Tropical Talk...Caribbean Invest & Track Discussion.

Let's talk about the tropics and what may or may not happen with regard to the new Invest 97 in the Carib.

From Tallahassee...

Note the constant discussion on timing below. I underlined a few points...

".LONG TERM [Wednesday through Sunday]...

Complex forecast throughout the long term period. A variety of
factors are at play here during the period and the lack of
consistent model agreement doesn`t help things very much. At the
start of the period a tropical disturbance will be nearing the
Yucatan Channel moving around the southwestern edge of a ridge of
high pressure off the Eastern CONUS. As moisture from this
disturbance streams northward, the large scale western CONUS
trough will continue to amplify as a potent upper low drops out of
the Gulf of Alaska and into the Pacific Northwest. As the pattern
evolves throughout the long term period, the Western CONUS trough
is expected to amplify and progress eastward into the Plains in
the Fri-Sun timeframe. Surface cyclogenesis is anticipated ahead
of this highly amplified and progressive trough by Friday in the
Central Plains. The aforementioned tropical disturbance and
associated moisture will gradually lift northward starting
Thursday night and continue into the weekend. The speed and
movement of this upper trough will have a significant impact on
how much tropical moisture gets into the region.

There has been some marginal consistency today with the last three
runs of the GFS, though there are the usual timing differences
with a Day 6-8 forecast. The 29/12z GFS has slowed slightly from
it`s 06z predecessor, but still is ahead of the Euro with this
system. The Canadian remains slow and given its difficulties
handling the tropical side of this system, it`s solution has been
discounted. It did increase forecast confidence slightly that the
29/12z GFS was reasonably close to the 29/00z GFS Ensemble mean,
indicating that we might be moving toward some sort of model
agreement with this system. Nevertheless, overall confidence in
the longer range portion of the forecast continues to be much
lower than normal.

With this forecast package, used a model blend weighted closer to
the 29/06z GFS solution with a smaller contribution from the 29/00z
Euro to account for potential slower progression of the system.

"

Tampa Bay has a shorter long term discussion. Also the same concerns over timing ...

and the model forecasts. 

"/ISSUED 418 AM EDT SUN SEP 29 2013/

HIGH DEGREE OF UNCERTAINTY REMAINS IN THE LONG RANGE DUE TO A
TROUGH OF LOW PRESSURE OVER THE CENTRAL AND SOUTHWESTERN CARIBBEAN
SEA WHICH IS EXPECTED TO GRADUALLY MOVE NORTHWEST TOWARD THE
SOUTHEAST GULF OF MEXICO WEDNESDAY AND THURSDAY. CANADIAN AND GFS
SHOW A RELATIVELY WELL DEVELOPED AREA OF LOW PRESSURE MOVING OVER
THE EASTERN GULF OF MEXICO. HOWEVER THE GFS SLOWS THE SYSTEM
BEFORE MOVING IT TOWARD WEST CENTRAL FLORIDA BY THE WEEKEND
WHEREAS THE CANADIAN IS MUCH MORE PROGRESSIVE MOVING IT TOWARD THE
FLORIDA PANHANDLE LATE THURSDAY. AND THE 28/12Z ECMWF IS MUCH
FURTHER WEST OVER THE CENTRAL GULF. REGARDLESS OF THE STRENGTH OF
THIS SYSTEM...DEEP TROPICAL MOISTURE ON THE EAST SIDE OF THE
TROUGH/LOW WILL LIKELY ADVECT OVER WEST CENTRAL AND SOUTHWEST
FLORIDA LATE WEDNESDAY INTO THURSDAY. INCREASING INSTABILITY
COMBINED WITH THE DEEP LAYER MOISTURE WILL GENERATE SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS THE AREA LATE WEDNESDAY
THROUGH FRIDAY WITH THE THREAT OF LOCALLY HEAVY RAIN. SYSTEM MAY
BE VERY SLOW MOVING...PER THE GFS...AND WAIT TO BE PICKED UP BY A
L/W TROUGH MOVING OVER THE SOUTHEAST U.S. LATE FRIDAY AND
SATURDAY. WILL TREND POPS AROUND 50 IN THE EXTENDED BASED ON
UNCERTAINTY IN EVOLUTION AND TRACK OF SYSTEM TO THE SOUTH."

The NWS loop out shows the path of the "system" taking a HARD right turn from the 6th Day to the 7th Day. It moves up into the Gulf of Mexico and then gets grabbed fast and pulled from west to east almost across South Florida.

Day 6:

See the low in the middle of the GOM?

Now watch....

Day 7:

It pulls to the right....

http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html

On www.canetalk.com tvsteve posted this great graphic that shows the models well.

http://canetalk.com/2013/09/1380450120_1380399004.shtml

Note the hard right turn towards Florida?

Really hard to say what will happen, because the TIMING issue here is the biggest question. 

It's forecast to stay a weak system by almost all models. The intensity is not in question, the timing is...

If the storm was developing right away it would most likely be sucked up towards the NNE... but, the forecast is for slow development.

Look at the dry air pushing down into the Caribbean from the north. Note though that the current set up will change and high pressure could develop aloft in the path of the system which would help it develop. Or... shear could kill it.

It's not a "sure thing"...it's not even a "50/50" thing but it is worth watching. Nothing else to watch. If there was a blizzard about to sling ten inches of snow across the Appalachians or spread flakes into the South I'd be watching something else. It's sort of like watching football on a Sunday afternoon when your team plays on Monday Night Football. Still fun to watch football, but not as fun...but worth watching. Yes, Miami Dolphins are for one more day Undefeated :)

So  thing to watch for fun is the slow progression of the wave out in the middle of the Atlantic making it's way slowly west.

One wave comes off low...one is a bit high as it travels across the Atlantic...

"...TROPICAL WAVES...                                             

A TROPICAL WAVE AXIS EXTENDS WEST OF THE CAPE VERDE ISLANDS FROM 
19N28W TO 07N29W AND MOVES W NEAR 15 KT. THE WAVE REMAINS 
EMBEDDED WITHIN A VERY MOIST ENVIRONMENT AS DEPICTED ON THE 
TOTAL PRECIPITABLE WATER IMAGERY. MIDDLE-LEVEL DIFFLUENCE FROM A 
HIGH CENTERED NW OF MAURITANIA AND AN INVERTED TROUGH WEST OF 
THE CAPE VERDE ISLANDS IS SUPPORTING SCATTERED MODERATE 
CONVECTION AND ISOLATED TSTMS FROM 10N-16N BETWEEN 24W-31W.

TROPICAL WAVE AXIS EXTENDS FROM 20N62W INTO THE CARIBBEAN TO 
13N66W MOVING W-NW NEAR 20 KT. THE WAVE IS MOVING AROUND THE 
BROAD SURFACE RIDGE THAT DOMINATES THE CENTRAL AND E ATLC AND 
REMAINS EMBEDDED WITHIN AN AREA OF MODERATE MOISTURE AS DEPICTED 
ON THE TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED SHOWERS AND 
TSTMS ARE WITHIN 110 NM WEST OF THE AXIS FROM 14N-16N."

I'll be back with more discussion soon. 

If for any chance something forms south of Panama or West of Central America...you can really kiss a named storm goodbye anytime in the very near future for the Caribbean. Not that it will happen, but you never know.

Bottom line as of the newest models for Invest 97...

Not expecting a lot...but something from this Invest.

What that "something" will be....check back later...

Sweet Tropical Dreams

Bobbi Storm