[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 212351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT APR 21 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.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE NRN COAST OF
SIERRA LEONE AT 9N13W TO 6N15W. THE ITCZ CONTINUES FROM 6N15W
ALONG 3N20W 1N30W CROSSING THE EQUATOR AT 32W TO THE COAST OF
BRAZIL AT 3S40W. WIDELY SCATTERED MODERATE/STRONG CONVECTION IS
FROM EQ-4N BETWEEN 11W-20W. SIMILAR ACTIVITY EQ-3N BETWEEN
31W-34W.

...DISCUSSION...

GULF OF MEXICO...
A NEARLY CUT-OFF UPPER LEVEL LOW IS MOVING ACROSS THE NRN GULF
CURRENTLY CENTERED NEAR 29N89W. THIS UPPER LOW SUPPORTS A
COMPLEX SURFACE LOW PRESSURE SYSTEM THAT CONTINUES TO IMPACT
MUCH OF THE ERN HALF OF THE BASIN. AS OF 2100 UTC...A 1001 MB
LOW IS CENTERED JUST S OF THE FLORIDA PANHANDLE NEAR 30N86W. A
WARM FRONT EXTENDS SE FROM THE LOW CENTER ACROSS THE PENINSULA
ALONG 28N83W 30N81W. A COLD FRONT EXTENDS TOWARDS THE S ALONG
24N87W 21N92W. A SECONDARY COLD FRONT EXTENDS SW FROM THE LOW
CENTER ALONG 28N89W 26N94W. THERE DOESN'T APPEAR TO BE MUCH OF A
TEMPERATURE GRADIENT ALONG THIS SECONDARY FRONT AND IT MAY BE
TRANSITIONED INTO A SURFACE TROUGH ON THE NEXT ANALYSIS. MODEL
GUIDANCE INDICATES ANOTHER FRONT WILL FORM ALONG THE NE GULF
COAST LATER TONIGHT AND WILL SWEEP ACROSS THE ERN BASIN
TOMORROW. WATER VAPOR IMAGERY ALONG WITH TOTAL PRECIPITABLE
WATER INDICATES A VERY MOIST AIRMASS COVERS THE FAR ERN GULF
WHERE WIDESPREAD SHOWERS/THUNDERSTORMS ARE PRESENT. CURRENTLY
STRONG SHOWERS/THUNDERSTORMS COVER THE FLORIDA STRAITS AND WRN
CUBA WITHIN 100 NM SE OF A LINE FROM 25N80W TO 22N86W. SCATTERED
SHOWERS ARE ACROSS MUCH OF THE FLORIDA PENINSULA E OF 84W. A
LINE OF THUNDERSTORMS IS BETWEEN THE WARM AND COLD FRONT FROM
26N85W TO 28N85W. STRONG SHOWERS/THUNDERSTORMS ALSO COVER MUCH
OF NRN FLORIDA AND THE PANHANDLE. A LINE EXTENDS ALONG THE NE
FLORIDA COAST FROM 29N81W TO 31N83W AND INTO GEORGIA. A SECOND
LINE EXTENDS FROM ALABAMA NEAR 31N86W TO 29N89W. OVER
WATER....SCATTERED SHOWERS/THUNDERSTORMS ARE NEAR THE LOW CENTER
AND TO THE W FROM 26N-30N BETWEEN 86W-91W. A SLIGHT RISK OF
SEVERE WEATHER IS ALSO PRESENT ACROSS THE ERN GULF THROUGH
TOMORROW MORNING. DRY AIR ALOFT WRAPPING AROUND THE WRN SIDE OF
THE UPPER LOW IS PROVIDING FAIR CONDITIONS ACROSS THE REMAINDER
OF THE WRN GULF. EXPECT THE FIRST FRONT TO MOVE THROUGH THE AREA
TONIGHT WITH A SECOND FRONT SWEEPING OVER THE AREA BY MONDAY.
STRONG SHOWERS/THUNDERSTORMS WITH THE RISK OF FLOODING WILL
REMAIN ACROSS THE ERN GULF WITH 20-25 KT NE WINDS SPREADING
ACROSS THE AREA IN THE WAKE OF THE BOUNDARIES.

CARIBBEAN SEA...
COMPARED THE GULF OF MEXICO THE CARIBBEAN IS QUITE TRANQUIL THIS
EVENING DUE TO DRY AIR ALOFT AROUND A BROAD UPPER LEVEL RIDGE
OVER VENEZUELA. HOWEVER...STRONG SHOWERS/THUNDERSTORMS HAVE
BEGUN TO IMPACT WRN CUBA ASSOCIATED WITH THE LOW PRESSURE SYSTEM
OVER THE GULF. CLUSTERS OF SHOWERS/THUNDERSTORMS HAVE ALSO
POPPED UP OVER PORTIONS OF CENTRAL AMERICA...COLOMBIA...AND
VENEZUELA. TRADEWIND FLOW OF 10-15 KTS IS ACROSS MUCH OF THE
BASIN WITH SOME EMBEDDED LOW-LEVEL SHOWERS. MORE SCATTERED
ACTIVITY IS ACROSS THE NE CARIBBEAN ISLANDS ASSOCIATED WITH A
SURFACE TROUGH IN THE CENTRAL ATLC. THE FIRST FRONT OVER THE
GULF OF MEXICO WITH REACH THE NW CARIBBEAN SHORTLY WITH
SHOWERS/THUNDERSTORMS LIKELY ALONG WITH NE WINDS OF 20-25 KTS.
THE REMAINDER OF THE BASIN WILL REMAIN UNDER FAIR CONDITIONS.

ATLANTIC OCEAN...
SHOWERS/THUNDERSTORMS ASSOCIATED WITH THE LOW PRESSURE SYSTEM IN
THE GULF ARE ALREADY BEGINNING TO SPREAD OVER THE WRN ATLC.
SCATTERED SHOWERS ARE MAINLY W OF 76W WITH STRONG THUNDERSTORMS
EMERGING FROM THE FLORIDA STRAITS TO 77W INCLUDING ANDROS
ISLAND. THE REMAINDER OF THE W ATLC IS DOMINATED BY SURFACE
RIDGING AROUND A 1021 MB HIGH NEAR 36N59W. THE RIDGE IS
SUPPORTED BY AN UPPER LEVEL RIDGE ALONG 70W. AN UPPER LEVEL
TROUGH N OF THE AREA IS CONTROLLING THE CENTRAL ATLC SUPPORTING
A DISSIPATING COLD FRONT ALONG 30N44W TO 24N51W. POSSIBLE
ISOLATED SHOWERS ARE ALONG THE AXIS. A SURFACE TROUGH IS FARTHER
E ALONG 27N44W 22N49W 18N63W. SCATTERED SHOWERS ARE WITHIN 115
NM EITHER SIDE OF THE AXIS. A SECOND WEAK SURFACE TROUGH IS W OF
THE FRONTAL BOUNDARY EXTENDING FROM A 1015 MB LOW NEAR 31N51W TO
27N53W. POSSIBLE ISOLATED SHOWERS ARE NEAR THE LOW CENTER. AN
UPPER LEVEL RIDGE ALONG 30W SUPPORTS A 1027 MB HIGH NEAR THE
AZORES ISLANDS AT 36N28W PROVIDING FAIR CONDITIONS ACROSS THE
REMAINDER OF THE E ATLC. EXPECT THE FIRST FRONTAL BOUNDARY IN
THE GULF OF MEXICO TO REACH THE W ATLC BY TOMORROW.

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

$$
WALTON





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