[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222347
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU JAN 22 2009

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 5N8W CROSSING THE EQUATOR A 20W
THEN EXTENDING TO 2S30W INTO NE BRAZIL NEAR 5S37W. ISOLATED
MODERATE CONVECTION IS FROM EQUATOR TO 3N BETWEEN 14W AND 30W. A
CLUSTER OF MODERATE CONVECTION IS NEAR 1.5N36W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS ALONG THE N COAST OF
BRAZIL AND OVER FRENCH GUIANA.

...DISCUSSION...

GULF OF MEXICO...
EARLY THIS MORNING...LOW TEMPERATURES PLUMMETED TO BELOW
FREEZING OVER MOST OF THE INTERIOR SECTIONS OF SOUTH FLORIDA
UNDER CLEAR SKIES AND RELAXING WINDS. LOWS BETWEEN 30 AND 32
WERE REGISTERED AS FAR SOUTH AS TAMIAMI TRAIL IN COLLIER
COUNTY...AND IN THE FAR WESTERN SUBURBS OF PALM BEACH, BROWARD
AND MIAMI-DADE COUNTIES. A 1026 MB SURFACE HIGH CENTERED OVER
FLORIDA JUST N OF TAMPA BAY WAS RESPONSIBLE FOR THESE WEATHER
CONDITIONS. WINDS THROUGHOUT THE GULF ARE QUITE WEAK UNDER THE
INFLUENCE OF THE ABOVE MENTIONED HIGH PRESSURE WHICH IS FORECAST
TO MOVE EWD ACROSS N-CENTRAL FLORIDA TOWARD THE W ATLC TONIGHT
AND FRI ALLOWING TEMPERATURES TO WARM UP ACROSS THE REGION. IN
THE UPPER LEVELS...THE STRONG SHORT-WAVE TROUGH OVER THE WESTERN
ATLANTIC IS HELPING TO PRODUCE SUBSIDENT WESTERLY WINDS OF UP TO
90 KT ACROSS THE GULF REGION. A WEAK COLD FRONT WILL MOVE OFF
THE NORTHWEST GULF COAST LATE SATURDAY AND MOVE TO THE FLORIDA
PANHANDLE TO SOUTH TEXAS ON SUNDAY.

CARIBBEAN SEA...
LOW TEMPERATURES BELOW 10 DEGREES CELSIUS/50 DEGREES FAHRENHEIT
WERE REPORTED IN PARTS OF WEST AND CENTRAL CUBA EARLY THIS
MORNING WITH THE LOWEST TEMPERATURE OF 7.8 C OR ABOUT 48 F IN
SANTO DOMINGO VILLA CLARA. THE COLD FRONT THAT BROUGHT THIS
WINTER WEATHER PRESENTLY STRETCHES FROM THE MONA PASSAGE
WEST-SOUTHWESTWARD SOUTH OF HISPANIOLA AND JAMAICA. SHOWER
ACTIVITY HAS INCREASED AHEAD OF THE FRONT. THE SAN JUAN DOPPLER
RADAR IS SHOWING SCATTERED MODERATE TO HEAVY SHOWERS OVER PUERTO
RICO...PARTICULARLY OVER THE NORTHERN MUNICIPALITIES JUST WEST
OF THE SAN JUAN METRO AREA. A DISTINCT SURFACE TROUGH CONTINUES
IN THE NORTHWESTERN CARIBBEAN SEA...WHICH MAY HAVE A CLOSED
CIRCULATION CENTER NEAR 17N85W. IN FACT...THE CLOUD PATTERN IS
EXHIBITING A WELL DEFINED CYCLONIC CIRCULATION ALTHOUGH VOID OF
CONVECTION. SOME LOW-TOPPED SHOWERS ARE OCCURRING OVER EASTERN
CUBA...HISPANIOLA AND JAMAICA. WINDS THROUGH THE EASTERN AND
CENTRAL CARIBBEAN ARE EAST TO NORTHEASTERLY UP TO 20 KT. AN
EARLIER ASCAT PASS SHOWED VERY WELL THE WIND SHIFT ASSOCIATED
WITH THE SURFACE TROUGH OVER THE NW CARIBBEAN. ACCORDING WITH
THE GFS MODEL...THIS TROUGH WILL GRADUALLY WEAKEN IN ABOUT 24-36
HOURS. MODEST EAST TO NORTHEAST SURFACE WIND SHOULD PREVAIL IN
THE CARIBBEAN DURING THE NEXT TWO DAYS AS THE FRONTAL BOUNDARY
DISSIPATES. IN THE UPPER LEVELS...A VIGOROUS SHORT-WAVE TROUGH
REMAINS OVER THE EXTREME WESTERN ATLANTIC. SOUTHWESTERLIES OF UP
TO 80 KT ON THE SOUTHEAST SIDE OF THIS TROUGH DOMINATES MOST OF
THE WEST AND CENTRAL CARIBBEAN INCLUDING CUBA. A WEAK UPPER-
LEVEL HIGH IS CENTERED OVER NORTHERN VENEZUELA. SUBSIDENCE AND
THE ASSOCIATED DRY AIR COVERS MOST OF THE BASIN AND NORTHERN
VENEZUELA.

ATLANTIC OCEAN...
A COLD FRONT ENTERS THE FORECAST AREA NEAR 31N53W. A 120-140 NM
WIDE BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS IS
ASSOCIATED WITH THE FRONTAL BOUNDARY. NW WINDS OF 15 TO 20 KT
ARE BLOWING BEHIND THE FRONT WHICH IS FORECAST TO BECOME DIFFUSE
ON SAT ACROSS THE SW N ATLC. BROKEN TO OVERCAST LOW/MID CLOUDS
COVER MOST OF THE W ATLC AND THE BAHAMAS. A LARGE SURFACE HIGH
OF 1031 MB IS CENTERED NEAR 31N28W...WHICH IS PRODUCING A
WIDESPREAD AREA OF GENERALLY EASTERLY WINDS UP TO 25 KT. THERE
WILL BE NO SIGNIFICANT CHANGE IN THIS SYNOPTIC PATTERN DURING
THE NEXT TWO DAYS. NO DEEP CONVECTION IS OCCURRING IN THE REGION
ASIDE FROM THAT ALONG AND NORTH OF THE ITCZ AXIS. IN THE UPPER
LEVELS...A CLOSED UPPER LOW IS CENTERED AT 14N52W AND IS
ADVECTING MID TO UPPER LEVEL CLOUDINESS AND MOISTURE FROM THE
ITCZ CONVECTIVE OUTFLOW ALONG ITS EASTERN SEMICIRCLE. AN
UPPER-LEVEL HIGH SITUATED NEAR 27N36W EXTENDS A RIDGE TO THE NE
TO BEYOND 31N28W. SOUTH OF THE RIDGE...THERE IS AN UPPER-LEVEL
TROUGH EXITING THE WEST COAST OF AFRICA NEAR 20N16W...THEN THE
TROUGH AXIS EXTENDS WWD JUST N OF THE CAPE VERDE ISLANDS TO NEAR
31W.

$$
GR





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