ATL: INVEST 91L - Discussion

[lbvbl]

Does anyone know if this is the system that the GFS was predicting to hit SFL as a weak system? This was a few days to a week ago...

[wyq614]

Havana rained this morning and the wind increases with gusting wind. Is this because of 91L?

[HURAKAN]

Havana rained this morning and the wind increases with gusting wind. Is this because of 91L?

There is a stationary front over northern Cuba. Winds here are also gusting but they are from the north, not related to 91L in any way.

[HURAKAN]

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 20 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1700 UTC.

...SPECIAL FEATURES...
SCATTERED MODERATE TO STRONG CONVECTION IN THE NW CARIBBEAN IS
ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE CENTERED NEAR
17N86W...OR ABOUT 100 NM E OF THE COAST OF BELIZE. CONVECTION IS
MOST PROMINENT N OF 16N AND W OF 80W. THE LOW IS NEARLY
STATIONARY AND SFC OBSERVATIONS IN THE VICINITY INDICATE RISING
PRESSURE. NE TO E WINDS 15-20 KT ARE OBSERVED TO THE NORTH AND
EAST OF THE LOW. ANY TROPICAL DEVELOPMENT OF THESE SYSTEM WILL
BE SLOW TO OCCUR...HOWEVER...HEAVY RAIN WILL PERSIST OVER
PORTIONS OF HONDURAS...GUATEMALA...BELIZE...THE YUCATAN
PENINSULA...AND THE NW CARIBBEAN SEA OVER THE NEXT COUPLE OF
DAYS.

[Blown Away]

Convection starting to pop rate over the low.
http://www.ssd.noaa.gov/goes/flt/t1/loop-avn.html

[HURAKAN]

Best Track 18z:

AL, 91, 2008102018, , BEST, 0, 163N, 869W, 25, 1009

Repositioned.

[gatorcane]

Best Track 18z:

AL, 91, 2008102018, , BEST, 0, 163N, 869W, 25, 1009

Repositioned.

Farther east right?

[Blown Away]

Best Track 18z:

AL, 91, 2008102018, , BEST, 0, 163N, 869W, 25, 1009

Repositioned.

This has been the year of land loving tropical systems.

[HURAKAN]

Farther east right?

AL, 91, 2008102012, , BEST, 0, 170N, 870W, 25, 1009,
AL, 91, 2008102018, , BEST, 0, 163N, 869W, 25, 1009,

Mostly south.

[Lifesgud2]

guys,

you are making this way more than it is. The NHC has this as a yellow. what gives?

[CourierPR]

guys,

you are making this way more than it is. The NHC has this as a yellow. what gives?

Probably because this system could be the last chance for development this season.

[HURAKAN]

No one is hyping anything.

1. We have a disturbance
2. It's over the Western Caribbean
3. The Western Caribbean is climatologically-speaking the prime area for development at this time of the year
3. It's expected to move northward over the next few days as a trough approaches Florida

Conclusion, we need to keep an eye on it. Nothing more, nothing less.

[gatorcane]

Very nice blowup of convection near the center continues, if this trend continues expect the NHC code to be upgraded over the next 12-24 hours. Personally I would not have downgraded this area so quickly.

[wxman57]

Does anyone know if this is the system that the GFS was predicting to hit SFL as a weak system? This was a few days to a week ago...

Yes, this is the same system that the models bring northward then merge with the cold front as it moves across Florida. SW-WSW winds aloft will be in the 50-80 kt range across the eastern Gulf when the low moves into the FL peninsula Friday/Saturday. So it would be a tremendously sheared low center by the time it would reach Florida. Lowest shear would be by the Yucatan where it may experience only 15-20 kts. But as it gets pulled northward Thursday/Friday it'll be ripped apart and elongated along the front, most likely.

[Sanibel]

I think the LLC is just inland over northern Honduras and drifting west. That's why you're seeing the decrease in convection.

I'm not certain but the deep flare over the Caribbean to the east is probably a refire of the little wave from yesterday. If it rips loose a second LOW center I won't speculate.

[cycloneye]

000
ABNT20 KNHC 202339
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON OCT 20 2008

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

AN AREA OF LOW PRESSURE LOCATED OVER THE GULF OF HONDURAS CONTINUES
TO PRODUCE DISORGANIZED SHOWERS AND THUNDERSTORMS OVER A LARGE
PORTION OF THE NORTHWESTERN CARIBBEAN SEA. THIS SYSTEM APPEARS TO
BE DRIFTING WESTWARD TOWARD LAND...AND SIGNIFICANT DEVELOPMENT IS
NOT EXPECTED. LOCALLY HEAVY RAINS ARE POSSIBLE OVER PORTIONS OF
HONDURAS...GUATEMALA...BELIZE...AND THE YUCATAN PENINSULA DURING
THE NEXT COUPLE OF DAYS.

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

$$

FORECASTER BERG/PASCH

[gatorcane]

Convection is on the increase in the NW Caribbean:

[gatorcane]

91L continues to organize. Using this link you can clearly see big thunderstorms wrapping around the center but just within the past hour so the NHC has not had a chance to mention this just yet. Just click the Fronts checkbox to see the "L" in the pic and notice the thunderstorms wrapping around the Low as it drifts NW...

http://www.ssd.noaa.gov/goes/flt/t1/loop-rb.html

[MiamiensisWx]

I briefly traversed the data for this system earlier today, and current data supports my original suspicions. Satellite imagery clearly indicates the LLC and primary 850 mb LL vorticity maximum is situated near northern Honduras and is moving west toward Belize and the southern Yucatan Peninsula. The greatest ascent is occurring farther east, where lifting mechanisms are enhancing convection east of 85 W. However, mid/upper level shear has remained very intense, mitigating further organization and development a second LLC farther NE over the open NW Caribbean Sea. A tropical wave axis is currently intersecting this region, which is providing greater divergence, LL convergence, and 850 mb vorticity. However, the wave axis is moving quickly west; consequently, the 850 mb vorticity maximum is merging with the primary vorticity center farther west. Since there are no substantive signs of a persistent 850 mb vorticity maximum and a developing secondary surface low (or LLC), the chances of a new system forming farther NE over the NW Caribbean Sea are steadily diminishing, especially in light of the fact that this area is still associated with 91L's circulation. Overall, 91L is an undisputed repeat of TD 16; several models were moving the center to the north too rapidly, so they failed to "pick up" the west trend as the system moved slower and was pushed west by the rebuilding low level ridging (between the first trough and the current impending trough). If I recall correctly, the ECMWF (Euro) was the only model that correctly forecasted this scenario in one of its runs. Overall, its future prospects over the Gulf of Mexico are very bleak, and the vast majority of intensity models do not forecast a system stronger than moderate TS intensity; in fact, the system will likely be even weaker than progged.

If a new system does not develop prior to October 25, the "season" for the CONUS will be rapidly closing after this date.

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8vor4.html

http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.html

http://www.ssd.noaa.gov/goes/flt/t1/loop-vis.html

Convection east of 85 W is diminshing at this time...

[gatorcane]

Good analyis but have you seen the last IR pics coming in from the past hour? See my post above yours. I also see it finally starting to gain some lattitude albeit it should still move ashore the Yucatan ultimately.