Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 04:17 PM GMT on Αύγουστος 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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It was like around 6 hours ago weather567.... what you think about ANA... you think it will make it by the end of the day Sunday?...The last frame in the Floater is attempting to pop some convention around it center....
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4063. IKE
Quoting FLHurricaneChaser:
LMAO you guys are all making a big fuss out of nothing. This will amount to no more than a weak 40 kt TS.


I'll take the NHC's advice...not saying you aren't right, but....

What about the SN...can't think of his name...who said the GOM was clear the rest of 2009!
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I hope the kid gets to go through a cat 4 or 5 to squelch those Jim Cantore wanna be asprirations.
Member Since: Ιούλιος 29, 2009 Posts: 0 Comments: 72
Nice

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Quoting FLHurricaneChaser:
LMAO you guys are all making a big fuss out of nothing. This will amount to no more than a weak 40 kt TS.


LMAO at your ignorance!!

Your funny.
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Quoting homelesswanderer:


Yep. But it looks like we'll be ok with this one. :)


:) - ok off to bed. check back tomorrow...oh wait , it is tomorrow....:)
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
This is Rainman's sat pic loop, quick tightening!
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Quoting btwntx08:

its a td already looks like those reading were wrong

I said it was a TD.....
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LMAO you guys are all making a big fuss out of nothing. This will amount to no more than a weak 40 kt TS.
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can I beat him now, please???
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Quoting Drakoen:


OMG A CONFESSION!?!?!?! I better screenshot this...


Hurry before he edits it! lol
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Quoting TampaSpin:


Yes we did....hope all is well with you.

I'm good, tomorrow will be fun when my friend in TX wakes up to TD4 in the gulf after 3 days or so of "no storms in the gulf" from him, while I said, "it's coming." I love this blog a little more every time. How's things in your corner of the world?
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Quoting TexasHurricane:


I probably would...If I saw that right you are in Vidor? I'm about 10 minutes away I believe.


Yep. But it looks like we'll be ok with this one. :)
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4050. IKE
Quoting Drakoen:


OMG A CONFESSION!?!?!?! I better screenshot this...


WS....you're unbelievable....lucky dog?

I'm almost speechless with you.
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Quoting Drakoen:


The pass was from a while ago. It is likely now that the system has a closed low.

I'm in Destin, northwest of the depression, and there are easterly winds here, so it's definitely down at the surface. The Navy wouldn't have upgraded it to TD 4 if that wasn't the case.
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This is one of the fastest growing storms we have seen......this thing is really get cranked up......
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This seems to be pulling a Humberto. Tightening up very quickly.

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4046. Drakoen
Quoting WeatherStudent:
Ike, you lucky dawg, your about to get hit by a storm. While I on the other hand, who actually wants one, it doesn't look like that wish will become a reality anytime soon, :(


OMG A CONFESSION!?!?!?! I better screenshot this...
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30615
4044. Drakoen
Quoting HurricaneFCast:

Drake.. That was an hour ago...actually may have been 2 hours.. 6:50 UTC is either 1:50 am EST, or 2:50 am EST.. I can't remember if its 4 or 5 hours ahead of EST. Either way it's not an old pass, and yes it has the ability, with such a define mid-level circulation, to reach the surface very quickly, but it'll still probably take about 6 hours or so, maybe 12.


The bottom purple is the time of the pass. That was from 8hrs+ ago
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30615
Quoting Giga2001:
TS - Thanks for the blog update earlier - I love how you explain things using words I can understand. If memory serves, we had some fun talking baseball/football last year - nice to see you again.


Yes we did....hope all is well with you.
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Quoting homelesswanderer:


GN Tex. Don't worry if it goes west you'll hear me scream. ;)


I probably would...If I saw that right you are in Vidor? I'm about 10 minutes away I believe.
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
It was like around 6 hours ago.... what you think about ANA... you think it will make it by the end of the day Sunday?...The last frame in the Floater is attempting to pop some convention around it center....
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Well some of us were bashed here yesterday because we were watching the gulf so intently, and not paying homage to the A & B storms. After what I saw and went through on Humberto, GOM Blobs are pretty high on my list
Member Since: Ιούλιος 29, 2009 Posts: 0 Comments: 72
4039. IKE
Quoting neonlazer:


Excellent radar...moving NNW....
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4038. jipmg
Bill having trouble getting organized due to some dry air intrusion it seems
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If this can develop a nice inner core nothing would stop if from rapid intensification.
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Quoting Catfish57:
SC2007...Thanks for the link. Something seems amiss though..... Why was it showing intensification after going inland? Glitch maybe?
okay I saw that too I thought maybe I was just tired!
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Banding this quickly
Does that indicate an overall push for quicker development
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Quoting TexasHurricane:
It is almost 3 in the morning here. I got to go to bed. I think we are ok over here unless it takes a jog more to the west...anyone think that may happen? For those that will be affected - take care.


GN Tex. Don't worry if it goes west you'll hear me scream. ;)
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Quoting IKE:


Looks like it's moving NW to NNW....right up here....

***reaches for BP meds***


Throw the lithium on the storm! It'll neutralise the depression...
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Quoting Drakoen:


The pass was from a while ago. It is likely now that the system has a closed low.

Drake.. That was an hour ago...actually may have been 2 hours.. 6:50 UTC is either 1:50 am EST, or 2:50 am EST.. I can't remember if its 4 or 5 hours ahead of EST. Either way it's not an old pass, and yes it has the ability, with such a defined mid-level circulation, to reach the surface very quickly, but it'll still probably take about 6 hours or so, maybe 12.
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Quoting nola70119:
That wasn't unexpected....has the pressure lowered?


By 2mb.
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4028. IKE
Quoting hurricanehanna:

want some of Press's thorazine?


Heck...I may need it.
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4027. Patrap
TD-4
NEXRAD Radar
Tampa, Storm Relative Mean Radial Velocity 0.50 Degree Elevation Range 124 NMI


Member Since: Ιούλιος 3, 2005 Posts: 426 Comments: 129093
Quoting Catfish57:
Me too..... Is that banding already?


Looks like it.
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4025. Drakoen
Quoting HurricaneFCast:

Actually, it has a mid-level circulation. Check QuikSCAT, no low level circulation. Check CIMSS low-level wind field...no low level circulation. Check pressure readings in the buoys of the GOM...no low level circulation.


The pass was from a while ago. It is likely now that the system has a closed low.
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30615
Quoting IKE:


Looks like it's moving NW to NNW....right up here....

***reaches for BP meds***

want some of Press's thorazine?
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Me too..... Is that banding already?
Member Since: Ιούλιος 29, 2009 Posts: 0 Comments: 72
Quoting Drakoen:


LOL ECMWF shows another two storms forming in the Tropical Atlantic over the next 10 days.


Just saw that. It'd be interesting how many more storms we can fit into August before the MJO becomes unfavorable.

Im in Germany for 7 more days so I should miss the activity if anything happens near PBC.
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4021. Drakoen
It looks like it has a tight core
Member Since: Οκτώβριος 28, 2006 Posts: 57 Comments: 30615
Doubt any of these systems will make it to Texas the High isn't as strong as last year
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Quoting victoriahurricane:


Not to burst your bubble, but it has a LLC and it's a tropical depression already.

Actually, it has a mid-level circulation. Check QuikSCAT, no low level circulation. Check CIMSS low-level wind field...no low level circulation. Check pressure readings in the buoys of the GOM...no low level circulation.
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I posted this shortly b4 we had TD 4 - This is not the center of the depression.

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Wifey will turn into a Cat 5 if I dont crash soon.
Maybe its my 3am eyes, but is td4 closing off?
Watching frame to frame isnt proper however it appears that the motion is more N than W.
Thoughts?
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4016. IKE
Quoting Patrap:


Looks like it's moving NW to NNW....right up here....

***reaches for BP meds***
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It is almost 3 in the morning here. I got to go to bed. I think we are ok over here unless it takes a jog more to the west...anyone think that may happen? For those that will be affected - take care.
Member Since: Ιούλιος 2, 2009 Posts: 0 Comments: 2811
Im impressed.

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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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