[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 012352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT DEC 01 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 6N10W 5N25W 3N40W 4N52W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
WITHIN 70 NM SOUTH OF AXIS E OF 14W TO THE COAST OF W AFRICA AND
BETWEEN 18W-22W. A CLUSTER OF MODERATE CONVECTION IS N OF THE
AXIS FROM 9N-13N BETWEEN 50W-54W. A DIFFLUENT PATTERN ALOFT IS
ENHANCING THIS SHOWER/TSTM ACTIVITY.

DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE DOMINATES THE E HALF OF THE U.S. EXTENDING SOUTH
OVER THE ENTIRE GULF OF MEXICO. AS A RESULT...MOSTLY FAIR
WEATHER AND LIGHT TO MODERATE WINDS PREVAIL ACROSS MOST OF THE
REGION WITH SLY 15-20 KT RETURN FLOW JUST OFF THE TEXAS COAST.
SOME PATCHES OF LOW LEVEL CLOUDS ARE ALSO SEEN. ALOFT...AN UPPER
RIDGE CENTERED ON A HIGH OVER THE N-CENTRAL GULF WATERS COVERS
THE AREA. MODERATE TO STRONG UPPER LEVEL SUBSIDENCE AND IMPLIED
DRY AIR MASS IS NOTED WITHIN THE RIDGE AXIS. A SUBTROPICAL JET
IS RIDING IN THE N PERIPHERY OF THIS ANTICYCLONE. THESE STRONG
WINDS ARE TRANSPORTING MID TO UPPER LEVEL MOISTURE FROM THE EPAC
THROUGH N-CENTRAL MEXICO INTO TEXAS AND THE SE U.S.. HIGH PRES
OVER THE EASTERN SEABOARD WILL SHIFT E THROUGH SUN IN ADVANCE OF
A STRONG COLD FRONT WHICH IS EXPECTED TO MOVE OFF THE TEXAS
COAST LATE SUN...BRINGING AN INCREASE IN WINDS AND SEAS.

CARIBBEAN SEA...
WEATHER CONDITIONS REMAIN TRANQUIL ACROSS MOST OF THE BASIN
UNDER THE INFLUENCE OF A BROAD UPPER RIDGE EXTENDING FROM
COLOMBIA TO THE S COAST OF CUBA COVERING THE AREA W OF 70W. THE
SOUTHERN EXTENSION OF A BROAD UPPER LOW/TROUGH IN THE CENTRAL
ATLC COVERS THE E CARIBBEAN E OF 70W WITH DRY STABLE AIR
DOMINATING THE ENTIRE REGION. MODERATE/STRONG NE WINDS AHEAD OF
A SURFACE TROUGH LOCATED OVER THE CENTRAL ATLC ARE USHERING IN
SCATTERED FAST MOVING SHOWERS THROUGH THE VIRGIN ISLANDS...
PUERTO RICO AND THE MONA PASSAGE. THE SAN JUAN DOPPLER RADAR
DEPICTS VERY WELL THIS SHOWER ACTIVITY. FRAGMENTS OF LOW LEVEL
MOISTURE ARE ALSO REACHING THE ABC ISLANDS UNDER THE PREVAILING
NELY WIND FLOW.

ATLANTIC OCEAN...
THE UPPER-LEVEL ANTICYCLONE LOCATED OVER THE GULF OF MEXICO
EXTENDS A RIDGE EWD ACROSS THE FLORIDA PENINSULA AND THE W ATLC.
A BROAD UPPER LEVEL TROUGH REMAINS OVER THE CENTRAL ATLC
EXTENDING SOUTH INTO THE E CARIBBEAN. AN UPPER LOW IS ALONG THIS
TROUGH NEAR 25N55W. ANOTHER UPPER LEVEL LOW IS NEAR 30N32W WITH
A RIDGE IN BETWEEN. UPPER RIDGE COVERS MUCH OF THE TROPICS S OF
20N E OF 50W TO INLAND OVER AFRICA. A JET STREAM WITH WINDS
ESTIMATED TO BE 80 TO 110 KT EXTENDS AROUND THE N BOUNDARY OF
THIS UPPER RIDGE WITH THE STRONGEST WINDS E OF 25W. WV IMAGERY
SHOWS A BROAD BAND OF TRANSVERSE HIGH CLOUDS ASSOCIATED WITH
THIS JET.

AT THE SURFACE...A WEAK COLD FRONT IS CURRENTLY PUSHING SOUTH
ACROSS THE W ATLC. THIS FEATURE EXTENDS FROM A WEAK SFC LOW
LOCATED NEAR BERMUDA ALONG 28N73W TO 29N79W. MAINLY LOW CLOUDS
AND ISOLATED SHOWERS ARE RELATED TO THE FRONTAL BOUNDARY.
FURTHER EAST...A SFC LOW...ANALYZED 1010 MB...HAS DEVELOPED
ALONG THE TROUGH THAT HAS BEEN NEARLY STATIONARY OVER THE
CENTRAL ATLC DURING THE PREVIOUS DAYS. LAST FEW VIS IMAGERY FROM
THE DAY SHOWS SOME INCREASE IN DEEP CONVECTION PARTICULARLY
NORTH AND EAST OF THE LOW CENTER LOCATED NEAR 25N55W. THIS
ACTIVITY IS AFFECTING FROM 24N-31W BETWEEN 50W-56W. ACCORDING TO
THE GFS MODEL...THIS LOW IS FORECAST TO LIFT NE AND BECOME
ABSORBED BY THE W ATLC COLD FRONT WITHIN THE NEXT 24 HRS. A 1028
MB HIGH SITUATED NEAR THE AZORES EXTENDS A RIDGE OVER THE
REMAINDER OF THE DISCUSSION AREA.

$$
GR




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