[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 120002
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 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 3N35W TO THE COAST OF BRAZIL AT 1N50W.
NO SIGNIFICANT CONVECTION ALONG THE ITCZ/MONSOON TROUGH AXES.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS LOCATED N OF
3N TO THE COAST OF AFRICA BETWEEN THE PRIME MERIDIAN AND 7W.

...DISCUSSION...

GULF OF MEXICO...

A WEAK COLD FRONT MOVED EASTWARD IN THE NW GULF THIS AFTERNOON.
AS OF 1800 UTC...IT EXTENDS FROM CENTRAL LOUISIANA TO NE MEXICO.
SOME HEAVY SHOWERS AND THUNDERSTORMS ARE NOTED AHEAD OF THE
FRONT IMPACTING THE NORTHEASTERN GULF WATERS. A DIFFLUENT
PATTERN ALOFT IS HELPING TO ENHANCE THIS CONVECTIVE ACTIVITY.
THE FRONT WILL EXTEND FROM THE FLORIDA BIG BEND TO THE CENTRAL
BAY OF CAMPECHE TOMORROW MORNING. 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. CURRENTLY...A
TROUGH EXISTS IN THE BAY OF CAMPECHE NORTHEASTWARD TO THE
CENTRAL GULF AHEAD OF THE FRONT...THOUGH NOT SIGNIFICANT WEATHER
IS ASSOCIATED WITH THIS FEATURE. GENTLE TO MODERATE
SOUTHEASTERLY WIND FLOW IS OBSERVED IN MOST OF THE GULF...WITH
MODERATE TO FRESH NORTHEASTERLY WINDS ON THE WEST SIDE OF THE
TROUGH AND FRONT.  ALOFT...AN UPPER LEVEL RIDGE CENTERED OVER
NORTHERN CENTRAL AMERICA COVERS THE MAJORITY OF THE GULF AND SE
MEXICO...INCLUDING THE YUCATAN PENINSULA.

CARIBBEAN SEA...

TRADE WIND FLOW OF 10-15 KT DOMINATES THE MAJORITY OF THE
EASTERN AND CENTRAL CARIBBEAN WITH WINDS OF 20 TO 25 KT NEAR THE
COAST OF COLOMBIA.  NO SIGNIFICANT DEEP CONVECTION IS OCCURRING
OVER THE CARIBBEAN THIS AFTERNOON...THOUGH DIURNALLY-AIDED
THUNDERSTORM ACTIVITY IS PRESENT OVER PORTIONS OF CENTRAL
AMERICA FROM BELIZE TO COSTA RICA. THIS CONVECTION MAY BE
CONTRIBUTED TO BY A WEAK LOW NEAR 10N85W OVER NW COSTA RICA WITH
TROUGHING EXTENDING NORTH-SOUTH. ALOFT...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 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 AFTERNOONS OF THE NEXT COUPLE OF DAYS.

ATLANTIC OCEAN...

A RIDGE/TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE DISCUSSION
AREA. AN UPPER LOW IS LOCATED NEAR 24N65W SUPPORTS A 1012 MB
SURFACE LOW PRES CENTERED NEAR 23N66W. SCATTEROMETER AND BUOY
41043 INDICATE THE PRESENCE OF A CLOSED LOW WITH A TROUGH
EXTENDING TO ITS SOUTHWEST.  DEEP CONVECTION HAS PERSISTED IN
ASSOCIATION WITH THE LOW TODAY. SHOWERS AND TSTMS ARE E OF THE
LOW CENTER...COVERING THE AREA FROM 21N TO 26N BETWEEN 62W AND
65W. ENVIRONMENTAL CONDITIONS...ESPECIALLY THE VERTICAL
SHEAR...DO NOT APPEAR TO BE CONDUCIVE FOR TROPICAL DEVELOPMENT.
THE SURFACE LOW IS FORECAST TO DRIFT TOWARD HISPANIOLA WHILE
WEAKENING TO A TROUGH BY LATE SUN. THIS TROUGH WILL MOVE
WESTWARD BEFORE DISSIPATING BY LATE MON. CURRENTLY...PRESSURE
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 58W AND 68W. THE CENTRAL ATLC IS
DOMINATED BY BROAD SURFACE RIDGING SUPPORTED BY AN UPPER LEVEL
RIDGE ALONG 52W. AN UPPER LEVEL TROUGH COVERS THE EASTERN
ATLANTIC CENTERED AROUND AN UPPER LOW NEAR 31N32W. THE UPPER LOW
SUPPORTS A WEAK 1020 MB SURFACE LOW NEAR 30N32W. A SURFACE
TROUGH EXTENDS FROM THE LOW CENTER TO NEAR 24N35W. SCATTERED
SHOWERS AND TSTMS ARE NOTED MAINLY ON THE NORTH SIDE OF THE LOW
CENTER AND AHEAD OF THE TROUGH AXIS. THIS SURFACE LOW IS
EXPECTED TO DISSIPATE ON SUN.  AN AREA OF SAHARAN DUST IS
OBSERVED ON VIS AND SAHARAN AIR LAYER SATELLITE IMAGERY REACHING
47W.

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/CWL

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