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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Quoting AussieStorm:
Goodnight all,
Stay safe, play safe, blog safe, and do what you need to do now to prepare before its to late.
Cheers AussieStorm

P.S
Its ment to be 30c in parts of Sydney today (Sunday).


G'night.
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could i get the nogaps link??
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Quoting canesrule1:
2PM EDT


Thanks!
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Quoting hydrus:
PATRAP- Have you looked at the latest NOGAPS model?


Im sipping my Bkfst java,looking at da Loops.
Not up to speed yet,but Ill peek at it soon
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Quoting Ameister12:
It looks like TS Ana's center has been separated from the thunderstorms a little more.

yup, it is completely exposed.
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Can someone point a link to 12Z GFS? Also, wasn't that one WAY south yesterday (around the Caymans)?
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Quoting CaneLover:
when is the next NHC update? How often?
2PM EDT
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It looks like TS Ana's center has been separated from the thunderstorms a little more.

Member Since: August 9, 2009 Posts: 10 Comments: 4907
PATRAP- Have you looked at the latest NOGAPS model?
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...even a blind hog will occasionally find an acorn...
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MJO downward motion will help them struggle even more.
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Quoting futuremet:
UM....

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O Gezzzz!!!
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Quoting KEEPEROFTHEGATE:
AOI
MARK
25N/81W


TS ANA


03L


Ana looks like a peasize compared to TD3!
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Quoting KEEPEROFTHEGATE:
HEHEHEHE
i agree, lol
Quoting Drakoen:


NOGAPS is very bullish
i agree one more time.
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when is the next NHC update? How often?
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NEXRAD RadarKey West, 1 Hour Running Surface Rainfall Accumulation Range 124 NMI



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The entity of the florida keys appears to be developing.
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UM....

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Member Since: July 19, 2008 Posts: 43 Comments: 4051
Gfs and its ensembles are wrong,ws is totally right this time.They show northwest motion while its moving southwest.Nogaps,hwrf best models for both systems right now.
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Kindly stop quoting trolls. If you must respond, use their moniker and not their entire post. Thank you so much! This will make the blog flow more freely. Not trying to be blog police here but I don't like having to read the posts of people I have on my ignore list. Thanks again!

So it looks like our systems are having some trouble with sustaining really deep tropical moisture around their centers this afternoon. Looks to be only a temporary setback for them. Will have to wait until tonight's model runs when they can really get a hold on TD3. They will do better with him once he is a Tropical Storm. Plenty of time to get our hurricane kits ramped up for the coming threats. But let's not waste time. Get what we need before it gets hectic when the media starts to really play these storms up.
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Quoting AussieStorm:
Goodnight all,
Stay safe, play safe, blog safe, and do what you need to do now to prepare before its to late.
Cheers AussieStorm

P.S
Its ment to be 30c in parts of Sydney today (Sunday).


nite aussie
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Quoting AussieStorm:
Goodnight all,
Stay safe, play safe, blog safe, and do what you need to do now to prepare before its to late.
Cheers AussieStorm

P.S
Its ment to be 30c in parts of Sydney today (Sunday).


Wow thats hot for it basically being mid-winter there
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Quoting LightningCharmer:


In the last blog, I included a link to a Florida Key's buoy that indicated continuous nearly 30 knots/hour west shifting winds on the southern end of circulation which although I am not an expert would indicate to me a surface low. No-one on this blog responded to my post which indicated to me that perhaps the buoy readings were not meaningful. Perhap everyone was too busy commenting on a sometimes annoying blogging who I will not name. Sorry if I offend, it is not my intention just wanted some expert analysis regarding the buoy readings I linked and posted.



You personalize this quite a bit, huh?

Having said that it is interesting that Sombrero Key has recently shifted to and is geting brisk WSW'ly winds.

Its it falling surface pressure to the NE causing this or is it a local daytime heating condition? ls it simply winds from developing convection in the vicinity? Its hard to create a meaningful surface analysis without more data than a point or two. Radar supports cyclonic circulation aloft, some higher resolution models support the idea of a weak surface circulation develping in association with this feature, and the extent of convection on radar supports strong mid level asent in the convective area which should reduce local surface pressures and increase local vorticity.

SO is a single buoy reading meaningful? Maybe it is, but only when the context and multiple uncertainties are examined. Maybe that's why you didn't get a quick answer.
Member Since: September 4, 2007 Posts: 0 Comments: 490
I don't think both of these systems are really going to get organized till they get closer to the islands. Too much shear and dry air is impacting them atm and its evident they are responding to the Diurnal cycles to keep themselves afloat.
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188. CJ5
I will not even mention what I see here.. this..Link
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Quoting Drakoen:


NOGAPS is very bullish


Only problem...its the nogaps
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Quoting 7544:
mets alrady saying td 3 could be a cat 2 in tha bahmmas if thaqt happens it could get stronger before it hits some where saty tuned
yup, i heard it too, Possible Cat 2 in the Bahamas do to very low shear and high waters, very rapid intensification.
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Models starting to seperate
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Quoting AussieStorm:
Goodnight all,
Stay safe, play safe, blog safe, and do what you need to do now to prepare before its to late.
Cheers AussieStorm

P.S
Its ment to be 30c in parts of Sydney today (Sunday).
sleep well friend later
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Model Diagnostic Discussion


THE NAM IS A FAST OUTLIER WITH INCORPORATING A HYBRID
TROPICAL/BAROCLINIC WAVE NEAR THE FLORIDA KEYS INTO THE TROUGH
ACROSS THE SOUTHEAST BEFORE ALLOWING IT TO ACCELERATE TOWARD THE
NORTHEAST...WHICH SEEMS UNLIKELY GIVEN WEAK FLOW ALOFT AND RISING
HEIGHTS. OTHER MODELS...INCLUDING THE GFS AND 00Z NON-NCEP
MODELS...ALLOW THE WAVE TO DISSIPATE...STALL...
OR BOTH OVER ALABAMA...WHICH IS PREFERRED.


...LONGWAVE TROUGH OVER THE ROCKIES...

MODEL PREFERENCE: BLEND OF NAM/00Z CANADIAN

THE MODELS HAVE SHOWN CONSIDERABLE MODEL DIFFERENCES AND
RUN-TO-RUN VARIABILITY FOR SOME TIME NOW. THUS...CONFIDENCE IN THE
FORECAST DETAILS IS NOT PARTICULARLY HIGH USING 12Z GUIDANCE.
HOWEVER...PREFER A SCENARIO CLOSER TO THE SOUTHERN EDGE OF THE
GUIDANCE FOR POSITION OF THE UPPER LOW THROUGH THE ENTIRE
PERIOD...AND A SCENARIO WITHIN THE SLOWER HALF OF THE GUIDANCE FOR
THE LINGERING TROUGH AXIS EXTENDING SOUTHWESTWARD INTO THE
ROCKIES. A BLEND OF THE NAM/00Z CANADIAN IS CLOSEST TO THIS
IDEA...AND IS SUPPORTED BY RECENT MODEL TRENDS INCLUDING ENSEMBLE
MEANS. MEANWHILE...THE GFS APPEARS TO OVER-AMPLIFY A PORTION OF
THE TROUGH ACROSS THE WESTERN DAKOTAS TONIGHT/SUNDAY AND AGAIN
ACROSS THE MIDWEST MON/TUE...WHILE THE ECMWF LIES WITHIN THE
NORTHERN HALF OF THE SOLUTION ENVELOPE WITH THE UPPER LOW CENTER
AND WITHIN THE FAST HALF OF THE GUIDANCE WITH THE TROUGH EXTENDING
INTO THE ROCKIES. IN ADDITION...THE CANADIAN HAS DISPLAYED MANY
PREFERRED ASPECTS OF THE TROUGH FOR A FEW CYCLES NOW WHILE THE
ECMWF HAS NOT.
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Quoting futuremet:


Ridge is expected to set up over the west Atlantic, allowing Ana to follow a relatively westward track.



TY
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Quoting LPStormspotter:


Drakoen, I respect your observation and you are usually right. But this time could you maybe lie... J/K anything but FL hit or GOM..


NOGAPS is very bullish
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TD3 will have to start gaining some latitude now if it's going to make it north of the island chain. The current trend for TD3 appears to be a weakening one, as far as thunderstorms go. DMIN seems to be affecting it. The weaker it is, the further west it will go.
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Good Afternoon,

For all those people that lived in the NE caribbean today is the day to stating to finish the preparation for a strormy week ahead tomorow business open for 5 hrs only, and we can be in an unpresedest back to back hit by two TC next week so if Ana pass over our area that means that will be almost no time to prepare for Bill, so I gone to Walmart to get my bateries flash light and food & water for one week... Is better be safe than sorry.
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Quoting presslord:


How 'bout...we keep the GFS...and throw you out?
HEHEHEHE
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Quoting Michfan:


Too far apart.
unless Ana slows and 03L speeds up, or vice-versa.
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12Z

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Goodnight all,
Stay safe, play safe, blog safe, and do what you need to do now to prepare before its to late.
Cheers AussieStorm

P.S
Its ment to be 30c in parts of Sydney today (Sunday).
Member Since: September 30, 2007 Posts: 9 Comments: 15932
Maybe we can attribute their unimpressive to this significant factor:

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Quoting Drakoen:
NOGAPS 12z takes Ana through the FL straits to become a significant hurricane in the GOM.


Drakoen, I respect your observation and you are usually right. But this time could you maybe lie... J/K anything but FL hit or GOM..
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172. 7544
mets alrady saying td 3 could be a cat 2 in tha bahmmas if thaqt happens it could get stronger before it hits some where saty tuned
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Quoting Drakoen:
NOGAPS 12z takes Ana through the FL straits to become a significant hurricane in the GOM.
i really dunno if it will be a direct impact here in SFLA or be a more southern one, i'm going with a SFLA impact because a lot of reliable models have it doing so.
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Careful ana llc is really becoming exposed dont wanna end up like 06 chris.
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Quoting Drakoen:
Surface pressures around the Keys are not falling. There is an 850mb vort maximum. There is an upper level trough in the GOM to prevent anything from getting too organized right now.

Thank you for your analysis. It is appreciated.
Member Since: September 1, 2007 Posts: 0 Comments: 1265
Both system look unimpressive right now.
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Thanks, Doc.
Member Since: August 9, 2009 Posts: 10 Comments: 4907
Well I see it setting up but until we can get an idea of its potential size/strnght I still think the models taking her;oops him into the South Florida area. However everytime I think im on track and have a handle on it off it goes in a totally unpredictable manner!! I think this is why mets drink!
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Oh my I posted here about 10 mins ago and it didn't take.. I know my post did "stall" so figured the site was over loaded.

Oh well, Thanks Dr Jeff, glad to get a new blog, of course it will be full by end of day. LOL

I agree, that blob in the Keys, has rotation and clouds and rainfall with it... and it is entering the hot GOM.. not good.

Ike, didn't you say there was a model on it?

The others, Ana and TD3/Bill...will take awhile.. and those models will swing back and forth on those two storms every time they have a new model run...

be patient little grasshoppers! LOL

it is fun to watch and comment our thoughts!

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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.