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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Work on your syntax I see 2 errors.
Well the 12Z UKMET had Bill cruising through the Caribbean and just north of us (at about 14N). The UKMET is a reliable models and it handles upper level features well
But I don't think this will go as far south as Ivan did, but in terms of intensity, very possible....
Ana TD once again? Some convective burst this evening closer to its llc d-max could be interesting.
It is an Invest.
Sorry, I do not think that is in much good taste.
Long Range Tampa Bay Radar
The new invest
Hi Baje and Stormdude. I guess our met people may mention something on Monday if we are lucky. Does our multi million dollar radar work yet?
Link?
My apologies if I offended you. For many of us on here we watch the storms, but hope for them to turn and go away and not actually bother anyone. I meant no disrespect with my comment.
(note, we already had 91L, some reason the Navy made 91L ex-TD2)
It's working, but you can't access it from the internet yet....
Invest
Hi Barbados, the Met mentioned Bill this evening, I think also that would be in the vicinity in a few days. Not too much else on expectations.
I have not a clue about the radar, I am just an amateur, with no official connections.
But, keep your eye on Bill.
Hopefully, the models are right and he will go to our North, but we need to watch closely.
I will check again first thing tomorrow morning.
Take care.
Yep, that is basic stuff I usually do too, as should everyone but like most on here I posted before I actually knew the facts..lol
yo estoy READY pa surfear! woooooooooooooo
y la planta electrica coming soon!
manana brego el problema del agua... ya hice comprita en walmart... increible como la gente pichea a estas cosas y se pone a comprar popcorn, celulares jeje
What are we looking at Pat?
Link
Hey Storm,
I'm fairly new to the site and always look forward to your post and read them regularly. Thanks for all the updates!!
Okay, sorry too. I guess I was over-sensitive, just was a fan of Carradine, the Actor, so reacted thusly when I saw the frame and comment.
Sometimes writing comes across different than intent, so reader reacts differently to intent.
Take care.
Latest CIMSS shows an anticyclone forming, low shear, warm SSTs, closed low (west winds reported from bouys)
Not much time for this to organize, but the panhandle might want to keep an eye on it. Definitely going to be a rainmaker for FL, but it's moving quickly so flooding shouldn't be an issue.
we have 91L
what a day
i am not yet fully prepared, but doing what i can
jeje xD
asi somos =P
The wave that just exited africa.
Should be interesting to see how the Invest,GOM Screamer handles the Loop edy and DMAX.
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