Ana and TD 3 take aim at the Lesser Antilles

By: Dr. Jeff Masters , 4:17 PM GMT on August 15, 2009

Share this Blog
7
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 3164 - 3114

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97Blog Index

Quoting WeatherStudent:


She's right, PressLord. You do not behave your age AT ALL, bud.
O man I might die form Laughter, I cant even push 911!!!1
Member Since: Posts: Comments:
Quoting PcolaDan:




Alright.. you went searching for one.. I emailed you one.. how many did you eventually find??
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Repost from earlier:

Y'all know what is more annoying than WS's posts? When he becomes a primary topic of conversation. Someone please post a WS drama blog in their own space and take it there. That would be nice.
Addendum: I see the effect worsened as I typed this post. Apropos.
Member Since: Posts: Comments:
Quoting WeatherStudent:


She's right, PressLord. You do not behave your age AT ALL, bud.


not sure what language you speak, pumpkin...but here we speak English...and that ain't at all what she said...
Member Since: Posts: Comments:
RSO
Member Since: Posts: Comments:
Quoting DM21Altestic:

You're 17, yet you act like you're still in 5th grade.


Im 42 and have a pic of me riding the Poomba at Wal Mart last week...
Member Since: Posts: Comments:
WS...you def need an upgrade to your shower curtain haha. Might want to get something with just stripes or one solid color haha.
Member Since: Posts: Comments:
3154. Patrap
Anyone have tonights Sat Blackout times,duration..?
Member Since: Posts: Comments:
Quoting stormno:
VERY DANGEROUS SITUATION DEVELOPING OFF THE SE COAST OF FLA...ITS CLEAR A SURFACE LOW HAS FORMED JUST WEST OF SARASOTA AND IS MOVING NW AT ABOUT 8 MPH...FEEDER BANDS ARE STARTING TO DEVELOP FROM THE SOUTH OF THE SYSTEM AND PRESSURES ARE CONTINUING TO FALL...FOLKS THIS COULD LEAD TO RAPID INTENSIFICATION AS IT MOVES AWAY FROM THE SE COAST OF FLA OUT INTO THE GULF...ALL INTERESTS ALONG THE NORTHERN GULFCOAST SHOULD BE READY TO TAKE QUICK ACTION IF WARNINGS ARE ISSUED SUNDAY NIGHT OR EARLY MONDAY..THIS SYSTEM IS DEVELOPING RAPIDLY AND IT WILL BE NAMED CLAUDETTE TOMORROW..THERE IS NO SHEAR AND THE SST ARE IN THE 90S ..THIS COULD LEAD TO EXPLOSIVE DEVELOPMENT...PLEASE KEEP IN TOUCH WITH THE LATEST STATEMENTS..I WILL HAVE MORE INFO COMING INTO MY OFFICE AT 7AM AND I WILL HAVE ANOTHER BULLETIN ISSUED AT THAT TIME...RECON ARE ON STANDBY READY TO GO OUT TOMORROW AFTERNOON..STAY TUNED FOR MORE INFO ON THIS DANGEROUS SITUATION THAT IS DEVELOPING...Stormno


Really? do you work for NHC? lol i'd crap my pants if they ever released an official warning like that. 40mph TS tops, probably not even TD4
Member Since: Posts: Comments:
Quoting TampaSpin:


No i believe there is a surface low.....just checked bouy data

What buoy number?
Member Since: Posts: Comments:
3151. KEEPEROFTHEGATE (Mod)
Quoting presslord:
that avatar is just killin' me...Goober Beefcake...
ROFLOL

i just wondering was he sitting on the john when they took that picture
Member Since: Posts: Comments:
TampaSpin, what buoy did you check? I am here in Largo, and my barometer is 29.99, hardly impressive. Although I got to admit the radar appearance is ominous.
Member Since: Posts: Comments:
K-man's keen sense of observation along with Presslord's commentary are LMAO entertaining. Thanks guys.
Member Since: Posts: Comments:
I knew 91L was going to harvest today.
Member Since: Posts: Comments:
Quoting HaboobsRsweet:

You are dead right...when i was in high school i was so excited for storms to hit my area. I loved it. Now that I own a house 2 cars and a bunch of crap in the house, I dont want a storm to even think about coming near by plus here in Biloxi they have finally started making progress on rebuilding so we dont need another one right now.
thanks for the backup on that one
Member Since: July 31, 2009 Posts: 0 Comments: 324
.
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Quoting presslord:
that avatar is just killin' me...Goober Beefcake...


omg i think i might have injured a rib!
Member Since: Posts: Comments:
91l can't become a TD until it gets down to the surface

I dont expect it to be upgraded at 5 am
Member Since: Posts: Comments:
Quoting Orcasystems:


Ok, you guys forced me to look at what your talking about... not nice.. not nice at all.. that picture is just not right


Member Since: Posts: Comments:
omg look at the model that brings it off the coast, this might pull a humberto tonight then pull an ivan next week.


Member Since: Posts: Comments:
3139. Patrap
Member Since: Posts: Comments:
SHIPS has 91L at 40 knots at lanfall. Seems fairly conservitave to me. Any flights scheduled out there in the AM?
Member Since: Posts: Comments:
91L may be the Mobile hit that probability models showed on Aug 9th for later in the week...hmmm
Member Since: Posts: Comments:
Quoting hurricane23:
Just mid-levels mike nothing at the surface.Should be inland soon


No i believe there is a surface low.....just checked bouy data
Member Since: Posts: Comments:
know what do you think weather456 about 91L.... it is just getting better by the minute...
Member Since: Posts: Comments:
Member Since: October 1, 2007 Posts: 81 Comments: 26511
JFVs going for the Fans look with a finding Nemo theme.
Member Since: Posts: Comments:
Quoting stormno:
VERY DANGEROUS SITUATION DEVELOPING OFF THE SE COAST OF FLA...ITS CLEAR A SURFACE LOW HAS FORMED JUST WEST OF SARASOTA AND IS MOVING NW AT ABOUT 8 MPH...FEEDER BANDS ARE STARTING TO DEVELOP FROM THE SOUTH OF THE SYSTEM AND PRESSURES ARE CONTINUING TO FALL...FOLKS THIS COULD LEAD TO RAPID INTENSIFICATION AS IT MOVES AWAY FROM THE SE COAST OF FLA OUT INTO THE GULF...ALL INTERESTS ALONG THE NORTHERN GULFCOAST SHOULD BE READY TO TAKE QUICK ACTION IF WARNINGS ARE ISSUED SUNDAY NIGHT OR EARLY MONDAY..THIS SYSTEM IS DEVELOPING RAPIDLY AND IT WILL BE NAMED CLAUDETTE TOMORROW..THERE IS NO SHEAR AND THE SST ARE IN THE 90S ..THIS COULD LEAD TO EXPLOSIVE DEVELOPMENT...PLEASE KEEP IN TOUCH WITH THE LATEST STATEMENTS..I WILL HAVE MORE INFO COMING INTO MY OFFICE AT 7AM AND I WILL HAVE ANOTHER BULLETIN ISSUED AT THAT TIME...RECON ARE ON STANDBY READY TO GO OUT TOMORROW AFTERNOON..STAY TUNED FOR MORE INFO ON THIS DANGEROUS SITUATION THAT IS DEVELOPING...Stormno
This is the best yet LMAO LOL
Member Since: Posts: Comments:
3127. Patrap
Central Atlantic WV Loop

Member Since: Posts: Comments:
Quoting DM21Altestic:

What, the one I posted?


No the WS avatar
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting TampaSpin:
Here is the first model runs...HUM it has time to strengthen on that track.


And the 0 UTC GFS isn't one of them. Likes 91L for development about as much as I do...doesn't.
Member Since: Posts: Comments:
I am given 91L TD by 8am and TS by 2pm Sunday
Member Since: Posts: Comments:
Quoting kachina:


91L looks pretty nasty to me. Are the water temps and wind favorable for development?


Water temps are near 31.5 C

And theres an upper level high right over it.

Yeah its favorable.
Member Since: Posts: Comments:
Quoting code1:
Is it possible to gain a bit more of young and old testosterone in here? sheesh


Watch it, lady...old testosterone still works just fine....
Member Since: Posts: Comments:
Quoting TampaSpin:
Here is the first model runs...HUM it has time to strengthen on that track.

UH....nice red line there Tampa thanks for that image...sleeping with one eye open now...
Member Since: July 31, 2009 Posts: 0 Comments: 324
3117. kachina
Quoting Orcasystems:


Ok, you guys forced me to look at what your talking about... not nice.. not nice at all.. that picture is just not right


LOL!
Member Since: Posts: Comments:

Viewing: 3164 - 3114

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.