000 AXNT20 KNHC 211803 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST SAT FEB 21 2015 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 1745 UTC. ...SPECIAL FEATURES... ...GALE WARNING FOR THE SW CARIBBEAN... A GALE WARNING IS IN EFFECT OFF THE NW COAST OF COLOMBIA FROM 10N TO 13N BETWEEN 74W AND 76W WITH ASSOCIATED SEAS RANGING FROM 10 TO 13 FT. GALE FORCE WINDS WILL DIMINISH SUNDAY MORNING. PLEASE SEE THE LATEST HIGH SEAS FORECAST UNDER AWIPS/WMO HEADERS MIAHSFAT2/FZNT02 KNHC FOR MORE DETAILS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL ATLC NEAR 06N11W TO 01N18W ALONG THE EQUATOR TO 24W. THE ITCZ BEGINS CONTINUES FROM THERE TO 01N30W TO 02S37W TO THE NORTHERN COAST OF BRAZIL NEAR 02S42W. SCATTERED MODERATE CONVECTION AND TSTMS ARE FROM 01N TO 07N E OF 15W. SCATTERED MODERATE CONVECTION IS FROM 04S TO 05N W OF 35W. ...DISCUSSION... GULF OF MEXICO... A 1036 MB HIGH PRESSURE CENTER OVER THE NW ATLC WATERS NEAR 39N69W ANCHORS A BROAD SURFACE RIDGE THAT EXTENDS SW ACROSS THE EASTERN CONUS...THE SW N ATLC AND THE EASTERN GULF OF MEXICO. THIS RIDGE CONTINUES TO ADVECT COLD AIR ACROSS THE FLORIDA PENINSULA AS WELL AS THE EASTERN GULF. RIDGING IS ALSO PROVIDING SOUTHEASTERLY TO SOUTHERLY WIND FLOW IN THE RANGE OF 20 TO 25 KT BASIN-WIDE. LOW-LEVEL MOISTURE CONVERGENCE ALONG THE NW GULF COAST SUPPORTS BROKEN TO OVERCAST SKIES N OF 27N...HAZE AND POSSIBLE ISOLATED SHOWERS. FAIR WEATHER PREVAILS ELSEWHERE. ALOFT...WESTERLY FLOW ADVECTS MOISTURE FROM THE EPAC WATERS TO THE GULF N OF 25N. SURFACE RIDGING WILL CONTINUE TO DOMINATE ACROSS THE BASIN THROUGH SUNDAY NIGHT. A NEW COLD FRONT WILL ENTER THE GULF AND FLORIDA PENINSULA EARLY MONDAY MORNING. CARIBBEAN SEA... A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE WESTERN ATLC WITH BASE EXTENDING N OF THE MONA PASSAGE. THIS TROUGH ALOFT SUPPORTS A STATIONARY FRONT EXTENDING ACROSS THE SW N ATLC TO NORTHERN HAITI TO THE WINDWARD PASSAGE WHERE IT TRANSITIONS TO A SHEAR LINE NEAR 18N74W SW ACROSS JAMAICA TO 17N81W. LOW-LEVEL MOISTURE ASSOCIATED WITH THE FRONT AND A MIDDLE-LEVEL DIFFLUENT ENVIRONMENT SUPPORT SCATTERED TO ISOLATED SHOWERS OVER HISPANIOLA AND ADJACENT WATERS. ISOLATED SHOWERS ARE WITHIN 75 NM EITHER SIDE OF THE SHEAR LINE. SHOWERS AND TSTMS ARE FORECAST ACROSS PUERTO RICO THIS AFTERNOON ASSOCIATED WITH A WEAK SURFACE TROUGH WITH NORTHERN AXIS MOVING THROUGH THE ISLAND. THE RIDGE ACROSS THE GULF OF MEXICO AND W ATLC HAS INCREASED THE SURFACE PRESSURE GRADIENT ACROSS THE BASIN...RESULTING IN TRADES OF 15 TO 20 KT ACROSS THE BASIN AND GALE FORCE WINDS ALONG THE COAST OF COLOMBIA. SEE SPECIAL FEATURES SECTION. THE SURFACE TROUGH IS FORECAST TO DISSIPATE SUNDAY MORNING OVER THE EASTERN DOMINICAN REPUBLIC. ...HISPANIOLA... A MIDDLE TO UPPER LEVEL TROUGH OVER THE WESTERN ATLC WITH BASE EXTENDING EXTENDING N OF THE MONA PASSAGE SUPPORTS A STATIONARY FRONT EXTENDING ACROSS THE SW N ATLC...NORTHERN HAITI TO THE WINDWARD PASSAGE WHERE IT TRANSITIONS TO A SHEAR LINE NEAR 18N74W SW ACROSS JAMAICA TO 17N81W. LOW-LEVEL MOISTURE ASSOCIATED WITH THE FRONT AND A MIDDLE-LEVEL DIFFLUENT ENVIRONMENT SUPPORT SCATTERED TO ISOLATED SHOWERS OVER HISPANIOLA AND ADJACENT WATERS. SHOWERS ARE FORECAST TO CONTINUE THROUGH SUNDAY MORNING AS A DISSIPATING SURFACE TROUGH APPROACHES THE EASTERN ISLAND. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE WESTERN ATLC WITH BASE EXTENDING N OF THE MONA PASSAGE. A STATIONARY FRONT IS BEING SUPPORTED BY THE TROUGH ALOFT ENTERING THE SW N ATLC ALONG 30N57W SW TO NORTHERN HAITI TO THE WINDWARD PASSAGE WHERE IT TRANSITIONS TO A SHEAR LINE NEAR 18N74W SW ACROSS JAMAICA TO 17N81W. SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS ARE N OF 25N BETWEEN 55W AND 63W. A 1041 MB HIGH NEAR 36N35W ANCHORS A BROAD SURFACE RIDGE THAT COVERS THE REMAINDER CENTRAL AND EASTERN ATLC N OF 16N. THE FRONT WILL DISSIPATE SUNDAY MORNING AND RIDGING WILL DOMINATE. A NEW COLD FRONT ENTERS THE SW N ATLC EARLY MONDAY MORNING. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR