000 AXNT20 KNHC 282351 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN APR 28 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 ACROSS THE COAST OF LIBERIA FROM 7N11W TO 1N17W. THE ITCZ BEGINS FROM 11N17W AND CONTINUES SOUTH OF THE EQUATOR ALONG 3S28W 1S42W 1S48W. THE ONLY CONVECTION NORTH OF THE EQUATOR IS A SMALL AREA OF ISOLATED MODERATE CONVECTION FROM 1N-4N BETWEEN 39W-41W. ...DISCUSSION... GULF OF MEXICO... HEAVY SHOWERS AND SCATTERED THUNDERSTORMS ARE IN THE NW GULF OF MEXICO FROM 25N-29N BETWEEN 93W-97W. THIS ACTIVITY IS ASSOCIATED WITH A SHORTWAVE UPPER TROUGH MOVING ACROSS SOUTHERN TEXAS. THE THUNDERSTORM ACTIVITY WAS PREVIOUSLY LINEAR AND ANALYZED AS A SQUALL AXIS AT 1800 UTC. HOWEVER...BY 2100 UTC THE ACTIVITY WAS MORE CONCENTRATED IN A BLOB...AND WIND OBSERVATIONS ALSO INDICATED SURFACE TROUGHING IN THE AREA. A SURFACE TROUGH IS NOW ANALYZED ALONG 28N95W TO 26N97W. SHOWERS AND THUNDERSTORMS ARE ALSO ALONG THE SE LOUISIANA COAST AS WELL AS ACROSS PORTIONS OF THE FLORIDA PANHANDLE. A FEW SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO IN THE SE GULF FROM 25N-26N BETWEEN 83W-87W. THE REMAINDER OF THE BASIN IS UNDER MOSTLY FAIR CONDITIONS DUE TO DRY AIR ALOFT IN WESTERLY FLOW. A WEAK UPPER RIDGE IS ACROSS THE FLORIDA PENINSULA SUPPORTING SURFACE RIDGING ACROSS THE WEST ATLC WHICH CONTINUES SLIGHTLY INTO THE GULF. SURFACE FLOW IS MAINLY SOUTHEAST RANGING FROM 10-15 KT. SURFACE OBSERVATIONS ALONG WITH VISIBLE SATELLITE IMAGERY ALSO INDICATE THAT AN AREA OF SMOKE SPREADS ACROSS THE WESTERN GULF W OF 91W DUE TO WILDFIRES IN SOUTHERN MEXICO. WEAK SURFACE TROUGHING IS EXPECTED TO MOVE EASTWARD ACROSS THE NORTHERN GULF OVER THE NEXT DAY OR SO WITH SHOWERS/THUNDERSTORMS LIKELY. MOIST CONDITIONS ARE ALSO EXPECTED ACROSS THE SW GULF IN THE BAY OF CAMPECHE AS WELL AS ACROSS FLORIDA. CARIBBEAN SEA... MOSTLY DRY AIR ALOFT COVERS THE CARIBBEAN AROUND BROAD UPPER TROUGHING COVERING THE BASIN WITH AXIS NEAR 70W. THE DRY AIR ALOFT IS HELPING MAINTAIN MOSTLY FAIR CONDITIONS AT THE SURFACE. HOWEVER...A FEW AREAS OF ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS INCLUDING INLAND CUBA...HISPANIOLA AS WELL AS SOUTH OF THE ISLAND...AND ACROSS HONDURAS...NICARAGUA...AND COSTA RICA. SCATTERED SHOWERS ARE ALSO IN THE VICINITY OF THE WINDWARD ISLANDS. THE ACTIVITY IS MAINLY TO THE EAST...BUT SOME OF THE ISLANDS MAY BE RECEIVING RAIN. A WEAK PRESSURE GRADIENT CONTINUES THROUGHOUT THE AREA SUPPORTING ONLY 10-15 KT TRADEWIND FLOW. LITTLE CHANGE IS EXPECTED BESIDES A POSSIBLE INCREASE IN SHOWER ACTIVITY ACROSS THE SE CARIBBEAN. ATLANTIC OCEAN... UPPER LEVEL RIDGING EXTENDING UP THE EASTERN SEABOARD SUPPORTS SURFACE RIDGING ACROSS THE WEST ATLC ANCHORED BY A 1028 MB HIGH OFF THE NEW ENGLAND COAST NEAR 42N69W. AN UPPER LEVEL TROUGH TO THE EAST NEAR 60W SUPPORTS A COLD FRONT NORTH OF THE AREA WHICH TRANSITIONS INTO A SURFACE TROUGH ALONG 31N60W 26N64W. A SECOND SURFACE TROUGH IS TO THE E ALONG 32N58W TO 29N56W. ISOLATED SHOWERS ARE WITHIN 120 NM EAST OF BOTH TROUGHS. A WEAK THIRD SURFACE TROUGH IS FARTHER SOUTH ALONG 19N65W 24N66W. ISOLATED SHOWERS ARE ALONG THE AXIS. AN AREA OF SHOWERS/POSSIBLE THUNDERSTORMS IS EAST OF THE WINDWARD ISLANDS FROM 9N-15N BETWEEN 51W-61W. THE ACTIVITY IS LIKELY LINKED TO MOIST SOUTHWESTERLY FLOW ALOFT AROUND A BROAD UPPER TROUGH ACROSS THE CARIBBEAN. FARTHER NORTH...AN UPPER LEVEL LOW NEAR 38N41W CONTINUES TO SUPPORT A SURFACE LOW PRESSURE SYSTEM NORTH OF THE DISCUSSION AREA. WEAK HIGH PRESSURE HAS FORMED BETWEEN THE LOW PRESSURE SYSTEM AND THE FRONTAL SYSTEM TO THE WEST. A 1017 MB HIGH IS CENTERED NEAR 27N53W. A BROAD UPPER RIDGE COVERS THE REMAINDER OF THE EASTERN TROPICAL ATLC PROVIDING MOSTLY FAIR CONDITIONS ACROSS THE AREA. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON