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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Quoting kmanhurricaneman:
give him an A... go to the head of the class!


that wasn't nice
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can someone tell me if bill's center of circulation is wrapped in the large thunderstorms i am seeing?
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Gulf coast, do not be surprised what you wake up to in the gulf tomorrow.
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Quoting Weather456:


What the heck


Every one take a look at Bill's 18Z Models. How the heck is Bill going to go straight NW from its current position. It's not even going west.


These models need to wake up and smell the roses.


lol we'll being seeing major shifts come tomm
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2509. szqrn1
Hello! Okay, just camein from encountering baby snake in pool.... to find a 90 and 91?
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Link

Wiki's just sayin....
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Quoting weatherboykris:
Here are the 18z models interpolated to the current position:







What the heck


Every one take a look at Bill's 18Z Models. How the heck is Bill going to go straight NW from its current position. It's not even going west.


These models need to wake up and smell the roses.

Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
That's pretty strong convection over Bill's center.
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doesn't look like much of a surface circulation... 90 degree water... looks like it has a shot of developing... it might want to slow down though if it wants too.
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Quoting midgulfmom:

Evenin' all. Hey that's what happened to my 150 rated metal roof in Katrina. Just make sure all the wood underneath is sound and/or clipped down. Mine peeled like a potato on one side of the house.

got it triple clipped and strapped and foamed in all the really long screws ! house is old though..and your welcome Fisky !
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Quoting AllStar17:


JMO, but I think you should re-observe at what you are looking at. Models are already wrong with Bill, as some have said. Just watch, wait, and get prepared, as it seems just a bit too early to assume a certain track with Bill, as is the case even with Ana


I'm just basing what I said off the models. If they change then they change.
Member Since: Απρίλιος 26, 2009 Posts: 3 Comments: 3667
Quoting hurricanehanna:

Freeroam - Storm gave an update this AM. Normally doesn't do it on the weekend, but under these circumstances, we may see him do another one tomorrow.

StormW's latest Blog
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2500. chawk
I'm just south of Tarpon Springs and we got a heavy band of storms at about 7PM with winds 30-40mph and a lot of lightning. Looks like 91L is winding up pretty quickly. According to my dive buddies the Gulf is 87F all the way down to 120' deep so this storm has a lot of heat to work with.
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2499. rxse7en
Quoting weatherboykris:
Here are the 18z models interpolated to the current position:





I can't read the bottom line, is that Bill?
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Quoting weatherboykris:
Here are the 18z models interpolated to the current position:






Which storm are these models for?
Member Since: Ιούνιος 11, 2008 Posts: 0 Comments: 31
2497. Skyepony (Mod)
More south side shear on ANA from Gonzo
Date: Near the closest hour of 1Z on the 16th day of the month
Highest Mandatory Level For Which Wind Was Reported: 150mb
Coordinates: 12.1N 50.9W (View map)
Location: 592 miles (953 km) to the E (97°) from Bridgetown, Barbados.
Marsden Square: 042 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1011mb (29.85 inHg) Sea Level (Surface) 27.6°C (81.7°F) 24.1°C (75.4°F) 205° (from the SSW) 7 knots (8 mph)
1000mb 101m (331 ft) 26.8°C (80.2°F) 23.2°C (73.8°F) 205° (from the SSW) 10 knots (12 mph)
925mb 786m (2,579 ft) 21.2°C (70.2°F) 19.2°C (66.6°F) 215° (from the SW) 9 knots (10 mph)
850mb 1,516m (4,974 ft) 17.4°C (63.3°F) 15.6°C (60.1°F) 190° (from the S) 5 knots (6 mph)
700mb 3,154m (10,348 ft) 10.8°C (51.4°F) Approximately -3°C (27°F) 320° (from the NW) 11 knots (13 mph)
500mb 5,880m (19,291 ft) -5.3°C (22.5°F) -7.5°C (18.5°F) 50° (from the NE) 12 knots (14 mph)
400mb 7,600m (24,934 ft) -14.9°C (5.2°F) Approximately -31°C (-24°F) 45° (from the NE) 9 knots (10 mph)
300mb 9,710m (31,857 ft) -30.3°C (-22.5°F) Approximately -58°C (-72°F) 105° (from the ESE) 9 knots (10 mph)
250mb 10,980m (36,024 ft) -40.7°C (-41.3°F) Approximately -57°C (-71°F) 120° (from the ESE) 8 knots (9 mph)
200mb 12,460m (40,879 ft) -53.7°C (-64.7°F) Approximately -61°C (-78°F) 75° (from the ENE) 17 knots (20 mph)
150mb 14,260m (46,785 ft) -65.1°C (-85.2°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 170° (from the S) 23 knots (26 mph)
Member Since: Αύγουστος 10, 2005 Posts: 164 Comments: 37866
91L has really warm temperatures to feed off of.
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Quoting CaneWarning:
Looks like Bill is for the fishes, while Ana could possibly be something to watch - based on the models at least.


JMO, but I think you should re-observe at what you are looking at. Models are already wrong with Bill, as some have said. Just watch, wait, and get prepared, as it seems just a bit too early to assume a certain track with Bill, as is the case even with Ana
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Bill is still up in the air, IMO...consider that at this time yesterday, instead of the fish/Florida debate, we were debating whether or not it would go through the Caribbean or Florida Straits...things change fast, models flip flop.
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Quoting superweatherman:
weather456 you think 91L will be a TD by morning or even a TS by tomorrow afternoon since it will be a good time in the water


I dont think its qualified enough to be a TD that early. some slow development possible b4 moving ashore in 48 hrs.
Member Since: Ιούλιος 24, 2005 Posts: 407 Comments: 19076
Quoting eye:
IMO you arent a meteorologist unless you got the schooling, there is a reason people go to school for it. It is a big difference getting a certificate vs 4 years or more of college. You can say this that or the other about the definition, but that is splitting hairs.

Many companies consider (and substitute) military training for college degrees. I'm sure they don't do this just for giggles!
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seeing a wave coming off of africa...
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2490. IKE
Quoting hurricanehanna:

Evening Ike..thanks for the "good news" - lol. West of NOLA is me. Oy


I'm just going by what it's listed as moving.
Member Since: Ιούνιος 9, 2005 Posts: 23 Comments: 37858
:) I am just up the street from you in PSJ. Definately has that feederband type of rain/wind to it. I bet they upgrade that one (91L) soon.
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I have a hard time seeing Ana ever being anything more than a relatively weak system, so I'm giving a bit more weight than usual to the BAMS.
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Looks like Bill is for the fishes, while Ana could possibly be something to watch - based on the models at least.
Member Since: Απρίλιος 26, 2009 Posts: 3 Comments: 3667
2484. IKE
Looks like it's moving more NW to me(91L).

not looking bad...
Member Since: Ιούνιος 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:


It's listed as moving at 300 degrees, which is true WNW.

It's listed at 25.9N and 83.1W on WU. That would put it coming in just west of NO,LA.

Evening Ike..thanks for the "good news" - lol. West of NOLA is me. Oy
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Quoting weatherboykris:
Here are the 18z models interpolated to the current position:







Models are already wrong, Xtrap shows the direction its moving, so how in the hell is it gonna follow those models, models are crap right now and should be avoided at all cost
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Quoting cajunkid:
I witnessed a few of those 150mph metal roofs looking like a spent sardine can

Evenin' all. Hey that's what happened to my 150 rated metal roof in Katrina. Just make sure all the wood underneath is sound and/or clipped down. Mine peeled like a potato on one side of the house.
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2480. Skyepony (Mod)
I've watched 91L's surface obs since Hispanolia. It has had west winds on & off the whole time. Many over land across Cuba today. NHC mentioned the west winds yesterday morning. The low has been hovering & building just above the surface for 2 days. ULL exited SW & it stepped off land. Been telling ya'll..
Member Since: Αύγουστος 10, 2005 Posts: 164 Comments: 37866
2479. jipmg
Quoting Tazmanian:



thats not good and 91L is not moveing that march has well this could go too 91L toa strong TS in no time


pressures are barely dropping, dont jump the gun just yet
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Quoting freeroam:
Any idea when StormW giving next update? I hate waking up to a weather surprise.

Freeroam - Storm gave an update this AM. Normally doesn't do it on the weekend, but under these circumstances, we may see him do another one tomorrow.
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2477. Grothar
Quoting jipmg:


guess I was correct about the center being a bit south than originally estimated, and yes it will affect the track
Hope you are still on. I forgot to comment. It appears you saw something which may prove to be correct. Weather456 provided a concise explanation for me as to the dynamics. Good observation on your part!!!
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2476. Melagoo


Ana his very little energy compared to Bill
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Link

anticylcone right over 91L. One of the several essential ingredients...
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Quoting Tazmanian:



thats not good and 91L is not moveing that march has well this could go too 91L toa strong TS in no time


reminds me of Humberto, tiny basically a vort cane, if it touches surface and this thing will spin up rapidly.
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Quoting WeatherStudent:
:)


A new avatar! Very nice.
Member Since: Απρίλιος 26, 2009 Posts: 3 Comments: 3667
Bill...

Member Since: Σεπτέμβριος 1, 2007 Posts: 0 Comments: 1979
2471. flsky
Quoting stormbottom:
before the storms get any closer- i dont post at all normally..just listen...let me thank you all in advance for your expertise and advice...most of you were here during my roof lift off during frances..and kept me from freaking out during jeanne and wilma and the rest...talking about the storms takes alot of the fear out...so thanks -glad you're here for everyone as we enter another exciting season of dodge the bullet !


What a nice post! Too bad we don't have more like this. Thanks!
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I just went for a bike ride and we have 91L and i think it has a good chance of becoming a TD by morning.
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2469. geepy86
Quoting stormshed:
oh yeah the boomers have started. where you at in brevard?

Canaveral Groves. It's raining cats and dogs. lol
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Quoting AllStar17:
Interesting trends with the models. 3 of them now take Ana SOUTH of the Caribbean islands, 1 takes them OVER the islands, and 1 takes Ana NORTH of the Caribbean islands. I would expect another shift slightly south at 11 from the NHC, more in conjunction with the UKMET, GFDL, as well as the NGFDL. The GFS does not even initialize the storm, and it also appears the HWRF dissipates the storm over the islands, and the NOGAPS seems to be the northern-most model solution. JMO, but I would think another shift south in the track could be in order at 11. A Caribbean track would not be good, as the TCHP is very high, and could produce rapid intensification of Ana if it were to traverse those waters, if it were to encounter a favorable upper air environment while passing south of the Caribbean islands. Just speculation, however.



Wow that would be a lot of time over warm water...
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Anyone notice those two pieces of energy down in Central America? Some pretty big cloud tops, and it looks like the energy split in two, with one piece heading west into the Pacific and the other trying to head NE into the Caribbean Sea. Probably have to wait to see if they hold convection together over the open water, but if so, that Caribbean water looks rips for something. Anyone have any read on wind shear down there?
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2465. IKE
Quoting TexasHurricane:
Can someone post a good picture of Bill please??
Quoting TexasHurricane:


so it is suppose to go towards LA not the Florida panhandle?


It's listed as moving at 300 degrees, which is true WNW.

It's listed at 25.9N and 83.1W on WU. That would put it coming in just west of NO,LA.
Member Since: Ιούνιος 9, 2005 Posts: 23 Comments: 37858
if tonites quikscat hts 91L that should tell us how organized it is at the surface.
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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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