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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go close up of visible on Ana.
Thoughts
Truth.
Link
The blog was uploaded like, an hour ago? Somethin like that... Pretty much a good update, considering these things are days from land
You cannot call PR spared at this point, that is misinformation and there has been no considerable movement N by Ana in the last 5 hours.
NATIONAL WEATHER SERVICE KEY WEST FL
203 PM EDT SAT AUG 15 2009
.DISCUSSION...
.CURRENTLY...
THE NORTHERN EXTENT OF A WESTWARD MOVING TROPICAL WAVE IS TRAVERSING
THE KEYS AND COASTAL WATERS. THE AXIS OF THE WAVE APPEARS TO BE
MOVING THROUGH THE LOWER KEYS AND THE FLORIDA STRAITS SOUTH OF THE
LOWER KEYS...WITH A BROAD CIRCULATION FROM AROUND 850 TO 700MB STILL
NOTICEABLE ON KEY WEST RADAR IN THE GENERAL VICINITY OF THE LOWER
KEYS. A SHEAR ZONE ALONG THE AXIS HAS BEEN EVIDENT ON KBYX RADAR
THROUGH THE MORNING...WITH NEAR SURFACE SOUTHWESTERLY WINDS OPPOSING
SOUTHEASTERLY WINDS. LOOKING AT BOTH THE KBYX AND KAMX RADARS...A
NORTHEASTWARD PROPAGATING WIND MAXIMUM FROM AROUND 2KFT TO 5KFT
SEEMS TO BE MOVING ALONG THE SHEAR LINE...WHICH MAY HAVE HELPED
INITIATE SOME OF THE STRONGER CELLS. THIS SHEAR ZONE HAS FORCED
SEVERAL VERY STRONG CELLS FROM 15 TO 40 MILES SOUTH OF THE LOWER
KEYS...INCLUDING AT LEAST THREE RELATIVELY DEEP MESOCYCLONES...
BASICALLY IN THE SAME GENERAL AREA...ONE OF WHICH TRIGGERED A MESO
ALERT. THE MESOS WERE FAIRLY SHORT LIVED...LASTING LESS THAT ONE HALF
HOUR. ALL OF THESE MESOCYCLONES WERE PRODUCING IMPRESSIVE
UPDRAFTS...WITH TOPS EXCEEDING 55KFT ABOVE THEM. THE SHEAR ZONE HAS
BEEN ALMOST STATIONARY FOR THE PAST SEVERAL HOURS...THUS THE
STRONGEST CELLS HAVE THANKFULLY REMAINED SOUTH OF THE LOWER KEYS.
EVEN WITH THE WORST SOUTH OF THE KEYS...AREAS ALONG THE LOWER KEYS
HAVE EXPERIENCED HEAVY RAIN WITHIN A RELATIVELY SHORT PERIOD OF TIME.
A SPOTTER ON CUDJOE KEY CALLED IN WITH 2 INCHES OF RAIN SINCE THE
BEGINNING OF THE EVENT EARLIER THIS MORNING. AN OFF DUTY NWS EMPLOYEE
ON BIG COPPITT KEY REPORTED ABOUT AN INCH OF STANDING WATER ON THE
LOWEST FLOOR OF HIS HOUSE...THE ACCUMULATION OF WATER POSSIBLY AIDED
BY 30MPH WINDS WHICH ACCOMPANIED THE HEAVER STORMS THAT TRAVERSED THE
LOWER KEYS.
.SHORT TERM...
THIS EVENING...AS STATED ABOVE...THE WORST OF THE CONVECTION HAS
REMAINED OFFSHORE. HOWEVER...THAT MAY NOT BE THE CASE THROUGH THE
REMAINDER OF THE PASSAGE OF THE TROPICAL WAVE...AND IT IS WITHIN
POSSIBLE...BUT NOT PROBABLE...THAT THE LOWER KEYS GET CLIPPED BY ONE
OF THESE STRONGER CELLS. THE POSITIVE NEWS IS THAT THE WAVE HAS BEEN
WELL BEHAVED...VERY SLOWLY MOVING TOWARDS THE WEST AT NEAR 10 KNOTS.
IF THIS REMAINS THE CASE THE AXIS OF THE WAVE SHOULD BE WEST OF THE
LOWER KEYS BY AROUND 22Z...AND WITH IT THE STRONGER CELLS ALONG THE
SHEAR ZONE. THE PRECIPITATION AND CLOUD SHIELD ASSOCIATED WITH THE
WAVE CURRENTLY EXTEND EASTWARD AS FAR AS KEY LARGO AND POINTS
SOUTH...SO SHOWERS AND OCCASIONAL THUNDERSTORMS WILL PERSIST UNTIL
AROUND 06Z UNTIL EVERYTHING CLEARS THE KEYS.
.MARINE...
STRONG STORMS WILL PERSIST OVER THE FLORIDA KEYS COASTAL WATERS
THROUGH THIS EVENING...WITH CONDITIONS SLOWLY IMPROVING AFTER
MIDNIGHT. IT WOULD NOT BE ADVISABLE TO VENTURE OUT UNTIL THE TROPICAL
WAVE HAS PASSED THROUGH THE AREA AND THE SHOWER AND THUNDERSTORM
ACTIVITY HAS CEASED. TOMORROW...EXPECT MAINLY EAST WINDS NEAR 15
KNOTS AND GUSTY.
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.
thelmores is thinking another tropical low could form in the EATL.....
Hey ya'll look at that! Me and the NHC agree! LOL
seems like people are NOT in the beach area :D
I am always an optimist =P
If Ana does not recover soon from her current condition it could dissipate before the Islands. We have to wait and see about that. TD3 is a more serious threat IMO. Further S and with a larger circulation it can fight off dry air better. It is also S of the shear that has undercut Ana's weak convection.
Stay tuned for that one as well. A wait and see game for now.
there is some convection firing now that the sun is starting to set over there near africa lol
Is is really necessary to be so rude?
Am I missing something. Can you name something in the future (August 17th, 2009) and Andrew isn't a name on the list this year?
word cj5. you go girl (or dude)
isnt cj5 a jeep?
syllogism
Hi Catfish, I am from SE TX too, you may appreciate what I am about to point out. I watch this site alot, its kinda like a hobby for a few months out of the year. Over the years I have learned how to kinda read the models. Just last year on my way home from evacuating from Gustav, a prominent local Met stated a certain storm would never make it to the GOM, and guess what it was IKE. I think that the Met is highly trustworthy and would follow his advice any day. When we are dealing with so many atmospheric variables it is just way too difficult to sat weather a person is "safe" from a storm.
My wife still tears up today sometimes. I grab my boards and hit the water when a swell kicks up. Our house was only house in our neighborhood that did not flood during Ivan here in Pensacola on the sound.
There were a bunch of tractor trailers parked that became missles in Biloxi. We kept a copy of the insurance policy and got back in the next day and unfortunately seeing bodies and the stench stays with you. Stuff can be replaced.
I have to disagree.. I expect it to be near 15 N by 5 or just on it, it seems its sustaining a somewhat WNW movement
Well, Ana is looking less dynamic, but will likely pick up again.
TD3 looks like it'll brush the north of the Antilles as a cat 2 by Wednesday.
I realize Ana is undergoing shear, but her circulation is VERY evident. If the shear weakens I see decent intensification in her future.
Amen! You are 100 percent correct.
I'll say it again... TD3/Bill will take time to strenghten...for God's sake it's not even a TS yet...
Yep and he was classy enough to eat crow.
Yea, I guess that's why it is so much more organized now.
True. Usually most of the storms/hurricanes are an eventual threat to the US, unless they recurve out to sea, unless it does a Dean, Emily, or Felix, what about the other little Islands or poor countries that take a real good pounding before it reaches the US. With TD#3 I see track, similar to , Dean 07, Emily05,Gilbert88,Felix07, Charley04 or Ivan04, jmo.
I understand.... I'm sorry to here about your loses. I know they say this is more of an east coast year, but that doesn't mean we won't get anything. Anything suspicious looking in the GOM bears watching....
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