[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 212341
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT 21 AUG 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC 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 ADDED ALONG 18W JUST W OF DAKAR S OF 19N MOVING W
10 KT.  THIS WAVE IS SEEN IN LONG-TERM SATELLITE LOOPS ALONG
WITH A PRESSURE FALL/RISE COUPLET OVER W AFRICA.  12Z DAKAR
SOUNDING HAD A 40 KT JET NEAR 700 MB ASSOCIATED WITH THE WAVE.
BROAD UPPER ANTICYCLONE OVER THE WAVE IS CAUSING A LARGE AREA OF
CIRRUS OVER THE E ATLC E OF 30W.  MID-LEVEL CENTER NOTED ALONG
11N WITH WIDELY SCATTERED MODERATE FROM 5.5N-9N BETWEEN 17W-23W.

TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 32W S OF 20N
MOVING W 15 KT.  THE WAVE HAS NO WELL-DEFINED AXIS AND IS
CHARACTERIZED BY A LARGE AREA OF LIGHT WINDS WITH A SMALL WIND
SHIFT.  CURRENT POSITION IS BASED ON A NORTHWARD KINK OF THE
ITCZ AND MID-LEVEL TURNING NOTED ON SATELLITE.  MOISTURE FROM
THIS WAVE IS FORECAST TO AFFECT THE LESSER ANTILLES ON THU.

CARIBBEAN TROPICAL WAVE ALONG 70W S OF 17N MOVING W 20 KT.  IT
HAS BEEN A SHOWERY DAY FOR THE ABC ISLANDS WITH EARLIER
CONVECTION DISSIPATED OVER WATER.  WLY SHEAR IS KEEPING ANY OF
THE TSTMS TO THE E OF THE WAVE AXIS.

W CARIBBEAN TROPICAL WAVE ALONG 84W/85W S OF 18N MOVING W 20
KT.  SCATTERED MODERATE OVER INLAND NORTHERN NICARAGUA AND E
HONDURAS IS DUE TO THE WAVE.

...ITCZ...
ITCZ AXIS IS ALONG 9N13W 9N21W 12N32W 8N43W 10N58W.  ISOLATED
SHOWERS WITHIN 60 NM OF AXIS BETWEEN 37W-50W.   ISOLATED
MODERATE CONVECTION FROM 5N-10N BETWEEN 17W-27W.

...DISCUSSION...
GULF OF MEXICO...
DEEP-LAYERED HIGH PRESSURE IS OVER THE CENTRAL GULF WITH TSTMS
FORMING ON THE N AND E SIDE OF THE RIDGING OVER THE DEEP SOUTH
INTO FLORIDA.  MODERATE SUBSIDENCE IS KEEPING THE GULF WATERS
RATHER QUIET WITH JUST SOME ISOLATED SHOWERS.  WET CONDITIONS
ARE LIKELY FROM LOUISIANA EASTWARD INTO S FLORIDA ON THE NE SIDE
OF THE RIDGE TOMORROW.

CARIBBEAN SEA...
UPPER LOW IS NEAR 20N85W WITH TROUGHING FROM CENTRAL CUBA TO N
BELIZE.  INSTABILITY BENEATH THE TROUGH IS ALLOWING FOR ISOLATED
TSTMS N OF 18N W OF 80W.  MID/UPPER DRY AIR OVER THE CENTRAL
CARIBBEAN W OF 73W N OF 13N IS KEEPING THE AREA MOSTLY DRY.
UPPER HIGH IS BUILDING INTO THE E CARIBBEAN WITH CENTER NEAR
BARBADOS.  DIVERGENCE ON NW SIDE OF THE HIGH ALLOWED TSTMS TO
DEVELOP NEAR THE TROPICAL WAVE ALONG 70W.  THE GFS INDICATES A
GENERALLY FAVORABLE PATTERN FOR TSTM REFORMATION IS LIKELY
TOMORROW AS THE WAVE MOVES NEAR JAMAICA.

SUBTROPICAL ATLANTIC OCEAN...
NARROW TROUGH IS ALONG 32N75W TO 23N80W.  TROUGH ENHANCED
ISOLATED TSTMS OVER THE NW BAHAMAS INTO THE W ATLC WATERS N OF
25N BETWEEN 70W-75W.  MID/UPPER HIGH IS NEAR THE SE BAHAMAS WITH
RELATIVELY BENIGN WEATHER BETWEEN IT AND AN EASTWARD-MOVING
UPPER LOW NEAR 23N60W.  LOW IS MOVING INTO A MUCH LARGER LOW
COMING FROM THE MID-LATITUDES NEAR 32N52W.  GENERALLY WLY FLOW
IS BETWEEN 50W-35W WITH PLENTY OF DRY AIR.  THE REMNANTS OF
DANIELLE ARE NEAR 31N39W OCCASIONALLY PUFFING A TSTM NEAR THE
CENTER.  UPPER RIDGING IS E OF 35W WITH A SMALL UPPER LOW NEAR
18N34W MOVING NORTHWARD INTO THE AREA FROM THE DEEP TROPICS.
WEAK SURFACE HIGH PRESSURE IS IN THE REGION WITH A BREAK IN THE
RIDGE DUE TO THE REMNANT LOW FROM DANIELLE.

TROPICAL ATLANTIC...
MID/UPPER LOW NEAR 18N34W IS BASICALLY THE DIVIDING LINE BETWEEN
INCREASING MOISTURE FROM AFRICAN AND DRY AIR/SUBSIDENCE IS
PRESENT W OF 35W.  A BIT OF WESTERLY SHEAR IS COMING INTO THE
WESTERN PART OF THE AREA N OF 15N W OF 50W OTHERWISE SHEAR IS
FAIRLY LIGHT.  UPPER HIGH IS JUST NE OF THE CAPE VERDES WITH
FORECAST DIVERGENCE OVER THE E ATLC TROPICAL WAVE LIKELY CAUSING
A RE-FIRING OF TSTMS OVERNIGHT.  PRESSURES CONTINUE TO FALL IN
THE DEEP TROPICS... PERHAPS HERALDING THE ARRIVAL OF THE ACTIVE
PHASE OF THE MADDEN-JULIAN OSCILLATION.

$$
BLAKE

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