[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 132351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 42W S OF 16N MOVING W 5 KT.  THIS IS A
SLOW-MOVING WAVE WITH THE BACKGROUND FLOW VERY WEAK DUE TO THE
STRONG LOW IN THE NE ATLC.  ANY CONVECTION IS LIMITED TO THE
ITCZ.

TROPICAL WAVE IN THE CENTRAL CARIBBEAN IS ALONG 74W S OF 18N
MOVING W 15 KT.   WAVE POSITION IS BASED ON EXTRAPOLATION WITH
NO CLOUD SIGNATURE PRESENT.

...ITCZ...
ITCZ AXIS IS ALONG 10N13W 8N21W 8N41W 10N62W.  ISOLATED MODERATE
WITHIN 75 NM OF 5N22W...4N30W AND 8.5N17.5W.  SCATTERED MODERATE
IS FROM 5N-8N BETWEEN 40W-45W WITH WIDELY SCATTERED MODERATE TO
THE N BETWEEN 8N-11N FROM 45W-50W.

...DISCUSSION...
GULF OF MEXICO...
ZONAL FLOW CONTINUES ACROSS THE NORTHERN GULF WITH UPPER JET
DYNAMICS INDUCING SCATTERED TSTMS ALONG SE TEXAS N OF 28N W OF
93W.  THESE TSTMS ARE INDICATIVE OF SOME CHANGES ON THE WAY WITH
UPPER ENERGY PULLING OUT OF THE SW USA INDUCING A FRONTAL WAVE
IN THE GULF OF MEXICO.  THE LOW PRESSURE WAVE WILL BE ON A
STRONG FRONT FORECAST INTO THE GULF BY MIDDAY TOMORROW WITH
ANOTHER ROUND OF  TSTMS.  FOR NOW WEAK HIGH PRESSURE DOMINATES
REST OF THE GULF WITH SOME DRIER AIR FILTERING INTO FLORIDA DUE
TO A WEAK COLD FRONT FROM ABOUT S FLORIDA TO 120 NM E OF
JACKSONVILLE.  MODERATE/STRONG SUBSIDENCE IS KEEPING THE E GULF
CONVECTION- FREE.  ANY SIGNIFICANT RAIN HAS PUSHED OFF THE
FLORIDA E COAST WITH THE GULF MOSTLY DEEP CONVECTION-FREE.
MID/UPPER HIGH OVER BELIZE HAS BEEN STATIONARY FOR DAYS WITH
ANTICYCLONIC FLOW AND CIRRUS CLOUDS OVER THE SOUTHERN
GULF...SOME OF WHICH FROM THE REMNANTS OF LESTER IN THE EPAC.

CARIBBEAN SEA...
STATIONARY MID/UPPER HIGH OVER BELIZE IS KEEPING GENERALLY DRY
ANTICYCLONIC FLOW OVER THE NW CARIBBEAN FROM JUST W OF PUERTO
RICO TO  COSTA RICA. NARROW MID/UPPER TROUGH IS SLIDING S ON THE
SIDE OF THE RIDGE... CUTTING THRU ABOUT THE NORTHERN WINDWARD
ISLANDS NEAR 14N60W WSW TO 13N74W.  ANOTHER ACTIVE WEATHER IS
DAY IS LIKELY IN PUERTO RICO WITH CONTINUING LIGHTER-THAN-
AVERAGE TRADES CONTRIBUTING TO STRONGER SEA-BREEZES AND HIGH
MOISTURE/STEEPER ATMOSPHERIC LAPSE RATES.  THIS MAY CHANGE BY
THE WEEKEND WITH A BIT DRIER AIR PUSHING INTO PUERTO RICO.

SUBTROPICAL ATLC...
A COLD FRONT HAS GENERALLY LEFT FAIR SKIES OVER THE AREA W OF
65W WITH AN UPPER TROUGH FROM 32N58W TO 22N66W SUPPORTING THE
FRONT'S SLOW ESE PROGRESS.  DRY AIR AT THE MID/UPPER LEVELS IS
PRESENT N OF 22N WHICH IS LIMITING ANY SHOWER DEVELOPMENT BEHIND
THE FRONT.  THE COLD FRONT IS ALONG 32N52W TO 23N63W WITH BROAD
DIVERGENCE/LIFT FROM THE UPPER FEATURE CONTRIBUTING TO WIDELY
SCATTERED WEAK/MODERATE CONVECTION AHEAD OF THE FRONT N OF 20N E
OF 48W.   WIDELY SCATTERED MODERATE FROM 23N-26N BETWEEN 40W-45W
IS AHEAD OF A WEAK SURFACE TROUGH ALONG LINE 19N49W 25N46W
30N48W.  UPPER RIDGE AXIS IS ALONG 45W WITH SCATTERED HIGH
CLOUDS DUE TO CIRRUS OUTFLOW FROM UPSTREAM TSTMS.  A LARGE
DEEP-LAYERED LOW IS NEARLY STATIONARY CLOSE TO 30N33W.  THE LOW
HAS SOME POTENTIAL TO TRANSITION INTO A SUBTROPICAL CYCLONE
THOUGH IT IS SLOWLY FILLING AND CONVECTION IS RATHER ASYMMETRIC
ON THE E SIDE OF THE CIRCULATION WITH WIDELY SCATTERED MODERATE
FROM 28N-32N BETWEEN 27W-33W.  THE REMNANTS OF ITS ASSOCIATED
COLD FRONT ARE STILL PRODUCING WIDELY SCATTERED MODERATE WITHIN
90 NM OF 24N28W AND 27N22W.  ELSEWHERE ZONAL FLOW IS E OF 20W.

TROPICAL ATLC...
UPPER RIDGING IS BEING NUDGED SOUTHWARD BY A MID/UPPER TROUGH
FROM 20N42W TO 14N60W.  THERE ARE NO TROPICAL WAVES IN THE
VICINITY WHICH IS KEEPING THE FEATURE MOSTLY DRY.  MID/UPPER
RIDGING SITS ALONG 10N50W 13N20W WITH SOME MID/UPPER SUBSIDENCE
FROM 12N-16N E OF 40W.  HIGH-LEVEL SW FLOW IS LEADING TO SOME
DIVERGENCE OVER THE ITCZ WITH TSTMS ESPECIALLY AROUND 7N41W.

$$
BLAKE


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