9 WX02A ANA OB 11
62626 SPL 1677N04687W 2347 MBL WND 08025 AEV 20801 DLM WND 11521
013145 WL150 07524 083 REL 1674N04678W 233242 SPG 1677N04686W 234
724 =
sure
LINK
Whats this? Is Bill happy? LOL!
If Bill doesn't make the WNW turn between 40-45W, then it might not go north of the islands. Tomorrow should be very interesting.....
Date: Near the closest hour of 0Z on the 16th day of the month
Highest Mandatory Level For Which Wind Was Reported: 150mb
Coordinates: 16.7N 46.8W (View map)
Location: 892 miles (1435 km) to the ENE (74°) from Bridgetown, Barbados.
Marsden Square: 041 (About)
Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1015mb (29.97 inHg) Sea Level (Surface) 26.6°C (79.9°F) 23.6°C (74.5°F) 75° (from the ENE) 21 knots (24 mph)
1000mb 129m (423 ft) 25.4°C (77.7°F) 22.7°C (72.9°F) 75° (from the ENE) 24 knots (28 mph)
925mb 811m (2,661 ft) 20.8°C (69.4°F) 19.1°C (66.4°F) 90° (from the E) 22 knots (25 mph)
850mb 1,541m (5,056 ft) 18.8°C (65.8°F) 15.4°C (59.7°F) 90° (from the E) 19 knots (22 mph)
700mb 3,189m (10,463 ft) 10.6°C (51.1°F) Approximately 0°C (32°F) 105° (from the ESE) 43 knots (49 mph)
500mb 5,900m (19,357 ft) -6.1°C (21.0°F) Approximately -24°C (-11°F) 80° (from the E) 17 knots (20 mph)
400mb 7,610m (24,967 ft) -15.9°C (3.4°F) Approximately -29°C (-20°F) 95° (from the E) 17 knots (20 mph)
300mb 9,720m (31,890 ft) -29.9°C (-21.8°F) Approximately -50°C (-58°F) 155° (from the SSE) 24 knots (28 mph)
250mb 10,990m (36,056 ft) -40.7°C (-41.3°F) Approximately -52°C (-62°F) 145° (from the SE) 29 knots (33 mph)
200mb 12,470m (40,912 ft) -53.3°C (-63.9°F) Approximately -64°C (-83°F) 155° (from the SSE) 10 knots (12 mph)
150mb 14,270m (46,818 ft) -65.7°C (-86.3°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 150° (from the SSE) 25 knots (29 mph)
Anyway, been following StormW for years and well aware of his credentials. He is 100% a MET with more personal experience than 99.8% of the qualified METS out there. Thank you for all that you do StormW!
not south but if it travels over the islands it could weaken significantly. If slides to the north, it will be over waters, and waters of 29 plus C. So the north slide would favor a more strengthening Ana, and could bring it to a 70 mph per the NHC. Most models dont really do anything with Ana, so intensity is a bit uncertain.
Quoting clwstmchasr:
StormW may not technically be a met but he is #2 on my list behind Dr. Masters. I also very much resect the work of weather456 and scottsvb.
Well, technically I am a met. Go to the AMS website...look at the Interperative Memorandum.
This part of it:
Sorry StormW! I was following the blog along and Iguess Drakeon had me convinced you were not a met. It seems a lot of people on this site don't like him.
I did say that you are #2 right behind Dr. M.
... with all the 'bruises' from past mistakes!!! 8-)
Lol!!!
If the models didnt forecast the shear, then what confidence do we have in the trough that they are predicting to be strong enough to pull "pre-bill" out to sea?
I'm not seeing an anti-cyclone with Bill. Link
Thanks for the thoughts. You're in Cayman, best wishes to you too.
yes he is happy
i think i give bill some cake
hurricane Marilyn 95'
Um... and Bill
And of course Bill...
and Oh hahaha.... Bill..
Ana Water Vapor
lol
Actually, you are right and I was wrong. I meant .2 N but after relooking at the latest coordinates it is .2S. I should have check coordinates than going by eye balling it..lol
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