[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201051
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 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 NEGATIVELY TILTED LONGWAVE TROUGH LIES OVER THE E
UNITED STATES AND GLFMEX WITH ATTENDANT COLD FRONT MOVING
QUICKLY SWD ACROSS THE AREA FROM S FLORIDA TO THE W GLFMEX NEAR
26N94W.  THE FRONT IS VIRTUALLY DRY IN TERMS OF CLOUDINESS OR
SHOWERS RENDERING IT NEARLY UNDETECTABLE IN SATELLITE IMAGERY.
HOWEVER...A SHARP DELINEATION IN TEMPERATURE AND DEWPOINT EXIST
BEHIND THE BOUNDARY WITH NUMERICAL GUIDANCE INDICATING A STRONG
SURGE OF CONTINENTAL AIR OVERSPREADING THE AREA MONDAY. THIS
SHOT OF COLD AIR WILL BE BRIEF THOUGH AS HIGH PRESSURE BUILDING
IN BEHIND THE FRONT PROGRESSES QUICKLY EWD OVER THE S UNITED
STATES MOVING INTO THE W ATLC BY EARLY TUE. THIS EVOLUTION WILL
ALLOW THE LOW LEVEL WINDS TO VEER AROUND TO THE EAST PRODUCING A
WARMING TREND TUE AND WED.  WITH DRY NW FLOW IN PLACE
TODAY...LITTLE TO NO SIGNIFICANT PRECIPITATION IS EXPECTED
DURING THE NEXT 24 HOURS.  THEREAFTER...MODERATE RETURN FLOW AND
A DEVELOPING AREA OF LOW PRES WILL REINTRODUCE SHOWERS OR TSTMS
OVER THE NW GULF TUE.

CARIBBEAN...
A STRONG MID/UPPER LEVEL RIDGE EXTENDS E/W ACROSS THE CARIBBEAN
FROM CENTRAL AMERICA NEAR NICARAGUA INTO THE CENTRAL ATLC OVER
THE LEEWARD ISLANDS.  RESULTING UPPER LEVEL 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 THROUGH THE WINDWARD PASSAGE 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 WITHIN 90 NM EITHER SIDE OF THE FRONTAL BOUNDARY.
E OF THE STATIONARY FRONT...A LOW LEVEL ELY TROUGH ALONG 67W IS
PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS S OF 15N E OF
68W.  THIS ACTIVITY IS EXPECTED TO SPREAD WNW INTO THE CENTRAL
CARIBBEAN OVER THE NEXT 24 HOURS.  ELSEWHERE OVER THE E
CARIBBEAN...LOW LEVEL MOISTURE IS LIMITED CREATING MAINLY CLEAR
SKIES.

ATLANTIC...
A HIGH AMPLITUDE TROUGH-RIDGE-TROUGH PATTERN PREVAILS OVER THE
SUBTROPICAL ATLC WITH A STRONG NEGATIVELY TILTED LONGWAVE TROUGH
OVER THE E UNITED STATES AND W ATLC...RIDGE OVER THE CENTRAL
ATLC FROM THE LEEWARD ISLANDS NEWD TO BEYOND 32N55W...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 ABUNDANT TROPICAL MOISTURE TO PRODUCE
WIDESPREAD CLOUDINESS AND SCATTERED SHOWERS/THUNDERSTORMS WITHIN
180 NM EITHER SIDE OF A COLD FRONT EXTENDING FROM JUST E OF
BERMUDA TO 25N70W WHERE IT BECOMES STATIONARY TO THE WINDWARD
PASSAGE. THE DEEPEST CONVECTION ASSOCIATED WITH THIS FRONTAL
BOUNDARY CURRENTLY RESIDES N OF THE AREA BUT STRONGER ACTIVITY
HAS BEEN DEVELOPING S OF 32N OVERNIGHT AS A POTENT SHORTWAVE
DISTURBANCES PUSHES OFF THE SE UNITED STATES COAST. THIS SAME
SHORTWAVE IS ALSO PUSHING A SECOND...MUCH STRONGER...COLD FRONT
OVER THE W ATLC WATERS CURRENTLY LOCATED HALFWAY IN BETWEEN
BERMUDA AND THE MID-ATLANTIC COAST. THE SECOND COLD FRONT WILL
RACE ACROSS THE W ATLC TODAY EVENTUALLY MERGING WITH THE WEAKER
FRONTAL BOUNDARY FURTHER E NEAR BERMUDA.  THIS EVOLUTION SHOULD
RESULT IN A MUCH MORE CONFINED AND INTENSE AREA OF
SHOWERS/THUNDERSTORMS ALIGNING FROM JUST E OF BERMUDA TO THE
TURKS AND CAICOS LATER THIS MORNING. FURTHER E...THERE HAS BEEN
LITTLE OVERALL CHANGE IN THE PATTERN OVER THE E/CENTRAL ATLC
WITH A BROAD MID/UPPER LEVEL TROUGH REMAINING OVER THE AREA FROM
THE CANARY ISLANDS TO 15N50W.  DIFFLUENT UPPER LEVEL FLOW AND A
70 KT UPPER LEVEL JET SE OF THE TROUGH CONTINUE TO SUPPORT
ENHANCED ITCZ CONVECTION BETWEEN 25W-45W WITH ASSOCIATED MID TO
HIGH LEVEL CLOUDINESS STREAMING NEWD OVER THE CAPE VERDE
ISLANDS.  THIS PATTERN WILL LIKELY BE AMPLIFIED FURTHER S AS A
STRONG SHORTWAVE TROUGH CURRENTLY DIVING SEWD OVER THE AZORES
MOVES INTO THE AREA LATER TODAY.  THIS WILL RESULT IN A LARGE
CUTOFF LOW FORMING BY MID-WEEK PRODUCING INCREASING CLOUDINESS
AND SHOWERS/THUNDERSTORMS N OF 20N.  MEANWHILE...STRONG ITCZ
CONVECTION WILL CONTINUE OVER THE FAR E PORTION OF THE AREA.

$$
RHOME





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