[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211819
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 21 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION EMILY CENTERED INLAND OVER NORTHERN MEXICO
NEAR 25.0N 101.2W AT 21/1500 UTC DRIFTING W AT 2 KT. MAXIMUM
SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO 35 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1007 MB. SEE THE LATEST
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC
FOR MORE DETAILS. EMILY CONTINUES TO WEAKEN AS IT MOVES SLOWLY W
ACROSS THE HIGH TERRAIN OF NORTHERN MEXICO...AND IS EXPECTED TO
DISSIPATE WITHIN 24 HOURS. LARGE ENVELOPE OF MOISTURE REMAINS
OVER MUCH OF THIS REGION...FROM 23.5N TO NEAR THE TEXAS BIG
BEND...AND FROM NEAR THE SIERRA MADRE ORIENTALES RANGE WESTWARD
TO 106W. STRONGEST CONVECTION IS OCCURRING ALONG THE SIERRA
MADRE FROM W OF TAMPICO TO NEAR CIUDAD VICTORIA. ADDITIONAL
RAINFALL ACCUMULATIONS OF 3 TO 5 INCHES...WITH ISOLATED MAXIMUM
AMOUNTS TO 8 INCHES IN THE MOUNTAINS...ARE EXPECTED AS THE
REMNANT CIRCULATION MOVES SLOWLY W.

TROPICAL DISTURBANCE HAS DEVELOPED NEAR THE CENTRAL BAHAMAS WITH
A LOW NEAR 24N75W 1014 MB...MOVING WNW 10 KT. SATELLITE IMAGERY
DURING THE PAST 12 HOURS INDICATES THAT AN AREA OF CONCENTRATED
CONVECTION HAS PERSISTED NEAR THE SOUTHEASTERN AND CENTRAL
BAHAMAS SINCE OVERNIGHT...WITH MORNING VISIBLE IMAGERY
SUGGESTING THE FORMATION OF A SURFACE LOW NEAR CAT ISLAND. THE
SYSTEM IS BECOMING BETTER ORGANIZED WITH BANDING OF STRONG
CONVECTION EVIDENT WITHIN 90-120 NM FROM N-SE QUADRANTS. UPPER
LEVEL OUTFLOW IS GOOD IN ALL BUT THE SW QUADRANT WHERE WESTERLY
WINDS FROM AN ANTICYCLONE OVER THE NW CARIBBEAN ARE LIMITING
DEEP CONVECTIVE DEVELOPMENT IN THAT QUADRANT. DEEP LAYERED
SUBTROPICAL RIDGE FROM THE SE UNITED STATES E ACROSS THE W ATLC
IS EXPECTED TO REMAIN NEARLY STATIONARY OVER THE NEXT DAY OR SO.
THIS SHOULD GENERALLY STEER THE SYSTEM TOWARDS THE WNW AND
PROVIDE A MORE FAVORABLE ENVIRONMENT FOR DEVELOPMENT NEAR THE
CENTRAL AND NW BAHAMAS...WITH TROPICAL DEPRESSION OR TROPICAL
STORM FORMATION POSSIBLE WITHIN THE NEXT 24 OR 36 HOURS.

...TROPICAL WAVES...

LARGE E ATLC TROPICAL WAVE IS ALONG LINE FROM 24N25W TO A LOW
1011 MB SW OF THE CAPE VERDE ISLANDS NEAR 13.5N28W...TO 7N27N
MOVING W 15 KT. CIRCULATION ASSOCIATED WITH THE WAVE EXTENDS
FROM THE CAPE VERDE ISLANDS W TO 42W...AND FROM THE ITCZ AXIS N
TO 26N. AN UPPER LEVEL HIGH IS NOTED ON WATER VAPOR IMAGERY
CENTERED W OF THE WAVE NEAR 20N33W...WHICH IS PROVIDING A
CLASSIC UPPER LEVEL ANTICYCLONIC SIGNATURE OVER THE WAVE.
VISIBLE SATELLITE IMAGERY AND SURFACE OBSERVATIONS FROM THE CAPE
VERDE ISLANDS INDICATE THAT THE WAVE IS EMBEDDED IN A LARGE AREA
OF SAHARAN DUST...ALTHOUGH RECENT OBSERVATIONS FROM THE CAPE
VERDES SHOW VISIBILITIES IMPROVING AS THE DUST MOVES W OF THE
ISLAND CHAIN. NO DEEP CONVECTION IS NOTED NEAR THE WAVE AXIS AND
LOW DUE TO THE STABLE ENVIRONMENT SURROUNDING THE SYSTEM...WITH
DEEP CONVECTION BEING PULLED N ALONG ITCZ WELL E OF THE WAVE
NEAR 13N21W.

CENTRAL ATLC TROPICAL WAVE IS ALONG 48W/49W S OF 21N MOVING W 15
KT. WAVE SEEMS TO HAVE ACCELERATED SLIGHTLY DURING THE MORNING
AND MAY BE MOVING CLOSER TO 15-20 KT. GOOD PRESENTATION OF WAVE
ON VISIBLE IMAGERY...WITH WIDELY SCATTERED SHOWERS AND TSTMS
MAINLY W OF THE WAVE AXIS FROM 13N-14N BETWEEN 51W-56W.

WEAK SE CARIBBEAN TROPICAL WAVE IS ALONG 66W/67W S OF 13N MOVING
W 15-20 KT. WAVE REMAINS VERY LOW IN AMPLITUDE WITH LITTLE
INDICATION OF ITS LOCATION ON SATELLITE AND SURFACE DATA.

W CARIBBEAN TROPICAL WAVE IS ALONG 79W/80W FROM CUBA SOUTHWARD
TO PANAMA MOVING W 20 KT. THIS WAVE HAS SPLIT FROM THE TROPICAL
DISTURBANCE NEAR THE CENTRAL BAHAMAS AND IS MOVING FASTER THAN
PREVIOUSLY INDICATED. WAVE IS MOVING INTO PRE-EXISTING AREA OF
CONVECTION OVER THE FAR W CARIBBEAN...WITH NUMEROUS MODERATE TO
SCATTERED STRONG CONVECTION FROM 15N-20N BETWEEN 79W-84W...
COVERING THE CAYMAN ISLANDS. UPPER LEVEL ANTICYCLONE JUST SW OF
JAMAICA IS MOVING W IN TANDEM WITH THE WAVE AND IS CONTRIBUTING
TO STRONG UPPER LEVEL DIFFLUENCE OVER AND W OF THE WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N16W TO THE SOUTHERN CAPE VERDE
ISLANDS NEAR 15N24W...THEN CONTINUES W OF LARGE E ATLC WAVE FROM
10N30W-8N45W-9N60W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 120 NM S OF AXIS BETWEEN 21W-28W...WITH
SIMILAR CONVECTION NOTED WITHIN 60 NM OF AXIS BETWEEN 43W-49W.
SCATTERED MODERATE CONVECTION IS ALONG W END OF ITCZ FROM
7.5N-11N BETWEEN 56W-61W...JUST S OF TRINIDAD.

...DISCUSSION...

GULF OF MEXICO...
MID/UPPER LEVEL HIGH IS ANCHORED OVER E CENTRAL TEXAS...WITH
MID/UPPER LEVEL TROUGH EXTENDS NE-SW FROM CENTRAL FLORIDA TO A
WEAK LOW NEAR 21N91W...THEN SW TO 19N92W. TROUGH SEPARATES NE
FLOW OVER NORTHERN AND WESTERN GULF FROM SE-S FLOW OVER SE GULF
AND SOUTHERN HALF OF FLORIDA PENINSULA. SE-S FLOW IS ACCOMPANIED
BY A SLIGHT INCREASE IN HIGH LEVEL MOISTURE MOVING ACROSS THE
YUCATAN CHANNEL AND STRAITS OF FLORIDA. NW OF THE TROUGH...
MODERATE SUBSIDENCE AND ASSOCIATED DRIER AIR ALOFT IS NOTED. THE
TROUGH AND LOW ARE EXPECTED TO MOVE W-NW ACROSS THE GULF DURING
THE NEXT 24 HOURS AS AN MID/UPPER LEVEL HIGH BUILDS IN FROM THE
NW CARIBBEAN. SHOWERS AND TSTMS ASSOCIATED WITH THE W CARIBBEAN
TROPICAL WAVE ARE FORECAST TO SPREAD ACROSS THE YUCATAN
PENINSULA INTO THE BAY OF CAMPECHE AS UPPER LEVEL DIFFLUENCE AND
MOISTURE INCREASE S OF THE TROUGH AXIS.

CARIBBEAN...
THE AREA IS DOMINATED BY A MID/UPPER LEVEL HIGH CENTERED JUST SW
OF JAMAICA NEAR 17N79W. STRONG UPPER LEVEL DIFFLUENCE BETWEEN
THIS HIGH AND THE LOW OVER THE SOUTHERN GULF OF MEXICO IS
SUPPORTING NUMEROUS MODERATE/SCATTERED STRONG CONVECTION ALONG
AND W OF THE W CARIBBEAN WAVE NEAR 79W/80W. OVER THE E
CARIBBEAN...MOSTLY DRY NE MID/UPPER LEVEL FLOW IS EVIDENT ON
WATER VAPOR IMAGERY. THE DRY AIR IS SPREADING W ACROSS THE
CENTRAL AND SOUTHERN CARIBBEAN. THE HIGH SW OF JAMAICA IS
EXPECTED TO MOVE NW AND OUT OF THE AREA DURING THE NEXT 24
HOURS...WITH CONVECTION SPREADING NW ACROSS THE YUCATAN
PENINSULA AND WESTERN PORTIONS OF CUBA WITH THE WAVE AND
UNDERNEATH STRONGEST UPPER LEVEL DIFFLUENCE. DRIER MID/UPPER
LEVEL AIR WILL CONTINUE TO ADVECT W ACROSS THE CENTRAL
CARIBBEAN.

CENTRAL AND W ATLANTIC...
NARROW SUBTROPICAL RIDGE EXTENDS NEAR 32N FROM THE SOUTHEASTERN
UNITED STATES E TO NEAR 55W. SURFACE HIGH PRES 1021 MB NEAR
28N64W IS NEARLY STATIONARY. S OF THE RIDGE...A SMALL MID/UPPER
LEVEL HIGH NEAR 23N70W IS PRODUCING E-SE FLOW OVER THE TROPICAL
DISTURBANCE NEAR THE CENTRAL BAHAMAS AND PROVIDING GOOD OUTFLOW
OVER ALL BUT THE SW QUADRANT OF THE DISTURBANCE. A RIDGE EXTENDS
SE FROM THIS HIGH TO JUST N OF PUERTO RICO NEAR 20N65W TO E OF
THE LESSER ANTILLES NEAR 16N52W.

FARTHER E...MID-OCEANIC TROUGH SITS ALONG 32N42W-20N57W AND IS
DRIFTING E. THE TROUGH IS PRODUCING A BREAK IN THE OVERALL RIDGE
PATTERN OVER THE CENTRAL AND W ATLANTIC...HOWEVER LITTLE IN THE
WAY OF DEEP CONVECTION IS NOTED DUE TO MODERATE SUBSIDENCE/DRY
AIR ALOFT.

THE MID-OCEANIC TROUGH WILL MOVE W TO NEAR PUERTO RICO AND
HISPANIOLA OVER THE NEXT 24-36 HOURS...WITH HIGH PRES REMAINING
ON BOTH SIDES OF THE TROUGH W OF 45W. UPPER HIGH OVER THE W
ATLANTIC AND OFF THE FLORIDA COAST WILL PROVIDE FAVORABLE
CONDITIONS FOR DEVELOPMENT OF THE TROPICAL DISTURBANCE.

E ATLANTIC...
LARGE MID/UPPER HIGH IS CENTERED NEAR 20N33W...WITH ANTICYCLONIC
FLOW ALOFT DOMINATING MOST OF E ATLANTIC. ONLY EXCEPTION TO THIS
IS A SMALL WESTWARD-MOVING MID/UPPER LOW ABOUT 240 NM N OF THE
CAPE VERDE ISLANDS NEAR 21N24W. DEEPER MOISTURE SPREADING W IS
EVIDENT ON WATER VAPOR IMAGERY E OF 24W AS THE SINKING AIR AND
SAHARAN DUST LAYER ASSOCIATED WITH THE LARGE HIGH SHIFTS W.
LARGE TROPICAL WAVE IS EXPECTED TO REMAIN EMBEDDED IN THE
SAHARAN DUST LAYER AS THE HIGH MOVES W AHEAD OF THE WAVE. THIS
IN COMBINATION WITH RELATIVELY COOL SEA SURFACE TEMPERATURES
WILL PRECLUDE FURTHER DEVELOPMENT OF THE WAVE IN THE SHORT TERM.

$$
MOLLEDA






This weather bulletin was brought to you by:
www.nashvilleweather.net