Low Pressure near Northern Leewards

[Derek Ortt]

It does weaken some over Hispaniola

I do not toally disregard the CMC. Instead, I have been using it this season as a first overview model. If it shows a TC, I then look at other models to see if they show the same solution. If they do, then I start looking at the feature being developed. if it does not, I disregard the CMC.

However, if the CMC does not show something developing, its almost a shoe in to never develop

[ronjon]

23 of October 12z CMC

The pro mets rank CMC as not credible for the deep tropics so I am only posting this 12z run for pure entretainment. Imagine a hurricane moving thru Puerto Rico and Hispañola and gets stronger after it moves thru the 12,000 feet mountains.

Actually, Luis, it strengthens it south of PR and then weakens it over Hispanola - but really bombs it out in the SE Bahamas. The CMC has it's bias of over development but the overall track of the disturbance is somewhat similar to the 00Z NOGAPs.

[wxman57]

12Z GFS still develops a low NE of PR then tracks it out to sea to the NE-ENE. 12Z NOGAPS develops a low and tracks it westward across DR and eastern Cuba to the NW Caribbean by 7pm CDT Sunday. Both models indicate a strong cold front across south Florida to the NW Caribbean by then. GFS develops a frontal low in the SE Gulf Sunday night/Monday.

No sign of 12Z Canadian yet, and no 12Z EC for a few more hours. All in all, not a good consensus. I don't think the models are handling the upper low well. The 12Z Canadian will develop it into a hurricane, no doubt. None of these models has proven to be very good at predicting the development of TCs. Canadian ranks near the bottom with NOGAPS just above it. European hasn't proven itself at all except with the westward tracks of Felix & Dean. GFS has probably done the best of those 4 global models this year, and it shows no TC development (at least not in the NW Caribbean). It develops a weak front low but is no longer indicating an east coast Nor'Easter next week.

[Brent]

This is one of those "get back to me when its an invest" situations for me.

Put me on the "get back to me when it's a decent storm and not a sheared mess" list.

[cycloneye]

ABNT20 KNHC 232113
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT TUE OCT 23 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A WEAK AREA OF LOW PRESSURE HAS DEVELOPED IN ASSOCIATION WITH THE
AREA OF DISTURBED WEATHER AND TROPICAL WAVE LOCATED NORTHEAST OF
THE LESSER ANTILLES. UPPER-LEVEL WINDS ARE NOT CONDUCIVE FOR
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. THE LOW IS EXPECTED
TO MOVE VERY LITTLE DURING THE NEXT COUPLE OF DAYS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$

FORECASTER BROWN
WWWW

[Cyclone1]

Interesting wording. They refrain from saying no development expected from the low... so it's not out of the question.

But now I'm nitpicking.

[cycloneye]

Barbados Observations



The lowest pressure has been 1009 mbs earlier this afternoon.Winds are from the SSE.

[cycloneye]

ABNT20 KNHC 240212
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1030 PM EDT TUE OCT 23 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A WEAK AREA OF LOW PRESSURE CENTERED ABOUT 150 MILES EAST-NORTHEAST
OF THE NORTHERN LEEWARD ISLANDS IS PRODUCING A LARGE AREA OF
DISORGANIZED SHOWERS AND THUNDERSTORMS. UPPER-LEVEL WINDS ARE NOT
FAVORABLE FOR SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. THE LOW IS
EXPECTED TO DRIFT WESTWARD DURING THE NEXT COUPLE OF DAYS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$

FORECASTER BROWN

[Opal storm]

This is one of those "get back to me when its an invest" situations for me.

Put me on the "get back to me when it's a decent storm and not a sheared mess" list.

Your gonna be on that list for a while.

[cycloneye]

The low Pressure is at 18n-60w at the right part of image.

[flwxwatcher]

[Meso]

000
ABNT20 KNHC 240910
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 AM EDT WED OCT 24 2007

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A WEAK AREA OF LOW PRESSURE CENTERED ABOUT 150 MILES EAST-NORTHEAST
OF THE NORTHERN LEEWARD ISLANDS IS PRODUCING A LARGE AREA OF
CLOUDINESS AND SHOWERS. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. THE LOW IS EXPECTED TO
MOVE SLOWLY WESTWARD DURING THE NEXT COUPLE OF DAYS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$

FORECASTER COBB/BROWN

[cycloneye]

The AFD of the NWS in San Juan,Puerto Rico explains in detail all about this complex system and what will occur in the NE Caribbean in the next few days.


000
FXCA62 TJSJ 240950
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
550 AM AST WED OCT 24 2007

.SYNOPSIS...OLD TUTT AXIS EXTENDS FROM BAHAMAS ESE INTO FILLING
TUTT LOW JUST NE OF THE NORTHERN LEEWARDS...WITH WLY FLOW ALOFT
ACROSS MUCH OF THE NE CARIB PRODUCING CONVERGENCE AND GENERAL
SUBSIDENCE. ELONGATED LOW LVL LOW WITH A 1009 MB LOW CENTERED
NEAR 17.8 NORTH 59.5 WEST THIS MORNING...WITH A TROUGH EXTENDING
SOUTHWEST ACROSS THE NORTHERN WINDWARD ISLANDS AND INTO THE
SOUTHEAST CARIBBEAN. THIS PRODUCING A NELY FLOW ACROSS LOCAL AREA
WITH STLT IMAGERY AND LOCAL RADAR DEPICTED NUMEROUS SHOWERS
APPROACHING N VIRGIN ISLANDS AND ADJACENT ATLC ATTM AND POISED TO
REACH NE PR LATER THIS MORNING.

&&

.DISCUSSION...COMPLEX PATTERN ACROSS THE AREA HAS EVOLVED PAST FEW
DAYS WITH ELONGATED CYCLONIC TURNING DEVELOPING FROM A SERIES OF
LOW LAT TROPICAL WAVES...AND AN ASSOCIATED WIND SURGE...AND SOME
LINGERING MID LEVEL VORTICITY EAST OF THE LEEWARDS DURING THE PAST
SEVERAL DAYS. THIS LOW TO MID LEVEL CIRCULATION HAS BECOME PULLED
NW AND NOW CAPTURED BY TUTT LOW TO OUR NE. E CENTRAL ATLC UPPER
TROUGH AND LOW IS DIGGING S ATTM AND IS FORECAST TO EVENTUALLY
FORCE FILLING TUTT LOW SE...WITH UPPER LEVEL NWLY FLOW TO DEVELOP
ACROSS THE LOCAL AREA...TO PROVIDE DIVERGENCE ALOFT TONIGHT
THROUGH FRIDAY FOR DEEP CNVTV POTENTIAL. SURFACE LOW IS EXPECTED
TO DRIFT W TODAY...BUT BE FORCED WSW ACROSS THE LEEWARDS
TONIGHT...AND THEN SW INTO CENTRAL CARIB THU THROUGH FRI. PRES
GRADIENT AND APPROACH OF OLD LLVL BAROCLINIC BOUNDARY STRETCHED
ACROSS THE ATLC TO THE N OF THIS LOW...IS FORECAST TO INDUCE
STRONG LLVL FLOW ACROSS THE LOCAL AREA TO THE N AND NW OF THIS
FEATURE. MODELS HAVE BEEN ERRATIC IN RECENT FORECASTS OF THIS
EVOLVING SITUATION PAST FEW DAYS...BUT THIS RECENT GFS SOLUTION IS
IN GOOD AGREEMENT WITH NAM...AND SIMILAR BUT JUST A BIT SOUTH OF
UKMET AND ECMWF. THIS WILL ALSO BRING CONVERGENT BANDS OF LOW TO
MID LEVEL MOISTURE FOR PERIODS OF SCATTERED TO NUMEROUS SHOWERS
AND TSTORMS...WITH GUSTY WINDS THU AFTERNOON THRU FRI NIGHT. LOW IS
FORCED WELL SW OF LOCAL AREA BY SAT-SAT NIGHT...BUT CONTINUED
FRESH LLVL FLOW AND SUFFICIENT LLVL MOISTURE SHOULD MAINTAIN
SCATTERED RAIN CHANCES THROUGH THE ENTIRE WEEKEND.

http://www.srh.noaa.gov/fwd/productview ... &version=0

[ronjon]

Model consensus slowly coming together on low pressure near 18N-60W. This morning we have CMC, NOGAPs, ECMWF, FSU MM5, and 06Z GFS all moving low pressure from the NE LA toward the W or W-SW to south of Hispanola and then either near the Cayman Islands (GFS/NOGAPs) or across eastern Cuba into the SE Bahamas (CMC/ECMWF). If this system can stay south of the Greater Antilles, then we may be looking at a good chance of a strong system evolving south of Cuba in the western caribbean in 4-5 days, as upper level winds are forecast to be light.

[cycloneye]

06z NAM



I almost never post the NAM runs,but the NWS of San Juan mentions the model in the discussion that I posted above,so here is the 06z run about this complex system.

[wxman57]

It does appear as though we now have good model consensus of a TD/TS forming south of Cuba late this weekend or early next week. But all models also agree on a strong cold front lying off the east U.S. Coast extending to western Cuba and the northern Yucatan by that time. That would mean any tropical system which approaches the far NW Caribbean and/or southern Gulf would be experiencing increasing wind shear in association with the jet core along the front.

So a track as the European, GFS, or Canadian models across Cuba toward the Bahamas would most likely lead to weakening in a high-shear environment as the system merges with the cold front. Another possibility is suggested by the NOGAPS model - a slower westward movement farther south toward Central America. Such a track would put the system in a lower-shear environment where strengthening could occur, maybe even to a hurricane. Every other storm has struck down there (it seems) this year, so maybe that's not so far-fetched?

In any case, if the system tracks across the big islands of the northern Caribbean over the next 2-3 days, I don't look for any significant development until Sunday at the earliest. But if it slips south of Puerto Rico, it could develop as early as late Friday or Saturday. It's not likely to become a TD over the next 48 hours, though. I'd give it a 30% chance of developing now, in agreement with Derek.

[Evil Jeremy]

Florida at risk with this one?

[wxman57]

Florida at risk with this one?

Can't rule out potential impact to southern FL peninsula. But that cold front should be in your vicinity next week, meaning strong SW wind shear across the lower peninsula. That should limit any impact to a sheared TS along the frontal boundary.

[caneman]

WXMN57. Please explain to me why that owuld mean a weak system. Was not Wilma steered NE by a cold front as well? And we see what happened there. Not saying this will be a Wilma but... I don't think you can either state it will be a completely sheared out weak system either.

[Derek Ortt]

I think it would depend where the shear is located.

If we have stronger upper winds than we had with Wilma, but it is north of the core, all that will do is enhance the outflow and create a monster hurricane (assuming we have a TC to begin with). However, if the strong shear hits the core, bye bye TC

That is what makes these trough cases so very difficult. The shear was expected to weaken Wilma before landfall. However, the shear was in the wrong place, and Wilma intnsified quickly