000 AXNT20 KNHC 081137 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST TUE DEC 08 2009 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1030 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 8N12W 3N20W 4N35W 2N40W INTO EXTREME NORTHERN BRAZIL NEAR 1N50W. THERE IS NO NOTABLE DEEP CONVECTION ASSOCIATED WITH THE ITCZ AT THIS TIME. ...DISCUSSION... GULF OF MEXICO... A COMPLICATED WEATHER PATTERN LIES OVER THE GULF OF MEXICO AT THE MOMENT AS THE SOUTHERN STREAM JET EXTENDING OVER THE NW GULF OF MEXICO BEGINS TO MERGE WITH THE NORTHERN STREAM UNDER AN INCREASINGLY MORE AMPLIFIED PATTERN OVER THE CONTINENTAL U.S. COASTAL RADARS SHOW THE BULK OF THE SHOWER AND THUNDERSTORM ACTIVITY LIES OVER THE CENTRAL GULF COAST IN THE LEFT FRONT QUADRANT OF THE SOUTHERN STREAM JET WHERE THE INCREASED VERTICAL MOTION IS ACTING UPON THE MOIST LOW TO MID LEVEL SOUTHEASTERLY RETURN FLOW. SATELLITE-BASED TOTAL PRECIPITABLE WATER VALUES ARE IN THE 1.75 TO 2.00 INCH RANGE. A STATIONARY LOW LEVEL BOUNDARY BETWEEN THE MOIST RETURN FLOW OVER THE GULF AND COOLER NORTHERLY WINDS CONTINUES TO LIE OVER THE NW GULF FROM FRANKLIN...LOUISIANA TO CORPUS CHRISTI...TEXAS. MEANWHILE...A POTENT DEEP LAYERED TROUGH IS TRAVERSING THE SOUTHERN/CENTRAL ROCKY MOUNTAINS AND WILL INCREASE THE DEEP LAYER SOUTHERLY FLOW OVER THE GULF LATER TODAY...PUSHING THIS LOW LEVEL BOUNDARY NORTHWARD AS WINDS INCREASE TO 20 TO 25 KT OVER THE WESTERN AND CENTRAL GULF. THE STRONG COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL MOVE OFF THE TEXAS COAST BEFORE SUNRISE WED. SHOWERS AND THUNDERSTORMS ARE EXPECTED ORGANIZE ALONG AND AHEAD OF THIS COLD FRONT. CARIBBEAN SEA... THE CARIBBEAN CONTINUES TO BE MARKED BY MODERATE TO STRONG SUBSIDENCE. TOTAL PRECIPITABLE WATER SATELLITE IMAGERY SHOWS THE AVAILABLE MOISTURE IS INCREASING IN THE CARIBBEAN UNDER EASTERLY FLOW...BUT RELATIVELY TRANQUIL WEATHER CONTINUES TO BE IN PLACE. NUMEROUS SHOWERS CAN BE FOUND IN THE GULF OF HONDURAS AND JUST W OF JAMAICA WHILE MORE SCATTERED TRADE WIND SHOWERS ARE PRIMARILY FOCUSED OVER THE EASTERN HALF OF THE CARIBBEAN. THE EARLIER 0102 AND 0242 UTC ASCAT PASSES REVEALED THE WIND FIELD IN THE CARIBBEAN WITH THE STRONGEST WINDS...25 TO 30 KT...ALONG THE COAST OF COLOMBIA. THESE WINDS ARE GENERATED BY THE PRES GRADIENT BETWEEN LOW PRES OVER COLOMBIA AND THE SURFACE RIDGE STEMMING FROM A ZONALLY ORIENTED RIDGE AXIS FROM 1023 MB HIGH PRES OVER THE CENTRAL ATLANTIC NEAR 25N51W THROUGH THE BAHAMAS AND INTO THE SE GULF OF MEXICO. NO SIGNIFICANT CHANGE IS EXPECTED IN THIS PATTERN UNTIL WED WHEN THE NORTHERN STREAM BECOMES MORE AMPLIFIED AND THE CENTRAL ATLANTIC RIDGE REORGANIZES FARTHER NORTH...ALLOWING THE TRADE WINDS TO DROP A NOTCH OVER THE CENTRAL CARIBBEAN. ATLANTIC OCEAN... A STATIONARY FRONT LIES OVER THE SW N ATLANTIC FROM 31N52W TO JUST OFF THE EAST COAST OF FLORIDA NEAR 28N80W. THIS FRONTAL BOUNDARY BISECTS THE HIGH PRES RIDGE OVER THE CENTRAL ATLC BETWEEN 1023 MB HIGH PRES NEAR 37N57W AND 1023 MB HIGH PRES NEAR 25N51W. THE EARLIER ASCAT PASSES FROM 0106 AND 0246 UTC SHOWED ONLY LIGHT WINDS ASSOCIATED WITH THIS BOUNDARY AND THE THERMAL CONTRAST ACROSS THE WARM FRONT HAS DECREASED CONSIDERABLY OVER THE PAST 24 HOURS...BUT THE DEW POINTS NORTH OF THE FRONT ARE 6 TO 8 DEGREES FAHRENHEIT LESS THAN SOUTH OF THE FRONT. TOTAL PRECIPITABLE WATER IMAGERY SHOWS MOISTURE CONTINUING TO CONVERGE ON THIS BOUNDARY WHILE NIGHT CHANNEL AND CONVENTIONAL INFRARED SATELLITE IMAGERY DISPLAY OVERCAST CONDITIONS AND SHOWER ACTIVITY NEAR THE FRONT PRIMARILY E OF 72W. COASTAL RADAR SHOWS A FEW ISOLATED THUNDERSTORM CELLS ON THE WESTERN EDGE OF THE BOUNDARY OFF THE COAST OF CAPE CANAVERAL...FL. WHAT REMAINS OF THIS WEAK LOW LEVEL BOUNDARY WILL LIFT NORTHWARD OVERNIGHT TONIGHT IN ADVANCE OF THE DEEP LAYERED TROUGH CURRENTLY OVER THE ROCKIES AS IT PULLS EASTWARD INTO THE PLAINS AND MISSISSIPPI VALLEY. FARTHER E...THE SOUTHERLY POSITION OF THE RIDGE AXIS ACROSS THE CENTRAL ATLANTIC HAS ENHANCED THE PRES GRADIENT BETWEEN THE RIDGE AND THE ITCZ. THE 0100 UTC ASCAT PASS SHOWED 20 TO 25 KT NORTHEASTERLY TRADE WINDS BETWEEN 40W AND 50W S OF 15N AS A RESULT. MODERATE TRADES WILL CONTINUE HERE TODAY BUT SHOULD DIMINISH AS THE HIGH PRES RIDGE REORGANIZES FARTHER N ON WED. FINALLY...THE 100 KT WESTERLY UPPER JET OVER THE TROPICAL ATLC ALONG 13N WILL WEAKEN AND TURN NORTHWESTERLY AS THE PATTERN DOWNSTREAM BEGINS TO AMPLIFY WED. A SHRINKING BAND OF CIRRUS CONTINUES TO BE FOUND NORTH OF THE ITCZ AND SOUTH OF A LINE FROM FAR NORTHERN BRAZIL TO THE CAPE VERDE ISLANDS AS A RESULT OF THIS WESTERLY JET TRANSPORTING MOISTURE ALOFT. SHOWER AND THUNDERSTORM ACTIVITY HAS DECREASED MARKEDLY OVERNIGHT ALONG THE ITCZ. WITH THE UPPER JET BEGINNING TO WEAKEN AND VERE MORE NORTHERLY...EXPECT A REDUCED CHANGE OF CONVECTION ALONG THE ITCZ. $$ SCHAUER