Gaston still a threat to redevelop

By: Dr. Jeff Masters , 3:17 PM GMT on September 05, 2010

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For the first time since August 22, when Danielle became a tropical storm, there are no named storms active in the Atlantic. An extratropical storm absorbed Tropical Storm Earl last night, bringing an end to the 11-day life of the 2010 season's longest-lived storm. While Earl was mostly a non-event for North Carolina and New England, the storm gave Nova Scotia a solid pounding, reminding us of what could have easily happened to New England had the forecast track deviated slightly to the left. Kudos go to the computer models and NHC, who successfully predicted the path of Earl very accurately four days in advance. As we approach the climatological peak of Atlantic hurricane season, which occurs on September 10, there are no indications that today's break in the action represents a beginning of an extended quiet period in the Atlantic. Indeed, we have two systems that could become tropical depressions in the next day, and we also have model predictions of another storm to come late in the week.


Figure 1. Morning satellite image of the remains of Gaston, approaching the Lesser Antilles Islands.

Gaston near tropical depression status again
The remains of Tropical Storm Gaston, located about 700 miles east of the Lesser Antilles Islands and moving west at about 13 mph, are close to reaching tropical depression status again. Recent satellite imagery shows that Gaston's remains have developed a well-organized surface circulation, but not enough heavy thunderstorm activity to be considered a tropical depression. A large amount of dry air surrounds Gaston's remains on all sides, as seen on water vapor satellite loops. This dry air will continue to be a major impediment to development. The latest SHIPS model forecast predicts shear will remain moderate, 10 - 15 knots, for the next three days, then fall to the low range. The winds creating the shear are coming from the east, where a tongue of dry air has intruded. These easterly winds will be able to drive the dry air into Gaston's core, disrupting it, unless the storm can find a moister environment, or moisten its environment on its own by generating enough heavy thunderstorms. Gaston has managed to develop more heavy thunderstorms near its center of circulation late this morning, but the amount of dry air it is battling is formidable. Even if Gaston does manage to become a tropical depression today, development will be slow over the next few days, due to the dry air. When Gaston passes over or just to the northeast of the Lesser Antilles Islands early Tuesday morning, the storm is unlikely to have more than 50 mph winds. More significant development is possible later in the week, as the atmosphere should be moister for Gaston. Gaston may threaten Puerto Rico on Wednesday, the Dominican Republic on Thursday, and Haiti, Jamaica, and/or the Turks and Caicos Islands by Friday, depending upon the storm's interaction with a trough of low pressure expected to move off the U.S. East Coast later this week. The earlier Gaston develops into a tropical storm, the more likely it is to "feel" the upper-level winds of the approaching trough, and curve more to the northwest. The HWRF model predicts Gaston will develop by Monday, and pass just northeast of the Lesser Antilles Islands Tuesday morning. The GFDL model, on the other hand, delays development until Wednesday, keeping Gaston in the Caribbean. The GFDL has Gaston hitting Jamaica as a strong tropical storm on Friday morning. However, the GFDL forecast is dubious, because on Wednesday and Thursday, Gaston may have an encounter with the high mountains of the island shared by the Dominican Republic and Haiti, Hispaniola, which could easily destroy a system as fragile as Gaston. Gaston has a 70% chance of developing into a tropical depression by Tuesday, according to NHC.

Gulf of Mexico disturbance 90L
A concentrated area of heavy thunderstorms (90L) has developed over the extreme southwestern Gulf of Mexico, in the Bay of Campeche. Satellite imagery shows that this disturbance is disorganized, but has some modest spin to it. The disturbance is under a moderate 10 - 15 knots of wind shear, and has a 60% chance of developing into a tropical depression by Tuesday, according to NHC. The disturbance is headed northwest at 5 - 10 mph, and should bring heavy rains to the Texas/Mexico border region on Monday, according to the latest run of the GFS model. The main impediment to development will be the limited time 90L has over water; the storm will be ashore by Tuesday, which doesn't give it much time to develop.

Elsewhere in the tropics
The GFS and NOGAPS models are predicting development on Thursday of a tropical wave that will emerge from the coast of Africa on Tuesday or Wednesday.

Next post
I'll have an update Monday morning.

Jeff Masters

Sunrise Surf was cranking (RIWXPhoto)
Sunrise Surf was cranking
Post Hurricane Earl surf photos at Newport, RI (RIWXPhoto)
Post Hurricane Earl surf photos at Newport, RI

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1985. xcool
63k wo
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Quoting KoritheMan:


Correct. I'm willing to bet that the tropical storm force winds are confined to that large amorphous convective band stretching from southern Mexico and wrapping halfway around the eastern semicircle of the cyclone.


Yes, I'd expect so.

I would think the NHC might just up the maximum winds in the discussion to 50kt prior to landfall. A moderate-to-strong TS would seem about right, providing it continues to organise.
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Quoting Cotillion:
The centre doesn't appear to be right under the heaviest of the convection yet.

If it does, then the waters are plenty warm enough to get spinning. Shear is low. Land proximity is about the only issue (and the fact it won't be on water that long).


Correct. I'm willing to bet that the tropical storm force winds are confined to that large amorphous convective band stretching from southern Mexico and wrapping halfway around the eastern semicircle of the cyclone.
Member Since: March 7, 2007 Posts: 575 Comments: 20547
Thanks post 1977. Sheds some light on the steering and why she is expected to move NW.
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The centre doesn't appear to be right under the heaviest of the convection yet.

If it does, then the waters are plenty warm enough to get spinning. Shear is low. Land proximity is about the only issue (and the fact it won't be on water that long).
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1978. xcool
Hermine just sit there not moved much..
Member Since: September 26, 2009 Posts: 2 Comments: 15669
1975. Plokit
ah thank you
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Is this the ridge that is going to move Hermine?

http://www.ssd.noaa.gov/goes/east/gmex/loop-wv.html

or is it something else building from the east that will hold her back?

Thanks...

(Wow, the first cup of coffee in the morning is the best)
Member Since: Posts: Comments:
Quoting Plokit:
What is 8-3-2?


The totals for this season to date.
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1972. Plokit
What is 8-3-2?
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1971. xcool
8.3.3 MAYBE
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Quoting btwntx08:

its being for a bit but it wont last to much longer a ridge is expected to move her nw later on today
thanks
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Never a dull moment lately! Welcome Hermine!
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1966. xcool
:0
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Quoting btwntx08:
Hermine is born
AL, 10, 2010090606, , BEST, 0, 211N, 948W, 35, 1002, TS, 34, NEQ, 90, 60, 0, 0, 1007, 120, 40, 0, 0, L


Can you give me a link where you find this information? Thanks.
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will hermine follow frontal boundary
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1963. JLPR2
There goes the convection. XD


Now I'm off to bed, night/morning all!
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1962. xcool
shift TO right BY NHC next advisory
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Gaston looks like he did yesterday, though slightly better in the windspeed/pressure. Conditions will only improve. See if he takes advantage... it's been near a week now since he lost his 'name', so to say.

You would have thought some Atlantic sailor would have staked him by now.
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1959. xcool
Hermine HAS been moved NE
Member Since: September 26, 2009 Posts: 2 Comments: 15669
1958. ackee
I am thinking if EX Gaston does regain TS status before reach the leeward dont think it will devlop until reach the westrn carrb
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1957. xcool
btwntx08 .guess so
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Quoting xcool:
Cotillion we have HERMIE


I see we do.
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TropicalDepression10's heading had turned eastward to (1.8degrees north of) NorthEast
from its previous heading of (9.6degrees east of) NorthNorthEast
TD.10's average speed moving between its last 2 reported positions was ~6.3mph(~10.2km/h)

Invest90L -- 6hour intervals between positions
05Sep . 06amGMT - - 19.1n95.6w - - 20knots - - 1007mb - - NHC-ATCF *19.2n95.7w
05Sep . 12pmGMT - - 19.5n95.7w - - 25knots - - 1005mb - - NHC-ATCF *19.4n95.6w
05Sep . 06pmGMT - - 19.9n95.7w - - 25knots - - 1004mb - - NHC-ATCF *95.9w
06Sep . 12amGMT - - 20.4n9.54w - - 25knots - - 1003mb - - NHC-ATCF
TD.10 -- 3hour intervals between positions (including the previous one and the next)
06Sep . 03amGMT - - 20.7n95.2w - - 30mph - - 1003mb - - NHC.Adv.#1
06Sep . 06amGMT - - 20.9n95.0w - - 35mph - - 1003mb - - #1A

20knots=~23mph __ 25knots=~28.8mph __ ~26.1knots=30mph

Copy and paste 19.1n95.6w, 19.5n95.7w-19.9n95.7w, 19.9n95.7w-20.4n95.4w, 20.4n95.4w-20.7n95.2w, 20.7n95.2w-20.9n95.0w, mid, bro into the GreatCircleMapper for a look at the last 18^hours.

* Before NHC reevaluated&alterered the ATCF numbers.
^ The last 2 line segments between the last 3 coordinates individually span 3hours.
The previous 2 line segments individually span 6hours.
Member Since: Posts: Comments:
1937 msphar "anybody have idea when that storm once called Gaston will arrive near Eastern Puerto Rico? and at what Latitude?"

Nope. It's still 750Miles away from Vieques, and underdeveloped. How much it develops controls how much steering currents at the various atmospheric levels will affect its forward movement.

Ask again when it becomes a TropicalDepression, then again after it becomes a TropicalStorm, then yet again after it becomes a Hurricane.
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Quoting msphar:
sorry to disturb your chatter, I'll look elsewhere.


Please calm down. Some people probably don't know, and thus can't answer your question.

I'll take a shot at it, though. Based on steering layer maps and model data, I'd say 48-60 hours, and at around 19N.
Member Since: March 7, 2007 Posts: 575 Comments: 20547
1950. xcool
btwntx08 ,interesting
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Quoting msphar:
sorry to disturb your chatter, I'll look elsewhere.

I have the same question, but it is a waste of time sometimes here make a question when they are so excited because they have a tropical cyclone so close!
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1947. xcool
Cotillion we have HERMIE
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Good morning.

I see the BoC area has indeed come to fruition.

Kudos to the GFS, only model to really pick it.
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1945. xcool
pressures are falling
Member Since: September 26, 2009 Posts: 2 Comments: 15669
1944. xcool


hmm maybe moved ne
Member Since: September 26, 2009 Posts: 2 Comments: 15669
1943. msphar
sorry to disturb your chatter, I'll look elsewhere.
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1941. xcool
new Steering Layer come soon..
Member Since: September 26, 2009 Posts: 2 Comments: 15669
1940. xcool


woww
Member Since: September 26, 2009 Posts: 2 Comments: 15669
Quoting xcool:
cloud tops


Good thing that thing isn't forecast to go Northeast!
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1937. msphar
anybody have idea when that storm once called Gaston will arrive near Eastern Puerto Rico ? and at what Latitude ?
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1936. xcool
btwntx08 lol
Member Since: September 26, 2009 Posts: 2 Comments: 15669
1935. xcool
my September Forecast call for 10 named storms .
Member Since: September 26, 2009 Posts: 2 Comments: 15669

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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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