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 have been coming here for years..and at times I sense stupidity.. but I don't say it :)
Some models say he will.
Thanks for the info..
I think the shear will keep her at bay too..
Awesome on the avatar I miss the great days of the old time of rock and roll..
Today stuff is just crap and repetitive imho..
looks nice, td4 by morning?
done
CONVECTION IS GROWING RAPIDLY AND IS SURROUNDING THE CENTER, KEEPING A W-WSW MOTION.
the models are still pulling it to be a fish storm but.... like Ike... anything can happen.... I Ike was not good I was without light for a week.
Thanks!!!!!
The Terminator just called, he wants his hat and glasses back..Jk
YES!
get some help
CONVECTION IS GROWING RAPIDLY AND IS SURROUNDING THE CENTER, KEEPING A W-WSW MOTION.
notice how they are moving it WNW at this point, and its still moving south of due west
Great post!
ALL CAPS AND BOLD MAKES YOUR SMARTER
The UKMET has been so far out to lunch in since 2005 it's laughable.
http://wind.mit.edu/~emanuel/storm.html
http://www.ssd.noaa.gov/PS/TROP/float3.html
Its too far out to know.
The UKMET hasn't even initialized properly with either storm
No that was not my intention, just had problems with the internet and the post appeared twice. Regarding the bold and caps i did it so that the text could appear without being overwhelmed by the image. Sorry if it bothered you, it's been a long time since my last post.
:D
Hey Fire! Glad to see you. I am looking for the same. That one has my interest right now.
Watching the east coast closely.
Hey maybe we're going to catch up with the Pacific, yet.
HI! Haven't heard from you in a while. How are you?
91L is deepening. Radar shows nice LLC and even possible banding features. Not much time for strengthening, obviously...but I'm calling TD04 by 5am.
Right now I believe the UKMET track
Tropical Storm ANA Forecast Discussion
WTNT42 KNHC 160247
TCDAT2
TROPICAL STORM ANA DISCUSSION NUMBER 16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
1100 PM AST SAT AUG 15 2009
THE CONVECTION NEAR THE CENTER OF ANA HAS BEEN PULSATING AND AFTER AN INCREASE FOR A FEW HOURS...THE LOW LEVEL CENTER HAS BECOME EXPOSED AGAIN. THIS MEANS ANNA IS NOT STRENGTHENING AND THE INITIAL INTENSITY IS KEPT AT 35 KNOTS. A NOAA JET FLEW AGAIN TONIGHT AND ONE OF THE DROPS NEAR THE CENTER MEASURED A SURFACE PRESSURE OF 1004 MB WHICH WAS USED FOR THIS ADVISORY. THE SHEAR IS NOT VERY STRONG AS DIAGNOSED BY THE SHIPS MODELS BUT THE LOW-LEVEL CENTER OF ANA IS SIMPLY MOVING TOO FAST. THIS RAPID MOTION IS PROBABLY NOT TOO CONDUCIVE FOR INTENSIFICATION. IN FACT...THE ONLY DYNAMICAL MODELS THAT KEEP ANA ARE THE UK AND THE NOGAPS. THE REST OF THEM WEAKEN ANA TO A TROPICAL WAVE. I AM TEMPTED TO SHOW WEAKENING BUT FOR NOW...I AM GOING TO FOLLOW THE PREVIOUS FORECAST AND SHIPS MODEL GUIDANCE. THE OFFICIAL FORECAST SHOWS SLOW STRENGTHENING THROUGH 48 HOURS FOLLOWED BY WEAKENING AS THE CYCLONE INTERACTS WITH HISPANIOLA AND CUBA.
THE INITIAL MOTION IS 270/15. ANA IS EMBEDDED WITHIN STRONG AND PERSISTENT TRADE WINDS AND ONLY A SMALL TURN TO THE WEST-NORTHWEST WITH AN INCREASE IN FORWARD SPEED IS ANTICIPATED. THE OFFICIAL FORECAST IS A LITTLE BIT SLOWER THAN MOST OF THE GUIDANCE BUT IS WELL INSIDE THE ENVELOPE THROUGH 48 HOURS. THEREAFTER...SOME MODELS KEEP A WEAKER ANA SOUTH OF CUBA AND OTHERS BRING THE CYCLONE OVER
CUBA AND INTO THE GULF OF MEXICO. THE OFFICIAL TRACK FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND FOLLOWS THE NORTHERNMOST GROUP
OF MODELS.
agreed
I hope so. But don't turn your back on it. From a Humberto "survivor" lol.
alllllll right. sassy pants.
You need to check the AB high in about four days once we have a core system that is feeling the mid to upper levels of the atmosphere and then check the steering flow in said levels.
Viewing: 2901 - 2951
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