Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 4:17 PM GMT on August 15, 2009

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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

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Puerto Rico now under a Tropical Storm watch.
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000
WTNT24 KNHC 160858
TCMAT4
TROPICAL DEPRESSION FOUR FORECAST/ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042009
0900 UTC SUN AUG 16 2009

AT 5 AM EDT...0900 UTC...A TROPICAL STORM WARNING HAS BEEN ISSUED
FROM THE ALABAMA/FLORIDA BORDER EASTWARD TO THE SUWANNEE RIVER
FLORIDA. A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM
CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 24
HOURS.

TROPICAL DEPRESSION CENTER LOCATED NEAR 27.7N 83.9W AT 16/0900Z
POSITION ACCURATE WITHIN 20 NM

PRESENT MOVEMENT TOWARD THE NORTH-NORTHWEST OR 330 DEGREES AT 14 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1011 MB
MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 27.7N 83.9W AT 16/0900Z
AT 16/0600Z CENTER WAS LOCATED NEAR 27.0N 83.5W

FORECAST VALID 16/1800Z 29.2N 85.0W
MAX WIND 45 KT...GUSTS 55 KT.
34 KT... 45NE 45SE 0SW 30NW.

FORECAST VALID 17/0600Z 31.0N 86.7W...INLAND
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 0NE 60SE 0SW 0NW.

FORECAST VALID 17/1800Z 33.0N 87.5W...DISSIPATING INLAND
MAX WIND 20 KT...GUSTS 30 KT.

FORECAST VALID 18/0600Z...DISSIPATED

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 27.7N 83.9W

NEXT ADVISORY AT 16/1500Z

$$
FORECASTER FRANKLIN

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4162. drj27
looks like its going to hit the bigbend
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wow

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4160. IKE
THE DEPRESSION IS MOVING TOWARD THE NORTH-NORTHWEST NEAR 16
MPH...AND THIS MOTION IS EXPECTED TO CONTINUE TODAY. ON THE
FORECAST TRACK...THE CENTER OF THE DEPRESSION SHOULD BE VERY NEAR
THE NORTHERN GULF COAST OF FLORIDA BY LATE THIS AFTERNOON.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
4159. KEEPEROFTHEGATE (Mod)
WTNT34 KNHC 160858
TCPAT4
BULLETIN
TROPICAL DEPRESSION FOUR ADVISORY NUMBER 1
Member Since: Posts: Comments:
TD4 and Bill out...
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000
WTNT34 KNHC 160858
TCPAT4
BULLETIN
TROPICAL DEPRESSION FOUR ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042009
500 AM EDT SUN AUG 16 2009

...TROPICAL STORM WARNING ISSUED FOR NEW DEPRESSION IN THE EASTERN
GULF OF MEXICO...

AT 5 AM EDT...0900 UTC...A TROPICAL STORM WARNING HAS BEEN ISSUED
FROM THE ALABAMA/FLORIDA BORDER EASTWARD TO THE SUWANNEE RIVER
FLORIDA. A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM
CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 24
HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA PLEASE MONITOR PRODUCTS
ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE.

AT 500 AM EDT...0900 UTC...THE CENTER OF TROPICAL DEPRESSION FOUR
WAS LOCATED NEAR LATITUDE 27.7 NORTH...LONGITUDE 83.9 WEST OR ABOUT
90 MILES...140 KM...WEST-SOUTHWEST OF TAMPA FLORIDA AND ABOUT 155
MILES...245 KM...SOUTH-SOUTHEAST OF APALACHICOLA FLORIDA.

THE DEPRESSION IS MOVING TOWARD THE NORTH-NORTHWEST NEAR 16
MPH...AND THIS MOTION IS EXPECTED TO CONTINUE TODAY. ON THE
FORECAST TRACK...THE CENTER OF THE DEPRESSION SHOULD BE VERY NEAR
THE NORTHERN GULF COAST OF FLORIDA BY LATE THIS AFTERNOON.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. STRENGTHENING IS EXPECTED AND THE DEPRESSION IS FORECAST TO
BECOME A TROPICAL STORM PRIOR TO REACHING THE COASTLINE.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1011 MB...29.85 INCHES.

RAINFALL ACCUMULATIONS OF 3 TO 5 INCHES...WITH ISOLATED MAXIMUM
AMOUNTS OF 10 INCHES ACROSS PORTIONS OF NORTH FLORIDA NEAR THE PATH
OF THE CENTER.

COASTAL STORM SURGE FLOODING OF 3 TO 5 FEET ABOVE NORMAL TIDE
LEVELS CAN BE EXPECTED NEAR AND TO THE EAST OF WHERE THE CENTER
MAKES LANDFALL.

...SUMMARY OF 500 AM EDT INFORMATION...
LOCATION...27.7N 83.9W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...NORTH-NORTHWEST OR 330 DEGREES AT 16 MPH
MINIMUM CENTRAL PRESSURE...1011 MB

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 800 AM EDT FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 1100
AM EDT.

$$
FORECASTER FRANKLIN
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4156. bcn
Quoting Weather456:


where?



Ana is pulling against dry:

Now:



Yesterday:
Member Since: Posts: Comments:
4155. IKE
BULLETIN
TROPICAL DEPRESSION FOUR ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042009
500 AM EDT SUN AUG 16 2009

...TROPICAL STORM WARNING ISSUED FOR NEW DEPRESSION IN THE EASTERN
GULF OF MEXICO...

AT 5 AM EDT...0900 UTC...A TROPICAL STORM WARNING HAS BEEN ISSUED
FROM THE ALABAMA/FLORIDA BORDER EASTWARD TO THE SUWANNEE RIVER
FLORIDA. A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM
CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 24
HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA PLEASE MONITOR PRODUCTS
ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE.

AT 500 AM EDT...0900 UTC...THE CENTER OF TROPICAL DEPRESSION FOUR
WAS LOCATED NEAR LATITUDE 27.7 NORTH...LONGITUDE 83.9 WEST OR ABOUT
90 MILES...140 KM...WEST-SOUTHWEST OF TAMPA FLORIDA AND ABOUT 155
MILES...245 KM...SOUTH-SOUTHEAST OF APALACHICOLA FLORIDA.

THE DEPRESSION IS MOVING TOWARD THE NORTH-NORTHWEST NEAR 16
MPH...AND THIS MOTION IS EXPECTED TO CONTINUE TODAY. ON THE
FORECAST TRACK...THE CENTER OF THE DEPRESSION SHOULD BE VERY NEAR
THE NORTHERN GULF COAST OF FLORIDA BY LATE THIS AFTERNOON.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. STRENGTHENING IS EXPECTED AND THE DEPRESSION IS FORECAST TO
BECOME A TROPICAL STORM PRIOR TO REACHING THE COASTLINE.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1011 MB...29.85 INCHES.

RAINFALL ACCUMULATIONS OF 3 TO 5 INCHES...WITH ISOLATED MAXIMUM
AMOUNTS OF 10 INCHES ACROSS PORTIONS OF NORTH FLORIDA NEAR THE PATH
OF THE CENTER.

COASTAL STORM SURGE FLOODING OF 3 TO 5 FEET ABOVE NORMAL TIDE
LEVELS CAN BE EXPECTED NEAR AND TO THE EAST OF WHERE THE CENTER
MAKES LANDFALL.

...SUMMARY OF 500 AM EDT INFORMATION...
LOCATION...27.7N 83.9W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...NORTH-NORTHWEST OR 330 DEGREES AT 16 MPH
MINIMUM CENTRAL PRESSURE...1011 MB

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 800 AM EDT FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 1100
AM EDT.

$$
FORECASTER FRANKLIN
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting homelesswanderer:


Good Morning Joanie. This is Stefanie from acros the boarder in SE TX. Yep so far so good on TD4. The CMC has a regenerated Ana on our doorstep Sunday. But our girl's not looking too good right now. Looks like she's outrun her convection. But she's come back before. Guess we'll see.


Good morning Stephanie...my neighbor..:) I just hope we don't get one this year at all.. we had enough last year...
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4153. IKE
Quoting neonlazer:

Im thinking
Do you know if a good site that has information on terms such as tighten up?...im kinda curious exactly what you mean when you say that...


Means it could be revving up...intensifying.....
Member Since: June 9, 2005 Posts: 23 Comments: 37860
4152. jipmg
The radar, the storms are blowing up near the center, and the "eye" like feature is getting tighter, usually means its strengthening
Quoting IKE:


Looks like it's tightening up.

Do you know if a good site that has information on terms such as tighten up?...im kinda curious exactly what you mean when you say that...
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4150. jipmg
Bill slows down
Guillermo just hanging on to Cat 2 strength, about 100mph.
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Bill's out.

Brings it up to 115mph at the end of the 5 days, MH.

Thought they'd do him first, Ana/TD4 require watches and warnings, takes more time.
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Quoting Joanie38:
Good morning all...

WHEW, I guess we can rest easy here in SWLA...


Good Morning Joanie. This is Stefanie from acros the boarder in SE TX. Yep so far so good on TD4. The CMC has a regenerated Ana on our doorstep Sunday. But our girl's not looking too good right now. Looks like she's outrun her convection. But she's come back before. Guess we'll see.
Member Since: Posts: Comments:
4146. jipmg
Bill up to 45 mph
NHC advisories coming out now. TD4 confirmed.
Member Since: Posts: Comments:
4144. IKE
Quoting neonlazer:


Does it seem it looks less organized on radar?..or do i need to get some sleep, haha.


Looks like it's tightening up.
Member Since: June 9, 2005 Posts: 23 Comments: 37860


Does it seem it looks less organized on radar?..or do i need to get some sleep, haha.
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Now...Bill will be upgraded to 45 mph! :)
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4141. jipmg
TWC saying a trough is going to dip and take BILL out to sea based on latest model runs
Quoting Catfish57:
I don't put much faith in TWC anymore, (at least post John Hope)

John Hope was the best, by far. God bless him.
Member Since: Posts: Comments:
Think ADT's got Ana's centre fix wrong, though.

That, or she's relocated her COC east a bit.
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Good morning all...

WHEW, I guess we can rest easy here in SWLA...
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can't.... keep... eyes.... open.... much.... longer..

please NHC release the 5 AM early..
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4136. DDR
Morning all,
Interesting stuff out there,too bad i wont be home for the day.
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Etch-a-sketch intensity graph:



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Quoting hawtee:
thank you Quake..Just now reading the blog and trying to catch up..Does this look like it may spin up to anything besides ts?

Eh, I don't anticipate anything beyond a 50 mph tropical storm or so (will be named Claudette). Not to mention it'll be rather small, so the effects won't be felt too far away from it.
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Bill continues to organize

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The NHC will sure be earning their pay this week, and then some.
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I don't put much faith in TWC anymore, (at least post John Hope)
Member Since: July 29, 2009 Posts: 0 Comments: 72
4130. hawtee
thank you Quake..Just now reading the blog and trying to catch up..Does this look like it may spin up to anything besides ts?
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Quoting IKE:


Imagine from Mobile or Pensacola, eastward....

Sounds about right. Anxiously awaiting the 4AM advisory...
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4128. IKE
Quoting quakeman55:

Expect TS warnings to go out for our area in a few minutes here...


Imagine from Mobile or Pensacola, eastward....
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting hawtee:
Good morning to all..I have been a member for a while but tend to lurk . I am also in the Fl. Panhandle, Ft. Walton..
thank you all for your info you put out..

Expect TS warnings to go out for our area in a few minutes here...
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4126. jipmg
TWC is saying that ANA might move into favorable conditions soon before reaching the DR
* AT 306 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS...PRODUCING STRONG WINDS 34 KNOTS OR GREATER...
COVERING MOST OF THE GULF WATERS BETWEEN 15 AND 60 NM OFFSHORE
FROM ENGLEWOOD NORTH TO CLEARWATER BEACH. THESE STORMS ARE
ASSOCIATED WITH AN AREA OF LOW PRESSURE MOVING NORTHWEST THROUGH
THE EASTERN GULF. THE STORMS ARE MOVING NORTH AT 25 TO 30 KNOTS

Member Since: Posts: Comments:
4124. hawtee
Good morning to all..I have been a member for a while but tend to lurk . I am also in the Fl. Panhandle, Ft. Walton..
thank you all for your info you put out..
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You Tampa folks might be impacted, too. NWS there just issued a statement about 50-mph wind gusts and chance of tornadoes today.
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4121. jipmg
interesting radar picture
4120. Patrap
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Thanks Ike

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4118. jipmg
TD4 looking like its moving NW, and its tightning up a bit
4117. IKE
Quoting NervousPanhandle:
Good evening to all from Pensacola. I've been a lurker and student of this blog since Ivan. First I'd like to say thanks to all of you that keep us informed and take the time to explain the complex tropics.

I still have a hard time picking out the center of a developing storm. Could someone please give there take on where the center is currently located. TIA :)


See post 4061...it's a radar image of TD4.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting jipmg:


its clearer here:

http://www.ssd.noaa.gov/goes/east/catl/loop-wv.html


ohok
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Quoting AussieStorm:



12 hrs old,

a new one is coming up
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Quoting jipmg:
if there are any recent quick skats on BILL it would be aprreciated if someone could post them

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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