000
AXNT20 KNHC 070600
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 6N10W 
7N20W 4N30W 2N40W INTO EXTREME NORTHERN BRAZIL NEAR 1N50W. SCATTERED 
MODERATE CONVECTION WITHIN 120 NM N AND 90 NM S OF THE ITCZ AXIS E 
OF 33W.

...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 CENTRAL PLAINS AND MID MISSISSIPPI 
VALLEY. THE 0306 UTC ASCAT PASS SHOWS THE STRONGEST WINDS LIE OVER 
THE NW GULF AT 20 TO 25 KT. SKIES ARE OVERCAST OVER MUCH OF THE GULF 
N OF 24N AND COASTAL U.S. RADARS SHOW THE BULK OF THE SHOWER 
ACTIVITY IS 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. 
SHOWERS ARE PRIMARILY CONFINED TO THE ROUTE BETWEEN THE 
NICARAGUA/HONDURAS BORDER TO THE WINDWARD PASSAGE INCLUDING JAMAICA 
AS WELL AS NEAR THE VENEZUELAN COAST E OF 70W. THE 0122 AND 0302 UTC 
ASCAT PASSES SHOW THE WIND FIELD IN THE CARIBBEAN IS 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 OVER THE EASTERN GULF OF MEXICO STEMMING FROM A 1029 MB HIGH 
PRES CENTER NEAR CHARLOTTE...NC. 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 31N61W TO 29N67W TO 
25N76W. THE ASCAT PASS FROM 0126 UTC SHOWS NE WINDS HAVE GENERALLY 
DROPPED BELOW 20 KT N OF THE FRONT. THE GOES TOTAL PRECIPITABLE 
WATER IMAGERY IS SHOWING MOISTURE OVERRUNNING THIS SURFACE BOUNDARY 
WITH INFRARED AND EARLIER VISIBLE SATELLITE IMAGERY CONFIRMING THIS 
BY SHOWING MULTI-LAYERED CLOUDINESS AND SHOWER ACTIVITY MAINLY N OF 
THE FRONT. THE PORTION OF THIS FRONT S OF 29N IS EXPECTED TO STALL 
AND THEN RETREAT NORTHWARD TODAY AS A WARM FRONT WHILE THE REMAINDER 
OF THE FRONT CONTINUES TO CHARGE EASTWARD INTO THE CENTRAL ATLANTIC. 
FARTHER E...A WEAK FRONTAL TROUGH LIES FROM 30N25W TO 27N38W. THIS 
BOUNDARY IS CUTTING THROUGH THE SURFACE RIDGE BETWEEN THE 1023 MB 
HIGH PRES NEAR 35N29W AND THE 1024 MB HIGH PRES NEAR 25N45. 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 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 E OF 33W.
 
$$
SCHAUER