Disturbance 90L close to tropical depression strength; TD 2 may rise again

By: Dr. Jeff Masters , 2:02 PM GMT on August 14, 2009

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A strong tropical wave (90L), with a large circulation and a moderate amount of heavy thunderstorm activity, is a few hundred miles southwest of the Cape Verdes Islands, off the coast of Africa. This morning's QuikSCAT pass shows that 90L has a large circulation, but this circulation is not yet well-formed, as it is elongated along an east-west axis. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are gradually becoming better organized, with some spiral banding evident on the south side of the storm. Satellite intensity estimates from NOAA already put 90L at tropical depression strength with 30 mph winds, but the storm does not yet have a well enough formed circulation to be classified as a depression. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two was. However, there is some dry air from the SAL being sucked into the circulation of 90L, and this is retarding its development.

Wind shear is moderate, about 10 - 15 knots, but is forecast to fall to the low range, 5 - 10 knots, later today. Shear is then forecast to remain low for the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow 90L to develop into a tropical depression by Saturday, and potentially reach hurricane strength by Wednesday. Most of our reliable models strengthen 90L into a hurricane by Wednesday, when the storm is expected to be near the northern Lesser Antilles Islands. One important outlier is the ECMWF model, which has 90L passing to the north of the islands, and eventually recurving out to sea east of Bermuda. The ECMWF was by far the most reliable model for forecasting hurricane tracks last year. However, all of our models are pretty unreliable going out 5 days in advance for systems that have yet to reach tropical depression strength. Once 90L becomes a tropical depression and develops a well-formed circulation, the models will have a better handle on forecasting where it will go.


Figure 1. The remnants of Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).

Tropical Depression Two may come back
Tropical Depression Two died yesterday, but may rise again. Satellite loops of the remnants of the storm show that heavy thunderstorms are again attempting a comeback near the axis of what is now a tropical wave. However, dry air continues to interfere with the development of the thunderstorm activity, and moderately high wind shear of 15 - 20 knots is also inhibiting the process. Wind shear over the remnants of TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next four days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to the north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that any re-development of the storm will be slow to occur. NHC has given the system a medium (30 - 50% chance) of becoming a tropical depression again by Sunday morning. Only one reliable model, the NOGAPS, is predicting regeneration of TD 2. The NOAA Hurricane Hunters are flying research missions into the remnants of TD 2 today and Saturday.

I'll have an update Saturday morning, or earlier, if significant developments occur.

Jeff Masters

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5684. keithneese
7:43 PM GMT on August 15, 2009
I'm watching the satellite of the GOMEX, and there is quite a bit of thunderstorm activity out there. I can't see any type of spin though. Here's my local radar from Mobile Alabama. Got some rain coming in over the FL panhandle.


img
Member Since: February 7, 2008 Posts: 67 Comments: 186
5683. chucky7777
7:16 PM GMT on August 15, 2009
here is the latest from NWS Key West concerning the tropical "WAVE" currently moving through the Keys.............DISCUSSION...
.CURRENTLY...
THE NORTHERN EXTENT OF A WESTWARD MOVING TROPICAL WAVE IS TRAVERSING
THE KEYS AND COASTAL WATERS. THE AXIS OF THE WAVE APPEARS TO BE
MOVING THROUGH THE LOWER KEYS AND THE FLORIDA STRAITS SOUTH OF THE
LOWER KEYS...WITH A BROAD CIRCULATION FROM AROUND 850 TO 700MB STILL
NOTICEABLE ON KEY WEST RADAR IN THE GENERAL VICINITY OF THE LOWER
KEYS. A SHEAR ZONE ALONG THE AXIS HAS BEEN EVIDENT ON KBYX RADAR
THROUGH THE MORNING...WITH NEAR SURFACE SOUTHWESTERLY WINDS OPPOSING
SOUTHEASTERLY WINDS. LOOKING AT BOTH THE KBYX AND KAMX RADARS...A
NORTHEASTWARD PROPAGATING WIND MAXIMUM FROM AROUND 2KFT TO 5KFT
SEEMS TO BE MOVING ALONG THE SHEAR LINE...WHICH MAY HAVE HELPED
INITIATE SOME OF THE STRONGER CELLS. THIS SHEAR ZONE HAS FORCED
SEVERAL VERY STRONG CELLS FROM 15 TO 40 MILES SOUTH OF THE LOWER
KEYS...INCLUDING AT LEAST THREE RELATIVELY DEEP MESOCYCLONES...
BASICALLY IN THE SAME GENERAL AREA...ONE OF WHICH TRIGGERED A MESO
ALERT. THE MESOS WERE FAIRLY SHORT LIVED...LASTING LESS THAT ONE HALF
HOUR. ALL OF THESE MESOCYCLONES WERE PRODUCING IMPRESSIVE
UPDRAFTS...WITH TOPS EXCEEDING 55KFT ABOVE THEM. THE SHEAR ZONE HAS
BEEN ALMOST STATIONARY FOR THE PAST SEVERAL HOURS...THUS THE
STRONGEST CELLS HAVE THANKFULLY REMAINED SOUTH OF THE LOWER KEYS.
EVEN WITH THE WORST SOUTH OF THE KEYS...AREAS ALONG THE LOWER KEYS
HAVE EXPERIENCED HEAVY RAIN WITHIN A RELATIVELY SHORT PERIOD OF TIME.
A SPOTTER ON CUDJOE KEY CALLED IN WITH 2 INCHES OF RAIN SINCE THE
BEGINNING OF THE EVENT EARLIER THIS MORNING. AN OFF DUTY NWS EMPLOYEE
ON BIG COPPITT KEY REPORTED ABOUT AN INCH OF STANDING WATER ON THE
LOWEST FLOOR OF HIS HOUSE...THE ACCUMULATION OF WATER POSSIBLY AIDED
BY 30MPH WINDS WHICH ACCOMPANIED THE HEAVER STORMS THAT TRAVERSED THE
LOWER KEYS.
Link
Member Since: October 19, 2005 Posts: 0 Comments: 174
5682. ncwxman68
5:22 PM GMT on August 15, 2009
Just a real quick post concerning the area near the keys...observations from Long Key Light since 3:00 am EDT...

Station LONF1 - Long Key, FL

MM DD TIME (EDT) WIND PRES TEND ATMP WTMP SAL
08 15 11:00 am S 24 G28 - - - - 30.04 +0.07 76.6 86.4 - 38.60 -
08 15 10:00 am SSE 18 21 - - - -30.01 +0.04 77.7 86.7 - 37.94 - -
08 15 9:00 am ESE 7 8 - - - - 30.00 +0.04 82.2 87.1 - 37.17 - -
08 15 8:00 am - 0 2 - - - - 29.98 +0.01 82.4 87.1 - 36.77 - -
08 15 7:00 am SE 6 7 - - - - 29.97 +0.00 82.6 87.3 - 36.76 - -
08 15 6:00 am SE 15 17 - - - - 29.96 -0.01 80.2 87.4 - 36.97 - -
08 15 5:00 am SSE 13 15 - - - -29.97 -0.01 83.7 87.8 - 38.25 - -
08 15 4:00 am SE 14 16 - - - - 29.97 -0.03 83.8 88.0 - 38.71 - -
08 15 3:00 am ESE 14 15 - - - -29.97 -0.06 84.7 88.2 - 38.58 -

Water Temp 86.4 degrees. WOW.
Member Since: August 13, 2009 Posts: 0 Comments: 17
5681. largeeyes
5:22 PM GMT on August 15, 2009
Ah-na....reminds me of a Jeff Dunham skit.
Member Since: August 22, 2006 Posts: 0 Comments: 1459
5680. jipmg
5:04 PM GMT on August 15, 2009
Bill no longer moving WSW
5679. jipmg
5:01 PM GMT on August 15, 2009
Quoting hurricanejunky:
Any thoughts on the newly swirling area in the central Gulf? Is that a ULL?


no its a strong middle level low with a strengthening surface area of low pressure based on observations
5678. ncwxman68
5:00 PM GMT on August 15, 2009
roger that stormwatcherCI!

off to work folks, back tonight.
Member Since: August 13, 2009 Posts: 0 Comments: 17
5677. stormwatcherCI
4:54 PM GMT on August 15, 2009
Quoting ncwxman68:
Oh yeah, I believe it will maintain its integrity and could potentially really take off under the right conditions. Very small systems, especially fast moving ones, are difficult for the models to resolve and can be a real pain to forecast from an intensity standpoint. Have to keep a sharp eye on it.
That's what I am afraid of. Can't help remembering all the weird systems last year.
Member Since: October 9, 2008 Posts: 0 Comments: 8424
5676. ncwxman68
4:53 PM GMT on August 15, 2009
Ana, that is.
Member Since: August 13, 2009 Posts: 0 Comments: 17
5675. ncwxman68
4:51 PM GMT on August 15, 2009
Oh yeah, I believe it will maintain its integrity and could potentially really take off under the right conditions. Very small systems, especially fast moving ones, are difficult for the models to resolve and can be a real pain to forecast from an intensity standpoint. Have to keep a sharp eye on it.
Member Since: August 13, 2009 Posts: 0 Comments: 17
5674. super064
4:50 PM GMT on August 15, 2009
I think the event south of MIA is getting more organized and seeing some rotation.
Member Since: August 30, 2008 Posts: 0 Comments: 2
5673. stormwatcherCI
4:42 PM GMT on August 15, 2009
Quoting ncwxman68:
Area near the keys looks pretty interesting!

Am looking for "AH-NA" to kind of come and go, typical for these very tiny systems. Also moving pretty fast for this latitude, doesn't make it any easier to get its act together. Not ready to write it off though, been pretty tenacious thus far.
Just thinking that since Ana weakened before to a remnant low and came back even stronger that more of a chance of it holding together throughout the day although not looking too good right now but better than yesterday at this time.
Member Since: October 9, 2008 Posts: 0 Comments: 8424
5672. ncwxman68
4:35 PM GMT on August 15, 2009
could be a "backyard" system developing there around the keys...got me a bit concerned.
Member Since: August 13, 2009 Posts: 0 Comments: 17
5671. OnTheFlats
4:32 PM GMT on August 15, 2009
Quoting Orcasystems:


Its a 50/50 split in the groups.

Florida/NOLA
We in Florida have the protection of the mountains of Hisanolia and Eastern Cuba and any storm coming form the WNW is usually unlikely to make it to SE Florida and that coupled with troughs moving in tend to creat sterring currents that drive storms NW, N, then hopefully NE or they miss them and go south into the GOM and then it gets scary. I feel for those in the GOM when a storm is stuck in there with only land to kill it. My point is that a WNW track through Hispanolia and eastern Cuba is the best case scenario for everyone in the U.S. and worst case scenario for the poor people living on the islands. Either way people are in harms way and being prepared is the only thing you can do.
Member Since: May 29, 2008 Posts: 0 Comments: 64
5670. ncwxman68
4:32 PM GMT on August 15, 2009
Area near the keys looks pretty interesting!

Am looking for "AH-NA" to kind of come and go, typical for these very tiny systems. Also moving pretty fast for this latitude, doesn't make it any easier to get its act together. Not ready to write it off though, been pretty tenacious thus far.
Member Since: August 13, 2009 Posts: 0 Comments: 17
5669. WindynEYW
4:26 PM GMT on August 15, 2009
last week off key west in the gulf
Member Since: September 13, 2007 Posts: 0 Comments: 331
5668. ncwxman68
4:25 PM GMT on August 15, 2009
Howdy folks! New to this blog, but not new to the weather biz.

Just wanted to say hello!
Member Since: August 13, 2009 Posts: 0 Comments: 17
5667. LPStormspotter
4:22 PM GMT on August 15, 2009
Quoting ALCoastGambler:
Orca, you forgot TX


Why do you wanna throw TX in there? lol
Member Since: July 17, 2008 Posts: 0 Comments: 385
5666. Orcasystems
4:22 PM GMT on August 15, 2009
Quoting hurricanejunky:

Your guess is as good as mine...


Its almost impossible to permanently ban someone.
They just need to change their name.. or get a hotmail account.

And no, you cannot IP ban someone.. their IP changes all the time also (very few people have static IP's). The only way to make it harder is to Ban the MAC address, and even that can be spoofed.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
5664. Relix
4:21 PM GMT on August 15, 2009
New blog!
Member Since: August 3, 2006 Posts: 0 Comments: 2741
5661. hurricanejunky
4:19 PM GMT on August 15, 2009
Ana and Bill are far away...what about the area in the central Gulf and now the blowup from the wave over the Keys? Wow...the switch has been flipped!
Member Since: August 28, 2006 Posts: 6 Comments: 2899
5659. hurricanejunky
4:18 PM GMT on August 15, 2009
Quoting AussieStorm:

Why hasn't he been permanently banned then?

Your guess is as good as mine...
Member Since: August 28, 2006 Posts: 6 Comments: 2899
5658. alpha992000
4:18 PM GMT on August 15, 2009
The heck?!? Went out to Hell on Earth (aka Walmart) to stock on a few things I needed and came back to Anna, TD 3 & Invest 90? Eh... think it's time to go back to the store and stock on a few dozen more vienna sausages & canned soups. *sigh* VERY interesting days ahead for us Puerto Ricans.
Member Since: October 16, 2005 Posts: 0 Comments: 126
5657. cbsrq
4:18 PM GMT on August 15, 2009
Java posted an entry yesterday in Spanish. For those still interested it translates roughly as follows: "The low pressure associated with TD 2 that was declassified yesterday today has encountered conditions and may be strengthened slowly and could by tonight or tomorrow be considered a Tropical Depression. The direction puts a risk to Puerto Rico to receive torrential rains between Monday and Tuesday."

(Sorry I wasn't able to post a translation earlier. I've just joined the blog and there's a 12-hour wait period before a first post).
5656. mikatnight
4:17 PM GMT on August 15, 2009
new blog!
Member Since: October 18, 2005 Posts: 4 Comments: 3052
5655. Seastep
4:17 PM GMT on August 15, 2009
I am also surprised by the 3.0/1000mb/45kt ADT on Ana.

No humans involved, though.
Member Since: September 9, 2008 Posts: 6 Comments: 3414
5654. melwerle
4:17 PM GMT on August 15, 2009
Georgia never gets his - way overdue for it and if that were a scenario, all hell would break loose - people there tend to be complacent and don't think anything will ever hit there (excluding SavannahStorm).
Member Since: June 28, 2006 Posts: 12 Comments: 1837
5653. canesrule1
4:17 PM GMT on August 15, 2009
Quoting Vortex95:


strange
no really, it's just going to make the curve over Florida, which I think is Highly possible.
5652. RadarNerd
4:17 PM GMT on August 15, 2009
Aside from everything else going on..

Can someone with a better eye than mine comment on the slight rotation at roughly 67W 25N? Looks like an accumulation of water vapor starting to rotate under the Bermuda high. Vorticity maps are picking it up a well.
Member Since: June 25, 2008 Posts: 0 Comments: 75
5651. AussieStorm
4:16 PM GMT on August 15, 2009
Quoting hurricanejunky:


Circumventing supposedly earns you a permanent ban.

Why hasn't he been permanently banned then?
Member Since: September 30, 2007 Posts: 9 Comments: 15962
5650. HurrikanEB
4:16 PM GMT on August 15, 2009
Quoting P451:
GFS 6Z - 168HR



"Tag- your it!"
Member Since: May 2, 2008 Posts: 12 Comments: 1342
5649. weathersp
4:16 PM GMT on August 15, 2009
Just woke up... I sated up till the 2 AM update..

Well the long awaited Ana has come and TD3 has formed.. for those of you who were up at the 11PM update last night...

Everybody go home the torches and pitchfork stand is closed.
Member Since: January 14, 2007 Posts: 17 Comments: 4140
5648. breald
4:15 PM GMT on August 15, 2009
Quoting WPBHurricane05:
12Z GFS shows Bill hitting S. Florida in 204 hours.


Are you sure that is not Anna? I don't see TD3 getting close enough. I am sure that will change though.
Member Since: May 28, 2008 Posts: 38 Comments: 5303
5647. WPBHurricane05
4:15 PM GMT on August 15, 2009
Quoting Relix:
WPB...is that the ridge the systems are supposed to ride?


I guess. I think a weakness is supposed to develop in the Central Atlantic but it quickly closes off.

Strongest winds right over my house:

Member Since: July 31, 2006 Posts: 56 Comments: 8112
5645. AussieStorm
4:14 PM GMT on August 15, 2009
Quoting scCane:


Link

Both systems are looking sick

I'd guess that's D-min doing that, Ana looked great last night/morning and so did TD3/90L
Member Since: September 30, 2007 Posts: 9 Comments: 15962
5644. atmoaggie
4:14 PM GMT on August 15, 2009
The statistical guys are warming up just a little to a GOM feature...slightly.
I don't see it happening, but I have been wrong before and will be again...someday.



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: August 16, 2007 Posts: 6 Comments: 12463
5643. melwerle
4:13 PM GMT on August 15, 2009
Quoting canesrule1:
yup, he used to be JFV now he is weather student.


You missed "presidentialelection"

He's been banned several times and gets around it.
Member Since: June 28, 2006 Posts: 12 Comments: 1837
5642. Relix
4:13 PM GMT on August 15, 2009
WPB...is that the ridge the systems are supposed to ride?
Member Since: August 3, 2006 Posts: 0 Comments: 2741
5639. hurricanejunky
4:12 PM GMT on August 15, 2009
Quoting presslord:


he's been banned...several times...created a new handle and circumvented it...


Circumventing supposedly earns you a permanent ban.
Member Since: August 28, 2006 Posts: 6 Comments: 2899
5638. canesrule1
4:12 PM GMT on August 15, 2009
Quoting presslord:


he's been banned...several times...created a new handle and circumvented it...
yup, he used to be JFV now he is weather student.
5637. WPBHurricane05
4:11 PM GMT on August 15, 2009


Than basically goes right up the west coast of Florida and into Georgia.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
5636. scCane
4:11 PM GMT on August 15, 2009


Link

Both systems are looking sick
Member Since: May 9, 2007 Posts: 0 Comments: 154
5635. ClearwaterSteve
4:11 PM GMT on August 15, 2009
Hello everyone back for a two hour beach soccer practice for my daughter. Honeymoon Island is a little rocky but nice. Saw a Dolphin as well.

StormW, I noticed we in the middle of the 5 day cone for Ana. Looks like we are safe.

LOL

Hows it Kman

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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.