[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 221134
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST WED 22 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
1115 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N11W 4N25W 5N45W 4N53W.  ISOLATED
SHOWERS WITHIN 120 NM OF 8N38W.  ISOLATED MODERATE CONVECTION
WITHIN 90 NM OF 4.5N24.5W.

...DISCUSSION...

GULF OF MEXICO...
SCATTERED SHOWERS/TSTMS ARE ALONG THE LOUISIANA SHORE WITH THE
COMBINATION OF A NEARBY WEAK SURFACE TROUGH AND DIVERGENCE AHEAD
OF UPPER ENERGY PULLING OUT OF THE SOUTHWEST USA ASSISTING THE
SHOWERS N OF 28N BETWEEN 88W AND 95W.  OTHERWISE MOIST RETURN
FLOW COVERS THE GULF WITH SLY WINDS NEAR 25 KT IN THE N GULF.
SEVERE STORMS APPEAR TO BE POSSIBLE LATER TODAY ALONG THE GULF
COAST AS A STRONG COLD FRONT ENTERS THE REGION COMBINED WITH THE
UPPER DISTURBANCE PROVIDING LIFT AND SOME INSTABILITY.
FORECAST WIND PROFILES ALSO SUGGEST THE THREAT FOR A FEW
TORNADOES GIVEN THE STRONG TURNING IN THE LOWER TROPOSPHERE
THOUGH CAPE VALUES ARE NOT PARTICULARLY HIGH.  MUCH COLDER
CONDITIONS ARE LIKELY FOR THU OVER MUCH OF REGION AS THE ARCTIC
FRONT JUST ABOUT BISECTS THE AREA.  A WAVE SHOULD FORM ON THE
FRONT IN THE W-CENTRAL GULF LATE THU AS ANOTHER PIECE OF ENERGY
EXITS THE SW USA.  THE TRACK OF THIS LOW PRESSURE WAVE IS
CRITICAL IN DETERMINING WHETHER PLACES IN THE DEEP SOUTH HAVE
ANY CHANCE OF WINTRY PRECIPITATION XMAS EVE INTO XMAS DAY.  THE
GFS CONTINUES TO SUGGEST A BETTER CHANCE OF WINTRY WEATHER THAN
THE ETA WHICH KEEPS MOST SIGNIFICANT PRECIP OFFSHORE.  THE TREND
IN THE MODELS HAS BEEN TO DEVELOP THE LOW FARTHER SOUTHWARD...
WHICH WOULD LESSEN THE THREAT OF FROZEN PRECIP ALONG THE GULF
COAST EXCEPT FOR SE TEXAS. IN ANY EVENT A COLD XMAS IS LIKELY
FOR A GOOD CHUNK OF THE SRN US EXCEPT FOR MAYBE S FLORIDA.

WEST ATLANTIC...
STATIONARY FRONT LIES ALONG 31N53W TO NW DOMINICAN REPUBLIC WITH
ISOLATED TSTMS WITHIN 90 NM OF THE FRONT BETWEEN 22N-27N. 1029
MB HIGH IS NEAR BERMUDA WITH RIDGING WSW THRU S FLORIDA STRAITS
INTO THE SRN GULF.  THERE ARE PLENTY OF LOW/MID CLOUDS W OF THE
FRONT WITH COLD AIR ONLY SLOWLY MODIFYING OVER THE WARM W ATLC
WATERS W OF THE FRONT... BECOMING MORE SCATTERED OVER THE
BAHAMAS.  FAST-MOVING SHORTWAVE JUST E OF BERMUDA IS ZIPPING E
IN MOSTLY ZONAL FLOW AND IS PRODUCING AN AREA OF HIGH LEVEL
CLOUDINESS N OF 25N BETWEEN 53W-73W.    COLD FRONT SCHEDULED TO
ENTER THE GULF LATER TODAY SHOULD HIT THE W ATLC BY LATE THU BUT
IS NOT EXPECTED TO HAVE NEARLY THE PUNCH OF THE LAST SYSTEM WITH
THE MAIN UPPER TROUGH AXIS HANGING AROUND IN THE CENTRAL US.

CARIBBEAN...
STATIONARY FRONT HAS DISSIPATED WITH ONLY A FEW SHOWERS FROM W
JAMAICA TO CENTRAL HONDURAS.  ELSEWHERE IN THE LOW-LEVELS WEAK
TROUGHING IS MOVING W IN THE SW CARIBBEAN WITH WIDELY SCATTERED
SHOWERS S OF 15N W OF 73W.  UPPER LEVEL HIGH IS LINGERING IN NW
VENEZUELA...CONTINUING BROAD SW/W FLOW ACROSS THE CARIBBEAN
SEA.  DRY AIR IN THE MID/UPPER LEVELS LIMITS MOST CONVECTION
WITH ONLY SHALLOW SHOWERS OCCURRING EXCEPT NEAR SAN ANDRES
ISLAND.  MOSTLY DRY WEATHER APPEARS LIKELY FOR THE AREA FOR THE
NEXT COUPLE DAYS WITH ONLY ISOLATED TRADEWIND SHOWERS.

CENTRAL AND EASTERN ATLANTIC...
MID/UPPER LEVEL LOW IS NEAR 18N40W WITH TROUGHING S TO 5N42W AND
A SURFACE TROUGH REFLECTION FROM 12N39W TO 23N37W.  LOW IS PART
OF A BROAD TROUGH IN THE CENTRAL ATLC ALONG 38W WITH THE NEXT
SPOKE OF ENERGY ROTATING ON THE N SIDE NEAR 30N37W.  THIS SECOND
UPPER DISTURBANCE ALSO HAS A SURFACE REFLECTION.. CONTINUING THE
SURFACE TROUGH FROM 23N37W TO 32N34W.  ISOLATED SHOWERS ARE
WITHIN 150 NM E OF THE BOUNDARY.  VERY DRY AIR ALOFT LIES BEHIND
THE UPPER TROUGH AXIS DUE TO CONVERGENCE ON THE BACKSIDE OF THE
TROUGH.  HOWEVER BROAD DIFFLUENCE CONTINUES TO ENHANCE WIDELY
SCATTERED MODERATE CONVECTION IN THE TROPICAL ATLC FROM 12N-23N
BETWEEN THE CAPE VERDE ISLANDS AND 40W.   A WEAK LOW SHOULD FORM
BY THU AROUND 22N35W AND WILL HAVE TO BE MONITORED AS SEVERAL
MODELS SUGGEST IT COULD BE OF A "HYBRID" TYPE WITH SOME POSSIBLE
SUBTROPICAL CHARACTERISTICS.  HOWEVER THIS SITUATION IS
UNCERTAIN AS THE LOW WILL LIKELY BE OVER VERY COOL WATER TEMPS
NEAR 23C.. MAKING ANY SUBTROPICAL SYSTEM LESS LIKELY.
ELSEWHERE...SCATTERED/BROKEN LOW CLOUDS REMAIN OVER THE
SUBTROPICAL ATLC OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE
CENTRAL ATLC TROUGH.  UPPER LEVEL RIDGING COVERS THE E ATLC...
BRINGING AREAS OF HIGH CLOUDINESS OVER THE E ATLC INTO W AFRICA.

$$
BLAKE

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