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 pretty much have to have a smartarsed remark for Drak everytime he posts, don't you? Why is that? It would be refreshing to everyone on the blog if you would stop.
I believe those are Herbert Boxes:
A Hebert box (pronounced AY-bear, also known as Hebert's box) is one of two regions of the tropical Atlantic Ocean that are useful as predictors of hurricanes that will strike South Florida, USA. They are named for former National Weather Service and National Hurricane Center forecaster Paul Hebert, who observed in the late 1970s that most strong hurricanes (characterized as those with winds exceeding 110 miles per hour (177 km/h)) which had struck South Florida since 1900 had also passed through one of these two small 335-mile-by-335-mile (517-km-by-517-km) square geographic regions.[1]
Examples include unnamed hurricanes in 1926, 1928, 1933, and 1935, as well as the major hurricanes Donna and Betsy, all of which came through a Hebert box. Collectively these storms killed more than 2,000 people in Florida. Conversely, storms such as the major hurricanes Floyd and Gert in 1999, which both were headed for Florida at one point, missed the Hebert boxes and turned away from Florida at the last minute.[1]
(from Wikipedia)
it seems dr. masters reasoning does not mean anything to certain people. to them, if he would not say anything would be perfect to them.
Has Ana hit 50 mph yet?
If you stopped posting and looked around the site you could find it.
You are putting steel doors on your windows????
Sounds intelligent!
My Cosmo tipped over, all over my pants no less.
Been here for so long and still doesn't know how to get to the ECWMF
.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.Link
hi honey, #1 youre gorgeous, #2 i dont know... i sure hope it doesnt amount to much
after watching patrap's radar image, it does look kinda worth watchin. keep those met eyes peeled
there was a nhc discussion i believe posted in latter pages about it. called for attention but low chance of it developing.
Miami, Base Reflectivity 0.50 Degree Elevation Range 248 NMI
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SAT AUG 15 2009
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM ANA...LOCATED ABOUT 920 MILES EAST OF THE LEEWARD ISLANDS...
AND ON NEWLY-DEVELOPED TROPICAL DEPRESSION THREE...LOCATED ABOUT
740 MILES WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.
1. THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE HAS BECOME
MORE CONCENTRATED TODAY OVER THE FLORIDA KEYS AND THE ADJACENT
SOUTHEASTERN GULF OF MEXICO. 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.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
PUBLIC ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER
WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2. FORECAST/ADVISORIES
ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER WTNT22 KNHC AND
UNDER AWIPS HEADER MIATCMAT2.
PUBLIC ADVISORIES ON TROPICAL DEPRESSION THREE ARE ISSUED UNDER WMO
HEADER WTNT33 KNHC AND UNDER AWIPS HEADER MIATCPAT3.
FORECAST/ADVISORIES ON TROPICAL DEPRESSION THREE ARE ISSUED UNDER
WMO HEADER WTNT23 KNHC AND UNDER AWIPS HEADER MIATCMAT3.
$$
FORECASTER BEVEN
Thank you .. I do believe most of us did.
we have so much going on out there to watch for the next few weeks.
Once your married, you can spend all day on the computer.
LOL...I must have been falling asleep when I wrote that. Lets try it again.
Wouldn't be surprised if the NHC keeps Ana at a generous 35 knots. The intensity forecast is gonna be real tough with wind shear, dry air, and Hispaniola.
I wish! *dreamy eyes*
NEXRAD Radar
Miami, Echo Tops Range 124 NMI
i keep remembering ivan. it was suppose to north and miss florida, then turn n again to go up over cuba and then the pennisula of florida and did not turn until it was south of the southern tip of cuba.
Very well put!
There is a possibility, but for now there are not any low pressures near it.
Ouch. That is pretty funny. I guess we are all a bunch of nerds.
Right. td-3. Talked about 90L so much since the models started sending to us in SE LA, changing the name has been like changing one of kids' names. And RAMMB didn't help by having the same problem I am.
Oh crap, sorry guys/gals, its that reality thing agan.
totally ignored. lol
well, back to my soup
You can educate yourself by reading a NHC TWO. "Surface pressures remain high in the area." Boom...now I know you need low surface pressures for a cyclone to form.
Viewing: 801 - 851
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