[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SAT 12 FEB 2005

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 4N1W 4N30W 2N50W. SCATTERED SHOWERS
AND A FEW ISOLATED THUNDERSTORMS EXIST WITHIN 90 NM EITHER SIDE
OF THE ENTIRE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
COOL/DRY WEATHER REMAINS OVER THE E GULF OF MEXICO AND FL AS
CONTINENTAL AIR CONTINUES TO FILTER SWD BEHIND A COLD FRONT NOW
WELL SE OF THE AREA. MEANWHILE...RETURN FLOW IS BEGINNING TO
DEVELOP OVER THE W GULF AS HIGH PRES BUILDS SWD ALONG 90W.  THE
DEVELOPMENT OF THE RETURN FLOW OVER THE W GULF IS RESULTING IN
THE SCOURING OUT OF BLOCKED FLOW AND STATIONARY FRONT ALONG THE
SIERRA MADRE ORIENTAL MOUNTAINS OF MEXICO.  LOOKING UPSTREAM...A
MIDDLE TO UPPER LEVEL TROUGH LOCATED OVER THE SW UNITED STATES
INTO NW MEXICO WILL BE THE NEXT WEATHER SYSTEM TO AFFECT THE
AREA AS IT ADVANCES QUICKLY EWD REACHING THE CENTRAL UNITED
STATES TOMORROW.  ASSOCIATED COLD FRONT WILL MOVE OFF THE SE
COAST OF TEXAS LATE SUNDAY INTO SUNDAY NIGHT PRECEDED BY
INCREASING CLOUDINESS AND A DEVELOPING AREA OF SCATTERED
SHOWERS/THUNDERSTORMS.  THE FRONT WILL LOSE MUCH OF ITS SUPPORT
AND STRENGTH AS IT SWEEPS ACROSS THE GULF THROUGH EARLY NEXT
WEEK.  MEANWHILE...HIGH PRES CURRENTLY OVER THE CENTRAL GULF
WILL SLIDE QUICKLY EWD INTO THE ATLC WATERS DURING THE NEXT 24
HOURS IN ADVANCE OF UPSTREAM COLD FRONT WITH RIDGE EXTENDING
ACROSS CENTRAL FLORIDA BY SUNDAY EVENING.

CARIBBEAN...
MIDDLE TO UPPER LEVEL RIDGING GRIPS MOST OF THE CARIBBEAN WITH
MODERATE/STRONG SUBSIDENCE PRODUCING A DRY/STABLE ENVIRONMENT
ALOFT.  STRONG MID-LATITUDE UPPER TROUGH OVER THE W ATLC SKIRTS
THE N EXTENT OF THE AREA WITH ATTENDANT COLD FRONT ENTERING THE
AREA OVER HISPANIOLA THEN DISSIPATING TO COSTA RICA.  CLOUDINESS
AND SHOWERS ALONG THE BOUNDARY HAS MOSTLY DISSIPATED AS THE
BOUNDARY WASHES OUT AND NLY FLOW BLEEDS ACROSS WHAT REMAINS OF
THE AIRMASS DISCONTINUITY.  COLD AIR STRATOCUMULUS CLOUDS
CONTINUE OVER THE NW CARIBBEAN WITH SOME LOW CLOUDS AND A FEW
ISOLATED SHOWERS ALONG THE WINDWARD FACING SLOPES OF CENTRAL
AMERICA.  FARTHER E...A LOW LEVEL TROF IS LOCATED OVER THE
LESSER ANTILLES FROM GUADELOUPE TO THE ABC ISLANDS. SCATTERED
SHOWERS LIE WITHIN 125 NM EITHER SIDE OF THE BOUNDARY N OF 14N
WITH WIDELY SCATTERED SHOWERS ELSEWHERE.  THIS ACTIVITY AND
ASSOCIATED MOISTURE IS EXPECTED TO POOL ALONG THE APPROACHING
UPSTREAM COLD FRONT PRODUCING INCREASING SHOWERS AND
THUNDERSTORMS OVER THE LEEWARD ISLANDS TONIGHT AND TOMORROW.
THE FRONT AND SHOWER ACTIVITY THEN BEGINS TO MIGRATE WESTWARD
TOWARD PUERTO RICO EARLY IN THE WEEK.

ATLANTIC...
A MODERATE TO STRONG COLD FRONT IS SWEEPING ACROSS THE W ATLC
WATERS FROM 32N55W SW TO THE NE TIP OF HISPANIOLA WITH A BAND OF
LOW CLOUDS/WIDELY SCATTERED SHOWERS WITHIN 90 NM E OF THE FRONT
PRIMARILY N OF 26N.  ELSEWHERE W OF FRONT...A BROKEN
STRATOCUMULUS FIELD EXTENDS BACK TO WITHIN 200 NM OF THE
FLORIDA/SE U.S. COAST.  WATER VAPOR IMAGERY INDICATES THAT THE
ASSOCIATED UPPER TROF HAS BEGUN TO LIFT NEWD AS A STRONG
SHORTWAVE BEGINS TO ROUND THE BASE. THE SHORTWAVE HAS BROUGHT
DOWN A REINFORCING SURGE OF COLD AIR CURRENTLY EXTENDING FROM
31N60W TO THE CENTRAL BAHAMAS. THE SHORTWAVE WILL ALSO PRODUCE A
BRIEF PERIOD OF STRONG DIFFLUENT FLOW ALOFT AS IT ROUNDS THE
BASE POSSIBLY ALLOWING AN INCREASE IN SHOWER AND THUNDERSTORM
ACTIVITY ALONG THE FRONT LATER TODAY MAINLY N OF 25N.  SHIFTING
EWD...AN UPPER RIDGE IS LOCATED OVER THE CENTRAL ATLC FROM JUST
E OF THE LESSER ANTILLES NEWD TO THE CANARY ISLANDS. UPSTREAM
MOISTURE IS PRIMARILY RIDING UP AND OVER THE RIDGE LEAVING THE
AREA E OF 45W MAINLY UNDER SUBSIDENCE AND DRY AIR.  OVER THE E
ATLC...A LARGE AND ELONGATED UPPER LEVEL LOW IS CENTERED JUST NW
OF THE CANARY ISLANDS NEAR 30N18W WITH ASSOCIATED TROF TRAILING
SWD PENETRATING INTO THE TROPICAL ATLC ALONG 20N30W 12N42W.
THE UPPER LOW IS UNDERLAIN BY A BROAD SFC RIDGE STRETCHING FROM
A 1041 MB HIGH NEAR THE AZORES SW INTO THE CNTRL ATLC NEAR
22N55W. THE SURFACE HIGH IS PRODUCING A TIGHT PRES GRADIENT OVER
THE SUBTROPICAL E ATLC WATERS RESULTING ELY WINDS TO NEAR GALE
FORCE.  THIS STRONG EASTERLY FLOW HAS ADVECTED A DENSE PLUME OF
AFRICAN DUST OFFSHORE FROM 20N-30N E OF 32W...INCLUDING THE
CANARY ISLANDS.  SEVERAL SITES IN THE CANARY ISLANDS...WHICH
LIES ON THE EDGE OF THE PLUME...ARE REPORTING VISIBILITIES
REDUCED TO 4-5 MILES AND IS IT LIKELY THAT VISIBILITIES ARE EVEN
LOWER WITHIN THE MAIN PART OF THE PLUME TO THE SOUTH. ELSEWHERE
OVER THE TROPICAL E ATLC...STRONG ZONAL WESTERLY UPPER FLOW
EXTENDS ACROSS THE REGION IN ASSOCIATION WITH AN ACTIVE 100 KT
JET ALONG 12N40W NEWD INTO AFRICA OVER W SAHARA. DYNAMICS/LIFT
ASSOCIATED WITH THE JET ALONG WITH COPIOUS TROPICAL MOISTURE
ADVECTION IS PRODUCING WIDESPREAD CLOUDINESS AND POSSIBLE
SHOWERS WITHIN 250 NM EITHER SIDE OF A LINE FROM 5N36W TO BEYOND
20N10W.

$$
RHOME




WWWW
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