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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Updated: 2 sec ago
79.8 °F
Clear
Humidity: 88%
Dew Point: 76 °F
Wind: 6.0 mphfrom the SE
Wind Gust: 18.0 mph
Pressure: 30.05 in (Steady)
i think ana is scary because now it could slide into middle gulf...yikes
Bill east coast disaster movie potential
Also, with Humberto, pressures were already low over the western gulf before the storm began to develop, and an eye like feature was noticed when Humberto was a 45 mph tropical storm.
TD4 will be nothing like Humberto. Humberto's pressure was at 986 mb right before landfall, while TD4's pressure is supposedly 1011 mb.
Direction change or wobble wobble:
Link
The models show enough structure to regenerate when in the GOM. Expect at least a strong tropical storm. She might get stronger though since it would pass over waters with the highest energy in the gulf. Ana is a fighter and I would worry if she remains intact and gets in there.
Was in the Keys yesterday in Islamorada. There were some good gusts in this overblown thunderstorm as some have refered to it but overall it was a rainmaker. Today you're going to need sunscreen or a good hat for your kayaking. It's a bright one outside. Good luck on the flats.
TD4 is embedded in a area of high pressure, higher than normal, thats why the pressure is so high for TD4. Dr. Lyons said Pre-Ana and pre-Bill would dissipate and yesterday only briefly mentioned pre-TD4 but as you would expect didn't think much of it.
I also see the track she is so far taking, but any jog to the N would put it closer to FL, right?
The UKMET has a pretty good handle on Ana, why not Bill? There is no way that whatever is left of Ana will go over Hispaniola when it is going 20 mph due west.
The UKMET is also the southern outlier with Bill too.
The NHC track will yet again shift further up and right in an hour.
I think the east coast and Bermuda needs to watch Bill closely. If Bill is a major hurricane expect 1-10 deaths from Florida to North Carolina due to rough waves.
NOUS42 KNHC 161345
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0945 AM EDT SUN 16 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 17/1100Z TO 18/1100Z AUGUST 2009
TCPOD NUMBER.....09-080
I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM ANA
FLIGHT ONE -- TEAL 72
A. 17/1800Z,18/0000Z
B. AFXXX 0302A ANA
C. 17/1600Z
D. 16.8N 64.6W
E. 17/1700Z TO 18/0000Z
F. SFC TO 10,000 FT
FLIGHT TWO -- TEAL 73
A. 18/0600Z,1200Z
B. AFXXX 0402A ANA
C. 18/0330Z
D. 17.6N 68.2W
E. 18/0500Z TO 18/1200Z
F. SFC TO 10,000 FT
2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES IF
SYSTEM REMAINS A THREAT.
3. REMARKS: A RESOURCES PERMITTING TASKING ON TROPICAL
DEPRESSION 2 IN THE GULF OF MEXICO WILL BE LAUNCHED
TODAY AT 16/1500Z.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
JWP
I think they mean TD4 in the Gulf
Not sure what you mean by that, but the majority of people don't go anymore, especially outside of the "Bible belt". Anyway, I'm not going to discuss it further.
Thats a real big "IF">
Ya want a cargo ship to drop you into Bill's centre, for REAL waves?
;-)
Refer to post 4766. :)
Which puts him much south of what the satellite images make you believe.
I agree, with one major caveat. I think the models are really overdoing the intensity of Bill. Dry air is in the core of Bill right now, as shown by the latest imagery. Also, many of these same models a couple days ago had Bill approaching hurricane strength at this time, but that simply has not occurred.
So, even though all indications are that Bill will turn out to sea well in advance of any land mass, I would like to see more strengthening before that is an absolute certainty. JMHO.
Thanks I saw that post after I posted.
Correct and contrary to the thoughts of some here "Bill" is still moving due west its just the expansion of this storm giving the illusion of a WNW movement, just my opinion of course.
Her environment is starting to moisten up.
can't make out a closed low on Ana, maybe semi closed but thats it, jmo
LOL. Thanks.
Reflector site for those at work, which includes
Weather456, daily update.
ANA
Bill
TD4
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