[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181749
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI 18 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 8N1W 2N20W 2N30W EQ50W. WIDELY
SCATTERED STRONG CONVECTION WITHIN 60 NM EITHER SIDE OF ITCZ
FROM 15W-30W. SCATTERED TO LOCALLY NUMEROUS STRONG CONVECTION S
OF 2N BETWEEN 40W-46W.

...DISCUSSION...

GULF OF MEXICO...
IN THE UPPER LEVELS...BROAD RIDGING DOMINATES THE GULF AND
MEXICO KEEPING UPSTREAM DISTURBANCES N OF THE AREA. THE
SUBTROPICAL JET AND ASSOCIATED PACIFIC MOISTURE RIDES UP AND
OVER THE RIDGE INTO THE S UNITED STATES LEAVING THE AREA S OF
30N UNDER MODERATE SUBSIDENCE AND DRY/STABLE AIR ALOFT. AT THE
SURFACE...A WEAKENING COLD FRONT IS PUSHING SWD OVER THE GULF
FROM THE FLORIDA STRAITS WNW THROUGH 26N90W WHERE IT BECOMES
STATIONARY INTO INTERIOR MEXICO ALONG THE SIERRA MADRE ORIENTAL
MOUNTAINS JUST S OF THE TEXAS BORDER.  WHILE LACKING SIGNIFICANT
UPPER SUPPORT...LOW LEVEL MOISTURE POOLING ALONG THE BOUNDARY IS
PRODUCING SCATTERED SHALLOW TOPPED SHOWERS WITHIN 60 NM EITHER
SIDE OF FRONT ESPECIALLY BETWEEN 83W-90W.  WIDELY SCATTERED
ACTIVITY ACCOMPANIES THE FRONT W OF 90W WITH A MAINLY DRY FROPA
OCCURRING OVER THE FLORIDA KEYS AND STRAITS.  POLEWARD OF THE
BOUNDARY...DRIER CONTINENTAL AIR IS FILTERING SWD RESULTING IN
MAINLY CLEAR CONDITIONS ALONG THE N GULF COAST AND MUCH OF
FLORIDA.  THE ONLY OTHER ACTIVITY OF NOTE IS A SMALL AREA OF
SCATTERED SHOWERS OVER THE SW GULF AND BAY OF CAMPECHE ALONG AND
WEST OF A WEAK TROF FROM THE ISTHMUS OF TEHUANTEPEC TO 23N94W.
SHOWER ACTIVITY OVER THE ENTIRE AREA SHOULD DIMINISH DURING THE
NEXT 24 HOURS AS THE FRONTAL BOUNDARY WASHES OUT AND LOW LEVEL
MOISTURE BECOMES MORE LIMITED.  RELATIVELY DRY CONDITIONS SHOULD
CONTINUE THROUGH MUCH OF SUNDAY PRIOR TO THE NEXT UPSTREAM
SYSTEM APPROACHING THE NW GULF LATE SUN.

CARIBBEAN...
MID/UPPER LEVEL RIDGE REMAINS IN PLACE FROM VENEZUELA TO THE
YUCATAN CHANNEL RESULTING IN MAINLY ZONAL FLOW ACROSS THE
CARIBBEAN SEA. STRONG SUBSIDENCE AND DRY/STABLE AIR ALOFT
CONTINUES TO DOMINATE THE AREA LIMITING SIGNIFICANT WEATHER TO
ISOLATED SHALLOW TOPPED SHOWERS. NE LOW LEVEL FLOW IS PRODUCING
CLOUDINESS AND SHOWER ACTIVITY ALONG THE WINDWARD FACING SLOPES
OF W PANAMA...COSTA RICA...AND SE NICARAGUA.  HIGH PRES RIDGE
BUILDING SWD JUST N OF THE AREA HAS TIGHTENED THE PRESSURE
GRADIENT LEADING TO INCREASING ELY TRADES. LOW LEVEL MOISTURE
AND SHOWER ACTIVITY SHOULD REMAIN MINIMAL THROUGH THE WEEKEND
PRIOR TO THE ARRIVAL OF A DIFFUSE FRONTAL BOUNDARY OVER THE NE
CARIBBEAN SUNDAY NIGHT.

ATLANTIC...
A BROAD/FLAT UPPER TROUGH IS SKIRTING THE N PORTION OF THE W
ATLC N OF 25N W OF 55W WITH ATTENDANT COLD FRONT ENTERING THE
AREA E OF OF BERMUDA ALONG 32N58W TO THE N BAHAMAS. THE FRONT
LACKS SIGNIFICANT UPPER SUPPORT WITH ONLY A NARROW CLOUD LINE
AND ISOLATED SHOWERS ALONG THE LEADING EDGE.  THE FRONT IS
QUICKLY LOSING ITS THERMAL GRADIENT WITH A NOTICEABLE ABSENCE OF
THE TYPICAL POST-FRONTAL COLD AIR STRATOCUMULUS.  SHIFTING
EWD...A SHORTWAVE MIDDLE TO UPPER LEVEL TROUGH OVER THE CENTRAL
ATLC ALONG 45W IS PRODUCING AN AREA OF CLOUDINESS AND SCATTERED
SHOWERS/THUNDERSTORMS FROM 20N-32N BETWEEN 33W-43W.  THIS
ACTIVITY SHOULD WEAKEN OVER THE NEXT 24 HOURS AS THE UPPER
SHORTWAVE BECOMES SHEARED OUT BY THE MUCH LARGER SCALE UPSTREAM
TROUGH. OVER THE E ATLC...A MID/UPPER LEVEL TROUGH IS SAGGING
SWD OVER NW AFRICA WITH ACCOMPANYING LOW LEVEL WIND SURGE
EXTENDING FROM CENTRAL W SAHARA NW TO BEYOND 32N30W. BROKEN LOW
TO MID LEVEL CLOUDINESS WITH ISOLATED SHOWERS AND WINDS
INCREASING TO 20-30 KT IS NOTED POLEWARD OF THE SURGE.  FURTHER
S...VISIBLE SATELLITE IMAGERY CONTINUES TO INDICATE AN AREA OF
AFRICAN DUST MAINLY S AND E OF THE CAPE VERDE ISLANDS TO THE
ITCZ.  THE HIGHEST CONCENTRATION EXTENDS AS FAR WEST AS 30W WITH
LESSER AMOUNTS TO 40W.

$$
RHOME


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