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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You know you are going to catch it from people who don't understand the context of this. :)
For those interested in the origin. http://www.wnd.com/index.php?pageId=34378
atmoaggie, you'll thank me later for this LOL
What are you thinking? Thinking it will start to go more south or north?
OK folks, the above from Dr Master's header... It is a TYPO people..
the world is not coming to an end over that typo..
any of us here with any weather knowledge remembers Andrew and it was 1992.
If you do not see the innocent typo error and keep on harping on it..get a life.
Give Dr Master's a break please.
Isn't it suppose to go wnw and reach latitude 18n 66w by Monday?
What time do they come out?
saludos de ponce!
Future met - what storm is that? Ana or TD3? WOW!!
You may be sarcastic, but I already have a screen door to replace from a higher gust. Your melodramatic undertones aren't helping the situation.
Do I detect a note of sarcasm here? :) lol
I could actually hear the inflection.
Leave Dr. Masters Alone - ish link
Someone ban him. (Stormtop)
Very often in my years of watching storms, they often don't do what they were suppose to do.
But I got a question for you Super Mets here. What are those 2 1/2 boxes that are located jutting SSW from the storm (on the map) during it's mid course?
The casualties...oh the humanity!
No it's expect to stall their for the rest of your life!
LOL!
Back later. Replacing all my windows with permanent steel doors. (j/k)
hmmmmm, I have been kinda wondering about that too...
The ECMWF take it into the Caribbean
LOL
I highly doubt that its illegal. He's been around since the beginning and it adds a little humor. We all need that when a storm is headed in our general direction. At least he doesn't post non stop crap like some others on this board.
You should have secured it. What the other buffoon is trying spray us with is a situation where you would have to replace a bunker.
How do you know? It's not even off Africa yet.
That was hilarious. I brought all my lawn chairs in. My porch door not so lucky.
We better close our storm shutters or board our houses up.
CAN YOU BE A LITTLE MORE VAGUE?
I wanted to agree with that too, but didn't have enough specifics! LOL
Hopefully by neither, altough I do wish they come by either the north or south so as to get my surf on...
you know what? ponce IS ponce. in fact, anywhere BUT the metro area (and mayaguez) deserves to be proud. lived in the metro 25 years (all me life) and one year here, and the quality of life is much better (no traffic) (light and water almost never are out, metro its a weekly event)
so yeah, ponce IS ponce!
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