000 AXNT20 KNHC 060556 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN APR 06 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0545 UTC. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 6N11W 3N20W 1N30W...CROSSING THE EQUATOR NEAR 34W...TO THE NORTHEASTERN COAST OF BRAZIL NEAR 3S40W. SCATTERED MODERATE TO SCATTERED STRONG CONVECTION WITHIN 300 NM N OF AXIS BETWEEN 17W AND 24W. SCATTERED MODERATE CONVECTION S OF 7N W OF LINE FROM 6N31W TO ITCZ AND W TO 40W. ...DISCUSSION... THE GULF OF MEXICO... A SOUTHERN STREAM SHORTWAVE TROUGH PASSING THROUGH THE SOUTHEASTERN STATES IS DRAGGING A WEAK COLD FRONT ACROSS THE NORTH CENTRAL AND NE GULF OF MEXICO EARLY THIS MORNING ALONG 30N86W TO 27N89W...WITH A WEAK SURFACE 1011 MB LOW ANALYZED CLOSE TO 29N87W. THE FRONT CONTINUES SW INTO THE W CENTRAL GULF OF MEXICO FROM 27N89W TO 23N97W AND THEN BARELY INLAND OVER FAR NE MEXICO. A 0032 UTC QUIKSCAT PASS DISTINCTLY SHOWS THE FRONT OVER THE CENTRAL GULF...BUT THE FRONT BECOMES MUCH HARDER TO IDENTIFY OVER THE W CENTRAL GULF...ONLY GIVEN BY A BROAD CYCLONIC SHEAR AND A SUBTLE INCREASE TO THE LOW-LEVEL WINDS. QUIKSCAT DATA OVER THE EASTERN GULF WAS ENTIRELY RAIN- CONTAMINATED AND THUS NOT RELIABLE FOR PLACING THE FRONT...AS BOTH SATELLITE AND RADAR IMAGERY SHOW A WELL-ORGANIZED CONVECTIVE LINE PROPAGATING WELL AHEAD OF THE FRONT ACROSS THIS AREA AS WELL AS THE CENTRAL FL PENINSULA. HOWEVER...A SINGLE ...NON-FLAGGED OBSERVATION NEAR 25N85W DID SUGGEST A SE INFLOW OF 35 KT INTO THE CONVECTIVE LINE AT THAT TIME. ELSEWHERE SE OF THE FRONT...A GENERAL SE TO S WIND FLOW OF 10- TO 15 KT IS THE RULE EXCEPT IN THE BAY OF CAMPECHE WHERE NE WINDS 5 TO 10 KT PREVAIL. SKIES REMAIN GENERALLY CLOUD-FREE TOO...EXCEPT FOR OVER PORTIONS OF THE EXTREME SE GULF OF MEXICO WHERE HIGH CLOUDS ASSOCIATED WITH A LARGE AREA OF CONVECTION OCCURRING OVER THE EASTERN YUCATAN PENINSULA. W OF THE FRONT...SURFACE RIDGING IS NOTED FROM THE UPPER TX COAST INTO NE MEXICO...WITH WHATEVER STRATUS CLOUDS FROM EARLIER ALMOST ENTIRELY DISSIPATING. SHORT-MODEL GUIDANCE INDICATES THAT THE SE U.S. SHORTWAVE SHOULD BEGIN LIFTING OUT TODAY...UNABLE TO DIG FURTHER THANKS TO A SOLID AREA OF MID-LEVEL RIDGING PARKED OVER THE WESTERN ATLANTIC. WITH THE MAIN UPPER-LEVEL DYNAMICS SHIFTING NORTHWARD ...EXPECT THE BULK OF THE PRECIPITATION TO FALL FROM GEORGIA THROUGH THE CAROLINAS WITH THE COVERAGE AND INTENSITY DECREASING OVER THE EASTERN GULF AND FLORIDA. HOWEVER...MOIST...LOW-LEVEL AIR INTERSECTING THE MAIN CONVECTIVE OUTFLOW BOUNDARY MARCHING DOWN THE SOUTHERN HALF OF FL AND ADJACENT WATERS COMBINED WITH FAVORABLE UPPER-LEVEL DIVERGENCE SHOULD BE ENOUGH TO SUPPORT SCATTERED TO LOCALLY NUMEROUS RAIN SHOWERS AND TSTMS ESPECIALLY AROUND THE TIME OF PEAK HEATING. WITH THE MAIN UPPER SUPPORT ALREADY WELL NE OF THE AREA AND THE MID- TO UPPER-LEVEL FLOW BECOMING NEARLY PARALLEL TO THE FRONT...THE FRONT SHOULD STALL ALONG THE NORTHERN GULF AND N FLORIDA...WITH THE WESTERN END LOSING ITS IDENTITY. THEREAFTER...MODELS INDICATE THAT A SEPARATE AND MUCH WEAKER SOUTHERN STREAM SHORTWAVE RACING THROUGH THE NE GULF SUN EVENING SHOULD SPARK THE DEVELOPMENT OF A NEW WAVE ALONG THE FRONT OVER THE NE GULF...WHICH SHOULD TRACK ACROSS N FLORIDA AND EMERGE INTO THE ATLANTIC WATERS AND EVENTUALLY DRAG THROUGH THE FRONT DOWN THE STATE OF FL MON. CARIBBEAN SEA... WATER VAPOR REVEALS HIGH-LEVEL WESTERLY FLOW DOMINATING MUCH OF THE BASIN...WITH THE REMAINS OF A WEAKENING UPPER-LEVEL TROUGH LYING FROM 19N80W TO 9N85W. MODERATE TO STRONG UPPER TROPOSPHERIC SUBSIDENCE ASSOCIATED WITH A LARGE AND DOMINANT MID- TO UPPER-LEVEL ANTICYCLONE IN THE TROPICAL E PACIFIC CONTINUES TO BE OBSERVED AS FAR E AS THE WESTERN CARIBBEAN W OF THE DISSIPATING TROUGH AXIS. LIKE YESTERDAY...A PLUME OF MOISTURE WITH ORIGINS FROM CONVECTIVE DEBRIS OVER THE AMAZON IS BEING DRAWN NORTHWARD FROM NORTHERN COLOMBIA TO JUST SOUTH OF HISPANIOLA AND PUERTO RICO. DESPITE THE SUBTLE INCREASE IN UPPER TROPOSPHERIC MOISTURE AND DIFFLUENT UPPER-LEVEL FLOW... LITTLE IN THE WAY ON CONVECTION IS NOTED EXCEPT OVER NORTHERN COLOMBIA EARLIER THIS EVENING. IN FACT...THE ONLY CONVECTION TO REPORT IS OVER CUBA...WHERE LOCAL SEA BREEZE CIRCULATIONS AND A GRADUALLY DESTABILIZING ATMOSPHERE LED TO LATE AFTERNOON TSTMS WHICH ARE DIMINISHING AND BLOWING OFF TO THE NE WITH THE UPPER-LEVEL WINDS. OTHERWISE...SURFACE HIGH PRESSURE OVER THE CENTRAL ATLANTIC NEAR NEAR 29N59W HAS AN EXTENSION INTO THE CARIBBEAN SEA AND IS PROVIDING A CONTINUED FRESH TRADE WIND FLOW ACROSS THE EASTERN AND CENTRAL PART OF THE BASIN. HOWEVER...COMPARED TO LAST NIGHT...TRADES ARE SLIGHTLY WEAKER THAN 24 HOURS AND ARE CLOSE TO CLIMATOLOGICAL AVERAGES AS SUGGESTED BY SOME OF THE REAL-TIME NCEP RE-ANALYSIS DATA. OVER THE NEXT FEW DAYS...A WELL-DEFINED MID- TO UPPER-LEVEL RIDGE SHOULD CONTINUE TO PREVAIL N OF THE CARIBBEAN IN THE VICINITY OF 25N60W. THIS SHOULD ALLOW FOR A PATTERN OF WEAKER- THAN-NORMAL WESTERLY FLOW AT UPPER LEVELS ACROSS THE REGION... WITH NOTABLE EASTERLY WIND ANOMALIES LIKELY THROUGH THE WEEKEND INTO EARLY NEXT WEEK. MEANWHILE...THE SURFACE RIDGE OVER THE CENTRAL ATLANTIC SHOULD GRADUALLY WEAKEN WHILE SHIFTING SSE... WHICH SHOULD CAUSE THE FRESH TRADE WIND FLOW ACROSS THE AREA TO RELAX. ATLANTIC OCEAN.... AN ANOMALOUSLY STRONG MID-LEVEL RIDGE REMAINS LOCKED IN PLACE OVER THE WEST CENTRAL ATLANTIC NEAR 25N60W...DIRECTING THE STRONG MID-LATITUDE FLOW OVER THE EASTERN CONUS N OF THE AREA. INSTEAD THE STRONGER MID-LATITUDE FLOW DIGS EASTWARD INTO A BROAD...DEEP-LAYERED TROUGH W OF 50 AND N OF ABOUT 15N...WITH AN ASSOCIATED CLOSED CYCLONIC CIRCULATION NEAR 37N30W. AT THE LEADING EDGE OF THE TROUGH LIES A SURFACE COLD FRONT EXTENDING FROM 31N23W TO 23N38W FOLLOWED BY A LARGE DOME OF SURFACE HIGH PRESSURE CENTERED NEAR 29N59W. THE STRONG PRESSURE GRADIENT BETWEEN THE HIGH AND THE LOWER LATITUDES IS RESULTING IN NORMAL TO ENHANCED TRADES...MOSTLY OVER THE AREA S OF 20N AND W OF 45W TO THE LESSER ANTILLES. IN FACT...AN EARLY EVENING QUIKSCAT PASS REVEALED STILL 20- TO 25-KT NE WINDS OVER MUCH OF THE ABOVE AREA...WITH SEAS GENERALLY 9 TO 12 FT IN NE SWELL. WITH THE SURFACE RIDGE FORECAST TO GRADUALLY WEAKEN AND SHIFT SSE...THE FRESH TRADES SHOULD RELAX GOING INTO EARLY NEXT WEEK...WITH SEAS SUBSIDING TO 6 TO 8 FT BY TUE NEXT WEEK. W OF 50W...A BROAD SURFACE CYCLONIC FLOW COVERS THE AREA N OF ABOUT 25N...DIRECTLY BEHIND A COLD FRONT MOVING E OF THE AREA. OTHER THAN A FAIRLY THICK DECK OF STRATOCUMULUS W OF THE FRONT ...THERE IS LITTLE ELSE THAT DEFINES THIS FEATURE. AS THE FRONT RACES FARTHER SE TODAY...A NEW INJECTION OF COOLER AIR SHOULD BRIEFLY RE-INVIGORATE THE LARGE CYCLONIC CENTER S OF THE AZORES. THIS...IN TURN...SHOULD KEEP THE CURRENT DEEP-LAYERED CYCLONIC FLOW OVER THE AREA IN PLACE INTO EARLY NEXT WEEK. ELSEWHERE...WATER VAPOR IMAGERY AND CLOUD-TRACKED WINDS INDICATE A NARROW MID- TO UPPER-LEVEL RIDGE S OF ABOUT 12N FROM THE NW COAST OF AFRICA TO JUST SE OF THE WINDWARD ISLANDS. THE DEEP EASTERLIES S OF THE RIDGE ALONG WITH THE PRESENCE OF AN EQUATORIAL KELVIN WAVE APPROACHING 0W HAVE BEEN PROVIDING A FAVORABLE ENVIRONMENT FOR ENHANCED CONVECTION ALONG THE ITCZ THE LAST FEW DAYS. THIS PATTERN OF ANOMALOUS EASTERLY FLOW AND ENHANCED CONVECTION SHOULD GRADUALLY DIMINISH BY EARLY NEXT WEEK...ONCE THE KELVIN WAVE PROPAGATES E OF THE AREA. $$ KIMBERLAIN