[Tropical] Tropical Weather Discussion

[EMWIN Server]

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


This weather bulletin was brought to you by:
www.nashvilleweather.net