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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4814. Patrap
01:32 AM GMT on Αύγουστος 31, 2009
2 Sept 2008

363 days ago.

Member Since: Ιούλιος 3, 2005 Posts: 414 Comments: 125569
4813. Patrap
04:02 PM GMT on Αύγουστος 16, 2009
NexSat GOM VIZ Loop
Member Since: Ιούλιος 3, 2005 Posts: 414 Comments: 125569
4812. TampaSpin
02:40 PM GMT on Αύγουστος 16, 2009
Here is my complete Tropical Update including TD4, ANA, and BILL
Member Since: Σεπτέμβριος 2, 2007 Posts: 177 Comments: 20430
4811. pinehurstnc
02:33 PM GMT on Αύγουστος 16, 2009
hello all. from the golf capital of the usa... been reading this blog for 3 years, hope all are safe and well.. first time here.. so. here goes,,,, i was watching the stormcarib.com site sat pics.. ana and td 4 look like a severe thunderstorm watch ought to be issued. i have seen bigger storms come thru nc than this ,, also there are quite a few here whom are met smart,, kudos ,, to you helping all.. i enjoy this site,, so thank you all..
Member Since: Αύγουστος 13, 2009 Posts: 0 Comments: 59
4810. theshepherd
02:04 PM GMT on Αύγουστος 16, 2009
Quoting LightningCharmer:


Was in the Keys yesterday in Islamorada. There were some good gusts in this overblown thunderstorm as some have refered to it but overall it was a rainmaker. Today you're going to need sunscreen or a good hat for your kayaking. It's a bright one outside. Good luck on the flats.

Good for you.
Yup, got the hat and long sleeves and pants. Better than sunscreen.
For those directly under it, it's was impressive.
There are some sailboaters and spongers anchored "a bit differently" than where they left them night before last.
Member Since: Σεπτέμβριος 11, 2008 Posts: 9 Comments: 10030
4808. CJ5
02:02 PM GMT on Αύγουστος 16, 2009
Ana and Bill both had a bad night. Ana seems to like to dress up at night fall only to lose it in the am. She continues the walk of shame each morning. Dyr air is an issue with her but unlike last morning she has some convection around her coc. She continues to move W as does Bill. I think both of these are vigorous storms and it will take a lot of different dynamics to kill them off. Another watch and see day. I will say I do not believe the NW turn for Bill as earlier a modeled righ now. If Ana does follow the models she will cross the hottest waters anywhere in a few days.
Member Since: Ιούλιος 4, 2007 Posts: 0 Comments: 1755
4807. KEHCharleston
02:01 PM GMT on Αύγουστος 16, 2009
Was wondering if TD4 will decrease SST's where it passes through

This buoy is at 28.5N and 84.5W - W. TAMPA 106NM West Northwest of Tampa, FL
Is this a normal variation?

Member Since: Αύγουστος 19, 2008 Posts: 6 Comments: 2490
4805. Progster
01:59 PM GMT on Αύγουστος 16, 2009
Quoting homelesswanderer:
Could those rising pressures around td4 be the bermuda high building in? Forgive me if this a stupid question.:) won't be the first...



there's a daily cycle of surface pressures in the tropics. From wikipedia (under atmospheric pressure):

"Atmospheric pressure shows a diurnal (twice-daily) cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with amplitude of a few millibars, and almost zero in polar areas. These variations have two superimposed cycles, a circadian (24 h) cycle and semi-circadian (12 h) cycle".

you can see this when you plot surface pressures from buoys in the tropical oceans. In the absence of storms, the pressure varies a few mb up and down every day in an even cycle.

you can see the daily pressure variation (green line) from this Carribean buoy (link below).

Link
Member Since: Σεπτέμβριος 4, 2007 Posts: 0 Comments: 490
4804. Cotillion
01:58 PM GMT on Αύγουστος 16, 2009
Quoting WPBHurricane05:


Her environment is starting to moisten up.


Yeah, not as much dry air to contend with, and not a moisture grabbing ULL either.

Not being sheared right now either, but it's really on the cusp of okay shear. Any quick job north and it has to face 20kts at least of westerlies.

It may be an open wave as some have indicated, the cyclonic turning doesn't seem nearly as much as it was. Even if that is the case, there's always the chance that she'll re-spin a LLC anyway.
Member Since: Αύγουστος 23, 2008 Posts: 7 Comments: 5300
4802. IKE
01:59 PM GMT on Αύγουστος 16, 2009
NEW BLOG!
Member Since: Ιούνιος 9, 2005 Posts: 23 Comments: 37858
4801. Orcasystems
01:57 PM GMT on Αύγουστος 16, 2009
Blog Update
Reflector site for those at work, which includes

Weather456, daily update.


ANA

Bill

TD4
Member Since: Οκτώβριος 1, 2007 Posts: 81 Comments: 26493
4800. bajelayman2
01:59 PM GMT on Αύγουστος 16, 2009
Quoting leftovers:
rehab is rehab. good luck in barbados this yr


LOL. Thanks.
Member Since: Αύγουστος 13, 2007 Posts: 0 Comments: 478
4799. stormpetrol
01:56 PM GMT on Αύγουστος 16, 2009

can't make out a closed low on Ana, maybe semi closed but thats it, jmo
Member Since: Απρίλιος 29, 2007 Posts: 0 Comments: 7506
4796. WPBHurricane05
01:55 PM GMT on Αύγουστος 16, 2009
Quoting Cotillion:
Ana has actually managed to hide beneath her convection for about 2 hours now. Almost tempted to give her a medal.



Her environment is starting to moisten up.
Member Since: Ιούλιος 31, 2006 Posts: 56 Comments: 8112
4795. Nolehead
01:55 PM GMT on Αύγουστος 16, 2009
surf alert for the GOM....i'm sure surfmom is already in.....heading to PC in a few hours gonaa hit Amazons...time for some real stuff for a change....waxem if you got em.....
Member Since: Ιούνιος 3, 2008 Posts: 0 Comments: 1923
4794. java162
01:55 PM GMT on Αύγουστος 16, 2009
looking at the models, the islands of guadeloupe and dominica are in the center of ana's path. cananyone explain to me why none of these islands have posted tropical storm advisories?
Member Since: Ιούλιος 24, 2009 Posts: 0 Comments: 300
4793. weatherwiz
01:55 PM GMT on Αύγουστος 16, 2009
Ana will more and likely be downgraded to a tropical depression or just a tropical low. This storm has endured extreme amounts of dry air from the north.
Member Since: Δεκέμβριος 24, 2006 Posts: 0 Comments: 30
4791. stormpetrol
01:54 PM GMT on Αύγουστος 16, 2009
Quoting Golladan:


Which puts him much south of what the satellite images make you believe.

Correct and contrary to the thoughts of some here "Bill" is still moving due west its just the expansion of this storm giving the illusion of a WNW movement, just my opinion of course.
Member Since: Απρίλιος 29, 2007 Posts: 0 Comments: 7506
4790. TheDawnAwakening
01:55 PM GMT on Αύγουστος 16, 2009
Quoting HurricaneKyle:


Refer to post 4766. :)


Thanks I saw that post after I posted.
Member Since: Οκτώβριος 21, 2008 Posts: 243 Comments: 3564
4788. amd
01:53 PM GMT on Αύγουστος 16, 2009
Quoting Thaale:
Models shifted Bill even more N and E at 8:00 AM and the GFS now has him going way E of Bermuda instead of right over. The wc crowd is getting desperate; instead of "follow the trend," it's "these things always zig-zag back and forth." Too bad for them it's been all zig.

The NHC track will yet again shift further up and right in an hour.


I agree, with one major caveat. I think the models are really overdoing the intensity of Bill. Dry air is in the core of Bill right now, as shown by the latest imagery. Also, many of these same models a couple days ago had Bill approaching hurricane strength at this time, but that simply has not occurred.

So, even though all indications are that Bill will turn out to sea well in advance of any land mass, I would like to see more strengthening before that is an absolute certainty. JMHO.
Member Since: Αύγουστος 29, 2005 Posts: 0 Comments: 1024
4787. LightningCharmer
01:53 PM GMT on Αύγουστος 16, 2009
Quoting cajunkid:
Hah, I thought pressure was too high for anything to develop in the gulf. When are people going to learn...never proclaim things as absolutes when dealing with weather
I'm no expert but have been studying weather as a hobby since childhood. It's not the pressure per se or absolute. It's the pressure relative to the surrounding area. The pressure in TD4 is not that low but lower than the surrounding pressure hence it's a low.
Member Since: Σεπτέμβριος 1, 2007 Posts: 0 Comments: 1113
4785. Cotillion
01:52 PM GMT on Αύγουστος 16, 2009
Ana has actually managed to hide beneath her convection for about 2 hours now. Almost tempted to give her a medal.

Member Since: Αύγουστος 23, 2008 Posts: 7 Comments: 5300
4784. Golladan
01:52 PM GMT on Αύγουστος 16, 2009
Quoting stormpetrol:

great quikscat of "Bill" COC around 11.5N in my estimation.


Which puts him much south of what the satellite images make you believe.
Member Since: Αύγουστος 16, 2009 Posts: 0 Comments: 17
4783. weatherwiz
01:51 PM GMT on Αύγουστος 16, 2009
By the 11am advisory TD#4 should be Claudette. The definition of this storm is good and multiple feeder bands are present, it won't have no time to strengthen though so I don't think a hurricane would be imminent.
Member Since: Δεκέμβριος 24, 2006 Posts: 0 Comments: 30
4782. stormpetrol
01:51 PM GMT on Αύγουστος 16, 2009
I think Ana is now an open wave.
Member Since: Απρίλιος 29, 2007 Posts: 0 Comments: 7506
4781. HurricaneKyle
01:51 PM GMT on Αύγουστος 16, 2009
Quoting TheDawnAwakening:
Pressures just seem out of wack for a storm that looks as good as TD4. Maybe this will be known as the almost Humberto.


Refer to post 4766. :)
Member Since: Αύγουστος 10, 2009 Posts: 3 Comments: 672
4780. WeatherGirl80
01:51 PM GMT on Αύγουστος 16, 2009
Anyone here think that TS Ana, IF it makes it to the GOM, could regenerate once it hits those warm SST's?
Member Since: Σεπτέμβριος 1, 2008 Posts: 0 Comments: 4
4778. MandyFSU
01:49 PM GMT on Αύγουστος 16, 2009
ITCZ- you're right near me then! I'm in Tallahassee!
Member Since: Αύγουστος 24, 2005 Posts: 82 Comments: 2525
4777. bajelayman2
01:48 PM GMT on Αύγουστος 16, 2009
Quoting leftovers:
reason surfers get wrapped up on drugs just not enough surf thank god for bill


Ya want a cargo ship to drop you into Bill's centre, for REAL waves?

;-)
Member Since: Αύγουστος 13, 2007 Posts: 0 Comments: 478
4776. TheDawnAwakening
01:48 PM GMT on Αύγουστος 16, 2009
Pressures just seem out of wack for a storm that looks as good as TD4. Maybe this will be known as the almost Humberto.
Member Since: Οκτώβριος 21, 2008 Posts: 243 Comments: 3564
4775. PensacolaDoug
01:48 PM GMT on Αύγουστος 16, 2009
Quoting WeatherGirl80:
Anyone here think that TS Ana, IF it makes it to the GOM, could regenerate once it hits those unobstructed warm SST's?



Thats a real big "IF">
Member Since: Ιούλιος 25, 2006 Posts: 0 Comments: 519
4774. tiggeriffic
01:48 PM GMT on Αύγουστος 16, 2009
TWC has td04 going toward Panama City at this point...people down play storms all the time, people die in flood water faster than wind all the time...think about it..you don't need a surge to die...the rain and floods in the Appalachian mts earlier this year killed a bunch...got family up there...no one expected anything like that just from rain..
Member Since: Σεπτέμβριος 16, 2007 Posts: 0 Comments: 3599
4773. CaneWarning
01:48 PM GMT on Αύγουστος 16, 2009
Quoting theshepherd:
That speaks volumes.


Not sure what you mean by that, but the majority of people don't go anymore, especially outside of the "Bible belt". Anyway, I'm not going to discuss it further.
Member Since: Απρίλιος 26, 2009 Posts: 3 Comments: 3667
4771. nrtiwlnvragn
01:47 PM GMT on Αύγουστος 16, 2009
000
NOUS42 KNHC 161345
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0945 AM EDT SUN 16 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 17/1100Z TO 18/1100Z AUGUST 2009
TCPOD NUMBER.....09-080

I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM ANA
FLIGHT ONE -- TEAL 72
A. 17/1800Z,18/0000Z
B. AFXXX 0302A ANA
C. 17/1600Z
D. 16.8N 64.6W
E. 17/1700Z TO 18/0000Z
F. SFC TO 10,000 FT

FLIGHT TWO -- TEAL 73
A. 18/0600Z,1200Z
B. AFXXX 0402A ANA
C. 18/0330Z
D. 17.6N 68.2W
E. 18/0500Z TO 18/1200Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES IF
SYSTEM REMAINS A THREAT.

3. REMARKS: A RESOURCES PERMITTING TASKING ON TROPICAL
DEPRESSION 2 IN THE GULF OF MEXICO WILL BE LAUNCHED
TODAY AT 16/1500Z.


II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
JWP




I think they mean TD4 in the Gulf
Member Since: Σεπτέμβριος 23, 2005 Posts: 13 Comments: 10462
4770. Walshy
01:47 PM GMT on Αύγουστος 16, 2009
Quoting tiggeriffic:
bounced in for just a few...tho i am no met... i have seen the so called wobble many times... especially over night...bill's center appears to be reforming...maybe even a tad to the south of the old one...if this is true then the models will shift again to the south closer to the UKMET...not that I trust the UKMET mind you...but radiational cooling does a lot to a forming storm...even big ones have eye wall replacement and they can reform in any direction of the original eye...no storm is a fish storm...last year a fish storm hit the UK...just cuz it isn't a US storm doesn't make it a fish storm by any means



I think the east coast and Bermuda needs to watch Bill closely. If Bill is a major hurricane expect 1-10 deaths from Florida to North Carolina due to rough waves.
Member Since: Μάιος 17, 2009 Posts: 2 Comments: 904
4769. Thaale
01:47 PM GMT on Αύγουστος 16, 2009
Models shifted Bill even more N and E at 8:00 AM and the GFS now has him going way E of Bermuda instead of right over. The wc crowd is getting desperate; instead of "follow the trend," it's "these things always zig-zag back and forth." Too bad for them it's been all zig.

The NHC track will yet again shift further up and right in an hour.
Member Since: Οκτώβριος 19, 2005 Posts: 0 Comments: 308
4768. WPBHurricane05
01:47 PM GMT on Αύγουστος 16, 2009
The problem with the models is that these same models had Ana hitting S. Florida, now look where she is at. I'm gonna have to jump in the "the models are underestimating the high pressure" boat.

The UKMET has a pretty good handle on Ana, why not Bill? There is no way that whatever is left of Ana will go over Hispaniola when it is going 20 mph due west.

The UKMET is also the southern outlier with Bill too.
Member Since: Ιούλιος 31, 2006 Posts: 56 Comments: 8112
4767. naplesdreamer28
01:47 PM GMT on Αύγουστος 16, 2009
Heck, I can barely make out where Ana even is on the map! But, as with any of these storms, she looks to be moving into some warmer waters and could make a come back.

I also see the track she is so far taking, but any jog to the N would put it closer to FL, right?
Member Since: Ιούλιος 3, 2008 Posts: 0 Comments: 242
4766. HurricaneKyle
01:47 PM GMT on Αύγουστος 16, 2009
Quoting amd:
for all the hype about TD4, radar clearly shows that showers not even 50 miles to the north of the system are not being pulled into TD4. This is what Dr. Lyons mentioned in his tropical update. These showers can not be wrapped into the system because the pressures are just too high.

Also, with Humberto, pressures were already low over the western gulf before the storm began to develop, and an eye like feature was noticed when Humberto was a 45 mph tropical storm.

TD4 will be nothing like Humberto. Humberto's pressure was at 986 mb right before landfall, while TD4's pressure is supposedly 1011 mb.


TD4 is embedded in a area of high pressure, higher than normal, thats why the pressure is so high for TD4. Dr. Lyons said Pre-Ana and pre-Bill would dissipate and yesterday only briefly mentioned pre-TD4 but as you would expect didn't think much of it.
Member Since: Αύγουστος 10, 2009 Posts: 3 Comments: 672
4765. LightningCharmer
01:47 PM GMT on Αύγουστος 16, 2009
.
Quoting theshepherd:
Nope... My bad if that came across wrong, I was not reffering to you at all. Keyboards can be a bain on communications sometimes.
Clearer skies yep, mucked up water Yep.
I realize it could be refering to who I was refering to also. I did not take offense even if you really had ment it which I realize you didn't.

Was in the Keys yesterday in Islamorada. There were some good gusts in this overblown thunderstorm as some have refered to it but overall it was a rainmaker. Today you're going to need sunscreen or a good hat for your kayaking. It's a bright one outside. Good luck on the flats.
Member Since: Σεπτέμβριος 1, 2007 Posts: 0 Comments: 1113
4764. homelesswanderer
01:46 PM GMT on Αύγουστος 16, 2009
Could those rising pressures around td4 be the bermuda high building in? Forgive me if this a stupid question.:) won't be the first...
Member Since: Αύγουστος 15, 2008 Posts: 10 Comments: 3665

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About JeffMasters

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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