[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201747
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED 20 OCT 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA... GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE OVER THE CENTRAL TROPICAL ATLC ALONG 50W MOVING W
10-15 KT.  THE CURRENT POSITION IS SEVERAL DEGREES AHEAD OF THE
O600 UTC POSITION BASED LATEST QUIKSCAT DATA AND SATELLITE
IMAGERY.  THE WAVE IS LOCATED JUST E OF A MID-UPPER LEVEL LOW
NEAR 14N55W WHICH IS PRODUCING UPPER LEVEL DIVERGENCE AND
ASSISTING THE DEVELOPMENT OF NUMEROUS MODERATE/STRONG CONVECTION
FROM 10N-19N BETWEEN 42W-48W. HOWEVER...THE UPPER LOW IS ALSO
PRODUCING STRONG WLY SHEAR LIMITING THE ORGANIZATION OF THIS
CONVECTION.  THE UPPER LOW IS FORECAST TO REMAIN NEARLY
STATIONARY OVER THE NEXT DAY OR SO MAINTAINING SHEAR OVER THE
WAVE AS IT CONTINUES WEST.

TROPICAL WAVE OVER THE CARIBBEAN ALONG 74W/75W S OF 20N MOVING W
10 KT. THE WAVE IS ENCOUNTERING STRONG SW SHEAR ASSOCIATED WITH
A LARGE MIDDLE TO UPPER LEVEL TROUGH TO THE WEST.  THE SHEAR IS
DISPLACING ALL OF THE DEEP CONVECTION EAST OF THE WAVE WITH
SCATTERED MODERATE ACTIVITY FROM 11N-15N BETWEEN 69W-73W.  THE
WAVE WILL CONTINUE TO BE IN AN UNFAVORABLE UPPER LEVEL
ENVIRONMENT OVER THE FEW DAYS LIMITING DEVELOPMENT.

...ITCZ...
ITCZ AXIS IS ALONG 10N10W 6N25W 10N40W 12N50W 11N60W 9N80W.
SCATTERED MODERATE TO STRONG CONVECTION FROM 9N-14N BETWEEN
30W-41W.  WIDELY SCATTERED MODERATE CONVECTION FROM 4N-9N
BETWEEN 30W-43W.  WIDELY SCATTERED MODERATE CONVECTION S OF 12N
BETWEEN 76W-83W INCLUDING COSTA RICA AND PANAMA.

...DISCUSSION...
GULF OF MEXICO...
LARGE MID/UPPER LEVEL ANTICYCLONE IS CENTERED OVER CENTRAL
MEXICO NEAR 22N100W WITH RIDGE AXIS EXTENDING ESE OVER THE
YUCATAN PENINSULA INTO THE NW CARIBBEAN. DRY NW FLOW COVERS THE
ENTIRE GLFMEX RESTRICTING SIGNIFICANT CLOUDS/CONVECTION.  A
SHORTWAVE TROUGH IS DROPPING RAPIDLY SEWD OVER THE SE UNITED
STATES BUT UPPER LEVEL DYNAMICS AND ASSOCIATED CLOUDS/CONVECTION
ARE E OF THE AREA OVER THE W ATLC WATERS.  THE OVERALL PATTERN
WILL BECOME MORE AMPLIFIED DURING THE NEXT 36 HOURS AS THE
AFOREMENTIONED SHORTWAVE TROUGH OVER THE SE UNITED STATES CARVES
OUT A MUCH LARGER TROUGH OVER THE W ATLC WHILE THE ANTICYCLONE
OVER MEXICO BUILDS NWD INTO THE CENTRAL UNITED STATES.  THIS
SHOULD KEEP THE GLFMEX UNDER DRY/TRANQUIL WEATHER SAVE FLORIDA
WHERE A WEAK FRONT SWEEPING THROUGH THE STATE TONIGHT AND
TOMORROW MAY SPARK WIDELY SCATTERED CONVECTION.

CARIBBEAN...
MIDDLE TO UPPER LEVEL TROUGH FROM HISPANIOLA TO CENTRAL AMERICA
NEAR COSTA RICA DOMINATES MUCH OF THE CARIBBEAN WITH DRY NLY
FLOW TO THE WEST PRODUCING TRANQUIL WEATHER AND MOIST SE FLOW TO
THE EAST PRODUCING HIGH CLOUDINESS AND WIDELY SCATTERED
SHOWERS/THUNDERSTORMS.  CONVECTION HAS BEEN PRIMARILY FOCUSED
JUST E OF A TROPICAL WAVE MOVING SOUTH OF HISPANIOLA AS WELL AS
ALONG A WEAK LOW LEVEL ELY DISTURBANCE ALONG 63W.  SCATTERED
SHOWERS/THUNDERSTORMS ARE ALSO NOTED OVER THE SW CARIBBEAN AND
PORTIONS OF CENTRAL AMERICA S OF 13N BETWEEN 80W-84W. THE
PATTERN WILL REMAIN ESSENTIALLY UNCHANGED DURING THE NEXT 24
HOURS.  THIS WILL KEEP MUCH OF THE CENTRAL TO E CARIBBEAN UNDER
A UNSETTLED/WET PATTERN AND THE NW CARIBBEAN UNDER A DRY
PATTERN.

SUBTROPICAL ATLANTIC...
VIGOROUS SHORTWAVE TROUGH MOVING OVER THE SE UNITED STATES IS
THE BIGGEST WEATHER MAKER WITH AN IMPRESSIVE AREA OF NUMEROUS
MODERATE CONVECTION TO THE EAST OVER THE NW ATLC WATERS.  THE
MAIN ACTIVITY IS CURRENTLY WITHIN 150 NM EITHER SIDE OF A LINE
FROM 32N75W TO SE FLORIDA NEAR PALM BEACH.  THIS ACTIVITY SHOULD
SLOWLY WEAKEN S OF 31N OVERNIGHT AS THE MAIN ENERGY/DYNAMICS
SHIFT N OF THE AREA.  HOWEVER...THE SHORTWAVE TROUGH WILL DROPS
INTO AND AMPLIFY A LARGER SCALE TROUGH OVER THE W ATLC FROM
32N60W TO THE S BAHAMAS/TURKS AND CAICOS.  THIS AMPLIFICATION
SHOULD PRODUCE LARGE SCALE DIVERGENT FLOW OVER THE CENTRAL ATLC
AND TAP INTO COPIOUS MOISTURE OVER THE E CARIBBEAN AND TROPICAL
ATLC.  THIS SCENARIO WILL PRODUCE INCREASING CLOUDINESS AND
SHOWERS/THUNDERSTORMS TO THE EAST OF THE UPPER TROUGH AXIS WHICH
WILL BE LOCATED ROUGHLY HALFWAY IN BETWEEN BERMUDA AND THE SE
UNITED STATES TO CENTRAL CUBA BY FRIDAY.  THE BEST DYNAMICS/LIFT
WOULD BE FOCUSED BETWEEN 45W-65W UNDER THIS REGIME.  OVER THE
CENTRAL AND E ATLC...BROAD/FLAT RIDGE CURRENTLY IN PLACE WILL
BUILD NWD DURING THE NEXT FEW DAYS.  A 70 KT SUBTROPICAL JET
EXTENDING AROUND THE N PERIPHERY OF THE RIDGE ALONG 27N IS
PRODUCING SOME HIGH CLOUDINESS.  OTHERWISE...GENERALLY DRY
CONDITIONS PREVAIL.  A MID-LATITUDE TROUGH N OF THE AREA
DROPPING RAPIDLY SWD ALONG 35N WILL CLIP THE NE PORTION OF THE
AREA LATE THU INTO FRIDAY POSSIBLY PRODUCING SOME WIDELY
SCATTERED SHOWERS OVER THE CANARY ISLANDS.

TROPICAL ATLANTIC...
NEAR STATIONARY...CUTOFF MID/UPPER LOW LIES OVER THE W TROPICAL
ATLC NEAR 14N55W WITH DIVERGENT FLOW TO THE EAST ENHANCING
CONVECTION ALONG A WAVE NEAR 50W. HOWEVER...THE UPPER LOW IS
ALSO PRODUCING SHEAR OVER THE WAVE AND LIMITING DEVELOPMENT.
ELSEWHERE...WELL DEFINED ANTICYCLONE IS LOCATED NEAR 12N30W.
DIVERGENT FLOW EQUATORWARD OF THE RIDGE IS PROMOTING ITCZ
CONVECTION FROM 30W-40W.

$$
RHOME


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