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: 1464 - 1414

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 canesrule1:
The highest winds Recon has picked up is 44 knots.

SHOW ME HOW YOU GOT THAT IS IT ON TROPICAL ATLANTIC RECON IF IT IS WHERE
Member Since: Posts: Comments:
1460. Patrap
T S BILL 2km Storm Relative IR Imagery with BD Enhancement Curve


Member Since: July 3, 2005 Posts: 426 Comments: 128668
Quoting wunderkidcayman:

SO AM I


Two in West Bay and two in South Sound !
Member Since: Posts: Comments:
Caicos Sailor, good resource there. Thanks
Member Since: Posts: Comments:
1457. jipmg
convection blows up over ana's center
Quoting StadiumEffect:


CI, I'm in West Bay.

SO AM I
Member Since: Posts: Comments:
Quoting wunderkidcayman:
HEY GUYS I DON'T SEE NO DATA FROM NOAA43 ONLY NOAA N49RF AND ONLY ON THERE SECOND DROPSONDE
The highest winds Recon has picked up is 44 knots.
Member Since: Posts: Comments:
Quoting Relix:
Looking at the Water Vapor image WBP posted I would dare say Ana is sightly N of the forecast points.


Not really, its actually spot on, you're looking at the convection which is slightly removed north of COC.
Member Since: Posts: Comments:
Quoting canesrule1:
I see all Bill's models are curving it out to see, is there still any chance of a hit for me here in Miami?


I don't know about that. I think it is going to be an east coast storm. FL GA, SC and perhaps NC bears watching with bill. Fl mostly with ana.

Member Since: Posts: Comments:
Quoting Weather456:
For those who think the wave coming off Africa is heading out to sea, just remember both Ana and Bill emerged at the same lat, with Ana much more north


Noteable is that each one seems to double in size. Also there is a symetric "helix" like flow surrounding the 3 systems.
Member Since: Posts: Comments:
Quoting WPBHurricane05:


Hebert is correct.

Pronounced A-bear. (j/k)
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting mobilegirl81:

StormW said that a ridge will build back in and maybe drive the system back west which would turn it into a double threat.
so we might have Ana and Bill in a period of 5 days, damn!
Quoting weatherblog:


Yes, models change all the time. Yesterday the models were pointing to the GOM, so who knows where this storm will go.
i agree.
Member Since: Posts: Comments:
South trend continues.
Member Since: Posts: Comments:
Hubby Bill is pleased about his new namesake.

Thinking of all the folks in harm's way.
Hope folks will prepare early.



Member Since: Posts: Comments:
center on Ana is not gonna be exposed much longer. convection firing right by it.
Member Since: Posts: Comments:
S FL wave actually building a little convergence, finally. We'll see if it holds after sunset.

And look at Bill! Big pick up in convergence.



From CIMMS: http://cimss.ssec.wisc.edu/tropic2/real-time/windmain.php?&basin=atlantic&sat=wg8&prod=conv&zoom=&t ime=
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting StadiumEffect:


CI, I'm in West Bay.
Seems like there are more West Bayers than any other district represented here.
Member Since: Posts: Comments:
RE:

1410. StadiumEffect 6:04 PM EDT on August 15, 2009

Quoting all4hurricanes:

Just last blog We proclaimed Cayman the Hurricane Capital of the World.

We must be, because in recent years not a year has gone by when we haven't had at least one warning for the season. It crazy that we get brushed so often.
------------------------------

For some actual statistics, I would recommend:


http://stormcarib.com/climatology/freq.htm

Climatology
of Caribbean Hurricanes

Hits & Misses


Below an overview of the number of named tropical systems (hurricanes and tropical storms) passing by within 60nm (or 69 miles) of each of all the major Caribbean islands and Bermuda. The locations below are sorted by number of severe hurricanes (category 3-5) over the period 1851-2008.


The prize for 'Hurricane Capital of the Caribbean' goes to the island of Abaco in the Bahamas, with 18 severe hurricanes since 1851 (which is on average one hurricane per 8-9 years), although in the last 60 years there were only 4 (one hurricane every 15 years). Since 1944 Nevis, Key West and Cuba (Habana) have seen the most severe hurricanes (7 or about one every 8-9 years).
Member Since: Posts: Comments:
Quoting WPBHurricane05:
Ana fighting dry air. Wonder if she'll have a real good DMAX.



Looks like some thunderstorms are starting to re-fire near the center... going to be interesting to see if this is the start of Ana getting better organized overnight or if she will continue to struggle for another day.
Member Since: Posts: Comments:
1441. jipmg
Quoting cajunkid:



dude, they're doing the same thing they always do. Just chill, we have a long ways to go.


it just irritates me how everyone jumps on them everytime they come in, and then see it as a confirmation as to were the storm will go.
1440. Patrap
T S ANA AVN CH Loop
Member Since: July 3, 2005 Posts: 426 Comments: 128668
Quoting SavannahStorm:


WOW you must be so impressed by it your Caps Lock key got stuck.

Now that was funny LOL!!!
Member Since: Posts: Comments:
HEY GUYS I DON'T SEE NO DATA FROM NOAA43 ONLY NOAA N49RF AND ONLY ON THERE SECOND DROPSONDE
Member Since: Posts: Comments:
Quoting canesrule1:
I see all Bill's models are curving it out to see, is there still any chance of a hit for me here in Miami?


Yes, models change all the time. Yesterday the models were pointing to the GOM, so who knows where this storm will go.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
how long until dmax.... someone has a picture
Member Since: Posts: Comments:
Quoting stormwatcherCI:
Didn't know you were in CAyman too. Which district ?


CI, I'm in West Bay.
Member Since: Posts: Comments:
1434. Relix
Looking at the Water Vapor image WBP posted I would dare say Ana is sightly N of the forecast points.

Member Since: Posts: Comments:
Quoting canesrule1:
I see all Bill's models are curving it out to see, is there still any chance of a hit for me here in Miami?

StormW said that a ridge will build back in and maybe drive the system back west which would turn it into a double threat.
Member Since: Posts: Comments:
Quoting TampaMishy:
Hebert box or however you spell it?


Hebert is correct.
Member Since: Posts: Comments:
Quoting btwntx08:

ok but im not saying 3 systems yet cause the nhc hasn't mention it yet


Wen i looked earlier today the Coordinates were the same for the new system and bill. Its just a misprint it did the same thing in the pacific early this month.
Member Since: Posts: Comments:
Quoting Weather456:
For those who think the wave coming off Africa is heading out to sea, just remember both Ana and Bill emerged at the same lat, with Ana much more north



True enough, but Ana is where it is because it not only remained weak for most of the trek across the Atl., but was also declassified as a TD once. Weak systems always come West in the low level flow and are prone to a WSW heading ( which Ana took for a while ) if they come under the influence of winds from the ENE.

Had Ana become a TS and strenghtened much earlier I dare say it would be much further N now IMO.
Member Since: Posts: Comments:
Quoting weatherblog:


Yeah, but at the same time it was rapidly strengthening to a hurricane. Also, it's landfall in western Cuba it was a cat 5. Not to mention it missed the worst mountains so that's why it didn't weaken much. Ike, on the other hand, was a category 4 when it traveled the spine of Cuba so of course it didn't dissipate fully.

Ana is expected to be a weak tropical storm. It's having enough problems with the shear and the dry air, so large mountains will certainly bring it to it's death.
I just read that Ike had a lot of problems getting organized due to dry air , wind shear and what have you yet as you just pointed out Ike became a Cat 4 and Ana is still a few days off from the islands. I have seen first hand how quickly hurricanes develop in the Caribbean so I am not discounting any possibilities this time of year.
Member Since: Posts: Comments:
Quoting Weather456:
For those who think the wave coming off Africa is heading out to sea, just remember both Ana and Bill emerged at the same lat, with Ana much more north


You got that right W456, looks like you might be right in the line of fire, keep safe, I'm sure you're always well prepared though.
Member Since: Posts: Comments:
Quoting Orcasystems:

ANA

TD3

AOI


I think Florida is in for one solid pounding
Ummm as a side note... did anyone notice Ana and Bill are both going thru a certain square area of Oceon?
Hebert box or however you spell it?
Member Since: July 30, 2007 Posts: 0 Comments: 1474
Quoting jipmg:


this is the thing, the models have been so stupid with these systems ever since they came of Africa, I honestly dont knwo why the hurricane center even trusts them..

In either case, I still see ana moving north of due west DESPITE model forecast in the short term, adn there is convection blowing over the center



dude, they're doing the same thing they always do. Just chill, we have a long ways to go.
Member Since: Posts: Comments:
I see all Bill's models are curving it out to see, is there still any chance of a hit for me here in Miami?
Member Since: Posts: Comments:
Ana fighting dry air. Wonder if she'll have a real good DMAX.
Member Since: Posts: Comments:
1421. Relix
Shouldn't Ana have started its WNW turn already?
Member Since: Posts: Comments:
1420. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 128668
does anyone have a link to the UKMET n NOGAPS model pages?
Member Since: Posts: Comments:
Quoting stormwatcherCI:
Gustav developed into a depression in the SE Caribbean.


Yeah, but at the same time it was rapidly strengthening to a hurricane, and it's landfall in western Cuba was at cat 5 intensity. Not to mention, it missed the worst mountains which explains why it didn't weaken too much. Ike, on the other hand, was a category 4 when it traveled the spine of Cuba so to nobody's surprise it didn't dissipate fully.

Ana is expected to be a weak tropical storm. It's having enough problems with the shear and the dry air, so large mountains will certainly bring it's tiny circulation to death.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
For those who think the wave coming off Africa is heading out to sea, just remember both Ana and Bill emerged at the same lat, with Ana much more north

Member Since: Posts: Comments:
Heavy rain bands here in south Palm Beach County.Squally weather from this system which certainly has some spin to it some 100 miles southeast of Naples.
Member Since: Posts: Comments:
Quoting btwntx08:

actually 2 systems where did u get three??


disturbance off the coast of S. florida (gulf coast)
Member Since: Posts: Comments:

Viewing: 1464 - 1414

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.

Local Weather

Overcast
64 °F
Overcast