[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202344
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI APR 20 2012

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS INLAND ACROSS THE TROPICAL REGIONS OF
WEST AFRICA INTO THE ATLC BASIN ACROSS THE COAST OF LIBERIA NEAR
6N11W TO 2N14W...WHERE THE ITCZ AXIS CONTINUES ALONG 1S30W TO
THE COAST OF BRAZIL NEAR 3S40W. SCATTERED MODERATE TO ISOLATED
STRONG CONVECTION IS NOTED FROM THE EQUATOR TO 5N BETWEEN THE
PRIME MERIDIAN AND 18W. SCATTERED MODERATE CONVECTION IS S OF 4N
BETWEEN 20W AND 30W.

...DISCUSSION...

GULF OF MEXICO...
SHOWERS AND TSTMS ARE FLARED UP OVER FLORIDA AND THE EASTERN
PORTION OF THE GULF AHEAD OF A SURFACE TROUGH EXTENDING FROM
27N85W TO 21N88W. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE
THIS CONVECTIVE ACTIVITY. AS AN UPPER LEVEL TROUGH DEEPENS OVER
THE CENTRAL PLAINS AND THE GULF OF MEXICO...EXPECT MORE SHOWERS
AND TSTMS TO DEVELOP OVER THE EASTERN GULF AND PARTS OF FLORIDA
THIS SATURDAY. SOME OF THESE TSTMS COULD BE STRONG OR SEVERE.

A COLD FRONT IS REACHING THE COAST OF TEXAS. A BAND OF SHOWERS
AND TSTMS IS JUST AHEAD OF THE FRONT AND IS PRESENTLY AFFECTING
THE NW GULF WATERS STRETCHING FROM THE TEXAS/LOUISIANA BORDER TO
BROWNSVILLE TEXAS. THE COLD FRONT IS EXPECTED TO ENTER THE GULF
WATERS THIS EVENING REACHING A POSITION FROM THE MISSISSIPPI
DELTA TO THE BAY OF CAMPECHE EARLY SAT AND FROM THE FLORIDA BIG
BEND TO YUCATAN PENINSULA EARLY SUN. A FRONTAL WAVE OR WEAK LOW
WILL DEVELOP ALONG THE FRONTAL BOUNDARY NEAR SE LOUISIANA ON
SAT. THE LOW PRES WILL MOVE EWD ACROSS THE NORTHERN GULF WATERS
INTO N FLORIDA SUN MORNING WHILE DEEPENING...THEN WILL CONTINUE
NE ALONG THE SE U.S. COAST SUNDAY AFTERNOON. AS THE LOW PRES
RACES NE LATE SAT NIGHT INTO EARLY SUN...THE COLD FRONT WILL
MOVE RAPIDLY SE THROUGH THE STRAITS OF FLORIDA LATE SUN. FRESH
TO STRONG WINDS OF 25-30 KT AND BUILDING SEAS OF UP TO 13 FT ARE
EXPECTED IN THE WAKE OF THE FRONT. STRONG TO SEVERE TSTMS ARE
ALSO POSSIBLE OVER PARTS OF FLORIDA WITH THE FRONTAL PASSAGE.
THE AFOREMENTIONED DEEPENING UPPER-LEVEL TROUGH SUPPORTS THE
EVOLUTION OF THIS WEATHER PATTERN.

CARIBBEAN SEA...
HIGH PRES LOCATED N OF AREA IS PRODUCING MODERATE TO FRESH NE TO
E WINDS ACROSS THE BASIN. THE MOST RECENT SCATTEROMETER DATA
CONFIRMED THE PRESENCE OF THESE WIND SPEEDS. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE NOTED ACROSS THE YUCATAN CHANNEL UNDER A
SE LOW LEVEL WIND FLOW. SOME SHOWERS ARE NEAR THE WINDWARD
ISLAND IN ASSOCIATION WITH A SURFACE TROUGH THAT HAS MOVED
LITTLE SINCE YESTERDAY. THIS TROUGH EXTENDS ACROSS THE TROPICAL
N ATLC FROM 18N57W TO 10N62W. AN EARLIER ASCAT PASS REVELED THE
WIND SHIFT RELATED TO THIS FEATURE. SOME SHOWER ACTIVITY IS ALSO
NOTED OVER THE SW CARIBBEAN IN THE VICINITY OF SAN ANDRES. WINDS
ARE FORECAST TO INCREASE ACROSS THE NW CARIBBEAN ON SAT AHEAD OF
THE COLD FRONT FORECAST TO MOVE ACROSS THE GULF OF MEXICO THIS
WEEKEND. THE SOUTHERN PORTION OF THE COLD FRONT WILL MOVE ACROSS
THE YUCATAN CHANNEL SAT EVENING REACHING FROM CENTRAL CUBA TO
NEAR CABO GRACIAS A DIOS NICARAGUA LATE SUN. FRESH W TO NW WINDS
ARE EXPECTED BEHIND THE FRONT. ALOFT...NEAR ZONAL WESTERLY FLOW
DOMINATES THE CARIBBEAN SEA.

ATLANTIC OCEAN...
A SHORTWAVE ALONG THE COAST OF SE U.S. SUPPORTS A WEAK TROUGH
EXTENDING FROM 31N79W TO THE COAST OF FLORIDA NEAR MELBOURNE.
SCATTERED SHOWERS AND TSTMS ARE AHEAD OF THE TROUGH AXIS JUST N
OF THE NW BAHAMAS. THE REMAINDER OF THE WESTERN ATLC IS UNDER
THE INFLUENCE OF A WEAK RIDGE ANCHORED ON A 1018 MB HIGH LOCATED
NEAR BERMUDA. THIS SYSTEM IS MAINTAINING MOSTLY FAIR WEATHER
CONDITIONS AND LIGHT WINDS ACROSS THE REGION BETWEEN 55W AND THE
BAHAMAS. SW AND W OF THIS RIDGE...SE TO S WINDS OF 10 TO 15 KT
ARE BLOWING. THESE WINDS WILL FURTHER INCREASE TO 25 TO 30 KT
LATE SAT AHEAD OF THE DEVELOPING LOW PRES AND STRONG COLD FRONT
FORECAST TO MOVE ACROSS THE GULF OF MEXICO. THE COLD FRONT IS
EXPECTED TO MOVE OFF THE SE U.S. COAST BY SUN.

A WEAK LOW PRES REMAINS OVER THE FORECAST REGION NEAR 30N49W.
THIS LOW IS FORECAST TO DISSIPATE IN ABOUT 24 HOURS. THE
ATTENDANT WEAKENING COLD FRONT IS WELL DISPLACED TO THE EAST AND
ENTERS THE AREA NEAR 31N43W THEN CONTINUES SW TO 26N45W. WHERE
IT BEGINS TO DISSIPATE. FRESH TO STRONG SLY WINDS ARE SEEN AHEAD
OF THE FRONT PER THE MOST RECENT ASCAT PASS DUE TO THE PRES
GRADIENT BETWEEN THE LOW PRES AND A HIGH CENTERED NEAR THE
AZORES. THIS HIGH EXTENDS A RIDGE OVER THE EASTERN ATLC. AS
PREVIOUSLY MENTIONED...A SURFACE TROUGH IS OVER THE TROPICAL N
ATLC WATERS JUST E OF THE LESSER ANTILLES AND IS GENERATING SOME
SHOWER ACTIVITY. ACCORDING TO THE COMPUTER MODEL...MOISTURE
ASSOCIATED WITH THIS TROUGH WILL REMAIN NEAR THE LESSER ANTILLES
THIS UPCOMING WEEKEND. A BAND OF TRANSVERSE HIGH CLOUDS
ASSOCIATED WITH STRONG UPPER-LEVEL WINDS EXTENDS FROM NORTHERN
SOUTH AMERICA ACROSS THE WINDWARD ISLANDS INTO THE ATLC AROUND
THE BASE OF AN UPPER LEVEL TROUGH EXTENDING BETWEEN 40W AND
50W...THEN UP ACROSS THE N PORTION OF A RIDGE ANCHORED ON A HIGH
NEAR 6N37W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GR





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