[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 240546
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST FRI 24 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...ITCZ...

ITCZ AXIS IS ALONG 8N14W 5N25W 5N40W 3N51W.  ISOLATED MODERATE S
OF 4N BETWEEN 25W-37W.  WIDELY SCATTERED MODERATE WITHIN 60 NM
OF LINE 6.5N22W 7.5N30W.

...DISCUSSION...

GULF OF MEXICO...
COLD AIR IS ENTRENCHED INTO THE DEEP SOUTH WITH FREEZING
TEMPERATURES TOUCHING THE NORTHERN GULF WATERS.  FRONT
RESPONSIBLE FOR ALL THE CHILLY WEATHER LIES FROM CENTRAL FLORIDA
TO THE NW TIP OF THE YUCATAN PENINSULA WITH OVERCAST MULTILAYER
CLOUDS COVERING THE ENTIRE AREA W OF THE FRONT.  PARTLY CLOUDY
CONDITIONS ARE AHEAD OF THE FRONT WITH A FEW SHOWERS AND RATHER
MUGGY AIR IN THE SE GULF.  THE SUBTROPICAL JET IS PULLING TONS
OF MOISTURE ACROSS MEXICO OVER THE NW GULF...SIGNS OF AN
OVERRUNNING PATTERN COMMENCING OVER THE COLD AIR DOME WITH
ENOUGH MOISTURE FILTERING INTO THE LOW-LEVELS FOR SOME SHOWERS
NEAR TEXAS.  UPPER SYSTEM RESPONSIBLE FOR THE CLOUDS/LIGHT RAIN
IS OVER NW MEXICO...SHIFTING EASTWARD WHICH SHOULD FORM A LOW IN
THE W-CENTRAL GULF LATER TODAY.  THERMAL/MOISTURE PROFILES ARE
MARGINAL FOR WINTRY PRECIP WITH LIMITED MOISTURE KEEPING THE
BULK OF THE PRECIP OFFSHORE.  LIGHT SLEET/FLURRIES COULD OCCUR
LATER TODAY INTO XMAS ALONG IMMEDIATE AREAS OF THE NORTHERN GULF
COAST AND INLAND S TEXAS BUT MODEL GUIDANCE HAS COME INTO FAIRLY
GOOD AGREEMENT SUGGESTING A GENERALLY CLOUDY RATHER THAN A WHITE
CHRISTMAS FOR THE SOUTH.  BIG WEATHER CHANGE IS LIKELY AFTER THE
WEEKEND WITH A NEGATIVE PNA PATTERN (WESTERN UPPER TROUGH/
EASTERN UPPER RIDGE) DEVELOPING OVER THE CONUS...BRINGING MUCH
WARMER WEATHER BY EARLY NEXT WEEK.

CARIBBEAN SEA AND W ATLC W OF 60W...
VERY DRY AIR IN THE MID/UPPER LEVELS DOMINATES THE CARIBBEAN
WITH WLY FLOW FROM INCREASING RIDGING OVER THE AREA BRIDGING NE
INTO THE W ATLC.  FEW POCKETS OF SHOWERS ARE STREAMING WESTWARD
THRU THE AREA OTHERWISE LESS SHOWERS THAN TYPICAL.  DEWPOINTS
HAVE DROPPED IN PUERTO RICO AND THE NORTHERN LEEWARD ISLANDS
TODAY WITH A BIT OF DRIER AIR FILTERING INTO THE AREA. NO
SYNOPTIC-SCALE SYSTEMS ARE FORECAST TO AFFECT THE CARIBBEAN THRU
THE WEEK OTHER THAN THE FRONT ENTERING THE NW CARIBBEAN BRIEFLY
LATE TODAY THEN RETREATING BEFORE RETURNING BY LATE XMAS.  A
DEEPENING TROUGH IN THE CENTRAL ATLC HAS LEFT THE W ATLC ON THE
DRY CONVERGENT SIDE OF THE UPPER TROUGH AXIS... WITH DECREASING
MID/UPPER MOISTURE FROM W TO E AND NW FLOW ALOFT.  CONSIDERABLY
LESS CLOUDINESS IS OVER THE W ATLC WITH ONLY SCATTERED LOW
CLOUDS AS ALL OF THE COLD AIR HAS MODIFIED OVER WARM WATERS.
COLD FRONT EXTENDS FROM CENTRAL FLORIDA TO 31N79W WITH A FEW
SHOWERS AND OVERCAST CLOUDS BLANKETING THE AREA BEHIND THE FRONT.

CENTRAL/E ATLANTIC...
1011 LOW IS ALONG A NW-SE ORIENTED SURFACE TROUGH FROM 32N48W TO
THE LOW WITH GALE-FORCE WINDS N OF THE LOW AND TROUGH.
EXTENDING THE LOW NW TO 32N40W.   DEEP MID/UPPER LOW NEAR 29N40W
CONTINUES TO PROVIDE LIFT/DIVERGENCE FOR A BAND OF WIDELY
SCATTERED WEAK/MODERATE CONVECTION WITHIN 90 NM OF LINE 24N27W
28N32W 31N43W.  COMPUTER MODELS SUGGEST THE LOW WILL CONTINUE TO
TRACK WNW WITH THE LOW PROBABLY STAYING MORE EXTRATROPICAL THAN
SUBTROPICAL.  OF COURSE NOW THE MODELS ARE HINTING AT THE
POSSIBILITY OF ANOTHER LOW FORMING IN A COUPLE DAYS NEAR 25N45W
OUT OF A MESS OF MOISTURE NOW IN THE CENTRAL ATLC.  I GUESS THIS
IS WHAT HAPPENS WHEN THE ATLC OCEAN IS MUCH WARMER THAN AVERAGE
WITH PERSISTENT TROUGHING OVER THE AREA.  SECOND LOW MAY FORM
DUE TO MID/UPPER TROUGH NOW ALONG 56W N OF 22N FORECAST TO SHIFT
EASTWARD SLOWLY.  WIDELY SCATTERED SHOWERS LIE FROM 17N-27N
BETWEEN 45W-55W WITH ONLY A FEW TSTMS WITHIN 75 NM OF 12N37.5W
AS THE DEEP TROPICS HAVE MOSTLY DRIED OUT.  SYSTEMS ALONG 40W
AND 56W FORM A DEEP TROUGH COVERING THE CENTRAL ATLC BETWEEN
25W-65W N OF 25N WITH ITCZ ACTIVITY LIMITED TO THE E ATLC WITH
LOTS OF DRY AIR ALOFT.  IN THE E ATLC... UPPER MOISTURE IS
LIMITED TO S OF 23N E OF 29W WITH UPPER RIDGING IN PLACE SAVE
DRY CYCLONIC FLOW FROM A MID/UPPER CYCLONE OVER SOUTHERN MOROCCO.

$$
BLAKE

This weather bulletin was brought to you by:
www.nashvilleweather.net