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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feeding outflow - fujiwara - clarification?
Member Since: Posts: Comments:
Quoting Nikko:
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SAT AUG 15 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON RECENTLY-
UPGRADED TROPICAL STORM ANA...LOCATED ABOUT 1010 MILES EAST OF THE
LEEWARD ISLANDS.

1. SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE CENTERED
ABOUT 600 MILES WEST-SOUTHWEST OF THE WESTERNMOST CAPE VERDE
ISLANDS CONTINUES TO BECOME BETTER ORGANIZED...AND A TROPICAL
DEPRESSION MAY BE FORMING. IF CURRENT TRENDS CONTINUE...ADVISORIES
WILL LIKELY BE INITIATED LATER THIS MORNING AS THE SYSTEM MOVES
WESTWARD AT ABOUT 15 MPH. THERE IS A HIGH CHANCE...GREATER THAN 50
PERCENT... OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT
48 HOURS.

2. A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING
DISORGANIZED CLOUDINESS AND SHOWERS FROM THE WESTERN CARIBBEAN SEA
NORTHWARD ACROSS CUBA AND THE BAHAMAS TO SOUTH FLORIDA. THIS
ACTIVITY IS EXPECTED TO SPREAD WEST-NORTHWESTWARD OVER THE
SOUTHEASTERN GULF OF MEXICO DURING THE NEXT COUPLE OF DAYS.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

PUBLIC ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER
WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2.
FORECAST/ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO
HEADER WTNT22 KNHC AND UNDER AWIPS HEADER MIATCMAT2.

$$
FORECASTER BEVEN




old
Member Since: Posts: Comments:
Quoting kmanislander:


I just took a look at that.There are two ULLs at work, one in the NW GOM and another in the NW Caribbean. Over the keys you have what's left of the N end of a Twave that is moving W at this time through the NW Caribbean. The interaction of all these features is creating a chaotic situation with rain showers all around.

I do not see anything suggesting that a surface feature of any concern is developing out there at this time.

Gotta go now. Catch you all later.


Look at the buoy data here. Backs up this statement. Presures are high and winds fairly light all over the gulf.
Member Since: Posts: Comments:
I love are illegal site,lol.
Quoting Cotillion:
First lot of advisories for Ana/TD3 should be here in roughly 15 minutes.

Don't all post at once...

Can we designate 1 person to post the advisory so there isn't 10 oh it
Member Since: Posts: Comments:
Quoting canesrule1:
my local news station.


Ana isn't strengthening right now, it's battling dry air which is causing havoc with its convection. A nearby ULL might also be stealing some moisture per the WV loops.

It'll probably recover at some point, it has done more than once already.
Member Since: Posts: Comments:
5076. Skyepony (Mod)
Quoting CycloneOz:
IMPORTANT: To Dr. Masters...

Please sir, expound if you will in your upcoming blog why the GoM wave will not develop into a serious TC as it has no model support to speak of.

I thank you.


Look at the models on 850vort. They all keep it small, figure it's weeak & small enough not really seeing it pick up well on MSLP..
Member Since: Posts: Comments:
5075. primez
Wow. Africa is just continuing to shoot storms into the Atlantic. Look at that one coming off right now!
Member Since: Posts: Comments:
NHC would probally keep Ana @ TS so that way the islands can prepare for at least TS conditions and even if it does weaken before it gets there then they'll be better safe than sorry. I can't remember the yr. or storm but I know the NHC went ahead and counted a trop. disturbance as a TS (I want to say) and put up warnings/watches so Floridians would take it serious. I remember a few people in here actually reporting clear to mostly sunny skies or a brief heavy shower when the trop. system was passing near/over their location.
Member Since: Posts: Comments:
Not exactly sure ana will survive... Combined southwesterly shear and dry air are giving this tiny circulation a fit. If it does conditions ahead could be favorable for some intensification depending on land interaction.

Adrian
Member Since: May 14, 2006 Posts: 8 Comments: 13841
99L continues to parallel the 10 deg lat line
Member Since: Posts: Comments:
THREE, AL, L, , , , , 03, 2009, TD,
Member Since: Posts: Comments:
Both systems seem to be skimming southerly. Models shoot west and wont go back as far east.
Member Since: Posts: Comments:
5068. Nikko
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SAT AUG 15 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON RECENTLY-
UPGRADED TROPICAL STORM ANA...LOCATED ABOUT 1010 MILES EAST OF THE
LEEWARD ISLANDS.

1. SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE CENTERED
ABOUT 600 MILES WEST-SOUTHWEST OF THE WESTERNMOST CAPE VERDE
ISLANDS CONTINUES TO BECOME BETTER ORGANIZED...AND A TROPICAL
DEPRESSION MAY BE FORMING. IF CURRENT TRENDS CONTINUE...ADVISORIES
WILL LIKELY BE INITIATED LATER THIS MORNING AS THE SYSTEM MOVES
WESTWARD AT ABOUT 15 MPH. THERE IS A HIGH CHANCE...GREATER THAN 50
PERCENT... OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT
48 HOURS.

2. A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING
DISORGANIZED CLOUDINESS AND SHOWERS FROM THE WESTERN CARIBBEAN SEA
NORTHWARD ACROSS CUBA AND THE BAHAMAS TO SOUTH FLORIDA. THIS
ACTIVITY IS EXPECTED TO SPREAD WEST-NORTHWESTWARD OVER THE
SOUTHEASTERN GULF OF MEXICO DURING THE NEXT COUPLE OF DAYS.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

PUBLIC ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO HEADER
WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2.
FORECAST/ADVISORIES ON TROPICAL STORM ANA ARE ISSUED UNDER WMO
HEADER WTNT22 KNHC AND UNDER AWIPS HEADER MIATCMAT2.

$$
FORECASTER BEVEN

Member Since: Posts: Comments:
Quoting Weather456:
Look at the umbilical cord, lol.
5066. jipmg
Quoting BenBIogger:


?


Ana is trying to hold on to that T storm.. I say it will struggle today, but at DMAX or right after the sun sets, its going to come back.
Member Since: Posts: Comments:
Does anyone have any maps with good views of the ridging forecast for the next week?
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Quoting Skyepony:


Definately. Alot of models picking up on it. Had a west wind SW of La Havana earlier on land.


interested to see if Dr. Masters talks about in his next entry.
Member Since: Posts: Comments:
5013. 996tt 2:17 PM GMT on August 15, 2009
Anna's center looks like it may be exposing. Any updated on the Key West wave. Even surf reports are not indicating any swell this week in Pensacola. Be nice if the Key West low would throw a swell this way.



oh i bet you we do get a swell out of....check the cross cam on innerlight and i bet you by this afternoon it will be bigger than you think....and for Sunday...could be like last weekend when it just popped up out of no where...we'll get something out of that blobby crap
Member Since: Posts: Comments:
Quoting Drakoen:
90L models
and after that it is all very uncertain.
This is for the model experts: now that they have a depression to initialize with, what runs of the models will start to have the more accurate tracks?
Member Since: Posts: Comments:
Quoting Funkadelic:
Will 90L Be a tropical storm, or a depression at 11am?

Poll:

A: Tropical Storm

B: Tropical Depression

A
Member Since: August 9, 2009 Posts: 10 Comments: 5082
5059. Skyepony (Mod)
Quoting wunderkidcayman:
so guys when is the recon going out to tropical storm Ana


Leaving around 4:00pm EST or 2000Z
Member Since: Posts: Comments:
Quoting BenBIogger:


?
my local news station.
islandres are hoping that the forecast weakness in the ridge materialise, or else we we will be in for it
Member Since: Posts: Comments:
Member Since: July 24, 2005 Posts: 407 Comments: 19076
I wounder what happend to Sammy's finger last night? and his F5 key? LMAO
5053. Drakoen
90L models
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Quoting Nolehead:
kman...just that convection of crap down there below the keys...there is a spin and granted it does look to be moving west but alot of the models have something coming out of it and heading north towards the panahandle...just curious is all...but of course like everything else...subject to change..."A LOT"


I just took a look at that.There are two ULLs at work, one in the NW GOM and another in the NW Caribbean. Over the keys you have what's left of the N end of a Twave that is moving W at this time through the NW Caribbean. The interaction of all these features is creating a chaotic situation with rain showers all around.

I do not see anything suggesting that a surface feature of any concern is developing out there at this time.

Gotta go now. Catch you all later.
Member Since: Posts: Comments:
Quoting canesrule1:
no because Ana is strengthening.


?
Member Since: March 19, 2009 Posts: 0 Comments: 1421
5048. Skyepony (Mod)
Quoting truecajun:
morning everyone. any thoughts on the wave near cuba? is it something to keep an eye on?


Definately. Alot of models picking up on it. Had a west wind SW of La Havana earlier on land.
Member Since: Posts: Comments:
Quoting mobilegirl81:
Hurricane Charley in 2004 went from a cat1 to a cat4 overnight.


I woke up that Friday morning and Charley was a cat 2 about 105. When the 11 am advisory came it was a cat 4. I was drinking soda and spit it out.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Melagoo:
I think this Blog is ready to go into the archives now .... start a new one

I would think Dr. Master's is waiting till after 11am before posting a new blog.
Member Since: Posts: Comments:
First lot of advisories for Ana/TD3 should be here in roughly 15 minutes.

Don't all post at once...
Member Since: Posts: Comments:
Quoting stoormfury:
with the exposed centre, this will allow ANA to continue on a west track
no because Ana is strengthening.
Quoting CycloneOz:


I'm giving your post one of my very rare, and highly coveted "+"s. :)


I feel honored... =)
Member Since: Posts: Comments:
Nice view of 90L's banding features with squalls spiraling outwards in all direction from the center.

Member Since: Posts: Comments:
5040. msphar
The interaction between ANA and 90L might become more interesting over the next 2 days.

Sorry to see ANA named. Back in Calif on way to Nevada. Timing is all off.
Member Since: Posts: Comments:
5039. Melagoo
Why are there two identical invests on the Hurricane page? One is invest 03 and 90L
Member Since: Posts: Comments:
Quoting cycloone:
Hurricane Charley in 2004 went from a cat1 to a cat4 overnight.

Don't give Bill any ideas lol

I am worried Bill already has the idea.
Member Since: Posts: Comments:
so guys when is the recon going out to tropical storm Ana
Member Since: Posts: Comments:
5036. ackee
Quoting Weather456:


B
TD#3
Member Since: Posts: Comments:
I agree I just know that I'd wait at least until the 11am came out and could get one good glance at all the availableinfo out there then put out an update.
Member Since: Posts: Comments:
with the exposed centre, this will allow ANA to continue on a west track
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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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