[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111730
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT MAY 11 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM NEAR THE SENEGAL/GUINEA BISSAU
BORDER TO 7N24W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
CONTINUES FROM 7N24W TO 2N40W TO THE COAST OF BRAZIL AT EQ50W.
NO SIGNIFICANT CONVECTION ALONG THE ITCZ/MONSOON TROUGH AXES.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION CAN BE FOUND N
OF 3N TO THE COAST OF AFRICA BETWEEN THE PRIME MERIDIAN AND 11W.

...DISCUSSION...

GULF OF MEXICO...

A COLD FRONT MOVED OFF THE COAST OF TEXAS THIS MORNING. AS OF
1200 UTC...IT EXTENDS FROM SW LOUISIANA TO SOUTH TEXAS THEN
ALONG NORTHERN MEXICO. SOME HEAVY SHOWERS AND THUNDERSTORMS ARE
NOTED AHEAD OF THE FRONT IMPACTING MUCH OF THE NORTHERN GULF
WATERS. A DIFFLUENT PATTERN ALOFT IS HELPING TO ENHANCE THIS
CONVECTIVE ACTIVITY. THE FRONT WILL EXTEND FROM THE WESTERN
FLORIDA PANHANDLE TO THE NW BAY OF CAMPECHE TONIGHT. THE
NORTHERN SEGMENT OF THE FRONT TO THE N OF 26N WILL MOVE E OF THE
AREA SUN NIGHT WHILE THE SOUTHERN PORTION WILL GRADUALLY
DISSIPATE FROM S FLORIDA TO THE CENTRAL BAY OF CAMPECHE SUN
THROUGH MON. WEAK SURFACE RIDGING FROM THE ATLC DOMINATES THE
REMAINDER OF THE REGION. GENTLE TO MODERATE SOUTHERLY WIND FLOW
IS OBSERVED AHEAD OF THE FRONT WHILE MODERATE TO FRESH NORTHERLY
WINDS WILL FOLLOW THE COLD FRONT. ALOFT...AN UPPER LEVEL RIDGE
CENTERED OVER NORTHERN CENTRAL AMERICA COVERS THE MAJORITY OF
THE GULF AND SE MEXICO...INCLUDING THE YUCATAN PENINSULA.
ABUNDANT CLOUDINESS COVERS MOST OF THE NORTHERN GULF WHILE
MOSTLY CLEAR SKIES ARE SEEN ON VISIBLE SATELLITE IMAGERY OVER
THE SE GULF AND THE BAY OF CAMPECHE.

CARIBBEAN SEA...

THE UPPER ANTICYCLONE CENTERED OVER NORTHERN CENTRAL AMERICA
ALSO EXTENDS A RIDGE ACROSS THE WESTERN CARIBBEAN PROVIDING
MOSTLY FAIR CONDITIONS THERE. AN UPPER LEVEL TROUGH PERSISTS
ACROSS THE EASTERN CARIBBEAN EXTENDING FROM THE MONA PASSAGE TO
NORTHERN COLOMBIA. STRONG UPPER LEVEL SUBSIDENCE AND IMPLIED DRY
AIR MASS HAS INVADED HISPANIOLA LIMITING THE DEVELOPMENT OF
SHOWER AND TSTM ACTIVITY. PUERTO RICO AND THE VIRGIN ISLANDS ARE
ON THE EAST SIDE OF THE UPPER TROUGH. THIS TROUGH WILL COMBINE
WITH LOCAL EFFECTS AND DIURNAL HEATING TO PRODUCE SOME SHOWERS
AND TSTMS OVER THOSE ISLANDS MAINLY DURING THE AFTERNOON.
CONVECTION HAS DIMINISHED OVER THE SW CARIBBEAN. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE NOTED S OF 11N W OF 81W. A 1010
MB LOW PRES IS ANALYZED ON THE 1200 UTC SURFACE MAP OVER COSTA
RICA...ALONG THE MONSOON TROUGH NEAR 9N84W. THE LOW IS FORECAST
TO DRIFT WESTWARD INTO THE EPAC REGION DURING THE NEXT 24 HOURS.
TRADE WIND FLOW OF 15-20 KT DOMINATES THE MAJORITY OF THE
EASTERN AND CENTRAL CARIBBEAN WITH WINDS OF 20 TO 25 KT NEAR THE
COAST OF COLOMBIA.

ATLANTIC OCEAN...

A RIDGE/TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE DISCUSSION
AREA. AN UPPER LOW HAS DEVELOPED ALONG THE TROUGH THAT WAS
AFFECTING WITH LOCALLY HEAVY RAIN THE GREATER ANTILLES DURING
THE PREVIOUS DAYS. THIS UPPER LOW LOCATED NEAR 24N66W SUPPORTS A
1012 MB SURFACE LOW PRES CENTERED NEAR 23N67W. SOME SHIP
OBSERVATIONS CONFIRMED THE PRESENCE OF THE SURFACE LOW THIS
MORNING. A TROUGH EXTENDS FROM THE LOW CENTER TO THE MONA
PASSAGE. THE SURFACE LOW IS FORECAST TO DRIFT TOWARD HISPANIOLA
ON SUN WHILE WEAKENING TO A TROUGH. THIS TROUGH WILL MOVE
WESTWARD. CURRENTLY...PRES GRADIENT BETWEEN THE SURFACE LOW AND
A RIDGE EXTENDING FROM BERMUDA TO SOUTH FLORIDA IS PRODUCING A
LARGE AREA OF FRESH TO STRONG WINDS TO N...NE AND SE QUADRANTS
OF THE LOW...PARTICULARLY S OF 27N BETWEEN 60W AND 67W.
SCATTEROMETER DATA PROVIDED OBSERVATIONS OF THESE WIND SPEEDS.
HEAVY SHOWERS AND TSTMS ARE E OF THE LOW CENTER...COVERING THE
AREA FROM 22N TO 26N BETWEEN 62W AND 66W. STRONGEST WINDS CAN BE
FOUND NEAR TSTMS. THE CENTRAL ATLC IS DOMINATED BY BROAD SURFACE
RIDGING SUPPORTED BY AN UPPER LEVEL RIDGE ALONG 54W/55W. AN
UPPER LEVEL TROUGH COVERS THE EASTERN ATLC CENTERED AROUND AN
UPPER LOW NEAR 31N34W. THE UPPER LOW SUPPORTS A WEAK 1020 MB
SURFACE LOW NEAR 31N32W. A SURFACE TROUGH EXTENDS FROM THE LOW
CENTER TO NEAR 25N35W. THE 1224 UTC ASCAT PASS REVEALS THE WIND
SHIFT ASSOCIATED WITH THE TROUGH. SCATTERED SHOWERS AND TSTMS
ARE NOTED MAINLY ON THE NORTH SIDE OF THE LOW CENTER AND AHEAD
OF THE TROUGH AXIS. AN AREA OF SAHARAN DUST IS OBSERVED ON VIS
SATELLITE IMAGERY REACHING 45W...AND IS CONFIRMED BY THE SAHARAN
AIR LAYER TRACKING PRODUCT FROM UW-CIMSS.

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

AT THE REQUEST OF METEO-FRANCE AND THE METEOROLOGICAL SERVICES OF
HAITI AND THE DOMINICAN REPUBLIC...THE TROPICAL ANALYSIS AND
FORECAST BRANCH (TAFB) WILL BEGIN PROVIDING...ON A TEMPORARY
BASIS...A SEPARATE DETAILED SECTION WITHIN THE ATLANTIC TROPICAL
WEATHER DISCUSSION (TWDAT). IT WILL COVER BOTH HAITI AND THE
DOMINICAN REPUBLIC DUE TO THE SHARED GEOGRAPHY OF BOTH COUNTRIES
ON THE ISLAND OF HISPANIOLA.

THE SECTION BEGINS ON MAY 15 2013 AT 1800 UTC...2 PM EDT. IT
WILL PROVIDE GUIDANCE FOR SIGNIFICANT WEATHER EVENTS THAT ARE
EXPECTED TO IMPACT THE REGION THROUGH 48 HOURS...WITH THE FOCUS
ON ASSESSING THE POTENTIAL FOR HEAVY RAINFALL.

$$
GR

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