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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4334. JRRP
Quoting Weather456:


slow

Quoting Prgal:

Carolina :)

JRRP, that's 11.508mph

Quoting serialteg:


thats like 13mph... not that fast, definitely not slow, typical for waves (15-20kt) and hurricanes out there in the open at'l i'd say...

ok thanks
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Quoting cg2916:
90L looks better than Ana.


since 24 hrs
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4331. Prgal
Quoting farhaonhebrew:
ana, although little is taking the classical form of torementa

Saludos desde Juncos..

Buenos dias (good morning) desde Carolina. JRRP, I used this page to convert from knots to mph: http://www.militaryfactory.com/conversioncalculators/speed_knots_to_miles_per_hour.asp Hope it helps.
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4330. cg2916
90L looks better than Ana.
Member Since: December 21, 2007 Posts: 13 Comments: 3032
Quoting cg2916:

Yesterday, TWC put it as a "sacrificial lamb". LOL.


it kinda was. when TD2 blew up, it made the whole area around it moist (based on water imagery). guess didn't do 90L no harm, but i'm no expert lol
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Quoting ackee:
can I see link to this please


GFDL
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ana, although little is taking the classical form of torementa

Saludos desde Juncos..
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Where are the people that said this season was over? Now we have two hurricanes bearing down on us. It only takes one.
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Quoting JRRP:

TROPICAL WAVE EXTENDS FROM 18N32W TO 7N29W WITH A 1009 MB LOW
ALONG THE WAVE NEAR 12N MOVING W NEAR 10 KT

is that slow or fast??


thats like 13mph... not that fast, definitely not slow, typical for waves (15-20kt) and hurricanes out there in the open at'l i'd say...
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4322. Prgal
Quoting serialteg:


mornin hun... where you at?

Carolina :)

JRRP, that's 11.508mph
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4321. cg2916
Quoting Weather456:
Ana has done alot and will continue to do alot for her brother 90L. She will block any dry air. The stage is set for 90L to develop quickly and uncertainty lies with Ana.

Yesterday, TWC put it as a "sacrificial lamb". LOL.
Member Since: December 21, 2007 Posts: 13 Comments: 3032
4320. FLDART1
Good Morning all... I have decided that for the next 3 days at least I am not going to sit here looking at models or reading wishcasts... lol It does however, look like we have trouble brewing.
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Quoting JRRP:

TROPICAL WAVE EXTENDS FROM 18N32W TO 7N29W WITH A 1009 MB LOW
ALONG THE WAVE NEAR 12N MOVING W NEAR 10 KT

is that slow or fast??


slow
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Ana has done alot and will continue to do alot for her brother 90L. She will block any dry air. The stage is set for 90L to develop quickly and uncertainty lies with Ana.
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Quoting Prgal:

Good morning serialteg, mrpuertorico, jrrp and all wg bloggers. Lets hope so serial. Fingers crossed.


mornin hun... where you at?
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4316. JRRP
Quoting Weather456:
From the NWS in Puerto Rico - 90L

IF THE SYSTEM MOVE
SLOWER...IT WILL REACH THE WEAKNESS BY THAT TIME...AND WILL TEND
TO MOVE MORE ON A NORTHWESTERLY COMPONENT. HOWEVER...IF THE SYSTEM
MOVE FASTER THAN INDICATED BY THE MODELS...THE RIDGE WILL BE
INTACT AND MORE STRONGER WHICH WILL ALLOW THE SYSTEM TO MOVE
CLOSER TO THE LOCAL AREA.

DUE TO THIS UNCERTAINTY IN THE FUTURE TRACKS OF BOTH SYSTEMS...RESIDENTS
OF PR AND THE USVI ARE ENCOURAGED TO MONITOR LATEST FORECASTS FROM
THE NATIONAL HURRICANE CENTER OVER THE WEEKEND AND GO OVER THEIR
HURRICANE DISASTER PLANS IN CASE THE THREAT FROM THESE TWO
TROPICAL SYSTEMS BECOMES MORE REAL.

TROPICAL WAVE EXTENDS FROM 18N32W TO 7N29W WITH A 1009 MB LOW
ALONG THE WAVE NEAR 12N MOVING W NEAR 10 KT

is that slow or fast??
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4315. ackee
Quoting kmanhurricaneman:
gfdl put anna over cayman on the 19th , these models just drives me bonkers!
Quoting kmanhurricaneman:
gfdl put anna over cayman on the 19th , these models just drives me bonkers!
can I see link to this please
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Quoting mrpuertorico:


Kinda Lucky yeah considering we haven't had a hurricane in 12 years or so but then again all that means is that when one hits it has a lot of stuff to break down like all those pretty trees that have had 12 years to grow


i'm looking forward to the surfing. gettin my grandma ready cause we've had plenty warning from the models and such.

clasificadosonline.com ... good place to buy stuff cheaper than $Home$Depot$

I'd actually get pi$$ed if I follow thru with my gardening work and these storms mess it up >:(
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4313. yamil20
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.

by the way good morning everyone, i guess TD 3 or Bill is coming at 11 am
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It will be interesting to seehow these two features interact with each other as the develop.
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From the NWS in Puerto Rico - 90L

IF THE SYSTEM MOVE
SLOWER...IT WILL REACH THE WEAKNESS BY THAT TIME...AND WILL TEND
TO MOVE MORE ON A NORTHWESTERLY COMPONENT. HOWEVER...IF THE SYSTEM
MOVE FASTER THAN INDICATED BY THE MODELS...THE RIDGE WILL BE
INTACT AND MORE STRONGER WHICH WILL ALLOW THE SYSTEM TO MOVE
CLOSER TO THE LOCAL AREA.

DUE TO THIS UNCERTAINTY IN THE FUTURE TRACKS OF BOTH SYSTEMS...RESIDENTS
OF PR AND THE USVI ARE ENCOURAGED TO MONITOR LATEST FORECASTS FROM
THE NATIONAL HURRICANE CENTER OVER THE WEEKEND AND GO OVER THEIR
HURRICANE DISASTER PLANS IN CASE THE THREAT FROM THESE TWO
TROPICAL SYSTEMS BECOMES MORE REAL.
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Good morning all!

Yes! Finally got rid of the name Ana....though it looks like she might pay me a visit.
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Quoting cg2916:

From that picture, it may be Bill, but it's not as organized in that picture as it is in the one Weather 456 posted.


they may have caught it at a bad time :D
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Advisory at 11am then, if 90L keeps it up.
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4307. Prgal
Quoting serialteg:


as i was taking a bath (too much info?) i was thinking about this... mosr storms have their winds and rains to the north and east, most storms pass north of PR, so we get kinda lucky.

let's hope

Good morning serialteg, mrpuertorico, jrrp and all wg bloggers. Lets hope so serial. Fingers crossed.
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HPC preliminary forecast for thursday Aug 20


Member Since: September 23, 2005 Posts: 14 Comments: 10875
Quoting tropicaltank:
If that feature gets into the gulf we may have three systems to contend with.



Marine Weather Discussion
--------------------------------------------------------------------------------


000
AGXX40 KNHC 150656
MIMATS

MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
300 AM EDT SAT AUG 15 2009

MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA
AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W.

WINDS ARE GENERALLY LIGHT ACROSS THE GULF OF MEXICO. HOWEVER
WINDS WILL START TO INCREASE OVER THE EASTERN GULF AS TROUGH
WHICH WAS THE NORTHERN END OF A TROPICAL WAVE MOVES INTO THE
AREA. THE TROUGH WILL MOVE ACROSS THE EASTERN AND MIDDLE GULF
TODAY AND SUN THEN INTO THE NW GULF MON AND INLAND TUE. THE
STRONGEST WINDS WILL BE OVER THE SE GULF THEN SPREAD W INTO THE
SW GULF BY MID WEEK.


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gfdl put anna over cayman on the 19th , these models just drives me bonkers!
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Quoting serialteg:


as i was taking a bath (too much info?) i was thinking about this... mosr storms have their winds and rains to the north and east, most storms pass north of PR, so we get kinda lucky.

let's hope


Kinda Lucky yeah considering we haven't had a hurricane in 12 years or so but then again all that means is that when one hits it has a lot of stuff to break down like all those pretty trees that have had 12 years to grow
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4302. JRRP
sorry
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Quoting mrpuertorico:


well that worries me if i loose power fromn ana it will be hard to keep track of possible bill! two days later!!! And i have my real estate test on friday.


I didn't think about that. Need to get more batteries for the portable radio along with the water, etc.
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90L moving a little south of due west , might well a Caribbean Storm.
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4299. IKE
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.

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.

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
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Quoting nrtiwlnvragn:
06Z HWRF Ana


as i was taking a bath (too much info?) i was thinking about this... mosr storms have their winds and rains to the north and east, most storms pass north of PR, so we get kinda lucky.

let's hope
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4297. cg2916
Quoting stormpetrol:

I think with some of those winds might go directly to "Bill"

From that picture, it may be Bill, but it's not as organized in that picture as it is in the one Weather 456 posted.
Member Since: December 21, 2007 Posts: 13 Comments: 3032
Quoting tropicaltank:
If that feature gets into the gulf we may have three systems to contend with.

Good Point.
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Quoting Weather456:
A tropical storm followed by a hurricane





well that worries me if i loose power fromn ana it will be hard to keep track of possible bill! two days later!!! And i have my real estate test on friday.
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4294. JRRP
GFDL shift a bit south than the previous run
Link
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If that feature gets into the gulf we may have three systems to contend with.
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Quoting mrpuertorico:


So 456 what are pr's chances for a double hit


Puerto Rico is seems a moderate chance, since the models kinda diverge 90L and Ana at that point.

The chances are greater for the Leewards since both Ana and 90L enter through there, whether it goes north or south of Puerto Rico. Ana seems ti catch you guys more than 90L.
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I think with some of those winds might go directly to "Bill"
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4289. java162
Quoting Weather456:
A tropical storm followed by a hurricane





the gfs develops another one after that.. so 3 in a row
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Morning all. Seeing we have our first storm...
0-0-0 lasted until August 15th.

Those models for Ana aren't looking so good for Florida it seems.
Quoting HIEXPRESS:
Some mid level spin with this wave S FL
Radar LOOP
Winds & PMSL
I see the twist,Maybee something forming.
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Quoting mrpuertorico:


So 456 what are pr's chances for a double hit


i know you didnt ask me but the chance is there it would be unlikely a little more probable than lightning striking twice in the same spot...

dont get caught in the model rat race...

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Quoting serialteg:


nice pic lol

saludos de ponce..


gracias igual!
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Quoting nrtiwlnvragn:


Goes out to 126 hrs, its displayed at the top of the screen.
yeah, sorry about that. I saw it and forgot to delete the post.
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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.