000 AXNT20 KNHC 070551 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN JUL 07 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 0445 UTC. ...SPECIAL FEATURES... A TROPICAL WAVE EXTENDS FROM 16N45W TO A WEAK 1009 MB SURFACE LOW NEAR 8N37W MOVING WEST AT 15-20 KT. THE WAVE AXIS IS EMBEDDED WITHIN A DRY SAHARAN AIR LAYER...WHICH IS LIMITING CONVECTION NEAR THE MAJORITY OF THE AXIS EXCEPT NEAR THE LOW CENTER. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WEST OF THE LOW CENTER FROM 6N-10N BETWEEN 37W-41W. THIS SYSTEM HAS A MEDIUM CHANCE OF DEVELOPMENT INTO A TROPICAL CYCLONE OVER THE NEXT 48 HOURS. ...TROPICAL WAVES... TROPICAL WAVE IN THE CENTRAL ATLC IS DISCUSSED ABOVE IN THE SPECIAL FEATURES SECTION TROPICAL WAVE IS ALONG 23N64W TO 15N69W MOVING WEST NEAR 15 KT. THE WAVE ALIGNS WITH A SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. NO DEEP CONVECTION IS CURRENTLY LOCATED NEAR THE WAVE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE COAST OF MAURITANIA NEAR 19N16W TO 13N22W 11N27W. THE ITCZ BEGINS NEAR 11N27W AND CONTINUES ALONG 9N35W 3N52W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 7N-12N BETWEEN 14W-22W. ...DISCUSSION... GULF OF MEXICO... MOIST CONDITIONS REMAIN ACROSS MUCH OF THE GULF OF MEXICO. THIS IS DUE TO A COMBINATION OF MOIST SOUTHERLY TO SOUTHEASTERLY FLOW AT THE SURFACE...AND MOIST FLOW ALOFT AROUND AN UPPER LEVEL RIDGE WITH AXIS FROM 31N85W TO 21N97W. ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS ARE THROUGHOUT THE AREA. A SURFACE TROUGH LINES THE NW GULF COAST ALONG 31N90W TO 26N97W...WHICH IS HELPING CONTRIBUTE TO SOME OF THE SHOWERS IN THE AREA. THE SURFACE TROUGH IS SUPPORTED BY AN UPPER TROUGH WHICH IS ALSO ALONG THE NW GULF COAST. A SECOND SURFACE TROUGH IS ALONG THE YUCATAN PENINSULA ALONG 23N89W TO 18N92W. THE SURFACE TROUGH IN THE NW CORNER IS EXPECTED TO DRIFT N2 OVER THE DAY DAY OR SO AS SURFACE RIDGING BUILDS OVER THE BASIN. MOIST CONDITIONS WILL REMAIN ACROSS MUCH OF THE AREA FOR AT LEAST THE NEXT 24 HOURS. CARIBBEAN SEA... MOISTURE FROM THE GULF OF MEXICO IS BEING DRAWN OVER THE NW CARIBBEAN IN NORTHERLY FLOW ALOFT AROUND AN UPPER LEVEL RIDGE OVER THE GULF. ONLY A FEW CLUSTERS OF SHOWERS/THUNDERSTORMS ARE FROM 19N-21N BETWEEN 77W-82W...AND FROM 21N-23N BETWEEN 82W-85W. SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE EXTREME SW CARIBBEAN OVER PANAMA AND COSTA RICA ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS THROUGH BOTH COUNTRIES TO NORTHERN COLOMBIA. THE REMAINDER OF THE BASIN IS FAIRLY DRY EXCEPT FOR ISOLATED SHOWERS OVER THE NE CORNER NORTH OF 16N EAST OF 71W ASSOCIATED WITH A TROPICAL WAVE MOVING THROUGH THE MONA PASSAGE. ALOFT...A NARROW UPPER TROUGH EXTENDS FROM THE WINDWARD PASSAGE TO NICARAGUA...BUT IS ACCOMPANIED BY DRY AIR ALOFT. UPPER LEVEL RIDGING COVERS THE REMAINDER OF THE BASIN ALSO ACCOMPANIED BY DRY AIR ALOFT. TRADEWIND FLOW OF 15-20 KT IS THROUGHOUT MUCH OF THE AREA. THE WAVE IS EXPECTED TO CONTINUE MOVING WEST WITH LITTLE CHANGE ELSEWHERE. HISPANIOLA... ONLY A SMALL AREA OF SHOWERS/THUNDERSTORMS IS OVER THE SOUTHERN PORTION OF HAITI WITH THE REMAINDER OF THE ISLAND EXPERIENCING FAIR CONDITIONS. DRY AIR ALOFT IS HELPING KEEP CONDITIONS FAIR. HOWEVER...MOISTURE ASSOCIATED WITH A TROPICAL WAVE IS JUST EAST IN THE MONA PASSAGE AND WILL LIKELY BEGIN TO IMPACT THE ISLAND SOON. THIS WILL MOST LIKELY LEAD TO INCREASED AFTERNOON CONVECTION. ATLANTIC OCEAN... BROAD SURFACE RIDGING DOMINATES THE WEST ATLC AROUND A 1023 MB HIGH NEAR 33N73W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED NEAR 34N74W. HOWEVER...AN UPPER LEVEL LOW TO THE SOUTH NEAR 24N69W SUPPORTS A WEAK SURFACE TROUGH NEAR 27N71W ALONG WITH A FEW ISOLATED SHOWERS FROM 22N-26N BETWEEN 66W-70W. A TROPICAL WAVE IS TO THE EAST SUPPORTING A FEW ISOLATED SHOWERS FROM 19N-23N BETWEEN 62W-66W. A DISSIPATING STATIONARY FRONT TO THE NORTH EXTENDS INTO THE AREA ALONG 31N41W TO 28N60W SUPPORTING ISOLATED SHOWERS WITHIN 60 NM. THE FRONT IS SUPPORTED BY AN UPPER LEVEL LOW NEAR 31N42W. THE REMAINDER OF THE BASIN IS DOMINATED BY BROAD SURFACE RIDGING ANCHORED BY A 1021 MB HIGH NEAR 28N33W. ALOFT...UPPER RIDGING DOMINATES THE TROPICAL ATLC CENTERED NEAR 13N59W. A SECOND UPPER RIDGE IS CENTERED NEAR 30N30W. VERY DRY AIR IS THROUGHOUT THE EAST ATLC DUE TO THE PRESENCE OF A BROAD SAHARAN AIR LAYER...WHICH IS KEEPING CONDITIONS FAIR ACROSS MUCH OF THE AREA. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON