000 AXNT20 KNHC 220550 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT MON JUL 22 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0525 UTC. ...TROPICAL WAVES... A TROPICAL WAVE HAS COME OFF THE AFRICAN COAST AND ITS AXIS EXTENDS FROM 18N18W TO 08N16W. THE WAVE AXIS IS EMBEDDED WITHIN A HIGH MOIST ENVIRONMENT AND IS MOVING NEAR 15 KT. SCATTERED MODERATE CONVECTION IS FROM 07N-13N E OF 20W. A TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES WITH AXIS EXTENDING FROM 21N54W TO 14N59W AND MOVING NEAR 10 KT. THE WAVE AXIS IS EMBEDDED WITHIN A MOSTLY MODERATE MOIST ENVIRONMENT WITH A PATCH OF HIGH MOISTURE LYING OVER THE LEEWARD ISLANDS. A CLUSTER OF MODERATE CONVECTION WITH ISOLATED THUNDERSTORMS COINCIDES WITH THAT PATCH OF HIGH MOISTURE. SOME OF THE WINDWARD ISLANDS HAVE REPORTED RAINSHOWERS AS WELL. SOME SAL DRY AIR CONTINUES TO INTERACT WITH THE WAVE ENVIRONMENT HINDERING FURTHER CONVECTION AT THE TIME. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC NEAR 14N17W AND CONTINUES ALONG 12N23W TO 10N28W. THE ITCZ AXIS EXTENDS FROM 10N28W TO 08N40W 04N51W. BESIDES THE CONVECTION ALREADY DISCUSSED ASSOCIATED WITH THE TROPICAL WAVE THAT CAME OFF WEST AFRICA...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 12N-16N BETWEEN 20W-24W. NUMEROUS MODERATE CONVECTION IS FROM 06N-11N BETWEEN 25W-31W AND SCATTERED MODERATE WITHIN 170 NM S OF THE ITCZ BETWEEN 39W-42W AS WELL AS WITHIN 100 NM N OF THE AXIS BETWEEN 46W-51W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE CENTERED OVER W NEW MEXICO EXTENDS OVER THE GULF W OF 89W WHILE A SHORT-WAVE TROUGH HAS ITS BASE OVER SE LOUISIANA. DIVERGENT FLOW FROM THESE TWO UPPER LEVEL FEATURES IS ENHANCING SCATTERED SHOWERS WITHIN 110 NM OF THE LOUISIANA COAST BETWEEN 89W-91W. SCATTERED SHOWERS ARE ALSO OVER THE BAY OF CAMPECHE S OF 20N ASSOCIATED WITH A 1011 MB LOW LOCATED NEAR THE CHIVELA PASS MEXICO. SE WIND FLOW IN THE RANGE OF 5-15 KT SPREADS OVER MOST OF THE GULF THIS MORNING. OTHERWISE...DRY AIR BEING ADVECTED FROM THE CARIBBEAN AS WELL AS DRY AIR IN THE MIDDLE LEVELS IS KEEPING THE REMAINDER GULF FREE OF CONVECTION. SURFACE RIDGING AND RETURN FLOW WILL PREVAIL ACROSS THE GULF DURING THE NEXT 48 HOURS. EXCEPT FOR THE N-NE GULF WHERE SOME SHOWERS MAY BE POSSIBLE...FAIR WEATHER IS EXPECTED FOR THE MOST PART DURING THIS TIME BEING SUPPORTED BY CONTINUOUS DRY AIR ADVECTION FROM THE CARIBBEAN. CARIBBEAN SEA... EXCEPT FOR THE EASTERN CARIBBEAN E OF 67W AND THE SOUTHERN CARIBBEAN S OF 14N...DRY AIR SPREADS ACROSS THE BASIN IN THE MIDDLE AND LOWER LEVELS AS DEPICTED IN TOTAL PRECIPITABLE WATER AND WATER VAPOR IMAGERY WHICH IS SUPPORTING FAIR WEATHER. NUMEROUS MODERATE CONVECTION WITH ISOLATED THUNDERSTORMS IS OVER THE SOUTHERN CARIBBEAN S OF 14N W OF 80W. THIS CONVECTION EXTENDS INLAND NICARAGUA...COSTA RICA AND PANAMA. THE CONVECTION IS ASSOCIATED WITH THE MONSOON TROUGH WHICH AXIS MOVES ACROSS COSTA RICA TO NORTHERN COLOMBIA AS WELL AS WITH BANKING OF HIGH LOW LEVEL MOISTURE BY STRONG EASTERLY WINDS. EXCEPT FOR THE WESTERN CARIBBEAN...A TIGHT PRESSURE GRADIENT IS SUPPORTING TRADEWINDS OF 20-25 KT ACROSS THE BASIN. A TROPICAL WAVE WILL MOVE ACROSS THE LESSER ANTILLES TONIGHT AND OVER PUERTO RICO DURING MONDAY...RAINSHOWERS ARE EXPECTED. HISPANIOLA... DRY AIR IN THE LOWER AND MIDDLE LEVELS IS ACROSS LA HISPANIOLA EARLY THIS MORNING WHICH IS LIMITING ANY CONVECTIVE ACTIVITY. HOWEVER IN THE AFTERNOON WEATHER CONDITIONS WILL START TO DETERIORATE AS A TROPICAL WAVE MOVES WESTWARD ACROSS PUERTO RICO. THE TROPICAL WAVE IS EXPECTED TO ENTER THE DOMINICAN REPUBLIC VERY EARLY ON TUESDAY. RAINSHOWERS ARE EXPECTED ACROSS THE ENTIRE ISLAND AS THE WAVE DRIFTS W-NW AND EXITS THE COAST OF HAITI ON TUESDAY AFTERNOON. ATLANTIC OCEAN... MODERATE MOISTURE AT THE LOWER AND MIDDLE LEVELS AS WELL AS MIDDLE LEVEL DIVERGENCE JUST EAST OF THE FLORIDA PENINSULA IS SUPPORTING ISOLATED SHOWERS AND THUNDERSTORMS FROM 26N-29N W OF 77W...INCLUDING THE NORTHERN BAHAMAS. A SURFACE TROUGH ENTERS THE AREA OF DISCUSSION NEAR 30N33W SW TO 29N37W AND NO CONVECTION IS ASSOCIATED WITH IT. OTHERWISE...SURFACE RIDGING IS ACROSS THE REMAINDER BASIN ANCHORED BY A 1023 MB HIGH NEAR 30N62W AND A PAIR OF HIGHS JUST N OF THE AREA OF DISCUSSION. BESIDES FOR THE AREAS FORMERLY MENTIONED...FAIR WEATHER IS ACROSS THE ATLC SUPPORTED BY DRY AIR AT THE LOWER AND MIDDLE LEVELS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ RAMOS