000 AXNT20 KNHC 121744 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON AUG 12 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 11N32W TO 18N31W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH A BROAD LOW-LEVEL MONSOONAL GYRE FOCUSED IN THE VICINITY OF A 1010 MB LOW CENTERED NEAR 11N32W. IN ADDITION...A MID-LEVEL 700 MB TROUGH AXIS ALSO EXTENDS ALONG 32W NORTHWARD TO NEAR 20N. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MAXIMUM VALUES FROM 07N-19N BETWEEN 24W-35W. CONVECTION REMAINS LARGELY EMBEDDED WITHIN THE MONSOON TROUGH AXIS WITH SCATTERED MODERATE FROM 08N-11N BETWEEN 28W-38W. TROPICAL WAVE EXTENDS FROM 09N53W TO 19N56W MOVING W AT 20 KT. THE WAVE REMAINS ON THE LEADING EDGE OF SAHARAN DUST WHICH IS NOTED ON VISIBLE SATELLITE IMAGERY TO THE EAST OF THE WAVE AXIS. THIS SAHARAN AIR LAYER IS INHIBITING ANY DEEP CONVECTION AND RESULTING IN ONLY A FEW POSSIBLE SHOWERS WITHIN 180 NM EITHER SIDE OF THE WAVE AXIS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO 14N27W TO 11N32W TO 07N43W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N43W TO 06N57W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM EITHER SIDE OF A LINE FROM 13N17W TO 07N37W. ...DISCUSSION... GULF OF MEXICO... NORTHEASTERLY UPPER LEVEL FLOW IS NOTED ON WATER VAPOR IMAGERY OVER THE GULF THIS AFTERNOON BETWEEN AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER NORTHERN MEXICO NEAR 30N106W AND AN UPPER LEVEL LOW CENTERED OVER THE NORTHWESTERN CARIBBEAN SEA NEAR 22N83W. OVERALL A DRIER AIRMASS IS ADVECTING WESTWARD WITH MOST MIDDLE TO UPPER LEVEL MOISTURE REMAINING W OF 93W. AS A RESULT...A SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED ACROSS THE FLORIDA PANHANDLE NEAR 31N86W CONTINUES TO FURTHER SUPPORT THE STABLE CONDITIONS ALOFT WITH MOSTLY CLEAR SKIES AND FAIR CONDITIONS. A FEW ISOLATED SHOWERS AND TSTMS ARE HOWEVER OCCURRING ON THE NORTHERN PERIPHERY OF THE UPPER LEVEL LOW ACROSS THE FLORIDA STRAITS AND SE GULF S OF 24N E OF 88W... INCLUDING THE YUCATAN CHANNEL AREA. FARTHER WEST...A WEAKENING SURFACE TROUGH ANALYZED FROM 19N96W TO 24N98W CONTINUES TO PROVIDE FOCUS FOR WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS S OF 24N BETWEEN 91W-98W. OTHERWISE...E-SE WINDS IN THE RANGE OF 10 TO 20 KT PREVAIL AND WITH A GRADUAL SHIFT WESTWARD OF THE SURFACE HIGH...LIGHT ANTICYCLONIC FLOW IS EXPECTED TO PERSIST THROUGH LATE TUESDAY. THEREAFTER...A RIDGE AXIS IS FORECAST TO ANCHOR ALONG 27N/28N UNTIL FRIDAY AS A SURFACE TROUGH PROGRESSES W-NW OUT OF THE NW CARIBBEAN SEA INTO THE SE GULF. CARIBBEAN SEA... AN UPPER LEVEL LOW IS CENTERED OVER THE NW CARIBBEAN NEAR 22N83W AND STRETCHES AN UPPER LEVEL TROUGH AXIS EASTWARD ALONG 22N TO 66W. MUCH OF THE BASIN LIES WITHIN WESTERLY UPPER LEVEL FLOW ALOFT ON THE SOUTHERN PERIPHERY OF THIS TROUGHING WITH WATER VAPOR IMAGERY INDICATING PLENTY OF MIDDLE TO UPPER LEVEL MOISTURE IN WHICH TO WORK WITH FOR CONVECTIVE PROCESSES. AS FOR THE UPPER LEVEL LOW...WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING N OF 16N BETWEEN 76W-89W...INCLUDING THE YUCATAN CHANNEL...CAYMAN ISLANDS...THE GULF OF HONDURAS...AND INLAND PORTIONS OF BELIZE. FARTHER SOUTH...CONVECTION BECOMES MORE SCATTERED IN COVERAGE WITH SHOWERS AND TSTMS OCCURRING S OF 16N BETWEEN 73W-84W. MUCH OF THIS CONVECTION IS AIDED BY LOW- LEVEL MOISTURE CONVERGENCE AND THE PRESENCE OF THE MONSOON TROUGH AXIS EXTENDING FROM NORTHERN COLOMBIA NEAR 12N73W TO NORTHERN COSTA RICA NEAR 11N85W. FINALLY...THE LAST FEATURE TO DISCUSS IS A SURFACE TROUGH ANALYZED FROM 12N71W TO EASTERN HISPANIOLA NEAR 19N69W. THIS SURFACE FEATURE COINCIDES WITH A BROAD 700 MB TROUGH AXIS ACROSS THE CENTRAL CARIBBEAN AND LIES BENEATH A MAXIMUM IN UPPER LEVEL DIFFLUENCE ACROSS THE EASTERN CARIBBEAN. SCATTERED SHOWERS AND WIDELY SCATTERED TSTMS ARE OCCURRING PRIMARILY EAST OF THE SURFACE TROUGH AXIS FROM 11N-19N BETWEEN 64W-72W. HISPANIOLA... CURRENTLY LOW-LEVEL MOISTURE AND INSTABILITY IS ON THE INCREASE ACROSS HISPANIOLA THIS AFTERNOON AS A SURFACE TROUGH EXTENDS FROM THE EASTERN TIP NEAR 19N69W SOUTHWARD INTO THE OPEN WATERS OF THE CENTRAL CARIBBEAN SEA. THE SAN JUAN PUERTO RICO AND CAYMAN ISLANDS SOUNDINGS FROM 12/1200 UTC INDICATE THIS TROUGHING EXTENDS INTO THE VERTICAL UP TO ABOUT 500 MB AND REMAINS RELATIVELY BROAD. MOST OF THE ONGOING CONVECTION IS NOTED S OF 18N...HOWEVER AS THE SURFACE TROUGH MOVES WESTWARD SCATTERED SHOWERS AND TSTMS ARE EXPECTED TO INCREASE ACROSS THE ISLAND FOR THE REMAINDER OF THIS AFTERNOON AND INTO THE EVENING. THE TROUGH IS FORECAST TO CLEAR WEST OF THE ISLAND BY LATE TUESDAY WITH E-SE WINDS PREVAILING IN THE RANGE OF 10 TO 20 KT. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NEAR 32N72W THAT INFLUENCES A LARGE PORTION OF THE SW NORTH ATLC THIS AFTERNOON. THE RIDGING ALOFT CONTINUES TO SUPPORT A SURFACE RIDGE OF HIGH PRESSURE ANCHORED BY A 1021 MB HIGH CENTERED NEAR 29N77W. THE SURFACE RIDGE AXIS EXTENDS WESTWARD TO THE NORTHERN FLORIDA PENINSULA. MOSTLY FAIR SKIES AND CONDITIONS ACCOMPANY THIS FEATURE W OF 63W...HOWEVER A FEW WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS CONTINUE TO DRIFT WESTWARD UNDER LIGHT EASTERLY SURFACE FLOW FROM 22N-26N BETWEEN 76W-82W...AND N OF 31N BETWEEN 63W-70W. FARTHER EAST ACROSS THE CENTRAL ATLC...AN UPPER LEVEL LOW IS CENTERED NEAR 30N57W AND SUPPORTS A SURFACE TROUGH ANALYZED FROM 24N55W TO 30N52W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING FROM 23N-31N BETWEEN 50W-63W IN ASSOCIATION WITH BOTH THE FEATURES AT THE SURFACE AND ALOFT. OTHERWISE...FAIRLY BENIGN CONDITIONS ARE NOTED ON SATELLITE IMAGERY E OF 50W AS A SURFACE RIDGE DOMINATES. THE RIDGING IS ANCHORED BY A 1026 MB HIGH CENTERED SW OF THE AZORES NEAR 33N41W. ASIDE FROM THE TROPICAL WAVES DISCUSSED IN DETAIL ABOVE...BETWEEN THE WAVES AND THE REGION TO THE NORTH OF THE WAVES...AN AREA OF SAHARAN DUST IS LOCATED GENERALLY N OF 15N E OF 50W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN