ATL: Ex-Tropical Storm GASTON - Discussion

[ConvergenceZone]

If that were so, then I don't think the NHC would give it an 80% chance of becoming a TC. Notice it's not stationary but moving west.

True, but the WV loop shows an environment that really isn't very favorable at all, at least at this time - as others said the ULL is forecast to at least move out of the way, but that is a large and formidable TUTT/ULL feature - if were a single and smaller ULL I'd have to agree, but what's out there now is much greater than ex-Gaston...

http://www.goes.noaa.gov/HURRLOOPS/huwvloop.html

I don't know Frank, they are giving it a 80% of a depression forming in the next 48 hours, so they are obviously seeing something that we aren't....and the chances of development seem to be increasing every few hours.

[jlauderdal]

anyone have the 12Z Bams with ships/lgem intensity forecast?

there is a model thread, fyi it isnt coming to fort lauderdale

[Aric Dunn]

you cant just look at WV to determine if an environment is conducive or not.. and again depending on the location of the upper trough and gaston will be key. you can have a semi sheared environment but very divergent which can aid convection or the upper trough begins to move faster and leaves the environment very conducive with upper ridge over gaston or it does not move much and gaston tries to plow through the shear axis which is not good.

[ConvergenceZone]

Plus, another thing frank, if it DOES run into hostile conditions that keep it from really developing, then it's headed straight into the carib....no fishy for this one

[Nimbus]

The convection is coming back, Gaston just wanted us to see his LLC so we know he is going to be a bad boy once conditions improve. Unfortunately the TUTT may just shear him again, in which case he may streak into the Caribbean.

[Aric Dunn]

Plus, another thing frank, if it DOES run into hostile conditions that keep it from really developing, then it's headed straight into the carib....no fishy for this one

it could become a hurricane and still likely head into the eastern carrib.. the ridge is becoming well established at least as far west as PR if not a tad farther. so west track with a wsw motion is quite possible if its weak or strong.

[Frank2]

LOL - no, the the "big fish" stories aren't going to work this time...

I agree that we can't just look at the WV loop, but as a few OCM's have mentioned it really is a good way to see what is really going on out there...

However, there are times like last Monday when using the WV was actually detrimental to understanding what was going to happen, because the ridge that could be seen on the WV was moving out of the way and allowing Earl to move NW, so true that other tools also need to be used, but it's hard for me to forget about that TUTT/ULL feature (lol)...

Oh, well - something to while away the long hours over the long weekend...

Frank

[ConvergenceZone]

The convection is coming back, Gaston just wanted us to see his LLC so we know he is going to be a bad boy once conditions improve. Unfortunately the TUTT may just shear him again, in which case he may streak into the Caribbean.

One thing for sure, if the TUTT does get Gaston, then I think it will be pretty obvious what the conditions in the carib and gulf are going to be like for the rest of the season.......TUTT's just seem to be in total control of the carib/gulf.

Gaston's survival will probably give us an indiction whether or not the Gulf or Carib is really going to get cooking or not, as we approaching the peak of the season in about a week or so...

[ColinDelia]

Frank,

I've been watching that TUTT for days and the development of the ULL.

It looks to me like the GFS has the ULL move to the SW Caribbean by 72 hours. Then it has an upper level high form North of Gaston and slide west with it. The TUTT keeps getting pushed west and doesn't look to be a factor.

I'm thinking maybe the GFS keeps Gaston weak because the high is considerably offset from Gaston. The GFS has the upper level high form a good 10 degree North of Gaston. Eventually though the GFS gets the high right over Gaston in the Bahamas and starts to strengthen it.

[cycloneye]

Does anyone have a graphic of how the ridge is if is strong or not? It continues to move at 290 degrees wnw at 16.6N, so maybe not strong? Is going to clear the Lesser Antilles if this motion continues.

[Nimbus]

Looking at the water vapor imagery it looks like the TUTT may be cutting off into an ULL centered over the Caribbean. Now that might roll west or get pushed south by the encroaching ridge. I need to get caught up on the upper air patterns.

Thanks for the update CD!

[Frank2]

ColinDelia,

As our IT guy would say...

Hmm...

That's what the 00Z GFS shows for Day 10 (not that I'm a Day 10 type of person when it comes to those 240-hour models, but it does show that)...

http://weather.unisys.com/gfsx/10d/gfsx_500p_10d.html

[gatorcane]

LOL - no, the the "big fish" stories aren't going to work this time...

I agree that we can't just look at the WV loop, but as a few OCM's have mentioned it really is a good way to see what is really going on out there...

However, there are times like last Monday when using the WV was actually detrimental to understanding what was going to happen, because the ridge that could be seen on the WV was moving out of the way and allowing Earl to move NW, so true that other tools also need to be used, but it's hard for me to forget about that TUTT/ULL feature (lol)...

Oh, well - something to while away the long hours over the long weekend...

Frank

No frank the big fish stories are not going to work this time. I've been saying this system is one of the cape verde systems to really watch for the united states. Climatology-wise tis the time of year for south florida strikes, in fact September is the month that more major hurricanes have made landfall in south Florida than any month. That said I am not saying it is coming to Florida. Just saying there is a possibility looking at the setup unfolding here. Now the ull you point out certainly will be closely watched but do think it should move off to the sw and bury itself in the Caribbean sea. That means the counterclockwise flow will create east southeast winds to the northeast of the Ull to help gaston move west especially a deeper stronger gaston. Of course the bermuda high appears it finally starts to strengthen once this larger trough moves off the eastern seaboard.

[ColinDelia]

I'm not a day 10 guy either, Frank. Just saying what the GFS is sayin'

[ColinDelia]

Regarding the TUTT, this was from the HPC Caribbean discussion on Sep 2.
Unfortunately, I don't believe they write discussions on weekends so this is
probably the last one we'll see until Tuesday (Maybe Luis can shed some light on that)



IN RESPONSE TO THE BUILDING SUBTROPICAL RIDGE...A TUTT IS DIGGING
ACROSS THE CENTRAL ATLANTIC AND IT WILL EXPAND INTO THE EASTERN
CARIBBEAN ISLES BY 30-36 HRS...WITH A CLOSED/CUT OFF LOW TO THEN
FORM NEAR 20N 60W THROUGH 42-48 HRS. THIS LOW IS FORECAST TO
RETROGRESS TO THE EASTERN CARIBBEAN BY 60-72 HRS...TO MEANDER
SOUTH OF PUERTO RICO/NORTH OF VENEZUELA. IN A TIGHT GRADIENT
BETWEEN THE SUBTROPICAL RIDGE TO THE NORTH...A 50-65KT JET MAXIMA
IS TO DEVELOP. THIS WILL MOVE OVER PUERTO RICO DURING THE
AFTERNOON HOURS ON FRIDAY. POTENTIALLY FAVORABLE JET DYNAMICS WILL
BE OF CONCERN THROUGH SATURDAY AFTERNOON. A CONSIDERABLY WEAKER
MAXIMA OF 35-45KT WILL THEN MOVE FROM THE EAST AS THE TUTT LOW
RELOCATES TOWARDS HISPANIOLA BY 84-96 HRS. AT MID LEVELS A GOOD
REFLECTION OF THE TUTT PATTERN IS EXPECTED...WITH AN INVERTED
TROUGH OVER THE ATLANTIC TO MOVE ALONG 50W/53W BY 48 HRS...AND
ACROSS THE ORINOCO DELTA REGION/ISLAND CHAIN TO THE CENTRAL
ATLANTIC BY 72-84 HRS. AT 700 HPA THE GFS NOW SHOWS A SOMEWHAT
STRONGER MID LEVEL TROUGH DEVELOPING TO THE EAST OF THE ISLAND
CHAIN AND ENTERING THE NORTHEAST CARIBBEAN BY 96-108 HRS...WITH
FAIRLY STRONG CYCLONIC VORTICITY ADVECTION TO ACCOMPANY THIS
PERTURBATION. ALTHOUGH STRONGER AT 700 HPA...THE CORRESPONDING 850
HPA INDUCED TROUGH IS ALSO BETTER DEFINED ON THE LATEST MODEL
RUN...AND GOOD CHANCE FOR MESO-SYNOPTIC FORCING TO DEVELOP ACROSS
THE FORECAST AREA ON SUNDAY TO MONDAY. ALTHOUGH THE TUTT ALOFT
APPEARS FAIRLY INTENSE...IT FAILS TO ESTABLISH A MOIST ADVECTIVE
PATTERN ACROSS THE BASIN. AS A RESULT...WE ARE NOT EXPECTING LARGE
AREAS OF ORGANIZED HEAVY RAINFALL AMOUNTS. INSTEAD...EXPECTING
TUTT PATTERN ALOFT TO ENHANCE LOCAL EFFECTS AND FAVOR HIGHLY
LOCALIZED HEAVY CONVECTION. UNDER FAVORABLE JET DYNAMICS SOME OF
THE CELLS MIGHT BECOME SEVERE. ALSO WORTH NOTING...DURING THE
LATEST IMPLEMENTATION OF THE GFS...EMC TRIED TO CORRECT MID LEVEL
COLD BIAS PREVIOUSLY EXHIBITED BY THE MODEL. NOT SURE WHAT IMPACT
THIS IS GOING TO HAVE ON FORECASTED STABILITY INDICES. AS THE
MODEL MIGHT BE SOMEWHAT UNDERDONE...OR PERHAPS JUST RIGHT. IN ALL
HONESTY WE DO NOT KNOW. SO BE CAREFUL WHEN LOOKING AT THE
STABILITY INDICES SUCH AS THE LI...SSI AND CAPE. MOST ACTIVE
CONVECTION IS LIKELY TO DEVELOP ACROSS NORTHEAST/EAST VENEZUELA TO
GUYANA AS THE TROUGH ALOFT INTERACTS WITH THE NEAR EQUATORIAL
TROUGH OVER THE CONTINENT...TO FAVOR A SURGE IN ACTIVITY WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-40MM/DAY.

[Sanibel]

The feared scenario is the north of Antilles monster tracking right towards Florida. However the other alternative is a small sheared storm lacking convection that tracks right over the islands and poofs embarrassingly in the ULL.

Of course the wise man guards against the worst and considers if this is a tiny dry sleeper about to pounce on a Labor Day track. As they say in the parlance -"just sayin'"...

[cycloneye]

It has work to do before it returns to TD.

[terrapintransit]

It has work to do before it returns to TD.

Wow...that's impressive. Currently looks like a relative of fiona...perhaps a younger brother.

[Blown Away]

Does anyone have a graphic of how the ridge is if is strong or not? It continues to move at 290 degrees wnw at 16.6N, so maybe not strong? Is going to clear the Lesser Antilles if this motion continues.

TAFB thinks the ridge is strong enough to get ex-Gaston to the islands.

[Gustywind]