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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Should be interesting to see how the Invest,GOM Screamer handles the Loop edy and DMAX.
I totally agree with you.
Word usage is in regards diction while syntax is in regards to sentence structure.
456...would really like your opinion of this invest. I looked at the latest radar loops and it looks impressive and to have a swirl. are you surprised by the markings as an invest this early and could this be a TD? guess it will run out of time before becoming anything significant, but the temps in the GOMEX are so warm right now. thanks in advance
we might also have 92L soon with the African wave...
we on the blog were up to DATE on this one right this afternoon. I'm very proud of you guys!
sadly my F5 session will end soon, but tomorrow will come full force.
I am actually a big fan too, my husband and I have watched the movies more times than I can count and I did not mean any disrespect in that manner.
I am mostly just a lurker (I really do not know much about weather other than what I have learned here the last year)
My apologies for the bad joke.
Returning to lurking....
456 am looking for word too what the mode runs say about 91L
More than warm HOT! 90-95 degrees for SST's. It will probably become a weak TS Claudette before it makes landfall.
I am not worried about the moisture out of the invest that is sitting over me right now...it really hasn't rained all that much considering what we get in any typical rainy season thunderstorm (I am in Cape Coral) BUT I am worried about already being wet from this, our rainy season pattern then getting a potential one-two punch from Ana and Bill. That may not happen, but if it does, the grounds may not be able to handle it.
look at the post before yours. Forgive me but I will get back to you with where it is going. I have not been paying much attention but noticing something may try to get going.
Just look at the dynamic models
P.S. Hi Taz
At this rate we may use-up all the Atlantic floaters.
yes bill looks good there
A 'TROLL' is the universal internet language for someone coming onto a blog purely to make trouble, disrupt the blog.
Sometimes we may misinterpret intent and then think a person is a troll, but be mistaken.
Generally, it is fairly clear after a while, whether the person is merely being disruptive.
Yeah, this one kind of came out of nowhere.
some regulars
I was amazed how it tried over the spine of Cuba.
FL could very well be quite soggy in a couple weeks.
What was that crazy lil storm that rapidly intensified at the beginning of season, was it last year or 2007 that hit SETX? Anyone remember off the top of their head. I suppose I could look it up. Not at home though so my bookmarks aren't available.
crap
The way you use your commas. When and when not to.
i think 91L will make land fall somm where in TX
Taz, it's heading somewhere between the Western FL Panhandle and New Orleans.
.. if the misinformation is going to be the agenda on Monday
Link
I figured it might get an invest.
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