[Tropical] Tropical Weather Discussion

[EMWIN Server]

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




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