000 AXNT20 KNHC 080546 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0430 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 8N13W 7N20W 3N35W INTO EXTREME NORTHERN BRAZIL NEAR 1N50W. SCATTERED MODERATE CONVECTION LIES WITHIN 270 NM S OF THE ITCZ AXIS BETWEEN 14W AND 19W AS WELL AS WITHIN 120 NM N AND 60 NM S OF THE ITCZ AXIS BETWEEN 38W AND 43W. ...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 LOWER MISSISSIPPI VALLEY IN THE LEFT FRONT QUADRANT OF THE SOUTHERN STREAM JET WHERE THE INCREASED VERTICAL MOTION IS ACTING UP THE MOIST LOW TO MID LEVEL SOUTHEASTERLY RETURN FLOW. SATELLITE-BASED TOTAL PRECIPITABLE WATER VALUES IN THE NW GULF HAVE RISEN TO THE 1.75 TO 2.00 INCH RANGE. A LOW LEVEL BOUNDARY BETWEEN THE MOIST RETURN FLOW OVER THE GULF AND DRY NORTHERLY WINDS CURRENTLY LIES 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 AHEAD OF THE 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 WHILE MORE SCATTERED TRADE WIND SHOWERS ARE PRIMARILY FOCUSED OVER THE EASTERN CARIBBEAN. THE 0102 AND 0242 UTC ASCAT PASSES REVEAL 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 27N51W TO THE NORTHERN BAHAMAS NEAR 26N77W. 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 31N54W TO 30N63W AND THEN BECOMES A WARM FROM TO THE EAST COAST OF FLORIDA NEAR VERO BEACH. THIS FRONTAL BOUNDARY BISECTS THE HIGH PRES RIDGE OVER THE CENTRAL ATLC BETWEEN 1025 MB HIGH PRES NEAR 37N64W AND WEAKER 1023 MB HIGH PRES NEAR 26N77W. THE ASCAT PASSES FROM 0106 AND 0246 UTC SHOW ONLY LIGHT WINDS ASSOCIATED WITH THIS BOUNDARY AND THE THERMAL CONTRAST ACROSS THE WARM FRONT HAS DECREASED CONSIDERABLY OVER THE PAST 24 HOURS. HOWEVER...THE GOES TOTAL PRECIPITABLE WATER IMAGERY SHOWS MOISTURE CONTINUING TO CONVERGE ON THIS BOUNDARY WHILE NIGHT CHANNEL AND CONVENTIONAL INFRARED SATELLITE IMAGERY SHOW MULTI-LAYERED CLOUDINESS AND SHOWER ACTIVITY NEAR THE FRONT PRIMARILY E OF 73W. WHAT REMAINS OF THIS LOW LEVEL BOUNDARY IS EXPECTED TO LIFT NORTHWARD BY THIS TIME TOMORROW 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 SCAT PASS SHOWS 20 TO 25 KT NORTHEASTERLY TRADE WINDS BETWEEN 40W AND 50W S OF 15N AS A RESULT. MODERATE TRADES WILL CONTINUE HERE THROUGH TUE...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 FINALLY WEAKEN AND TURN NORTHWESTERLY AS THE PATTERN DOWNSTREAM BEGINS TO AMPLIFY WED. A WIDE 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. DIFFLUENCE IN THE REAR RIGHT QUADRANT OF THIS UPPER JET IS CURRENTLY SUPPORTING SCATTERED MODERATE SHOWERS AND THUNDERSTORMS WITHIN 120 NM N AND 60 NM S OF THE ITCZ AXIS BETWEEN 38W AND 43W. $$ SCHAUER