[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200535
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST MON 20 DEC 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...ITCZ...

ITCZ IS CENTERED ALONG 7N10W 3N40W 2N60W 6N80W.  NUMEROUS
MODERATE CONVECTION FROM 10N-14N BETWEEN 29W-33W. SCATTERED
MODERATE CONVECTION FROM 2N-10N BETWEEN 25W-45W.

...DISCUSSION...

GULF OF MEXICO...
A SHARP DEEP-LAYERED TROUGH LIES OVER THE E HALF OF THE UNITED
STATES AND GLFMEX.  ATTENDANT COLD FRONT IS MOVING QUICKLY
ACROSS THE AREA CURRENTLY EXTENDING FROM CENTRAL FLORIDA TO S
TEXAS.  THE AIRMASS AHEAD OF THE FRONT IS DRY RENDERING THE
FRONT NEARLY UNDETECTABLE IN SATELLITE IMAGERY.  THE FRONT IS
HOWEVER DELINEATED BY A SHARP DECREASE IN TEMPERATURE AND
DEWPOINT WITH NUMERICAL GUIDANCE INDICATING ONE OF THE COLDEST
SURGES OF CONTINENTAL AIR THIS WINTER OVERSPREADING THE AREA
TONIGHT AND MONDAY.  MUCH OF THE EARLIER CLOUDINESS AND SHOWERS
OVER THE S GULF EARLIER TODAY HAS SLIDE SE OF THE AREA SAVE THE
BAY OF CAMPECHE.  HIGH PRESSURE BUILDING SWD BEHIND THE FRONT
WILL BE QUITE PROGRESSIVE MOVING OFF THE SE UNITED STATES COAST
BY EARLY TUE. THIS WILL ALLOW THE WINDS TO VEER AROUND TO THE
EAST ALLOWING A WARMING TREND TO BEGIN TUE.

CARIBBEAN...
A STRONG MID/UPPER LEVEL RIDGE LIES ACROSS THE CARIBBEAN FROM S
AMERICA NWD INTO THE CENTRAL ATLC OVER PUERTO RICO.  RESULTING
FLOW REMAINS PRIMARILY WESTERLY WITH THE SUBTROPICAL JET AND
PACIFIC MOISTURE CONFINED JUST N OF THE AREA.  MODERATE
SUBSIDENCE IS CREATING DRY/STABLE CONDITIONS THROUGHOUT THE
MIDDLE TO UPPER LEVELS OF THE ATMOSPHERE.  AT THE LOWER
LEVELS...A W ATLC STATIONARY FRONT EXTENDS ACROSS THE E TIP OF
CUBA TO NICARAGUA.  NLY FLOW AND WEAK COLD AIR ADVECTION BEHIND
THE FRONT IS SUPPORTING PATCHY LOW CLOUDINESS AND ISOLATED
SHOWERS WITH THE MOST SIGNIFICANT OF THIS ACTIVITY BEING ALONG
WINDWARD FACING SLOPES OF CENTRAL AMERICA.  E OF THE STATIONARY
FRONT...LOW LEVEL MOISTURE IS LIMITED SAVE A SMALL AREA NEAR A
LOW LEVEL ELY TROUGH ALONG 65W S OF 15N.  THIS FEATURE IS
PRODUCING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE
SE CARIBBEAN INCLUDING THE WINDWARD ISLANDS.

ATLANTIC...
A HIGH AMPLITUDE TROUGH-RIDGE-TROUGH PATTERN PREVAILS OVER THE
SUBTROPICAL ATLC WITH A TROUGH OVER THE E UNITED STATES AND
EXTREME W ATLC...RIDGE OVER THE CENTRAL ATLC FROM PUERTO RICO TO
BEYOND 33N55W...AND A BROAD E/W ORIENTED TROUGH OVER THE E
ATLC.  THE MOST ACTIVE WEATHER BY FAR LIES OVER THE W ATLC WHERE
STRONG MID-LATITUDE DYNAMICS INTERACT WITH A MOISTURE LADEN
SUBTROPICAL JET TO PRODUCE WIDESPREAD CLOUDINESS AND SCATTERED
SHOWERS/THUNDERSTORMS.  THE STRONGEST AND MOST NUMEROUS OF THIS
ACTIVITY RESIDES JUST N OF THE AREA WITH A 360 NM WIDE BAND OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG A STATIONARY
FRONT FROM BERMUDA TO E CUBA.  A MUCH STRONGER COLD FRONT
CURRENTLY OVER THE GLFMEX WILL PUSH ACROSS FLORIDA TONIGHT AND
RACE ACROSS THE W ATLC MONDAY AS THE UPPER TROUGH SHARPENS.
THIS WILL RESULT IN A MUCH MORE CONFINED AND INTENSE AREA OF
SHOWERS/THUNDERSTORMS ALIGNING FROM BERMUDA TO THE S BAHAMAS
OVERNIGHT. OVER THE E ATLC...A BROAD MID/UPPER LEVEL TROUGH
REMAINS PLANTED ACROSS THE E/CNTRL ATLC N OF 15N BETWEEN 20W-50W
BUT HAS FLATTENED OUT A BIT SINCE YESTERDAY.  MORE PRONOUNCED
ZONAL FLOW HAS DEVELOPED ACROSS THE TROPICS S OF 15N WITH A 70
KT JET ALONG 12N. RESULTING DIFFLUENT FLOW CONTINUES TO SUPPORT
ENHANCED ITCZ CONVECTION E OF 35W WITH ASSOCIATED CLOUDINESS
STREAMING NEWD OVER THE CAPE VERDE ISLANDS.

$$
RHOME




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