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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2184. jdjnola
Quoting louisianaboy444:
I think 02L will become TD2 again shortly


Agreed.
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Let's not forget that none of these are named and the models won't get a good grip on what's happening until they are named. I think the 2 yellow circles over us (Florida) and what's left behind after they move out will have huge impact on where these storms will go. The best we can do is prepare early and watch the models. They have been in agreement for a few days now but since other things are popping up the models aren't very accurate. I tend to agree with Reedzone and his comments are very relaxed and calm and that's what we need now. I hope it's an up the east coast event without landfall and we can break this flat spell and go surf! Plus the fishing would start to fire down here with the incoming swells. No landfalls, people safe, huge waves and good fishing. That makes a great hurricane season!
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They said former TD2 could be reclassified tonight, so it's possible with those Dvorak number, and deep convection.. So we might have TD2 again by 11 p.m.
Member Since: July 1, 2008 Posts: 13 Comments: 7432
Quoting Tropicaldan:
Hi weather 456 and others from the Lesser Antilles

Dan from St Martin checking in for first time this year

Looks like our part of the world could be in for a tense time next week?

Keep safe down there in SKB

Dan


hey

it looks so unfortunately.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2180. tbrett
Quoting Tropicaldan:
Hi weather 456 and others from the Lesser Antilles

Dan from St Martin checking in for first time this year

Looks like our part of the world could be in for a tense time next week?

Keep safe down there in SKB

Dan

Hey Dan..This is Tina in Montserrat, Hope you and yours will be safe too.
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2179. java162
Quoting Tropicaldan:
Hi weather 456 and others from the Lesser Antilles

Dan from St Martin checking in for first time this year

Looks like our part of the world could be in for a tense time next week?

Keep safe down there in SKB

Dan



yes it certainly looks so... (from the island of dominica to your south)
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PERSPECTIVAS DE LAS CONDICIONES DEL TIEMPO EN EL TROPICO NWS
TPC/CENTRO NACIONAL DE HURACANES MIAMI FL
800 PM EDT VIERNES 14 DE AGOSTO DE 2009

PARA EL ATLANTICO NORTE...EL MAR CARIBE Y EL GOLFO DE MEXICO...

LAS IMAGENES DEL SATELITE Y DATA OPTENIDO DESDE SONDAS ATMOSFERICAS
PORTADOS POR AVIONES INDICAN QUE LA ANTERIORMENTE LLAMADA DEPRESION
TROPICAL NUMERO DOS LOCALIZADO A UNAS 100 MILLAS AL ESTE DE LAS
ANTILLAS MENORES SE ESTA REGENERANDO Y PODRIA NUEVAMENTE CONVERTIRSE
EN CICLON TROPICAL ESTA NOCHE O TEMPRANO EN EL SABADO. LOS VIENTOS
EN LOS NIVELES ALTOS ESTAN MARGINALMENTE FAVORABLES PARA DESARROLLO
ADICIONAL A MEDIDA QUE EL SISTEMA SE MUEVA HACIA EL OESTE DE 12 A 15
MPH. EXISTE UNA ALTA PROBABILIDAD...MAS DE 50 POR CIENTO...DE QUE
ESTE SISTEMA SE CONVIERTA EN CICLON TROPICAL DURANTE LAS PROXIMAS 48
HORAS.

UN AREA AMPLIA DE BAJA PRESION CENTRALIZADA A 400 SUROESTE DE LAS
ISLAS DE CABO VERDE OCCIDENTALES SE ACOMPANA POR UN EXTENSO AREA DE
NUBES Y TRONADAS. ESTE SISTEMA GRADUALMENTE SE TORNA MAS ORGANIZADA
Y UNA DEPRESION TROPICAL TAMBIEN PODRIA FORMARSE ESTA NOCHE O EL
SABADO. SE ESPERA QUE ESTA BAJA PRESION SE MUEVA HACIA EL OESTE A 15
MPH. EXISTE UNA ALTA PROBABILIDAD...MAS DE 50 POR CIENTO...DE QUE
ESTE SISTEMA SE CONVIERTA EN CICLON TROPICAL DURANTE LAS PROXIMAS 48
HORAS.

UNA ONDA TROPICAL INTERACTUANDO CON UNA VAGUADA EN LOS NIVELES ALTOS
DE LA ATMOSFERA ESTA PRODUCIENDO UN AREA DESORGANIZADA DE NUBES Y
AGUACEROS SOBRE EL OESTE DEL CARIBE AL NORTE A TRAVES DE CUBA Y LAS
BAHAMAS. ESTA ACTIVIDAD ESTA MAS CONCENTRADA JUSTO AL NORTE DE LA
COSTA DE CUBA CENTRAL Y DEBERA ESPARCIRSE HACIA EL OESTE NOROESTE
SOBRE EL SUR DE LA FLORIDA Y LA PORCION SUDESTE DE GOLFO DE MEXICO
DURANTE LOS PROXIMOS DIAS. EXISTE UNA BAJA PROBABILIDAD...MENOS DE
30 PORCIENTO...DE QUE ESTE SISTEMA SE CONVIERTA EN CICLON TROPICAL
DURANTE LAS PROXIMAS 48 HORAS.

AGUACEROS Y TRONADAS DESORGANIZADOS SOBRE EL NORESTE DEL GOLFO DE
MEXICO ESTAN ASOCIADOS CON UNA VAGUADA DEBIL. LA PRESION EN LA
SUPERFICIE ESTA RELATIVAMENTE ALTA EN ESTA AREA. EXISTE UNA BAJA
PROBABILIDAD...MENOS DE 30 PORCIENTO...DE QUE ESTE SISTEMA SE
CONVIERTA EN CICLON TROPICAL DURANTE LAS PROXIMAS 48 HORAS.

PARA EL RESTO DEL AREA...NO SE ESPERA FORMACION DE CICLON TROPICAL
DURANTE LAS PROXIMAS 48 HORAS.

$$

PRONOSTICADOR AVILA


TRADUCCION CORTESIA DE LA OFICINA DEL SNM EN SAN JUAN PUERTO RICO

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Quoting CycloneOz:


I was in Mobile that night for Frederick. I was hunkered down. 2nd most frightening night of my life...2nd only to Ivan's night of terror.


I'll never forget the day after Frederic... having to walk miles to check on relatives as the roads were so covered in debris that you had to dig down just to see if you were still on the pavement or in someone's yard.
I've been lurking and learning for three seasons now and truly appreciate everyone taking the time to share their knowledge.
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Names I haven't heard mentioned on the blog this evening, or rarely this year: Bertha, Fran, Bonnie, Floyd, Isabel... and you could even throw in Jeanne and Frances... lol
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Pressure falling...
Member Since: April 26, 2009 Posts: 3 Comments: 3667
I see that ex-TD2 is reforming and 90L has become more organize, according to the NHC.
They both might become TD's by 11pm, or so.
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2173. MrSea
Quoting stormpetrol:
90L should become a depression at 11PM or 5AM

TD 2 still has a little ways to go

vice versa imo


agreed
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we will have TD2 very soon
14/2345 UTC 15.2N 44.9W T1.5/1.5 02L
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have they dropped a drop that measured the water temperture under our system?
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Hi weather 456 and others from the Lesser Antilles

Dan from St Martin checking in for first time this year

Looks like our part of the world could be in for a tense time next week?

Keep safe down there in SKB

Dan
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I think 02L will become TD2 again shortly
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90L should become a depression at 11PM or 5AM

TD 2 still has a little ways to go

vice versa imo
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Ivan was bad. Could have done the same Katrina did if it would have gone the same track.
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Quoting extreme236:


Doesn't need much more to become a TD.


...you're right...just some semblance of an NE flank and he/she's there!
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Quoting DM21Altestic:
90L should become a depression at 11PM or 5AM

TD 2 still has a little ways to go


and how about our Florida blob?


NHC says TD 2 is regenerating...
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might see the gulf system to combined with the bahama system take a couple days then it should move wnw
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2163. cg2916
02L strengthened:
14/2345 UTC 15.2N 44.9W T1.5/1.5 02L
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90L seems to have a burst of convection near the center. We will have TD3 within 24 hours.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting CycloneOz:
90L still needs to wrap up. NE flank is totally exposed.

It's going to be a chicken, but I'm not counting it yet.

Much more development needed.


Doesn't need much more to become a TD.
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keep an eye on this system in the gulf. Remember Charley? The Gulf is hot and we could be dealing with something before you know it.
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2159. cg2916
Quoting ALCoastGambler:
We don't even have an Ana yet!! OMG

I'm talking about the GFS.
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Quoting cg2916:

Bill, then.
We don't even have an Ana yet!! OMG
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Quoting jipmg:
I see something strange going on to TD 2.. It doesn't seem to have good ventilation on its east side, looks like there is still some easterly shear preventing it from being properly ventilated.

90L is shearing it.
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Quoting jdjnola:
I was right! The artist-formerly-known-as-TD2 has survived. I guess this makes up for me being wrong at every turn last season...


lol

its doing the moonwalk...
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90L should become a depression at 11PM or 5AM

TD 2 still has a little ways to go


and how about our Florida blob?
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2154. jipmg
I see something strange going on to TD 2.. It doesn't seem to have good ventilation on its east side, looks like there is still some easterly shear preventing it from being properly ventilated.
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Quoting mobilegirl81:

They were both bad. Frederic was real bad, but alot of people have forgotten. I know David was bad, but Frederic was stonger when it hit the US. Frederic was only responsible for 5 lives.


I was in Mobile that night for Frederick. I was hunkered down. 2nd most frightening night of my life...2nd only to Ivan's night of terror.
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2152. cg2916
Quoting ALCoastGambler:
I bet you do not see Claudette. I don't even see Ana or Bill yet!!

Bill, then.
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Quoting canesrule1:


Link
i also have some secret software i can't give away.
I have been watching metsat and GFS as well. Looks like a series of waves will be coming off the African coast. Should really knock out most of the dry area if there is any left after TD2 and 90L
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Quoting cg2916:

I see Claudette, too.
I bet you do not see Claudette. I don't even see Ana or Bill yet!!
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Quoting CycloneOz:
90L still needs to wrap up. NE flank is totally exposed.

It's going to be a chicken, but I'm not counting it yet.

Much more development needed.


There is convection forming over the COC, it's starting to move out of the higher shear environment.
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2147. jdjnola
I was right! The artist-formerly-known-as-TD2 has survived. I guess this makes up for me being wrong at every turn last season...
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look like a tropical D to me..i see the red again
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Quoting jurakantaino:
It happened in 1979, Sept.4, Frederick, and hurricane DAvidLink

They were both bad. Frederic was real bad, but alot of people have forgotten. I know David was bad, but Frederic was stonger when it hit the US. Frederic was only responsible for 5 lives.
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Quoting jipmg:


can you post a link to the obversvation's
Quoting cg2916:

Where is the recon data from?


Link
Quoting KerryInNOLA:
Agree with you Reed!

What happened to your forecast of nothing happening? Also the only thing he elimated is a Texas hit haha. i can forecast like that to. I think it will be a FL hit or sneak into the Gulf and curl up.
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2142. cg2916
Quoting IceSlater:
Oh boy... am I the only one seeing something ELSE behind 90L now via the GFS?

I see Claudette, too.
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I'm sorry if the cone doesn't reach Texas on my map, I went with the model spreads. I doubt this storm will even make it in the GOM, there will be a decent trough and timing is crucial on if it recurves or goes up the Eastern Seaboard. In my opinion, there is a slim chance that the 18Z GFS verifies.
Member Since: July 1, 2008 Posts: 13 Comments: 7432
Quoting Grothar:
TO: SavannahStorm

Saw your post on the intensity of the two models. Are these models reliable? One would hope they are just worst case scenarios. Thank you again for your responses.


The GFDL I think shows reasonable intensification. The HWRF, meanwhile, has always been very bullish on intensification. I think it's probably too aggressive right now. However, a strong Cat. 2 or weak Cat. 3 hurricane is not out of the question by mid-week next week.
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90L still needs to wrap up. NE flank is totally exposed.

It's going to be a chicken, but I'm not counting it yet.

Much more development needed.
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Quoting Vortex95:


thats outside 02L though they said they weren't going in.


its outside TD 2, cuz the obs was at 48W, while TD 2 is located near 45W, but this mission is dubbed "td2"

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting IceSlater:
Oh boy... am I the only one seeing something ELSE behind 90L now via the GFS?
yup, i've been watching it, the GFS as well has been hinting a low forming and getting into the Caribbean.
2136. jipmg
Quoting canesrule1:
yes they are, the lat/lon provided at the observations in very close to that of the COC.


can you post a link to the obversvation's
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2135. cg2916
Quoting canesrule1:
I'm following Recon's observations, and they have found 26 knot winds at the surface which is indicative of a TD.

Where is the recon data from?
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Quoting tikikopamsxm:
thanks Stormwatcher!
Sorry for the misundertood, i m just a bit worried about that two invest that will perhaps landfall on my home here in st martin.Our weather forecast here is not very relevant they used to tell us things very late.
Thanks all of you(sorry for my english)
Your english is okay and understandable. I am worried about both of them too. I live in Grand Cayman.
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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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