000 AXNT20 KNHC 071139 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST MON DEC 07 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 0830 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 7N10W 6N20W 3N35W INTO EXTREME NORTHERN BRAZIL NEAR 4N51W. SCATTERED MODERATE CONVECTION WITHIN 240 NM N AND 120 NM S OF THE ITCZ AXIS BETWEEN 15W AND 27W. ...DISCUSSION... GULF OF MEXICO... SOUTHEASTERLY WINDS CAN BE FOUND OVER THE CENTRAL AND WESTERN GULF OF MEXICO SIPHONING BETWEEN SURFACE RIDGING OVER THE EASTERN GULF AND TROUGHING OVER TEXAS AND NORTHERN MEXICO ASSOCIATED WITH A LOW PRES SYSTEM PASSING THROUGH THE MID MISSISSIPPI VALLEY. THE 0306 UTC ASCAT PASS SHOWED THE STRONGEST WINDS WERE OVER THE NW GULF AT 20 TO 25 KT. A PRE-FRONTAL TROUGH LIES ONSHORE FROM LITTLE ROCK...ARKANSAS SW TO THE COAST NEAR PALACIOS...TEXAS. COASTAL U.S. RADARS SHOW THE BULK OF THE SHOWER AND THUNDERSTORM ACTIVITY LIES JUST E OF THIS TROUGH ALONG THE SE TEXAS AND SW LOUISIANA COASTS. THE LOW PRES SYSTEM N OF THE AREA IS EXPECT TO RACE NORTHEASTWARD TODAY...ALLOWING WINDS TO DIMINISH A NOTCH IN THE NW GULF...BUT THE GENERAL PATTERN WILL REMAIN THE SAME WITH RIDGING OVER THE EASTERN GULF AND LINGERING TROUGHING ALONG THE NW GULF COAST. BY TUE...THE UPPER PATTERN IN THE NORTHERN STREAM WILL BECOME MORE AMPLIFIED AS A STRONG NEW SURFACE SYSTEM MAKES ITS WAY THROUGH THE GREAT BASIN AND ROCKIES. SOUTHERLY WINDS IN ADVANCE OF THIS SYSTEM WILL AGAIN EXCEED 20 KT OVER THE WESTERN GULF AND NORTHERLY MOISTURE TRANSPORT WILL INCREASE...WITH SHOWERS AND THUNDERSTORMS INCREASING OVER THE LOWER MISSISSIPPI VALLEY THROUGH THE DAY. CARIBBEAN SEA... THE CARIBBEAN CONTINUES TO BE MARKED BY STRONG SUBSIDENCE AND LIMITED MOISTURE...BRINGING TRANQUIL WEATHER TO MUCH OF THE AREA. NUMEROUS SHOWERS CAN BE FOUND ON THE ROUTE BETWEEN THE NICARAGUA/HONDURAS BORDER TO THE WINDWARD PASSAGE INCLUDING JAMAICA AS WELL AS NEAR THE VENEZUELAN COAST E OF 70W WHILE MORE SCATTERED TRADE WIND SHOWERS CAN BE FOUND THROUGH THE REMAINDER OF THE EASTERN CARIBBEAN. THE 0122 AND 0302 UTC ASCAT PASSES SHOWED THE WIND FIELD IN THE CARIBBEAN WERE STRONGEST N AND NW OF THE COAST OF COLOMBIA...WITH 20 TO 25 KT WINDS GENERATED BY THE PRES GRADIENT BETWEEN LOW PRES OVER COLOMBIA AND THE SURFACE RIDGE STEMMING FROM A 1029 MB HIGH PRES CENTER NEAR OCEAN CITY...MD AND EXTENDING SOUTH THROUGH THE EASTERN GULF OF MEXICO TO THE YUCATAN CHANNEL. EXPECT THIS PATTERN TO REMAIN IN PLACE UNTIL TUE WHEN THE RIDGING IN THE EASTERN GULF OF MEXICO IS ERODED BY THE NEXT SYSTEM PULLING E ACROSS THE ROCKIES...MAKING THE RIDGING STEMMING FROM WEAKER HIGH PRES OVER THE CENTRAL ATLANTIC AND EXTENDING ZONALLY ALONG 24N E OF THE BAHAMAS THE PRIMARY CONSIDERATION FOR THE PRES GRADIENT OVER THE CARIBBEAN. LOOK FOR WINDS TO WEAKEN A NOTCH OVER THE CENTRAL CARIBBEAN TUE AS A RESULT. ATLANTIC OCEAN... A COLD FRONT LIES OVER THE SW N ATLANTIC FROM 31N59W TO 28N68W AND THEN BECOMES A WARM FROM TO 28N73W TO 26N78W. THE ASCAT PASS FROM 0126 UTC SHOWED THE NE TO E WINDS HAVE GENERALLY DROPPED BELOW 20 KT N OF THE FRONT. THE GOES TOTAL PRECIPITABLE WATER IMAGERY SHOWS MOISTURE OVERRUNNING THIS SURFACE BOUNDARY. NIGHT CHANNEL AND CONVENTIONAL INFRARED SATELLITE IMAGERY CONFIRM THIS BY SHOWING MULTI-LAYERED CLOUDINESS AND SHOWER ACTIVITY MAINLY N OF THE FRONT. IN ADDITION...RADAR OVER FLORIDA SHOWS A BAND OF SHOWERS IN THE OVERRUNNING REGION OF THE WARM FRONT FROM NORTH OF TAMPA BAY TO NORTH OF CAPE CANAVERAL WITH SHOWERS PASSING EASTWARD OFFSHORE UNDER MID TO UPPER LEVEL WESTERLY STEERING FLOW. THE PORTION OF THIS FRONT S OF 28N IS EXPECTED TO STALL AND WEAKEN TODAY WHILE THE REMAINDER OF THE FRONT CONTINUES TO CHARGE EASTWARD INTO THE CENTRAL ATLANTIC. FARTHER E...A DISSIPATING COLD FRONT LIES FROM 31N22W TO 25N35W. THE TROUGHING DUE TO THIS BOUNDARY HAD WEAKENED THE EASTERN EDGE OF THE SURFACE RIDGE CENTERED BETWEEN THE 1022 MB HIGH PRES NEAR 33N29W AND THE 1024 MB HIGH PRES NEAR 28N44. IN ADDITION...THE ADVANCING COLD FRONT OVER W WATERS IS ERODING THE RIDGE FROM THE WEST. THIS RIDGING IS EXPECTED TO WEAKEN FURTHER AND SHIFT SOUTHWARD AS THE ADVANCING PORTION OF THE COLD FRONT ENCROACHES UPON IT. TO THE WEST OF THIS RIDGE LIES A POSITIVELY TILTED UPPER TROUGH THAT WILL PINCH OFF AN UPPER LOW SOUTH OF THE CANARY ISLANDS BY TUE. A 100 KT WESTERLY UPPER JET LIES ON THE SE EDGE OF THIS TROUGH AND IS TRANSPORTING TROPICAL MOISTURE ALOFT NORTHEASTWARD TOWARD WEST AFRICA...WITH A WIDE BAND OF CIRRUS FOUND ALONG AND S OF THE ROUTE FROM THE FRENCH GUIANA TO THE CAPE VERDE ISLANDS N OF THE ITCZ AS A RESULT. DIFFLUENCE IN THE REAR RIGHT QUADRANT OF THIS UPPER JET IS CURRENTLY SUPPORTING SCATTERED MODERATE SHOWERS AND THUNDERSTORMS ALONG THE ITCZ AXIS BETWEEN 15W AND 27W. $$ SCHAUER