[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 201032
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI 20 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURE...

TROPICAL STORM DANIELLE CENTERED NEAR 30.3N 37.0W...OR ABOUT 780
MILES SW OF THE AZORES...AT 20/0900 UTC MOVING NNE 1 KT. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1010 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE
DETAILS. DANIELLE HAS BEEN MEANDERING OVER THE PAST 24 HOURS AND
REMAINS IN THE GRIPS OF A LARGE MID/UPPER LOW ABOUT 250 NM TO
ITS NORTH. THE SWLY SHEAR HAS BEEN UNRELENTING...AND THE
LOW-LEVEL CENTER IS STILL COMPLETELY EXPOSED 35 NM TO THE SW OF
FREQUENT BURSTS OF CONVECTION. SCATTERED MODERATE CONVECTION
FROM 30.5N-33N BETWEEN 34W-38W.

...TROPICAL WAVES...

TROPICAL WAVE CROSSING THE CAPE VERDE ISLANDS ALONG 24W S OF
19N MOVING W 10-15 KT...WITH A 1012 MB LOW ALONG THE AXIS NEAR
16N. SW IR IMAGERY SHOWS A WELL-DEVELOPED LOW-LEVEL CIRCULATION
CROSSING THE ISLANDS...WHICH IS CONFIRMED BY A 0718Z QSCAT PASS
SHOWING THE LOW IN THE CENTER OF THE ARCHIPELAGO. CONVECTION HAS
BEGUN TO DEVELOP TO THE SE WITH WIDELY SCATTERED MODERATE FROM
12N-16N BETWEEN 21W-23W.

TROPICAL WAVE LOCATED 420 NM E OF THE WINDWARD ISLANDS ALONG 54W
S OF 17N MOVING W 20 KT. THE WAVE HAS A VERY LOW AMPLITUDE AND
ALL ASSOCIATED CONVECTION IS OUTRUNNING THE AXIS TO THE WEST.
WIDELY SCATTERED MODERATE CONVECTION FROM 8N-12.5N BETWEEN
54W-62W WILL SPREAD ACROSS PARTS OF THE WINDWARD ISLANDS AND NE
VENEZUELA THROUGH THE DAY.

E CARIBBEAN TROPICAL WAVE ALONG 67W S OF 16N MOVING W 15-20 KT.
THE WAVE IS VIRTUALLY INVISIBLE COMPARED TO 24 HOURS AGO...AND
CAN ONLY BE TRACED ALONG A DISSIPATING CLUSTER OF TSTMS OVER
WESTERN VENEZUELA. WIDELY SCATTERED MODERATE CONVECTION FROM
EQ-10N BETWEEN 66W-70W.

...ITCZ...

ITCZ AXIS EMERGES OFF THE COAST OF MAURITANIA ALONG 17N16W
20N21W...THEN ALONG 12N26W 9N40W 10N50W...THEN ALONG 7N56W 9N64W
8N80W. SCATTERED MODERATE CONVECTION WITHIN 130 NM OF THE AXIS
BETWEEN 32W-40W. ISOLATED MODERATE WITHIN 30 NM OF THE AXIS
BETWEEN 48W-50W. SCATTERED MODERATE/STRONG WITHIN 130 NM OF THE
AXIS BETWEEN 74W-84W OVER PARTS OF COLOMBIA...PANAMA...AND COSTA
RICA.

...DISCUSSION...

GULF OF MEXICO...
STRONG SFC RIDGING OVER THE SUBTROPICAL ATLC CONTINUES TO REACH
WWD ALONG 30W TO THE FLORIDA PANHANDLE WITH BROAD SE/S FLOW
BRINGING LOTS OF TROPICAL MOISTURE FROM THE GULF INLAND BETWEEN
ALABAMA AND SE TEXAS. A MID/UPPER LEVEL SHORTWAVE TROF IS MOVING
ACROSS THE NE GULF AND FLORIDA...WHICH WILL ONCE AGAIN ENHANCE
TSTM COVERAGE OVER THE PENINSULA LATER TODAY...BUT THE VERTICAL
LIFT AHEAD OF THIS FEATURE IS NOT ENOUGH TO CAUSE WIDESPREAD
CONVECTION AT THE MOMENT. A WEAK LOW-LEVEL CONVERGENCE LINE HAS
BEEN DRAPED ACROSS THE GULF WATERS SINCE YESTERDAY...TRIGGERING
ISOLATED SHOWERS/TSTMS WHICH NOW EXTEND UP TO 120 NM WSW OF
TAMPA BAY AND FROM 28N-31N BETWEEN 87W-89W. TSTM COVERAGE MAY
INCREASE ALONG THE GULF COAST ON SAT AS A FRONTAL BOUNDARY
BECOMES STATIONARY OVER THE SOUTHEAST U.S.

CARIBBEAN...
THE AIR MASS IS BEGINNING TO MOISTEN UP AGAIN...ESPECIALLY OVER
THE SOUTHERN HALF OF THE CARIBBEAN...AFTER A SURGE OF DRIER AIR
TRAVERSED THE BASIN OVER THE PAST COUPLE OF DAYS. EVEN
STILL...THE GREATEST UPPER AIR SUPPORT IS FROM PANAMA SWD INTO
THE EPAC...WHICH HAS BEEN KEEPING MOST OF THE CONVECTION ALONG
THE ITCZ FROM COLOMBIA TO COSTA RICA. THE AREA IS STILL
DOMINATED BY AN UPPER TROF WHICH EXTENDS FROM PUERTO RICO SWWD
TO A DEVELOPING UPPER LOW NEAR 10N78W IN THE SW CARIBBEAN.
MODERATE/STRONG SUBSIDENCE EXTENDS N OF THE AXIS TO THE GREATER
ANTILLES...WHICH HAS LIMITED TSTMS ACROSS MUCH OF THE AREA WITH
THE EXCEPTION OF WIDELY SCATTERED SHOWERS/TSTMS EXTENDING FROM
THE SRN PENINSULA OF HAITI WWD ACROSS JAMAICA TO 80 NM S OF THE
CAYMAN ISLANDS.

SUBTROPICAL ATLANTIC...
THERE IS LITTLE SIGNIFICANT WEATHER ACROSS THE SUBTROPICS THIS
MORNING...AND EVEN HIGH LEVEL CLOUDINESS IS LIMITED TO THE W
ATLC. STRONG SUBTROPICAL RIDGING ALONG 30N EXTENDS W OF 45W WITH
THE ELY TRADES LIMITED TO THE LOWEST LEVELS. A COLD FRONT OVER
THE NW ATLC IS SKIRTING THE AREA PAST BERMUDA BUT IS ONLY
INITIATING ISOLATED SHOWERS N OF 31N BETWEEN 59W-62W. A RESIDUAL
SFC TROF MAY CONTINUE SW OF THE FRONT AND WIDELY SCATTERED
MODERATE CONVECTION HAS DEVELOPED FROM 25N-28N BETWEEN 70W-73W.
TO THE S...A NEARLY STATIONARY MID/UPPER LOW IS CENTERED N OF
PUERTO RICO NEAR 24N64W AND CONTINUES TO SUSTAIN MOSTLY DRY AIR
E OF 70W. FARTHER E...MID/UPPER RIDGING LIES ALONG 20N47W 28N20W
WITH A SECOND MID/UPPER LOW RIDING ALONG THE NRN PERIPHERY OF
THE RIDGE N OF 30N BETWEEN 35W-45W. THIS LOW CONTINUES TO SHEAR
APART T.S. DANIELLE BUT SINCE THE UPPER AND LOW LEVEL
CIRCULATIONS ARE DECOUPLED...THE SWLY FLOW IS NOT SHOOTING THE
STORM TO THE NE AS PREVIOUSLY THOUGHT. THE RIDGE CONTINUES TO
BUILD E TOWARDS AFRICA BUT A LEFTOVER MID/UPPER LOW IS
LOITERING BETWEEN THE CANARY ISLANDS AND THE MOROCCAN COAST.

TROPICAL ATLANTIC...
A NEARLY CLOSED UPPER LEVEL ANTICYCLONE HAS DEVELOPED NE OF THE
LESSER ANTILLES NEAR 20N53W AND HAS INCREASED THE DEEP ELY FLOW
OVER THE TROPICS BETWEEN 40W-60W. TSTMS ASSOCIATED WITH THE 54W
TROPICAL WAVE AND THE ITCZ HAVE BEEN SPEEDING TO THE W AND
SHOULD BE AFFECTING THE SOUTHERN WINDWARD ISLANDS DURING THE
DAY. A COUPLE OF INVERTED TROFS ARE APPROACHING THE AREA FROM
THE E...ALONG ABOUT 34W AND 45W...WITH THE EASTERNMOST TROF
SUPPORTING A FLARE UP OF CONVECTION ALONG THE ITCZ BETWEEN
32W-40W. UPPER DIVERGENCE CONTINUES TO INCREASE OFF THE COAST OF
GUINEA AND SIERRA LEONE...WHICH SHOULD BE ABLE TO SUSTAIN
CONVECTION AS IT MOVES OFF THE COAST LATER TODAY.

$$
BERG



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