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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5283. SoFla
5249. serialteg:
Too bad the closing on our house is in So. FL instead of Utah - smack dab in the middle of all the predictions for these storms!
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Quoting ALCoastGambler:
I do hope with Dr. masters new update that admin. steps in. There is no reason for +5000 posts in a busy time like this. Too hard to keep up. +5000 posts and +2000 Is it coming to SFL


Um - That is just uber-off topic.

Anyway.. which do you prefer:

A) Ana gets into Gomex before disappating
B) Ana merges with TD 3
C) Ana becomes a fish
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This is off the subject, you all know the other night when someone put a virus on the blog? I downloaded noscript and since then I don't get the +,- or pictures of any kind. I don't know how to set it up. can someone tell me how? I am sorry for being off subject.

Sheri
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Quoting ALCoastGambler:
I do hope with Dr. masters new update that admin. steps in. There is no reason for +5000 posts in a busy time like this. Too hard to keep up. +5000 posts and +2000 Is it coming to SFL

I understand ur pain... when i sleep, u guys type and post like crazy. I go to bed at 100 posts and wake to 2000 posts
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Quoting robie1conobie:
s. fla is not the hurricane capital of the world. Someone posted earlier how rare it is for a storm not to hook it one way or the other away from s. fla.


when you have that many storms coming at ya there will be a % of storms that will 'hook one way or the other', lets just call the whole state of FL Hurricane capital of the world
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Thanks Dr. Masters.
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Ok, all you wound-up WUBloggers – take a minute to clear your mind, take a deep breath, gain some perspective, and enjoy this brief poem by Susan Hutton:


ATMOSPHERICS

Sometimes on a late clear night you can pull that station from Denver or Boston out of the dark.

All the elsewheres alter here, as what you remember changes what you think.

Not spider nor plum nor pebble possesses any of the names we give them.

A kite tugging on its string gives you a sense of what’s up there, though it’s translated, and by a string.

Out there, in the dark, the true thing.
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Quoting HurricaneKyle:
Right now if it continues its forward speed, this isn't going to go out to sea, 17 Mph is very fast.


Trying to work out in my head how that forward speed might affect consolidation attempts and spin up for td-3.
If the windfield stays as broad as it is, no way it gets any stronger than a mid-cat 3.
Anyone?
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5272. amd
Quoting cycloone:
it looks like TD 3 may become a fishy-cane


way, way, way, too early to call. IMO.
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Quoting AussieStorm:

Elsewhere, Tropical Storm formation is not expected through Saturday.

"Storm"


That's the last line of StormW's latest blog.... no mention of a post on saturday
He was on earlier and said he would BBL with an updated analysis.
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Quoting fire635:
My apologies... I misread your post. I was referring to Dr.M's last post.

apology accepted :-)
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cg, I will try to stay safe and not do anything foolish like with Omar which underestimated

No beach



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Looks like Ana could get into the GOMEX according to the new track. Where the SSTs are hotter than they where even in 2005..
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0Z 8 to 10 DAY 500MB MEAN

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I do hope with Dr. masters new update that admin. steps in. There is no reason for +5000 posts in a busy time like this. Too hard to keep up. +5000 posts and +2000 Is it coming to SFL
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Quoting Tazmanian:
poor FL


LMAO
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5263. fire635
My apologies Aussie... I misread your post. I was referring to Dr.M's last post.
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Quoting HurricaneKyle:


Not if it continues to truck west at 17 mph.
i was wondering if it keeps up that speed then where will it go, is it forcasted to keep up a fast pace or slow down?
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Quoting Tazmanian:
when will the 1st fight be for TD 3??


Not for a couple of days yet, one would think.

Still too far out into the Atlantic.
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Quoting P451:


Is strengthening 15kt a day all that big of a deal? I'd say no. This is going to be a formidable storm but that forecast is right in line with "slow strengthening".


What I posted was Deans first advisory 120 hours out.
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This is all so confusing :(
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Quoting fire635:


At the end of his last post it stated he will have an update Saturday morning

Elsewhere, Tropical Storm formation is not expected through Saturday.

"Storm"


That's the last line of StormW's latest blog.... no mention of a post on saturday
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Quoting cycloone:
it looks like TD 3 may become a fishy-cane


Not if it continues to truck west at 17 mph.
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1030 PDT Guillermo (125 mph after this forecast)GRADUAL WEAKENING IS
EXPECTED BY 24 HOURS AS THE CYCLONE ENCOUNTERS COOLER WATERS...AND
A MORE SIGNIFICANT WEAKENING IS EXPECTED BEYOND THAT TIME AS THE
VERTICAL WIND SHEAR IS FORECAST BY THE SHIPS MODEL TO INCREASE
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when will the 1st fight be for TD 3??
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Quoting Vortex95:


S Fla is the hurricane captial of the world but I get were you are going at :P.
s. fla is not the hurricane capital of the world. Someone posted earlier how rare it is for a storm not to hook it one way or the other away from s. fla.
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Quoting P451:
We have Ana, TD3, the big African wave, and now this Central African wave.



GFS develops the African wave in the Sunday-Monday range, something else to watch behind our two current systems. The environment is still pretty favorable in that area.
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Quoting SeniorPoppy:


I should have rephrased that. Any slight deviation might work in our favor. We should be keeping an eye on both these systems.
lol, ok
Quoting SoFla:
I don't think I would call South Florida the safest place. That is a bit naive.


you're safer in Pentasookee, Utah

watch for snow-ins tho - and the occasional bear / mormon
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it looks like TD 3 may become a fishy-cane
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Ana continues to be exposed.
Member Since: August 9, 2009 Posts: 10 Comments: 5080
5245. Drakoen
Quoting P451:


Is strengthening 15kt a day all that big of a deal? I'd say no. This is going to be a formidable storm but that forecast is right in line with "slow strengthening".


For a storm that just formed it is.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
5244. tbrett
Weather456: Posted this earlier.
Not looking good for the N. Leewards next week. Getting hit with 3 different systems in a row.

Link
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poor FL
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Quoting canesrule1:
Not at all.


I should have rephrased that. Any slight deviation might work in our favor. We should be keeping an eye on both these systems.
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5239. cg2916
Quoting Weather456:
I'm hoping Ana does not pull anything.

Weather, you better watch out for these. We don't wanna lose you. Who else will post accurate data other than Dr. Masters?
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it is cloudy rainy in key west already from they small cell offshore, if ana & td3 come visit next week tourism will go bye-bye for awhile
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5237. fire635
Quoting AussieStorm:

StormW doesn't post on weekends.


At the end of his last post it stated he will have an update Saturday morning
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I'm hoping Ana does not pull anything.
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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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