[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 170544
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN 17 OCT 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA... GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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.

...TROPICAL WAVES...
TROPICAL WAVE IN THE E CARIBBEAN IS ALONG 66W/67W S OF 18N
MOVING W 10-15 KT. WAVE IS BENEATH A MID/UPPER LEVEL RIDGE WITH
MODERATE SUBSIDENCE/DRY AIR WHICH IS LIMITING SHOWER ACTIVITY.
ISOLATED LOW LEVEL SHOWERS ARE WITHIN 75 NM OF 15N FROM THE
LESSER ANTILLES TO 66W.

...ITCZ...
ITCZ AXIS IS ALONG 11N15W 7N30W 9N44W 10N62W. UPPER LEVEL
SUBTROPICAL FEATURES EXTEND S INTO THE TROPICS ACROSS THE ATLC
ESPECIALLY W OF 40W. THUS CONVECTION ASSOCIATED WITH THE ITCZ IS
LIMITED TO E OF 40W. BROAD AREA OF CLOUDINESS WITH SCATTERED
SHOWERS COVERS THE AREA FROM 1N-10N E OF 40W. SCATTERED
MODERATE/STRONG CONVECTION IS WITHIN 75 NM ALONG THE COAST OF
LIBERIA FROM 9W TO THE BORDER OF SIERRA LEONE. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF 3N FROM
28W-38W.

...DISCUSSION...
GULF OF MEXICO INTO THE NW ATLANTIC...
BROAD DEEP LAYERED TROUGH COVERS THE E UNITED STATES INTO THE NW
ATLC N OF 23N IN THE GULF AND N OF A LINE FROM FLORIDA NEAR
25N80W TO E OF BERMUDA BEYOND 32N61W. THIS FLOW IS USHERING IN
STRONG SUBSIDENCE/DRY AIR ACROSS THE GULF EXCEPT IN THE SE WHERE
THERE IS A FRONTAL BOUNDARY. AT THE SURFACE...A COLD FRONT
ENTERS THE W ATLANTIC JUST E OF BERMUDA THROUGH 32N64W EXTENDING
SW TO THE BAHAMAS NEAR 23N74W WHERE IT CONTINUES AS A STATIONARY
FRONT ACROSS CUBA TO 23N86W THEN AS A DISSIPATING WARM FRONT TO
23N91W. SCATTERED SHOWERS ARE WITHIN 45/60 NM OF LINE FROM
ANDROS ISLAND IN THE BAHAMAS ACROSS CUBA NEAR 23N81W TO 21N85W
JUST S OF THE YUCATAN CHANNEL. A 1017 MB HIGH IS OFF THE E COAST
OF FLORIDA NEAR 28N80W.

CARIBBEAN SEA AND W ATLC W OF 55W...
LARGE MID/UPPER HIGH IS CENTERED W OF JAMAICA NEAR 18N81W WITH A
RIDGE AXIS EXTENDING NE INTO THE SW ATLANTIC ALONG 22N72W TO
BEYOND 32N58W. THIS IS PRODUCING SW ROTATING TO N FLOW OVER THE
W ATLC AND NE FLOW OVER ALL OF THE CARIBBEAN. THUS...MODERATE
SUBSIDENCE/DRY AIR AT THE UPPER LEVELS IS LIMITING SHOWER
ACTIVITY EXCEPT ACROSS THE ACROSS THE FAR W CARIBBEAN WHERE
TROPICAL MOISTURE IS BEING ADVECTED OVER CENTRAL AMERICA.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE S
OF 12N FROM COLOMBIA TO OVER CENTRAL AMERICA. DIURNAL SCATTERED
SHOWERS/THUNDERSTORMS REMAIN OVER S HAITI AND HAVE MOVED W WITH
THE UPPER LEVEL FLOW WITHIN 60 NM OF LINE FROM HAITI NEAR 18N74W
S OF JAMAICA TO 17N80W.

CENTRAL ATLANTIC...
NARROW DEEP LAYERED TROUGH EXTENDS FROM N OF THE REGION S INTO
THE TROPICAL JUST N OF THE EQUATOR. THE MID/UPPER LEVEL AXIS
EXTENDS FROM A MID/UPPER LEVEL LOW NEAR 33N44W S TO A UPPER
LEVEL LOW NEAR 26N47W CONTINUING S TO OVER S AMERICA NEAR 6N59W.
CYCLONIC FLOW IN THE SUBTROPICS IS FROM 41W-54W THEN NARROWS
DRAMATICALLY IN THE TROPICS FROM 50W-56W. AT THE SURFACE...A
SURFACE TROUGH EXTENDS FROM 31N40W SW TO 26N50W. SCATTERED
SHOWERS/THUNDERSTORMS ARE 45/60 NM OF LINE 30N40W-27N46W.

E ATLANTIC...
MID/UPPER LEVEL HIGH IS IN THE TROPICS ABOUT 700 NM SW OF THE
CAPE VERDE ISLANDS NEAR 8N32W WITH A RIDGE AXIS EXTENDING N
ALONG 19N33W THEN NE TO BEYOND 25W. THIS FLOW IS BRINGING STRONG
SUBSIDENCE/DRY AIR AT ALL LEVELS FROM 10N-21N BETWEEN 20W-35W
INCLUDING THE CAPE VERDE ISLANDS. AT THE SURFACE...A DISSIPATING
COLD FRONT EXTENDS ALONG THE W EDGE OF THE ANTICYCLONIC FLOW
INTO THE EASTERN/CENTRAL ATLC THROUGH 32N33W SW TO 21N45W.
DIVERGENCE IN THE TROPICAL ATLC CONTRIBUTING OVERCAST CLOUDS
WITH CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
WITHIN 300 NM OF LINE FROM 8N38W TO 22N48W AND A NARROWER BAND
OF OF OVERCAST CLOUDS WITH SCATTERED SHOWERS/THUNDERSTORMS FROM
20N46W TO 30N31W. MID/UPPER LEVEL TROUGH EXTENDS ALONG THE NW
COAST OF AFRICA WITH CYCLONIC FLOW N OF 20N W OF 18W.

$$
WALLACE


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