[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 182359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SUN NOV 18 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 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS IN THE CARIBBEAN ALONG 70W S OF 18N MOVING W
15-20 KT. LAST FEW SATELLITE PICTURES FOR THE DAY SHOWS AN
INVERTED-V LOW LEVEL CLOUD SIGNATURE ASSOCIATED WITH THE WAVE
JUST SOUTH OF HISPANIOLA. SCATTERED SHOWERS ARE BETWEEN
DOMINICAN REPUBLIC AND THE ABC ISLANDS.

A TROPICAL WAVE IS OVER THE NW CARIBBEAN AND CENTRAL AMERICA
ALONG 84W/85W S OF 20N MOVING W NEAR 10 KT. THE INTERACTION
BETWEEN THIS WAVE AND REMNANT TROUGHING FROM AN OLD FRONTAL
BOUNDARY IS PRODUCING A CLUSTER OF SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION FROM 16N-19N BETWEEN 82W-86W.
LIGHTNING DATA SUPPORTS SCATTERED TSTMS IN THIS AREA. POCKETS OF
SCATTERED MODERATE CONVECTION AREA OVER THE SW CARIBBEAN. UPPER
DIFFLUENCE IN ENHANCING ALL THIS ACTIVITY.

...THE ITCZ...
ITCZ IS CENTERED ALONG 10N15W 5N35W 6N50W 7N62W. THE ITCZ IS
SOMEWHAT ACTIVE AIDED BY UPPER DIFFLUENCE. CLUSTERS OF SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION ARE MOVING OUT OF THE
AFRICAN COAST THROUGH SIERRA LEONE AND LIBERIA. SIMILAR
CONVECTION IS WITHIN 80-120 NM NORTH OF THE AXIS BETWEEN
23W-32W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 80-100
NM N OF AXIS BETWEEN 39W-50W.

DISCUSSION...

THE GULF OF MEXICO...
A RIDGE ANCHORED ON A 1024 MB HIGH OVER SOUTH GEORGIA DOMINATES
THE GULF. PATCHES OF LOW/MID CLOUDS ARE NOTED OVER THE E GULF
AND THE N PORTION OF THE YUCATAN PENINSULA. CONVECTION HAS
FLARED UP OVER CENTRAL MEXICO WHILE A BAND OF SHOWERS WITH
EMBEDDED TSTMS IS CROSSING THE NW QUADRANT OF THE GULF EXTENDING
ROUGHLY FROM SE LOUISIANA TO JUST SOUTH OF BROWNSVILLE TEXAS.
THIS MOISTURE IS ASSOCIATED WITH DIFFLUENCE ALOFT TO THE E OF A
SHARP SHORTWAVE TROUGH LOCATED OVER CENTRAL TEXAS AND NORTHERN
MEXICO...AIDED BY MOIST LOW-LEVEL RETURN FLOW. A COASTAL TROUGH
WAS ANALYZED OVER NE MEXICO ON THE 2100 UTC MAP. A MID TO UPPER
LEVEL RIDGE CONTROLS THE REMAINDER OF THE GULF WITH DRY AIR.
CHANGES IN THE WEATHER PATTERN ARE IN STORE FOR THE GULF THIS
WEEK. THE NEXT COLD FRONT IS FORECAST TO MOVES ACROSS THE AREA
ON THU. GALE CONDITIONS ARE EXPECTED BEHIND THE COLD FRONT OVER
THE SW PORTION OF THE GULF WED NIGHT AND THU.

THE CARIBBEAN SEA...
TWO TROPICAL WAVES ARE MOVING WWD ACROSS THE BASIN GENERATING
SOME SHOWER/TSTM ACTIVITY. SEE TROPICAL WAVE SECTION. MODERATE
TO STRONG TRADE WINDS OF 20-25 KT ARE NOTED BETWEEN THE WAVES
AND MAINLY OFFSHORE THE COLOMBIAN COAST. N TO NE WINDS IN 20 KT
RANGE ARE BLOWING ACROSS THE NW CARIBBEAN. THE REMNANTS OF AN
OLD FRONTAL BOUNDARY STRETCHING ACROSS THE CENTRAL ATLC INTO
DOMINICAN REPUBLIC IS STILL GENERATING SOME SHOWER ACTIVITY OVER
HISPANIOLA AND NORTHERN COASTAL WATERS. THIS FEATURE IS FORECAST
TO PUSH SOUTH ACROSS PUERTO RICO AND THE UK/US VIRGIN ISLANDS
TONIGHT THROUGH MONDAY INCREASING THE CHANCE OF SHOWERS. THE SAN
JUAN DOPPLER RADAR CURRENTLY DEPICTS SCATTERED SHOWERS AND
ISOLATED TSTMS MAINLY N OF THOSE ISLANDS. ALOFT...BROAD RIDGE
COVERS MOST THE CARIBBEAN SEA WITH A SHORT WAVE TROUGH ALONG
65W. ABUNDANT MID/UPPER LEVEL MOISTURE IS SEEN OVER THE BASIN
WITH SUBSIDENCE AND IMPLIED DRY AIR OVER CENTRAL AMERICA. HIGH
PRES N OF THE AREA WILL MAINTAIN BRISK TRADE WINDS NEAR THE
COLOMBIAN COAST THROUGH MID WEEK.

THE ATLANTIC OCEAN...
FAIRLY ZONAL MID TO UPPER FLOW...BETWEEN A RIDGE OVER THE
CARIBBEAN SEA AND AN UPPER TROUGH TO THE N...DOMINATES THE STATE
OF FLORIDA AND MUCH OF THE W ATLC. DRY AIR RESULTING IN MODERATE
TO STRONG SUBSIDENCE IS NOTED SOUTH OF 29N...INCLUDING THE
BAHAMAS. AN UPPER SHORTWAVE TROUGH ALONG 49W/50W SUPPORTS THE
THE STATIONARY FRONT THAT ENTERS THE REGION NEAR 31N47W THEN
CONTINUES SW TO DOMINICAN REPUBLIC. A 1024 MB HIGH IS BEHIND THE
FRONT CENTERED W OF BERMUDA NEAR 32N67W. A CLUSTER OF MODERATE
CONVECTION IS AHEAD OF THE FRONT NEAR 28N47W. VERY NARROW DEEP
LAYERED RIDGE IS OVER THE CENTRAL ATLC BETWEEN 40W-46W. EAST OF
THIS RIDGE...A LARGE UPPER-LEVEL LOW IS SPINNING NEAR 33N30W. A
COUPLE OF SFC LOWS WERE ANALYZED ON THE 1800 UTC MAP N OF AREA
WITH A COLD FRONT EXTENDING ACROSS THE E ATLC ALONG 31N19W
24N23W 18N31W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE BETWEEN
THE MADEIRA AND THE CANARY ISLANDS RELATED TO THE FRONT. MOSTLY
ZONAL FLOW IS OVER THE TROPICAL ATLANTIC S OF 20N FROM THE
LESSER ANTILLES TO W AFRICA. WV IMAGERY SHOWS A BAND OF
TRANSVERSE HIGH CLOUDS ASSOCIATED WITH JET STREAM BRANCH WITH
CORE WINDS OF NEAR 70 KT OVER THE TROPICAL ATLANTIC BETWEEN
THE LESSER ANTILLES AND THE W COAST OF AFRICA.

$$
GR




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