[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181119
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST MON DEC 18 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...
CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...
NORTHEASTERN 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1100 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 6N10W 4N24W 4N40W 2N51W. NO AREAS OF
SIGNIFICANT CONVECTION. ONLY SCATTERED SHOWERS AND ISOLATED
TSTMS WITHIN 300 NM EITHER SIDE OF THE AXIS.

...DISCUSSION...
THE GULF OF MEXICO...
MAINLY FAIR WEATHER EXISTS ACROSS THE GULF OF MEXICO UNDER THE
INFLUENCE OF A MID TO UPPER LEVEL RIDGE ANCHORED OVER THE
REGION. PLENTY OF DRY AIR ALOFT LIES ABOVE THE AREA WITH THE
MOST STABLE CONDITIONS ALOFT ACROSS THE E PORTION WHERE THERE
IS STRONG UPPER LEVEL CONFLUENCE BETWEEN THIS RIDGE AND AN UPPER
LEVEL TROUGH IN THE W ATLC. SOME HIGH CLOUDINESS IS BEGINNING TO
STREAM INTO THE W GULF. THIS CLOUDINESS MAY SPREAD NE THRU THE
DAY...BUT WILL NOT BE A WEATHER CONCERN. AT THE SFC...RIDGING
EXTENDS ACROSS THE GULF FROM A NEARLY STATIONARY 1026 MB HIGH IN
THE W ATLC. THIS PATTERN IS PRODUCING 15-20 KT E WINDS IN THE
MIDDLE AND E GULF AND LIGHTER RETURN FLOW IN THE WRN GULF. THERE
ARE SOME PATCHES OF LOW/MID LEVEL CLOUDS AND SHALLOW ISOLATED
SHOWERS IN THE SE GULF...S OF 26N BETWEEN 84W-88W...LEFT OVER
FROM A DISSIPATED TROUGH. LOOKING AHEAD OVER THE NEXT FEW
DAYS...COMPUTER MODELS SHOW THE MID-UPPER LEVEL RIDGE HOLDING IN
PLACE KEEPING CONDITIONS MAINLY DRY ACROSS THE AREA. HIGH PRES
AT THE SFC WILL STRENGTHEN AND SHIFT W WHICH WILL INCREASE THE
WINDS AND SEAS SLIGHTLY.

THE CARIBBEAN SEA...
THE TAIL END OF A WEAKENING SFC TROUGH STRETCHES ACROSS THE SRN
BAHAMAS. MULTILAYER CLOUDINESS AND ISOLATED SHOWERS NEAR THE
TROUGH ARE BREAKING UP AS DRIER AIR PIVOTS INTO THE REGION...DUE
TO THE MID/UPPER LEVEL TROUGH IN THE W ATLC SHIFTING SE. THE
REMAINDER OF THE CARIBBEAN IS UNDER A WEAK MID-LEVEL RIDGE WITH
PLENTY OF DRY STABLE AIR ALOFT...ESPECIALLY S OF 17N. THERE ARE
PATCHES OF LOW LEVEL CLOUDS AND EMBEDDED SCATTERED SHOWERS
UNDERNEATH THE STRONG MID LEVEL CAP IN THE E CARIBBEAN...MAINLY
E OF THE DOMINICAN REPUBLIC AND N OF 13N. TRADE WINDS ARE MOSTLY
IN THE 15-20 KT RANGE...EXCEPT FOR SLIGHTLY STRONGER WINDS IN
THE SW CARIB WHERE THE PRES GRAD IS A LITTLE TIGHTER. OVER THE
NEXT FEW DAYS...LITTLE CHANGE IN STRENGTH OF THE TRADES IS
EXPECTED AS THE SFC PATTERN REMAINS SIMILAR. GFS SHOWS THE UPPER
SHORTWAVE IN THE ATLC PULLING SE WHICH MAY DRAG A LITTLE
MOISTURE INTO THE N CENTRAL AND E CARIB.

THE ATLANTIC OCEAN...
IN THE WRN AND CENTRAL ATLC...A MID TO UPPER LEVEL HIGHLY
ELONGATED TROUGH STRETCHES FROM JUST E OF BERMUDA TO THE SE
BAHAMAS. DRY STABLE AIR ALOFT COVERS THE AREA W OF THE TROUGH
AXIS INCLUDING FLORIDA AND THE GULF OF MEXICO. E OF THE TROUGH
AXIS...STRONG UPPER LEVEL WLY FLOW IS SPREADING THE MOISTURE
PLUME WELL E COVERING A LOT OF REAL ESTATE IN AN ZONAL E-W
FASHION...NAMELY FROM 20N-26N BETWEEN 30W-70W. AT THE SFC...A
COLD FRONT ENTERS THE AREA NEAR 32N44W AND EXTENDS SW TO A WEAK
1016 MB LOW IS NEAR 28N51W THEN CONTINUING TO SW TO 22N61W THEN
WWD AS A SFC TROUGH ACROSS THE SE BAHAMAS. THIS SFC LOW/FRONTAL
BOUNDARY IS PROVIDING LIFT WHICH IS DEEPENING THE MOISTURE PLUME
OUTLINED. A 1026 MB HIGH PRES SYSTEM IS CENTERED TO THE N AND W
OF THE FRONTAL BOUNDARY ABOUT 200 NM W OF BERMUDA NEAR 32N69W.
IN THE TROPICAL AND E ATLC...ONE OF THE MAIN FEATURES IS A
STRONG UPPER LEVEL TROPICAL JETSTREAM WHICH IS LOCATED BETWEEN
UPPER TROUGHING IN THE CENTRAL ATLC AND BROAD RIDGING OVER
AFRICA. THIS 90-110 KT JET APPROXIMATELY RUNS ALONG 8N42W 18N27W
TO THE CANARY ISLANDS. CONSIDERABLE MOISTURE LIES TO THE S AND E
OF THE JET AXIS WHILE UPPER LEVEL CONFLUENCE IS PROVIDING A
STABLE ENVIRONMENT WITHIN 300 NM W OF THE JET. THE OTHER MAIN
FEATURE IS THE LONG LIVED SLOW MOVING LARGE 1003 MB OCCLUDED LOW
PRES SYSTEM CENTERED NEAR 36N31W. THIS LOW IS SLOWLY WEAKENING
WITH ITS FRONTAL BOUNDARIES BECOMING DIFFUSE AND ITS LOW-LEVEL
CIRCULATION APPEARING MORE RAGGED. THE ASSOCIATED OLD FRONTAL
BOUNDARY...WHICH LIES WELL E OF THE LOW CENTER...IS ALONG 32N21W
24N24W 19N32W. THE NRN BRANCH OF THE SFC TROUGH IS LOCATED IN
THE MOIST REGION OF THE TROPICAL JET MENTIONED AND IS ENHANCING
SHOWER ACTIVITY N OF 28N BETWEEN 18W-22W. GFS SHOWS THE OCCLUDED
LOW FINALLY PULLING N AND BECOMING ABSORBED BY THE FAST MOVING
COLD FRONT IN THE CENTRAL ATLC.

$$
CANGIALOSI





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