Ana and TD 3 take aim at the Lesser Antilles

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

Share this Blog
7
+

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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 3764 - 3714

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97Blog Index

Quoting homelesswanderer:


Huh?? What update?


2AM model photo.

Try this link..
http://www.wunderground.com/tropical/tracking/at200991_model.html#a_topad

Member Since: July 2, 2009 Posts: 0 Comments: 2811
3762. Drakoen
Member Since: Posts: Comments:
watchout nola
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
its got her groove on pat this thing gonna take off


Where she lands will be the bigger question!
Member Since: Posts: Comments:
hmmmmmm the 2 am models have 91L practically over my house... interesting.
Member Since: Posts: Comments:
I think will have at least 6 name storms by the time August is over.. imagine September.... Tomorrow is going to be a long day for some people in the Gulf...
Member Since: July 18, 2009 Posts: 0 Comments: 307
3757. Ldog74
I wouldn't be surprised one bit if sometime between now and the 5 AM advisory NHC issues a special advisory announcing the arrival of Claudette and issuing watches/warnings along the N Gulf Coast.

Member Since: Posts: Comments:
Quoting jojofsu75:


I'm in Tallahassee also and just checked the local tv stations weather and they have us at 60% also. I haven't seen the 90% reported earlier (I'm not saying the other person was lying, I just can't find it).


Same in MS. scattered showers tommorow, ya think.
Member Since: Posts: Comments:
3755. Wariac
people where saying just a week ago, a 0,0,0 season and now we have three tropical storm in a mere two days. Incredible how weather can change so fast.
Member Since: Posts: Comments:
Patrap, me and you here in New Orleans could be getting it rought Sunday night into monday if it heads NW/ WNW
Member Since: May 25, 2008 Posts: 0 Comments: 250
Quoting TexasHurricane:
2AM update shows The Gulf storm going to LA.










Huh?? What update?
Member Since: Posts: Comments:
Quoting Vortex95:
Anyone What does a low within a low indicate in general.


A small vortex rotating around a larger one
Member Since: Posts: Comments:
At this rate of organization though we could see a TD at 5.
Member Since: Posts: Comments:
3750. Drakoen
Member Since: Posts: Comments:
FULL IMAGE
Member Since: Posts: Comments:
3748. KEEPEROFTHEGATE (Mod)
Quoting Patrap:
This in Nutz..I mean, this thing is in a Slot, a groove....itsa a Bad seed,we been saying it for 3 Days as we tracked it between Cuba and then thru the Straits.
Its got flavor..and the Upper Air from Sw La,..to Jacksonsiville is ripe aloft
its got her groove on pat this thing gonna take off
Member Since: Posts: Comments:
Amazing how fast out attention went from the Atlantic to the GOM...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
000
WHXX01 KWBC 160622
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0622 UTC SUN AUG 16 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL912009) 20090816 0600 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090816 0600 090816 1800 090817 0600 090817 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 27.0N 83.5W 28.7N 85.0W 30.1N 86.5W 31.4N 87.7W
BAMD 27.0N 83.5W 28.4N 85.0W 29.4N 86.3W 30.2N 87.4W
BAMM 27.0N 83.5W 28.4N 85.0W 29.7N 86.4W 30.7N 87.7W
LBAR 27.0N 83.5W 28.6N 84.6W 30.4N 85.9W 32.2N 86.9W
SHIP 30KTS 36KTS 43KTS 48KTS
DSHP 30KTS 36KTS 43KTS 39KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090818 0600 090819 0600 090820 0600 090821 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 32.5N 88.5W 34.2N 89.4W 37.5N 86.1W 42.0N 75.4W
BAMD 30.9N 88.2W 32.2N 89.0W 34.2N 86.0W 37.9N 77.8W
BAMM 31.5N 88.5W 33.0N 89.4W 35.5N 86.1W 39.7N 76.2W
LBAR 34.1N 86.8W 37.1N 82.3W 39.6N 71.9W 40.9N 62.1W
SHIP 53KTS 58KTS 59KTS 63KTS
DSHP 31KTS 27KTS 27KTS 28KTS

...INITIAL CONDITIONS...
LATCUR = 27.0N LONCUR = 83.5W DIRCUR = 330DEG SPDCUR = 12KT
LATM12 = 25.1N LONM12 = 81.9W DIRM12 = 309DEG SPDM12 = 17KT
LATM24 = 23.8N LONM24 = 79.1W
WNDCUR = 30KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1013MB OUTPRS = 1015MB OUTRAD = 90NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$
NNNN

Pressure still high, and quite a divergence from the intensity models.
Member Since: Posts: Comments:
Quoting hwmnpcola:
Local weather here in Navarre still isn't even giving a hint. 60% chance of scattered showers wind at 10-15mph.


I'm in Tallahassee also and just checked the local tv stations weather and they have us at 60% also. I haven't seen the 90% reported earlier (I'm not saying the other person was lying, I just can't find it).

Edit: I just found 70% on WCTV
Member Since: Posts: Comments:
SAB not too impressed yet.

16/0615 UTC 26.7N 83.5W T1.0/1.0 91L -- Atlantic
Member Since: Posts: Comments:
3742. Michfan
We need a microwave image on this sucker.
Member Since: Posts: Comments:
Image as of 6:30 UTC

Member Since: Posts: Comments:
3740. Patrap
I bet Spock would even raise an Eyebrow over 91L....


.."Interesting"...
Member Since: July 3, 2005 Posts: 427 Comments: 129439
3739. Michfan
When does blackout end?
Member Since: Posts: Comments:
3738. Drakoen
5:30utc
Member Since: Posts: Comments:
G'morning.

Wow, another one? And most of the people thought we may only just get Ana for now.

At this rate, the wave going off Africa will end up being Erika.
Member Since: Posts: Comments:
Wow, what a unique opportunity! Getting a chance to watch rapid cyclogenesis in real-time on radar!

Earlier I noticed that I could see what looked like multiple centers of rotation. I believe those were slightly-disjointed mid-level and low-level centers of rotation. But in the last hour or two, I've noticed the rotations coalesce into one. 91L is getting vertically stacked and is ripe for taking off....
Member Since: Posts: Comments:
Local weather here in Navarre still isn't even giving a hint. 60% chance of scattered showers wind at 10-15mph.
Quoting Joshfsu123:



On its current path, Apalachicola or points west to Panama City, Florida, would be a good landfall point. It has been moving NNW since starting to develop near Key West and I expect this path to continue. I'm in Tallahassee and expecting quite a rainy day tomorrow from the system.... Local meterologists have increased the rain chance from 50% to 90% today.
Member Since: Posts: Comments:
Quoting Drakoen:


But it's a SHIP report


They will have to put watches/warnings up tomorrow - regardless.
Member Since: Posts: Comments:
3731. Michfan
This thing is Claudette already .
Member Since: Posts: Comments:
3730. Patrap
NWS NOAA Radio yakking away here Uptown Now as well.
Member Since: July 3, 2005 Posts: 427 Comments: 129439
I'm tired but I'm staying up for this.. I missed humberto. I ain't going to miss learning from this one..
Member Since: Posts: Comments:
2AM update shows The Gulf storm going to LA.








Member Since: July 2, 2009 Posts: 0 Comments: 2811
3727. Drakoen
Quoting tennisgirl08:


TS Claudette by 5am. TS watches and warnings will go up tomorrow.


But it's a SHIP report
Member Since: Posts: Comments:
Quoting Drakoen:


That reading is close to the center...


TS Claudette by 5am. TS watches and warnings will go up tomorrow.
Member Since: Posts: Comments:
Quoting hwmnpcola:
Stormchaser I am in Navarre just east of Pensacola. I don't like what I see on that radar. What do you think the chances are that we could be looking at a possible hurricane. Is it just me or are the showers really starting to wrap.

Well as Pat said, feeder bands are beginning to take shape and the LLC is distinctly becoming better organized. I think theres a good shot that if this can hold up it could become a hurricane by the time it reaches the coast.
Member Since: Posts: Comments:
3724. Patrap
This in Nutz..I mean, this thing is in a Slot, a groove....itsa a Bad seed,we been saying it for 3 Days as we tracked it between Cuba and then thru the Straits.
Its got flavor..and the Upper Air from Sw La,..to Jacksonsiville is ripe aloft
Member Since: July 3, 2005 Posts: 427 Comments: 129439
This is eerily Humberto-ish
Member Since: Posts: Comments:
3721. Drakoen
Quoting weathersp:
Ummmm... Hey Guys...

COME LOOK AT THIS:

SHIP @ 6:00z
LOCATION: 27.40N -83.10W
WINDS: 40.0 KTS

Its the first OBS in the link..
National Data Bouy Center


That reading is close to the center...
Member Since: Posts: Comments:
with such good structure already, 91L could really spool up in a hurry...lots of 30+C bathwater out there. When the center completely closes off, look for fairly rapid intensification.
Member Since: Posts: Comments:
Quoting Patrap:
Not to sound alarmist,but if you kinda step back,..and look at the 91L Cyclonic vortex,..hopefully its not now becoming a Low within a bigger Low,where as the 91L would be in the Bigger Low,..at the Right front semi-circle




Pat - it's almost closed off! Wonder what the wind speeds are. They will send a HH in there tomorrow morning for sure.
Member Since: Posts: Comments:
anyone have the link for the long range nexrad.thanks
Member Since: Posts: Comments:
Storm total for rainfall today:
Link
You guys on the west coast of FL are pretty lucky. If this thing were another 50 miles east, you'd be pretty soggy right now!
Member Since: Posts: Comments:
Finally, NWS radio forecast (N.O.) is warning about 91L development that we have been watching.
Member Since: Posts: Comments:
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
215 AM EDT SUN AUG 16 2009

.SHORT TERM (TODAY - TUESDAY)...A TROPICAL WAVE WAS LOCATED OVER THE
EASTERN GULF OF MEXICO WITH A MID LEVEL CIRCULATION PRODUCING
WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS OVER THE CENTRAL AND
SOUTHERN COASTAL WATERS BRUSHING COASTAL AREAS SOUTH OF CLEARWATER.
AREA OF SHOWERS PRODUCING 20 TO 30 KNOT WINDS OVER THE WATERS WITH A
SMALL CRAFT ADVISORY IN EFFECT THROUGH THE DAY. A CLOSED SURFACE
CIRCULATION MAY DEVELOP AND THIS SYSTEM HAS A CHANCE OF BECOMING A
TROPICAL CYCLONE LATER TODAY WITH THE MAIN IMPACT OVER THE COASTAL
WATERS. THE CIRCULATION CENTER WAS LOCATED ABOUT 65 MILES SOUTHWEST
OF CLEARWATER BEACH AND WAS LIFTING NORTHWEST AT ABOUT 15 MPH
PARALLELING THE COAST SO THE BULK OF THE SHOWERS WILL REMAIN
OFFSHORE...BUT SOUTHEAST FLOW ACROSS THE PENINSULA COMBINED WITH
DAYTIME HEATING WILL PRODUCE BANDS OF SHOWERS AND THUNDERSTORMS WITH
STRONG GUSTY WINDS ACROSS ALL OF WEST CENTRAL AND SOUTHWEST
FLORIDA. MAX TEMPS NEAR THE COAST WILL LIKELY BE A FEW DEGREES
BELOW MOS GUIDANCE DUE TO THE INCREASED CLOUD COVER.
Member Since: Posts: Comments:

Viewing: 3764 - 3714

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97Blog Index

Top of Page

About

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

Local Weather

Overcast
31 °F
Overcast