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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I went down to help clean up after Andrew. It looked like someone dropped an atomic bomb on Naranja, Cutler Bay and Homestead. I told myself then that I would never see anything like that again in my life.
Don't forget PE
Seem's to def be a surface reflection Forming there,Sliding WNW
I agree - I was right in the Lion's mouth so to speak (the north eye wall of Andrew) huddled in the bathroom with my husband - it was terrifying!! Needless to say the only thing I had left after the storm were the clothes on my back.
I don't know about tomorrow, but there is a possibility during the next 48 hours or so.
NHC says it's moving NW. That would put it coming in around Mobile/Pensacola.
Quoting tropicaltank:
Get ready for explosive development in the gulf.
WISHCASTER LISTEN TO THE NHC
PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.
um no wishcaster here..look for yourself is all i can say...the NHC isn't always perfect...
True, you cant call someone a wishcaster, he is just saying what appears to be occuring.
Quoting Bailey1777:
Any chance the blob in the GOM gets far enough West to give us some precip in Houston?
NHC says it's moving NW. That would put it coming in around Mobile/Pensacola.
lol..great let me get my red carpet out..
its a small low, it can explode quickly, CMC was poiting to that earlier today, but it can also fall apart quickly.
I've been wanting to write this here now for a while but haven't, mainly because some people really hate hurricanes - and they have all the right in the world to do so.
15 days of no power is equal to something very extraordinary happening. Hurricanes do have this tendency to bring people together like few things can, on a regular basis, and dare I say so, not on a terribly catastrophic level depending on where you live and what the conditions are. I've been thru Hugo, Georges, and countless other hurricanes, tropical storms, depressions (personal and tropical) and always marvel at those times where life totally changes, if for a moment, maybe a couple of days, a week, and you reconnect with neighbors. Maybe even meet people you lived alongside and didn't even know. Helped with any debris on the road, with a neighbor's house, or even with a total stranger, maybe even putting your life on the line.
Adrenalin junkie? Maybe. I love these systems - there's no doubt about that. I respect them, though, and live in solid cement houses, in places where the ground is not shifting underneath me, and currents aren't gonna carry me away. In other words, 15 days of no power? Bring it on!
Sure hope the blob doesn't have any surprises. I can remember going to bed with a weak Cat 1 and waking up to a strong Cat 2 (Opal in 1995)
NHC will shift the track further south on Ana. HWRF has it into Cuba and GFDL has it going into the Caribbean.
??????
It's thundering here now in the panhandle.
More rain.
Well that is debatable. It depends on how fast it moves across the GOM and what track it takes.
I mentoned in an earlier post that a TD or weak TS might be what the doctor ordered to take the edge off some of these incredible GOM SST's. Your thoughts?
Quoting IKE:
NHC says it's moving NW. That would put it coming in around Mobile/Pensacola.
Sure hope the blob doesn't have any surprises. I can remember going to bed with a weak Cat 1 and waking up to a strong Cat 2 (Opal in 1995)
yep...remember that...everyone freaked cause of Erin a month before...
492. sporteguy03 2:05 PM EDT on August 15, 2009
and Ike.. thanks for the help, I appreciate it!
http://wavcis.csi.lsu.edu/forecasts/forecasts.asp?modelspec=currents" target="_blank">GOM 60 Hour Surface Current Forecast Model,Loop Current and Eddy's
Yes.wrong look up hurricane alicia
That's bad. Sadly, some people don't have the means to construct or move into solid, anti-hurricane settlements. Then again, there's something that my mother told me once when people kept rebuilding in tornado alley: "Why don't they just move?"
Well, I know moving ain't easy, and life sure gets complicated. But if I were these people, I would be sure to erect whatever I was to erect in a very hurricane - proof way from then on.
15/1745 UTC 11.3N 34.4W T2.5/2.5 03L -- Atlantic
15/1745 UTC 14.4N 49.2W T1.5/2.5 ANA -- Atlantic
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