[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 152341
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI APR 15 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTION 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 2300 UTC.

...THE ITCZ...

ITCZ AXIS EXTENDS FROM SRN LIBERIA NEAR 5N8W ALONG 3N25W 1N30W
3N37W CROSSING THE EQUATOR TO NRN BRAZIL NEAR 3S43W. NUMEROUS
STRONG CONVECTION IS MOVING ACROSS LIBERIA AND OFFSHORE FROM
2N-8N BETWEEN 8W-11W. SCATTERED MODERATE/STRONG CONVECTION IS
FROM EQ-5N BETWEEN 24W-29W. SIMILAR ACTIVITY IS S OF THE EQUATOR
TO 6S BETWEEN 20W-28W. A SURFACE TROUGH IS EMBEDDED WITHIN THE
ITCZ ALONG 6N37W TO 2N37W SUPPORTING WIDELY ISOLATED CONVECTION
NEAR THE AXIS.

...DISCUSSION...

THE GULF OF MEXICO...
THE MAJORITY OF THE GULF OF MEXICO IS EXPERIENCING FAIR WEATHER
AND MOSTLY CLEAR SKIES UNDER THE INFLUENCE OF MAINLY DRY AIR
ALOFT AROUND A BROAD UPPER RIDGE WHICH IS PROVIDING MOSTLY ZONAL
FLOW ACROSS THE BASIN. HOWEVER...A DEEP LAYER TROUGH TO THE N
OVER THE CENTRAL CONUS IS SUPPORTING A VIGOROUS LOW PRESSURE
SYSTEM. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM HAS BEGUN TO
PUSH OFF THE TEXAS COAST FROM NEAR LAKE CHARLES LOUISIANA TO
JUST N OF BROWNSVILLE TEXAS. WHILE SEVERE WEATHER IS ASSOCIATED
WITH THE FRONTAL BOUNDARY ACROSS THE SE UNITED STATES...IT
BECOMES MOSTLY DRY UPON ENTERING THE GULF REGION. ONLY A WEAK
CLOUD BAND AND WIND SHIFT DEFINE THE FRONT OVER WATER. SURFACE
OBS INDICATE 20-25 KT SLY WINDS ARE AHEAD OF THE FRONT WITH
WEAKER WINDS FARTHER E. A FEW ISOLATED STRONG SHOWERS ARE ALSO
NOTED OVER S FLORIDA...RESEMBLING AFTERNOON SUMMER CONVECTION.
EXPECT THE COLD FRONT TO CONTINUE TO PUSH SE ACROSS THE GULF OF
MEXICO WITH POSSIBLE ISOLATED SHOWERS ALONG THE BOUNDARY.

THE CARIBBEAN SEA...
MAINLY NWLY FLOW ALOFT COVERS THE CARIBBEAN IN COMBINATION WITH
DRY AIR AND SUBSIDENCE PROVIDING MOSTLY FAIR CONDITIONS ACROSS
THE BASIN.  A FEW ISOLATED SHOWERS ARE NOTED ACROSS THE NRN
ISLANDS OF CUBA...HISPANIOLA...JAMAICA...AND PUERTO RICO. A
SURFACE TROUGH EXTENDS OVER THE NRN LEEWARD ISLANDS FROM 20N60W
TO 16N66W SUPPORTED BY AN UPPER LEVEL SHORTWAVE TROUGH IN THE
ATLC ALONG 30N64W TO E OF THE LEEWARD ISLANDS. DIFFLUENCE ALOFT
AROUND THE ERN SIDE OF THE UPPER TROUGH ALONG WITH THE SURFACE
CONVERGENCE IS SUPPORTING SHOWERS/THUNDERSTORMS N OF 17N BETWEEN
60W-65W IMPACTING MUCH OF THE NRN LEEWARD ISLANDS. SHOWERS AND
THUNDERSTORMS IN THIS AREA SHOULD DIMINISH AS THE UPPER TROUGH
IS FORECAST TO MOVE EWD AWAY FROM THE CARIBBEAN. FAIR WEATHER IS
EXPECTED TO REMAIN ACROSS THE REST OF THE BASIN.

THE ATLANTIC OCEAN...
A BROAD UPPER LEVEL TROUGH IS OVER THE W ATLC ALONG 66W
SUPPORTING A SURFACE TROUGH...REMNANTS OF A FRONTAL
BOUNDARY...ALONG 31N69W TO 27N74W. POSSIBLE ISOLATED SHOWERS ARE
ALONG THE TROUGH. A SHORTWAVE UPPER TROUGH EXTENDS OFF THE MAIN
ONE TOWARDS THE ERN LEEWARD ISLANDS SUPPORTING A PAIR OF SURFACE
TROUGHS. THE FIRST EXTENDS FROM 30N60W TO 24N60W. THE SECOND
LIES ACROSS THE LEEWARD ISLANDS FROM 20N60W TO 16N66W. UPPER
LEVEL DIFFLUENCE AROUND THE E SIDE OF THE UPPER SHORTWAVE TROUGH
IS SUPPORTING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
17N-28N BETWEEN 54W-63W. A SHEAR LINE IS NOTED E OF THE WINDWARD
ISLANDS ALONG 15N BETWEEN 38W-59W AROUND THE BASE OF A SURFACE
RIDGE ANCHORED BY A 1027 MB HIGH NEAR 39N42W. SCATTERED SHOWERS
ARE WITHIN 60 NM OF THE SHEAR AXIS. ALOFT...AN UPPER LEVEL RIDGE
BETWEEN 27W-58W SUPPORTS THE AFOREMENTIONED SURFACE RIDGE IN THE
CENTRAL ATLC. FARTHER E...AN UPPER LEVEL LOW SPINS NEAR 32N29W
SUPPORTING A 1004 MB SURFACE LOW NEAR 33N27W. A COLD FRONT
EXTENDS FROM THE LOW CENTER ALONG 26N28W 24N33W TRANSITIONING
INTO A SHEAR AXIS NEAR 24N38W TO 26N48W. SCATTERED SHOWERS ARE
WITHIN 60 NM OF THE COLD FRONT...AND WITHIN 30 NM OF THE SHEAR
AXIS. THE SURFACE LOW IS EXPECTED TO DRIFT SOUTH OVER THE NEXT
24 HOURS. THE SYSTEM IN THE W/CENTRAL ATLC IS FORECAST TO DRIFT
E FOR A FEW DAYS BEFORE THEN DRIFTING BACK TO THE WEST.

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

$$
WALTON




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