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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good evenin to YOU, darlin... :D
bill looking mighty intense tonight.
Ana doing it's best dmax impersonation. still got that core chuggin along... and still 14.4n... raises more concern for me.
ATLANTIC REQUIREMENTS
1. TROPICAL STORM ANA
FLIGHT ONE -- TEAL 70
A. 16/1800Z,17/0000Z
B. AFXXX 0102A ANA
C. 16/1530Z
D. 15.6N 56.3W
E. 16/1700Z TO 17/0000Z
F. SFC TO 10,000 FT
FLIGHT TWO -- TEAL 71
A. 17/0600Z,17/1200Z
B. AFXXX 0202A ANA
C. 17/0330Z
D. 16.7N 60.0W
E. 17/0500Z TO 17/1200Z
F. SFC TO 10,000 FT
2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES.
A G-IV SURVEILLANCE MISSION IS PLANNED FOR 18/0000Z
WITH TAKEOFF AT 17/1730Z. A FOLLOW-ON G-IV MISSION
IS POSSIBLE FOR 18/1200Z WITH TAKEOFF AT 18/0530Z.
3. REMARK: NOAA43 AND THE G-IV WILL FLY FOUR SUCCESSIVE
RESEARCH MISSIONS INTO AND AROUND ANA DEPARTING FROM
TBPB AT 15/2000Z, 16/0800Z, 16/2000Z, AND 17/0800Z.
Excellent..and well said. I am sure someone will give you grief, however.
quickscat's been missing ana for a while now, huh?
the memories...
that would be kinda bad xD
I seriously hope it goes further north than Marilyn
Lmao!!!
456 if it keeps doing that then there no way that bill will go out too sea then right???
The only thing I can see that is hopeful is the dry air to the immediate North of Barbados, that may impede A BIT.
But, that seems to be fast diminishing, unfortunately.
I know that the models have very often been right, but can we really say that they have previously initialised 'low latitude' storms well? I have a suspicion not.
We shall see.
Could this be another Ivan?
Hey Storm! You're one of the bestest mets on here :o) I appreciate all your updates. You are the only blogger I read regularly!
AL 03 2009081600 BEST 0 112N 359W 35 1004 TS
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 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 735 MILES EAST-SOUTHEAST OF THE LEEWARD
ISLANDS...AND ON TROPICAL STORM BILL...LOCATED ABOUT 820 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS.
1. A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS OVER THE SOUTHEASTERN
GULF OF MEXICO IS PRIMARILY ASSOCIATED WITH A TROPICAL WAVE
INTERACTING WITH A MID- TO UPPER-LEVEL TROUGH. THIS ACTIVITY HAS
BECOME A LITTLE MORE CONCENTRATED OVER THE SOUTHEASTERN GULF OF
MEXICO WHERE SURFACE PRESSURES ARE BEGINNING TO FALL. THERE ARE NO
SIGNS OF A SURFACE CIRCULATION AT THIS TIME AND ANY ADDITIONAL
DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR. THIS SYSTEM SHOULD
MOVES TOWARD THE NORTHWEST OVER THE EASTERN GULF OF MEXICO ON
SUNDAY. 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.
Florida's still VERY much in the threat.
The models had the system in the Caribbean yesterday, but may I add only the ECMWF (which underestimates the speed of Bill and as jeff Masters stated the position is to far north) and the GFS take it out to sea, GFDL, HWRF, CMC, NOGAPS, arent on that boat.
Also its interesting to note for those who read Jeff's post how Bill consolidated farther south than expected made all those that indicated a more northen movement inaccurate.
15/2345 UTC 11.4N 35.2W T2.5/2.5 BILL
15/2345 UTC 14.5N 50.8W T2.0/2.0 ANA
still a little difficult for me to say, but if bill is expected to go out sea, the storm would have to swerve nw and continue. The storm is approaching the critical 40-45W point.
Besides, I would think being a Master Chief makes you that much MORE.... Just my two cents.
And yes, Dr. Masters is very good as well as the NHC forecasters, this isn't meant to take anything away from them AT ALL. Just that StormW has been able to put together a good forecast without waiting for them to release theirs!
I do enjoy the bantering back and forth on this blog and the weather discussion that you just don't get on the NHC site. Plus you have to wait at least 3 hours to get anything additional!
Agree 100%
I thin eye is still exposed in the lower west quadrant. Eye seems to be going pretty steady and remaining exposed. Convection giving it an appearance of Northern jog.
Dvoraks show her strengthening over the last 4 hours.
Looks like the area around the Keys may be a invest soon.
Looks to be a blowup of convection thats deceiving, not a real jog.
DATE/TIME LAT LON CLASSIFICATION STORM
15/2345 UTC 11.4N 35.2W T2.5/2.5 BILL -- Atlantic
15/2345 UTC 14.5N 50.8W T2.0/2.0 ANA -- Atlantic
15/2345 UTC 25.7N 82.9W T1.0/1.0 INVEST -- Atlantic
My eye is untrained, but on the loop, you can see a small "eye" right over the forecast point, then it disappears. I am not sure that it did a NW jog as much as there was a burst in convection while the defined "eye" retreated.
OMG!! Where's weatherstudent? What did you do with him? A very professional post. I almost had to pull out a dictionary too!
ok
Looking forward to the excellent discussion on this blog!
Looks like we have something in the gulf as well.
It has been made an INVEST
http://www.nhc.noaa.gov/satellite.shtml
looks like we have other INVEST
Work on your syntax I see 2 errors.
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