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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How about no one does?
There is not an 11 pm TWO, it is a 2 am TWO
so bill has the potential to move out of the cone of uncertainty then, since its continuing on a due west movement
I love you man
Bill is intensifying and is a possible threat down the road.
Land interaction is a big factor, the florida peninsula is right there.
Here we are under 30%
And it's a threat to me. I am worried focus will shift too much to 91L and people forget we at the antilles will get hammered =(. I don't think we in PR wll receive a direct impact but it won't do bad to check.
Continuing her waxing and waning trend, but do not write her off.
"Special outlooks may be issued as conditions warrant."
What about fluctuations in intensity, I noticed that most of the pm that the center was exposed, you think we can get more than what we're expecting?
No one has any idea about how the ridges will affect Ana, let alone Bill another few days out. Way too many variables out there...
I love when people try so hard! How could that possibly be for real. you could have studied english for 3 weeks and write better than that! I simply don't understand?????
MARK
26.1N/83.5W
There are watches for the leewards for Ana. So for now I'll keep my eye on Ana
ENSO chart shows it back to warm neutral conditions by February 2010. Looks likely a neutral with a possible cool bias for the 2010 season, like 2008.
South Florida StormWatch
has of right now all mode run most be thorn in the trash and we start all there worth less right now thorn them out the window
Maybe it is my eyes, but the latest image shows the COC way in front of the convection to her west..
Enlarge Image click here!
Yeah we are spared. Bill looks to be a monster storm, but the good thing is most of can just watch him go out to sea with no worries!!!!
System looks pathetic.
no its not your eyes, that little swirl of clouds you see there is ana's center.
WTNT32 KNHC 160246
TCPAT2
BULLETIN
TROPICAL STORM ANA ADVISORY NUMBER 16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
1100 PM AST SAT AUG 15 2009
...ANA STILL RACING WESTWARD WITH NO SIGNS OF STRENGTHENING...
AT 11 PM AST...0300 UTC...THE GOVERNMENT OF THE BRITISH VIRGIN
ISLANDS HAS ISSUED A TROPICAL STORM WATCH FOR THE BRITISH VIRGIN
ISLANDS WHICH INCLUDES MONTSERRAT... ANTIGUA...BARBUDA...
ST.KITTS...NEVIS AND ANGUILLA. AT 11 PM AST...0300 UTC...A
TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE U.S. VIRGIN ISLANDS. A
TROPICAL STORM WATCH REMAINS IN EFFECT FOR ST. MAARTEN...SABA...AND
ST. EUSTATIUS. A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM
CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 36
HOURS.
INTERESTS ELSEWHERE IN THE LEEWARD ISLANDS...AND PUERTO RICO SHOULD
MONITOR THE PROGRESS OF ANA. ADDITIONAL WATCHES AND WARNINGS MAY BE
REQUIRED FOR PORTIONS OF THESE AREAS TONIGHT AND SUNDAY.
FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA
OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR NATIONAL METEOROLOGICAL SERVICE.
AT 1100 PM AST...0300 UTC...THE CENTER OF TROPICAL STORM ANA WAS
LOCATED NEAR LATITUDE 14.4 NORTH...LONGITUDE 51.5 WEST OR ABOUT 710
MILES...1140 KM...EAST-SOUTHEAST OF THE LEEWARD ISLANDS.
ANA IS MOVING TOWARD THE WEST NEAR 17 MPH...28 KM/HR. A GRADUAL TURN
TO THE WEST-NORTHWEST AND AN INCREASE IN FORWARD SPEED IS EXPECTED
DURING THE NEXT TWO DAYS. ON THIS TRACK...THE CENTER OF ANA WILL BE
MOVING OVER THE LEEWARD ISLANDS ON MONDAY.
MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/HR...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24
HOURS.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110 KM
FROM THE CENTER.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB...29.65 INCHES.
...SUMMARY OF 1100 PM AST INFORMATION...
LOCATION...14.4N 51.5W
MAXIMUM SUSTAINED WINDS...40 MPH
PRESENT MOVEMENT...WEST OR 270 DEGREES AT 17 MPH
MINIMUM CENTRAL PRESSURE...1004 MB
AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 200 AM AST FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 500
AM AST.
$$
FORECASTER AVILA
Where is that???
Convection is starting to expand northwestward with Bill. He could be a 50mph storm at 11pm.
Viewing: 2701 - 2751
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