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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Quoting MiamiHurricanes09:
Nah, this has to be a larger scale pressure drop. Notice the 1004-1006mb pressures across Mexico and the Gulf of Mexico. The true central pressure then is near <1003mb, I assume.



If you are right then the NHC had good reason to put a 80% chance on it.
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I noticed something with most of the storms in the Caribbean/GoMEX.

Alex, TD2, and now 90L are huge storms.

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LOL, winds up 5mph and the pressure is down 1mb, yet the NHC dropped the percentage by 20%.

AL, 09, 2010090600, , BEST, 0, 171N, 524W, 30, 1008, LO,
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Kristina40:
Tampico is reporting a 1004.9 now.
Nah, this has to be a larger scale pressure drop. Notice the 1004-1006mb pressures across Mexico and the Gulf of Mexico. The true central pressure then is near <1003mb, I assume.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting futuremet:




Gaston into Gulf, then hooking over Florida ?
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1179. JLPR2
Quoting ElConando:


It is back up to 30 kts?


yep, apparently for most of today.
AL, 09, 2010090512, , BEST, 0, 169N, 500W, 30, 1008, LO
AL, 09, 2010090518, , BEST, 0, 170N, 512W, 30, 1008, LO
AL, 09, 2010090600, , BEST, 0, 171N, 524W, 30, 1008, LO
Member Since: September 4, 2007 Posts: 7 Comments: 8459
1178. BDADUDE
Quoting futuremet:



Your not reading the full picture. Why do you keep showing that map? That map does not show the weakness.
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Quoting Kristina40:
Tampico is reporting a 1004.9 now.

O_O
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BDADUDE: this is the layer that will steer Gaston, big high pressure.....thanks futuremet for posting. I too at one point did not know which steering layers to look at for the strength of systems..


Quoting futuremet:


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Quoting JLPR2:
AL, 09, 2010090600, , BEST, 0, 171N, 524W, 30, 1008, LO

yeah, its at 52W


It is back up to 30 kts?
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1173. JLPR2
AL, 09, 2010090600, , BEST, 0, 171N, 524W, 30, 1008, LO

yeah, its at 52W
Member Since: September 4, 2007 Posts: 7 Comments: 8459
Tampico is reporting a 1004.9 now.
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Quoting BDADUDE:

If Gaston does survive then he will be directed north in 3-4 days. The weakness in the ridge will catch him and send him between Bermuda and The United States of America.


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Quoting MiamiHurricanes09:
Odd, the on RGB the circulation is to the WNW of that location. Looks like we're dealing with a broad area of low pressure.


Well that explains that.
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I see the NHC pulled the ol' switcher-a-roo.

This TWO:
90l: 80%
Gaston: 60%

Last TWO:
90l: 60%
Gaston: 80%
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Quoting Kristina40:


22.01N 94.04W

Link
Odd, on RGB the circulation is to the WNW of that location. Looks like we're dealing with a broad area of low pressure.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Are we really arguing 60% v. 70%?? Seriously?
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1166. Kibkaos
Okay guys I was looking at the Caribbean Infrared Loop and it LOOKS like there is something starting up. Please let me know if there is anything to this. We already are watching the Invest near South Texas. It is getting very serious right now.
Caribbean Loop
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LOL, you still trying to sell that?.......good luck with that prediction....

Quoting BDADUDE:

If Gaston does survive then he will be directed north in 3-4 days. The weakness in the ridge will catch him and send him between Bermuda and The United States of America.
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Post Earl WX Synopsis:
Earls' eastward bias moved its landfall position to the SE shore, rather than the forecast SW shore of NS... following the warm water.
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Quoting MiamiHurricanes09:
That's a pressure of 1005.8mb. Not bad. What are the coordinates to that buoy?


22.01N 94.04W

Link
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Quoting Kristina40:
Things are livening out in the BOC...

That's a pressure of 1005.8mb. Not bad. What are the coordinates to that buoy?
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting flightweatherfan:
pretty cool!

What is pretty cool?
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1160. BDADUDE
Quoting futuremet:
My post from last night:

We will see a substantial increase in ex-Gaston's convection activity tomorrow. It is moving into an area of moist air with good diffluent flow aloft. The upper level low will provide good ventilation and will trigger quasi-persistent convection. This system will not move too close to the upper level low to get sheared apart.

If this system enters the Caribbean, it will be capable of pumping a lot of heat into the upper air and generate a vigorous upper level high. The GFS also expects the upper level low weaken slowly as it moves across the Caribbean. The upper level low is the only possible factor I see that can hinder ex-Gaston's tropical cyclognesis. However, this upper level low will actually prove to be beneficial tomorrow.

Water vapor imagery shows that Gaston is starting to interact with the ULL.

If Gaston does survive then he will be directed north in 3-4 days. The weakness in the ridge will catch him and send him between Bermuda and The United States of America.
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Quoting futuremet:
My post from last night:

We will see a substantial increase in ex-Gaston's convection activity tomorrow. It is moving into an area of moist air with good diffluent flow aloft. The upper level low will provide good ventilation and will trigger quasi-persistent convection. This system will not move too close to the upper level low to get sheared apart.

If this system enters the Caribbean, it will be capable of pumping a lot of heat into the upper air and generate a vigorous upper level high. The GFS also expects the upper level low weaken slowly as it moves across the Caribbean. The upper level low is the only possible factor I see that can hinder ex-Gaston's tropical cyclognesis. However, this upper level low will actually prove to be beneficial tomorrow.

Water vapor imagery shows that Gaston is starting to interact with the ULL.


Excellent analysis, tomorrow should be interesting!
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Things are livening up out in the BOC...

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51W on the NHC 8pm discussion is an error

Clearly it has moved westward since the 2pm discussion when it was also given as 51W, as can be clearly seen on the visible loop

There is no excuse for statistical errors like that when dealing with a potential tropical cyclone so close to land

Poor effort

Dan
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pretty cool!
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Quoting WeatherNerdPR:
My avatar finally changed to the Hurricane Earl Radar, again, thanks MH09!
No problem!
Member Since: September 2, 2009 Posts: 130 Comments: 21032
1153. bayeloi
Quoting Vero1:


It appears NEXRAD is down.. However NWS radars are up.


NEXRAD Radar's are what the National Weather Service uses pretty much exclusively.
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My avatar finally changed to the Hurricane Earl Radar, again, thanks MH09!
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My post from last night:

We will see a substantial increase in ex-Gaston's convection activity tomorrow. It is moving into an area of moist air with good diffluent flow aloft. The upper level low will provide good ventilation and will trigger quasi-persistent convection. This system will not move too close to the upper level low to get sheared apart.

If this system enters the Caribbean, it will be capable of pumping a lot of heat into the upper air and generate a vigorous upper level high. The GFS also expects the upper level low weaken slowly as it moves across the Caribbean. The upper level low is the only possible factor I see that can hinder ex-Gaston's tropical cyclognesis. However, this upper level low will actually prove to be beneficial tomorrow.

Water vapor imagery shows that Gaston is starting to interact with the ULL.
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Quoting StormW:
Back in a bit.
See you later.
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Quoting AllStar17:
A bit off-topic, but has any tropical cyclone stayed tropical while over Labrador? Earl came close. It's the first time I've ever included Labrador on a hurricane graphic:
Allstar, how do you make graphics like that? Been wondering for a while.
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Quoting InTheCone:


Thank you, but one must always be ready for some "crow"! BTW, you do a fantastic job on here!
LOL, thank you!
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting StormW:


Again, have to wait to see the steering once he's into the Caribbean for a little bit.


As long as its not the GOM..
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Quoting MiamiHurricanes09:
Hey, you're avatar is absolutely hilarious. LOL, "The Department Of Blob Watching".


Thank you, but one must always be ready for some "crow"! BTW, you do a fantastic job on here!
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Quoting cyclonekid:
Read post 1071. :D


Oh....I certainly agree with that post. I was just stating my thoughts.
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Quoting RecordSeason:
1121:

Whoever wrote that discussion is smoking dope, because that's a full degree of where the previous discussion had him fixed, and is also more than a degree east of where Colorado State has him fixed right now.

It's also a degree east of where I have him fixed.

Sad.
You are right because at the last uodate it was at 51.2W which according to what they are saying he is not moving at all.
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Storm W... How much north do you think 90L will go? From satellite view if you zoom in it look like it is moving N to NE not NW.Link
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Quoting InTheCone:


The ULL in front of Gaston is pulling moisture up from the south, probably what the NHC thinks will provide him with a better environment in the future.
Hey, you're avatar is absolutely hilarious. LOL, "The Department Of Blob Watching".
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting AllStar17:
'

Yuck. Those tracks would be horrible...especially if it got into the W. Caribbean.

I really do not understand why the NHC went with 60% because of dry air. At most, it should have dropped to 70%, if at all. It is moving west and into a more favorable environment, yet they lowered the percentages. Not to mention, it does have convection over the center.

I also do not believe 90L should have gotten 80%. They should have kept it at 60%.

Very confused by this TWO issued by Blake.
Read post 1071. :D
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.