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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It's all your fault!
the most use words for the few days will be... recurve abd the models will change
I cannot say. The models have the luxury of flipping back and forth as they please. I, however, don't have the patience to debate over whether or not the runs are valid. Best to wait until the system gets closer to the Lesser Antilles.
You're darn right I do. I want something to chase.
I just got back from a long vacation to visit family in Michigan, had a great time. Didn't have access to the WUnderground..
Ana, looks to be giving up, but she will probably make it through dust.
Bill, wish we will soon be callin Mr. Bill, is just pressin forward, and gettin it self lookin good. Models has this thing goin anywhere from the gulf to the east coast, and I think the gulf don't need another hurricane with the anniversary of Katrina coming up.
Claudette, well she is named yet, but like a meteorologist from da TWC said in a webcast, she could be right behind Bill. Why, look at this impressive vigorous wave comin off of africa.
Great now I can hear Phil say "Dirty Side" for the next 5 days...
Thank you I'm not alone with this thinking.
I agree with the statement as well.
Your local met hasn't a clue then or he has a crystal ball to determine that. No one wants a storm to hit them, I don't especially after Charley Frances Jeanne and Wilma. Right now the NHC has Bill right or just north of the Islands and Ana as a strong TS in the gulf. This will all change over time of course.
Yikes the dry air is clearing out, save the dry air to Ana's west. This is why I don't trust the models. Most of them killed off Ana, yet she's a TS and after tonight's Dmax... our last hope is shear or land. Even still, I'm not sure those are enough. She's like a Phoenix rising from the ashes, and we've even named her. Like a human, what doesn't kill her only makes her stronger...?
I doubt it!
sure...even though recent guidance are trending away from the southeast/eastcoast confidence in the long-term forecast is quite low.
Local met is an idiot then... WAAY to early to start telling people theres nothing to worry about
I think when he said "we" I think he just meant our area.
If you think Florida's in the clear your mistaken. Everything shifts massively, heck Ike was at one point forcasted to hit SFL as a Category 4/5 and Dean was going to go north of the Islands for quite a few advisorys.
WSVN is the most sensationalist news station in south florida! oh how i miss south florida...
No, we have more than one met...
Key West, Base Reflectivity 0.50 Degree Elevation Range 248 NMI
Wow! That's some monster Category 5.
Well back after my sons first football game and quoting myself...lol
It appears that the convection has covered the coc on Ana now. Lets see if she can hold it for a whole 24 hrs this time.
Been watching for a while now .... all you seem to do is cut on others ... heres a thought...why dont you go away ... that is unless your the blog police.
Oh im sorry, I thought you meant Florida as a whole. But he's wrong about Ana.
WS, coffeecrusader, jrweatherman, I'll tell you this if you think Florida is in the clear a week in a half out with a storm this southern in latitude your mistaken. The point is you should have been prepared regardless. I'm not wishcasting it to hit Florida, people that assume I am are greatly, greatly either paranoid or in obsessive denial. Right now the Islands are in a great threat from Bill and they need to watch it in the short term.
I also noticed that upper level low feature to the northwest of both of these systems. So, this would suggest a weakness in the strong Bermuda high.
I think Bill will feel this weakness and follow the path where more moisture and less resistance exists. Resulting in and more northwest direction?
Key West, Echo Tops Range 124 NMI
This is his warning, up to date info.
Ana is starting to cook up in the Atlantic. He predicts a landfall in the Miami area at Category 2 on around the 20th or 21st. It will then recurve and hit either Mobile or Tampa.
Bill, will become the monster of August, becoming a category 4 and hitting Charelston or Savannah on the 25th. It will be a Ghost of Hugo as he states.
One thing is certain, be prepared!!!
Join the tropics chat for one to track the storm and save lives!
...and what happens when Ana gets inthe Gulf?!
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