000 AXNT20 KNHC 112344 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI MAY 11 2012 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 FROM THE AFRICAN COAST NEAR 12N16W TO 09N22W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N22W TO 02N40W TO THE EQUATOR NEAR 47W. ISOLATED MODERATE CONVECTION IS FROM 01N-03N BETWEEN THE PRIME MERIDIAN AND 05W...AND FROM 04N-07N BETWEEN 24W-28W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE IS THE DOMINATING UPPER LEVEL FEATURE OVER THE GULF BASIN THIS EVENING WITH AN UPPER LEVEL RIDGE AXIS EXTENDING NORTHWARD FROM AN ANTICYCLONIC CIRCULATION CENTERED OVER EL SALVADOR NEAR 14N90W. THE AXIS STRETCHES FROM THERE TO THE NE GULF NEAR 30N86W THEN BECOMES SHARPLY AMPLIFIED OVER THE SE CONUS TO OVER THE OHIO RIVER VALLEY NEAR 38N88W. TO THE WEST OF THIS RIDGE AXIS...AN UPPER LEVEL LOW IS CENTERED OVER SOUTHWESTERN OKLAHOMA AND IS THE DRIVING FORCE BEHIND STRONG UPPER LEVEL DIFFLUENCE ACROSS THE LOWER MISSISSIPPI RIVER VALLEY THAT EXTENDS INTO THE NORTH-CENTRAL GULF WATERS. SCATTERED SHOWERS AND TSTMS...MOSTLY ALONG A SQUALL LINE FROM 29N91W TO 26N92W...ARE OCCURRING N OF 25N BETWEEN 88W-93W. THIS CONVECTION IS LIKELY ENHANCED BY THE UPPER LEVEL DIFFLUENCE BUT IS FUELED BY PLENTY OF WARM...MOIST...AND UNSTABLE LOWER LEVEL AIR ADVECTING FROM THE SOUTHEAST ON THE SOUTHERN PERIPHERY OF WEAK SURFACE RIDGING. A FEW ISOLATED SHOWERS AND TSTMS LINGER TO THE WEST OF THE SQUALL LINE OCCURRING FROM 26N-29N BETWEEN 93W-97W. EAST-SOUTHEASTERLY SURFACE FLOW IS FORECAST TO CONTINUE THROUGH THE OVERNIGHT HOURS AS A WEAK AREA OF LOW PRESSURE DEVELOPS ACROSS EASTERN TEXAS. AS THE LOW MOVES NORTHEAST DURING THE DAY ON SATURDAY...A WEAK SURFACE TROUGH BOUNDARY IS EXPECTED TO EXTEND INTO THE NW GULF WATERS AND GRADUALLY SHIFT EASTWARD THROUGH THE REMAINDER OF THE WEEKEND. AS A RESULT...LIGHT NORTH- NORTHEAST WINDS WILL PREVAIL W OF 90W THROUGH LATE SUNDAY. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER EL SALVADOR NEAR 14N90W AND EXTENDS INFLUENCE EASTWARD OVER THE CARIBBEAN TO 65W WITH NORTHWEST FLOW ALOFT. WATER VAPOR IMAGERY INDICATES THAT MUCH OF THIS AREA N OF 10N W OF 65W REMAINS VERY STABLE AND THAT A SUBSIDENT ATMOSPHERE PREVAILS. SKIES ARE NOTED ON SATELLITE IMAGERY AS MOSTLY CLEAR HOWEVER...A FEW ISOLATED SHOWERS ARE OCCURRING N OF 16N BETWEEN 65W-72W...INCLUDING PORTIONS OF PUERTO RICO AND HISPANIOLA. E OF 65W...WEAK UPPER LEVEL TROUGHING CONTINUES TO SHIFT EASTWARD INTO THE CENTRAL ATLC...HOWEVER LINGERING ISOLATED SHOWERS ARE OCCURRING FROM 10N-18N E OF 63W THIS EVENING. A BULK OF THE MORE SCATTERED SHOWER ACTIVITY IS OCCURRING EAST OF THE LESSER ANTILLES FROM 10N-23N BETWEEN 50W-61W. FRESH TO STRONG EASTERLY TRADES ARE EXPECTED TO PERSIST THROUGH THE WEEKEND AS STRONG HIGH PRESSURE REMAINS TO THE NORTH ANCHORED IN THE SW NORTH ATLC. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS OVER THE WESTERN ATLC THIS EVENING WITH A TROUGH AXIS EXTENDING FROM MAINE SOUTHWARD ALONG 70W TO A BASE NEAR 26N. THIS TROUGH SUPPORTS A COLD FRONT ANALYZED INTO THE DISCUSSION AREA NEAR 32N67W EXTENDING SOUTHWESTWARD ALONG 29N70W TO 27N76W WHERE IT BECOMES A DISSIPATING STATIONARY FRONT TO THE FLORIDA PENINSULA NEAR 26N80W. WITH MOST OF THE MIDDLE TO UPPER LEVEL DYNAMICS E OF 70W...SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING N OF 25N BETWEEN 62W-66W WITH ISOLATED SHOWERS OCCURRING ELSEWHERE N OF 25N BETWEEN 66W-72W...SE OF THE FRONT. THE REMAINDER OF THE SW NORTH ATLC WEST OF THE COLD FRONT IS UNDER DRY AIR AND SUBSIDENCE WITH NW UPPER LEVEL FLOW NOTED ON WATER VAPOR IMAGERY. SKIES CONTINUE TO BE CLEAR THIS EVENING WITH NE TO E WINDS IN THE RANGE OF 10 TO 15 KT. FARTHER EAST... UPPER LEVEL RIDGING OCCUPIES MUCH OF THE CENTRAL NORTH ATLC THAT STRETCHES INTO THE TROPICS FROM 32N56W TO 15N46W. THIS LARGELY SUPPORTS A SURFACE RIDGE LOCATED BETWEEN 35W-60W THAT EXTENDS SOUTHWARD TO 15N. EAST OF THIS SURFACE RIDGE JUST NORTH OF THE DISCUSSION AREA...AN UPPER LEVEL LOW IS CENTERED NEAR 34N30W THAT SUPPORTS A NEARLY COLLOCATED 1014 MB SURFACE LOW CENTERED NEAR 34N31W. A SURFACE TROUGH IS ANALYZED TO THE SE OF THE LOW CENTER FROM 32N24W TO 25N30W. MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO ADVECT AROUND THE SOUTHERN PERIPHERY OF THE UPPER LEVEL LOW FROM 21N45W TO 23N28W TO BEYOND 32N18W...WITH POSSIBLE ISOLATED SHOWERS OCCURRING WITHIN 150 NM EITHER SIDE OF THAT LINE. FINALLY...AN AREA OF SAHARAN DUST COVERS A LARGE PORTION OF THE TROPICAL EASTERN ATLC BOUNDED BY 27N13W TO 20N30W TO 14N59W TO 07N57W TO 07N30W TO 10N15W . MUCH OF THIS AREA ON SATELLITE IMAGERY IS UNDER CLEAR SKIES AND STABLE CONDITIONS DUE TO THE SUSPENDED DUST. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN