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 stormpetrol:
Mitch 98 & Michelle 2001 did some significant damage on Grand cayman from what I can recall, Gilbert Had high winds recorded here up to 158 mph gusts I think , but to me was just a Summer squall compared to Ivan.


Both of those events caused significant damage on the western side (turtle farm area especially). Won't ever forget the size of those waves, and watching one take down that small house which used to be right near the entrance of the launch ramp near the T. Farm.
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Quoting skydiver99:
Aggie, thank you for posting those links! I've saved all of them!

My pleasure (really is!). You can get to most anything in the world of TC from those.
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Quoting skydiver99:
Hey y'all....LONNNG time lurker here, from just outside Mobile. I stay glued to this blog daily! Just wanted to say I appreciate all the good info, even if I never post! Some of y'all are pretty hilarious! Keep the info coming--I don't know enough yet to add anything, but your info is very helpful!

First question....what is it about the Hebert Box that is so important? Is it just a persistent pattern among west FL falling hurricanes?


South Florida
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Quoting jdjnola:


Ana has proven she can be exposed yet survive.


True so far but even the greatest fighters have fallen to shear and dry air.
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Quoting PcolaDan:

Thinking maybe you need to have the head on wall banger as your signature line. LOL I've gotta find me a hangs and shakes his head one. ;)


How about this one??
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting kmanislander:


Very true. Many have passed by but no real blow other than Ivan and Gilbert since the 50's and one in the 60"s if I recall correctly. Even Gilbert was not that big a deal.
I know. I lived on Shedden Rd then and didn't even lose power or phone. Boy, South Sound road was messed up bad then too. East Enders were picking up conchs and lobster from in the road.
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Quoting Michfan:
I think the GFS is overestimating the trough.

Weird that it would do that at the 18 Z run, though, given that the pressures are higher in the obs now than any other time during the day.
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Quoting Funkadelic:
Do the 18Z models for Bill have the new recon data in them? To me the recurve is unlikely still. Storm still moving west at a good clip, and still a weak tropical storm. Means more of a western track.


Agree but the trend to a more northward track is evident in the last 24 hrs of models runs wich is good news! still way long to go, at this time of the game the best thing is heard NHC words.
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1554. hahaguy
Quoting Patrap:
.."Kaw-a-Bungaaaaa"..!

.."Looks Like da muther Load"..!







LMAO
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Aggie, thank you for posting those links! I've saved all of them!
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Quoting Kmanwoodie:


Me too! South Sound...makes three


Great. We may soon have to form a Cayman chapter of WU LOL. Nice kids incidentally !
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Quoting XL:


I don't unfortunately. I do fancy having one - not that I would necessarily understand what it was telling me. lol
Me either but would like to. There are two in East End but I don't know who has them. Their information is shown on weatherincayman.com
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Tropical Storm 03L

UW-CIMSS Automated Satellite-Based
Advanced Dvorak Technique (ADT)
Version 7.2
Tropical Cyclone Intensity Estimation Algorithm


Current Intensity Analysis




UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 15 AUG 2009 Time : 214500 UTC
Lat : 11:17:50 N Lon : 35:22:20 W


CI# /Pressure/ Vmax
2.7 /1003.0mb/ 39.0kt


Final T# Adj T# Raw T#
(3hr avg)
2.7 2.5 2.5

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -48.2C Cloud Region Temp : -38.3C

Scene Type : IRREGULAR CDO

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
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Quoting Patrap:
.."Okay,Lets get the CIRRUS and STRATUS in High Mode and lets also get another 2 Blade's added to the NHC server..

..and someone Brew up some strong Java,..and get me another Pencil,too"..

They might need to swap out the old dual-core procs for the new 6-core DDR3 type. (different sockets, I know, thanks)
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And to think I am going to drive back to Florida after midnight tonight. I am in Virginia now visiting family.... Should have taken another week off....
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1546. Michfan
I think the GFS is overestimating the trough.
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Mitch 98 & Michelle 2001 did some significant damage on Grand cayman from what I can recall, Gilbert Had high winds recorded here up to 158 mph gusts I think , but to me was just a Summer squall compared to Ivan.
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1544. jdjnola
Quoting kmanislander:


The center is still totally exposed. Follow it on this loop in which the last frame is under night vis imagery.


Ana has proven she can be exposed yet survive.
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Quoting PcolaDan:

Thinking maybe you need to have the head on wall banger as your signature line. LOL I've gotta find me a hangs and shakes his head one. ;)


I will see what I can find for you:)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting wunderkidcayman:

SHOW ME HOW YOU GOT THAT IS IT ON TROPICAL ATLANTIC RECON IF IT IS WHERE


If you have google earth, on tropical atlantic select Live Recon Data in Google Earth. When it comes up on the left select Non-Tasked Mission.

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Quoting mobilegirl81:
The swfl low may reach depression status, and that is going out on a limb. Rainmaker.
highest winds i recorded today where 14 knots with a 21 knot gust.
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Quoting XL:


I don't unfortunately. I do fancy having one - not that I would necessarily understand what it was telling me. lol


Unfortunately I don't either. I depend on online resources for the information I obtain when tracking/ observing systems that pass by.
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Quoting KerryInNOLA:
Will Ana upwell cooler water and inhibit Bill's intensification?

Not if GFS is correct about Ana being a nothing storm in a day.
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South texas needs bill or ana right now because their drought is getting worse.
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Quoting XL:


I don't unfortunately. I do fancy having one - not that I would necessarily understand what it was telling me. lol


A good station is easy to use once you get someone to help you install it. Putting up the anemometer is the hardest part as typically you need a high mast to mount it.

I really enjoy mine ( a Vantage Pro ) as it will also store a lot of data for review and the computer chip in it knows where the station is geographically once you input your latitide and longitude. That allows it to tell you when sunset, sunrise etc will be also the stages of the moon. Lots more too. Great stuff for a weather geek LOL
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Quoting kmanislander:


Two in West Bay and two in South Sound !


Me too! South Sound...makes three
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Quoting mobilegirl81:
The Bill models will change and i am afraid will trend more westward like Ana banana.
lol, like u mean a SFLA hit?
Quoting Michfan:
Looking very good, imo.
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Quoting mobilegirl81:
The Bill models will change and i am afraid will trend more westward like Ana banana.


Indeed. I try not to look past 120 hours but its so tempting (even though its likely to be wrong)...kind of like your horoscope.
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Quoting Halon056:
just noticed.... The nhc circled the low in sw fl. for possible development...

Yep, they just did that. Good eye. (sorry, that was tough to pass on)
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The swfl low may reach depression status, and that is going out on a limb. Rainmaker.
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Hey, well if one of these Tropical Storm do end up here in Miami, I will be outside giving u the temp, winds, gust, humidity and much more every 5 minutes.
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This GFS run is going to set off that guy that guaranteed us no US threat. Big recurve...misses almost all land...no CONUS landfall.
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Quoting kmanislander:


Very true. Many have passed by but no real blow other than Ivan and Gilbert since the 50's and one in the 60"s if I recall correctly. Even Gilbert was not that big a deal.


Ivan was of course the worst, but we have had close calls quite a few times. Anyone remember Isidore (can't remember the year) as she passed by as a TS? That was a very potent TS if I remember correctly. An excessive amount of rain and some pretty gusty winds.
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Hmm, maybe be Claudette will be the real player afterall.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
uoting kmanislander:


How many of you have a weather station ?. It might be good some time to compare stats if need be.


have one, but not uploading data right now, might put it back online later this week
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just noticed.... The nhc circled the low in sw fl. for possible development...
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The Bill models will change and i am afraid will trend more westward like Ana banana.
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1519. Michfan
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Quoting jipmg:


looks like we migth barely be in the cone, if those models continue on there southerly track, if ana gets organized tonight it will move WNW as models were picking up earlier today, really depends on what happens tonight
Well, we r sure to find 40+ knot winds at the 8PM EDT advisory, hen we will find out.
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Quoting Patrap:
.."Okay,Lets get the CIRRUS and STRATUS in High Mode and lets also get another 2 Blade's added to the NHC server..

..and someone Brew up some strong Java,..and get me another Pencil,too"..






Guess we won't be hearing the "Nuthing" for a while.
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Quoting stormwatcherCI:
It's funny but other than Gilbert I don't remember that many affecting us before Ivan although I know there were a few close calls but since Ivan it's like every other hurricane heads in our direction.


Very true. Many have passed by but no real blow other than Ivan and Gilbert since the 50's and one in the 60"s if I recall correctly. Even Gilbert was not that big a deal.
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1515. XL
Quoting kmanislander:


How many of you have a weather station ?. It might be good some time to compare stats if need be.


I don't unfortunately. I do fancy having one - not that I would necessarily understand what it was telling me. lol
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Quoting happybrats3:
Hi all! I have two questions.

1. If TS Ana sweeps S. Fl and heads into the GOM, what is the chance of it becoming a hurricane? I am thinking of the warm waters through there and how that fuels it.

2. If the above does happen, how fast could it develop through the GOM and into "roughly" what strength a hurricane? Thinking distance/heat/time here.

I am just an avid hurricane watcher, no exp WHATSOEVER as evident with my questions.

Thanks!
Tracey


1. It potentially could become a hurricane assuming it misses Cuba and all the other islands.

2. It may be strong, but, as I said, it needs to stay from Cuba, DR, etc...
Member Since: July 10, 2006 Posts: 27 Comments: 1623

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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.