Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 04:17 PM GMT on Αύγουστος 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: 3964 - 3914

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

3964. Drakoen
Quoting IKE:



Not sure I can go back to sleep.


I don't blame you. This thing is really close and could really ramp up.
Member Since: Posts: Comments:
3963. jipmg
wow TD 4 is now in the gulf.....

Member Since: Posts: Comments:
3962. Michfan
Member Since: Σεπτέμβριος 7, 2007 Posts: 0 Comments: 1736
Quoting IKE:



Not sure I can go back to sleep.

Haha, I gave up as well..got too much stuff to learn about this type of stuff..
Member Since: Posts: Comments:
Quoting serialteg:


td4? :/ where does it say so...

The past 20 posts...

Member Since: Posts: Comments:
Quoting CyberStorm:
does any one for the love of god have the extended loop for the radar on 91L.you know the one that shows more than 2 hours of loop


Go here

choose 40 frames and click update radar

Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
Quoting CyberStorm:
does any one for the love of god have the extended loop for the radar on 91L.you know the one that shows more than 2 hours of loop


theres a long loop on one of the back pages. sorry
Member Since: Αύγουστος 22, 2006 Posts: 2 Comments: 1988
Quoting Weather456:
I did not expected this,

not 1, not 2 but 3 depressions in less than a week.


Still got another wave moving off Africa, as well.

Could end up being TD5 later down the road.
Member Since: Αύγουστος 23, 2008 Posts: 7 Comments: 5300


Member Since: Posts: Comments:
3954. Drakoen
Ball of convection:

Member Since: Posts: Comments:
HurricaneFCast how fast can that change?
3952. IKE
Quoting Drakoen:


Watchout Ike! Lots of rain and strong TS winds possible



Not sure I can go back to sleep.
Member Since: Ιούνιος 9, 2005 Posts: 23 Comments: 37860
3951. Drakoen
The tropics are waking up LOL!
Member Since: Posts: Comments:
Quoting Weather456:
Tropical Depression 4

the tropics continue



td4? :/ where does it say so...
Member Since: Αύγουστος 22, 2006 Posts: 2 Comments: 1988
We officially have TD4.

ATLANTIC OBJECTIVE AIDS FOR

TROPICAL CYCLONE FOUR (AL042009) 20090816 0600 UTC
Member Since: Posts: Comments:
TRMM just made a good pass..

Member Since: Posts: Comments:
does any one for the love of god have the extended loop for the radar on 91L.you know the one that shows more than 2 hours of loop
Member Since: Posts: Comments:
3945. Drakoen
Quoting IKE:


Just woke up to use the restroom....

Not really surprised about 91L. Looks headed close to here.


Watchout Ike! Lots of rain and strong TS winds possible
Member Since: Posts: Comments:
3944. Drakoen
We have tropical depression four LMFAO!!! Look how fast this happened.
Member Since: Posts: Comments:
I did not expected this,

not 1, not 2 but 3 depressions in less than a week.
Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
Quoting victoriahurricane:
A depression already? Wow could this reach Cat. 1 status before landfall?

Easily, I'd say.
Member Since: Posts: Comments:
3941. IKE
Quoting Patrap:
Remember,..with a Landfalling Strong Tropical Storm's or Cat-1 Hurricane,that right front Quad where it cross's the coast,and to the right..can Have a Lot of Tornadoes as well.
Look at the rotation on these feeders.




Just woke up to use the restroom....

Not really surprised about 91L. Looks headed close to here.
Member Since: Ιούνιος 9, 2005 Posts: 23 Comments: 37860
Link to Navy/NRL's report on TD4: Link
Member Since: Posts: Comments:
Quoting Ldog74:


Well, it could. Other requirements besides 39mph winds can prohibit a tropical cyclone from forming. So there could be a storm that was a TS the second it gained tropical cyclone status. Ie. Vince, Tammy 2005.
I would have to agree. Since the official forecasts are spaced every six hours, I've seen AOI's go to TS's without officially every having been a numbered TD. It must have been a TD at one point, it's a stage of genesis, but it can all happen very, very quickly. We are used to storms that take a while to develop and stay in TD stage for a while before being named. It's kind of confusing, but it is was easy, everybody would understand the tropics. I'd have to say that all of us combined are pretty smart...a think tank that is useful and amusing at times. Maybe the crow pic was a little over the top, but we could chalk it off to plain ol' innocent fun, as long as no one was hurt.
Member Since: Posts: Comments:
Quoting LSUCaneGirl:
Hi everyone, new 2 the blog, but I've been reading it 4 about a week. GOM resident extremely concerned about Bill and also the system behind it. Have any of the models picked up on it yet? Also, do you guys think Ana will hang on long enough to reach the GOM as a hurricane?


Still way too early to speculate on Bill and the sys. behind it.

As for Ana, she could very well be toast. She outran all her convection, but as long as the low to mid-level circ. remains intact, she's not totally out of the game. Looking pretty bad for her though.
Member Since: Posts: Comments:
Buoy EGKF1, which is just east of the center, last reported wind speeds of 22.9 kts, but surprisingly it reported a pressure of 30.01 inches, or 1016 mb's. That's the problem with this system right now, it seems like the circulation is in the middle levels of the atmosphere, and its low pressure isn't very deep. You can clearly see a circulation on radar, but there are no indications elsewhere that the circulation has reached the surface. QuikSCAT doesn't pick up on it, lower level wind maps don't pick up on it, buoys aren't showing low pressure at the surface, and the reported wind speeds by the buoys only support Tropical Depression status.
Member Since: Posts: Comments:
That's gotta be a TD at this point....
Member Since: Ιούλιος 29, 2009 Posts: 0 Comments: 72
000
WHXX01 KWBC 160719
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0719 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

TROPICAL CYCLONE FOUR (AL042009) 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 28.7N 84.7W 30.6N 85.9W 32.4N 86.8W
SHIP 30KTS 36KTS 42KTS 48KTS
DSHP 30KTS 36KTS 42KTS 38KTS

...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 34.5N 86.7W 37.8N 81.8W 40.2N 70.4W 38.3N 64.2W
SHIP 52KTS 57KTS 58KTS 62KTS
DSHP 31KTS 27KTS 27KTS 28KTS

...INITIAL CONDITIONS...
LATCUR = 27.0N LONCUR = 83.5W DIRCUR = 330DEG SPDCUR = 13KT
LATM12 = 25.1N LONM12 = 81.9W DIRM12 = 309DEG SPDM12 = 17KT
LATM24 = 23.8N LONM24 = 79.1W
WNDCUR = 30KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1011MB OUTPRS = 1015MB OUTRAD = 90NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$
NNNN


Pressure has dropped 2mb in about an hour, seemingly.
Member Since: Αύγουστος 23, 2008 Posts: 7 Comments: 5300
A depression already? Wow could this reach Cat. 1 status before landfall?

Member Since: Posts: Comments:
Quoting tennisgirl08:
Models are very accurate on storms that have formed and where they are going within 1-2 days. 91L is going to the panhandle!


Link please, if you wouldn't mind. Thanks
Member Since: Posts: Comments:
Waiting for an official renumber on 91L.
Member Since: Posts: Comments:
TD4 "Claudette"? reminds me of a combination of both Humberto07 and Marco08
Member Since: Posts: Comments:
Tropical Depression 4

the tropics continue

Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
New Level II radar data in and thunderstorms are firing the SW side right next to the "eye" like feature on radar.
Member Since: Posts: Comments:
Quoting LSUCaneGirl:
Hi everyone, new 2 the blog, but I've been reading it 4 about a week. GOM resident extremely concerned about Bill and also the system behind it. Have any of the models picked up on it yet? Also, do you guys think Ana will hang on long enough to reach the GOM as a hurricane?


1) yes, for a very long time now
2) could be, too far out to be certain & its a fighter
Member Since: Αύγουστος 22, 2006 Posts: 2 Comments: 1988
FNMOC has 04L

And so does NRL.
Member Since: Posts: Comments:
at 45 mph, Bill is the strongest entity so far in the Atlantic basin.
Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
correction NW Quadrant!!
Quoting weathersp:
This.... is... scary...



Very strange. Not unexpected though. I live in Bonita Beach and it was off-and-on sun/rain/sun. We decided to jump on the boat and go up the back bay for a quick bite to eat for a few hours in between the "bands." It was a nice day except for a few quick squall-like wind/rain moments. I figured it would pour here tonight but besides a light breeze, none of the real rain made it here. Overall, very little effect from this disturbance but looking at this radar it is quite interesting to see it go from a blob of thunderstorms to a condensed, circulating "storm" so quick.

We did have some damage though... our Royal Palm lost a frond that flew about 15 feet in a "gust." :)
Member Since: Posts: Comments:
Quoting PtOConnorTXfisherman:



Amen. We haven't been the same since, nobody around this part of Texas wants anything to do with anything over 20 mph. Kids still get spooked during a regular thunderstorm.



Totally understand, Im here in Clear Lake... Just the mention of the "H" word spooks everyone around here. We were loving the quiet season...lol... Should have known better
Member Since: Posts: Comments:
Tropical depression 4 has formed, Navy is reporting.
Member Since: Posts: Comments:
Look at the outer Ne bands away from 91L on patraps post 3883 and 3906. That looks like a more NW movement than NNW?
More WNW it goes
Member Since: Posts: Comments:
Quoting Patrap:


That loop reminds me of Humberto. I think we'll see that kind of development as it moves between nnw and nw. Right now I just don't see the wnw some people are talking about. That could be because it's 3:22am and I can't sleep.
Member Since: Posts: Comments:
I just downloaded the remix

"Crazy over an invest, three in the morn"
Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
Hi everyone, new 2 the blog, but I've been reading it 4 about a week. GOM resident extremely concerned about Bill and also the system behind it. Have any of the models picked up on it yet? Also, do you guys think Ana will hang on long enough to reach the GOM as a hurricane?
Member Since: Posts: Comments:
3916. Patrap
Remember,..with a Landfalling Strong Tropical Storm's or Cat-1 Hurricane,that right front Quad where it cross's the coast,and to the right..can Have a Lot of Tornadoes as well.
Look at the rotation on these feeders.


Member Since: Ιούλιος 3, 2005 Posts: 426 Comments: 129093
Quoting serialteg:


how old are you?


What does that have to do with anything?
Member Since: Posts: Comments:
Quoting Ldog74:


Well, it could. Other requirements besides 39mph winds can prohibit a tropical cyclone from forming. So there could be a storm that was a TS the second it gained tropical cyclone status. Ie. Vince, Tammy 2005.


well stated.
Member Since: Posts: Comments:

Viewing: 3964 - 3914

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

Scattered Clouds
33 ° F
Διάσπαρτα Νέφη