[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 180543
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED JUN 18 2008

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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 40W S OF 17N MOVING W 15-20 KT. A BROAD
LOW TO MID LEVEL CYCLONIC TURNING IS APPARENT ALONG THE AXIS
BETWEEN 8N-14N. A BAND OF SCATTERED MODERATE CONVECTION IS ALONG
12N37W TO 13N41W. SIMILAR CONVECTION IS ALSO AHEAD OF THE WAVE
AXIS FROM 11N-13N BETWEEN 40W-44W. THE TPW PRODUCT FROM CIMSS
SHOWS A VERY GOOD SURGE OF MOISTURE ASSOCIATED WITH THIS WAVE.
850 MB RELATIVE VORTICITY SUPPORTS THE WAVE POSITION. MOISTURE
FROM THIS TROPICAL WAVE IS EXPECTED TO REACH THE LESSER ANTILLES
ON THU.

A WEAK TROPICAL WAVE IS ALONG 56W S OF 15N MOVING W 15-20 KT.
THE WAVE SHOWS SOME INVERTED-V CLOUD PATTERN AND CONVECTION IS
MAINLY CONFINED TO THE ITCZ. MIMIC-TPW SHOWS A SLIGHT BULGE OF
MOISTURE N OF SURINAME AND GUIANA. THE SAHARAN AIR LAYER FROM
CIMSS INDICATES THAT THE WAVE REMAINS AT THE LEADING EDGE OF A
EXTENSIVE AREA OF AFRICAN DUST. SO...HAZY CONDITIONS SHOULD BE
EXPECTED LATER TODAY ACROSS THE LESSER ANTILLES AS THE TROPICAL
WAVE ENTERS THE E CARIBBEAN.

A TROPICAL WAVE IS OVER THE YUCATAN PENINSULA. ITS AXIS IS ALONG
88W S OF 22N MOVING W AT 10-15 KT. THE WAVE IS EMBEDDED IN AN
AREA OF DEEP LAYERED MOISTURE. THE WAVE...COMBINED WITH A
DIFFLUENT PATTERN ALOFT IS ENHANCING SOME SHOWER/TSTM ACTIVITY
OVER THE YUCATAN PENINSULA AND NORTHERN CENTRAL AMERICA.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N12W 5N25W 7N38W 6N42W 7N54W.
CLUSTERS OF MODERATE TO STRONG CONVECTION ARE MOVING OFF THE
AFRICAN COAST COVERING THE AREA FROM 5N-11N BETWEEN 10W-14W.
THIS CONVECTIVE ACTIVITY MAY BE ASSOCIATED WITH A NEW TROPICAL
WAVE. SIMILAR CONVECTION IS WITHIN 100 NM N OF AXIS BETWEEN
41W-44W WHERE THE TROPICAL WAVE MEETS THE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER-LEVEL TROUGH EXTENDS ACROSS THE GULF REGION WITH ITS
AXIS STRETCHING FROM N FLORIDA TO THE SOUTHERN BAY OF CAMPECHE.
A DIFFLUENT PATTERN BETWEEN THE LEADING EDGE OF THE TROUGH AND
AN UPPER-LEVEL HIGH OVER THE CARIBBEAN IS GENERATING A WIDE AREA
OF SHOWERS AND THUNDERSTORMS ACROSS WESTERN CUBA...THE STRAITS
OF FLORIDA AND THE BAHAMAS. ADDITIONAL SHOWERS AND ISOLATED
THUNDERSTORMS ARE MOVING INTO THE FAR NORTHERN GULF AHEAD OF A
FRONTAL BOUNDARY OVER THE SOUTHERN CONUS. THE REMAINDER OF THE
GULF IS RATHER TRANQUIL UNDER THE INFLUENCE OF A WEAK SFC HIGH
ANCHORED IN THE NW GULF NEAR 27N93W AT 03Z. THE WEAK PRESSURE
GRADIENT AROUND THE HIGH IS PRODUCING MAINLY LIGHT WINDS ACROSS
THE BASIN. EXPECT THE COLD FRONT CURRENTLY OVER THE SOUTHERN
CONUS TO MOVE INTO THE NORTHERN GULF WATERS LATE TODAY.

CARIBBEAN...
A BROAD UPPER-LEVEL RIDGE AROUND A HIGH NEAR 15N81W DOMINATES
THE WEATHER PATTERN IN THE CARIBBEAN WITH MODERATE TO STRONG
SUBSIDENCE S OF 17N KEEPING THE THE CENTRAL AND EASTERN
CARIBBEAN MOSTLY CLEAR WITH ONLY PATCHY LOW CLOUDS MOVING
THROUGH THE AREA. THE SAN JUAN DOPPLER RADAR SHOWS SCATTERED
SHOWERS MOVING WWD ACROSS THE VIRGIN ISLANDS AND PUERTO RICO
UNDER A PREVAILING ELY WIND FLOW. DIFFLUENCE ALOFT BETWEEN THIS
RIDGE AND THE AFOREMENTIONED TROUGH OVER THE GULF OF MEXICO IS
GENERATING A WIDE SWATH OF SHOWERS AND THUNDERSTORMS ACROSS THE
NW CARIBBEAN AND WESTERN CUBA. A BUILDING HIGH PRESSURE IN THE
ATLANTIC IS INCREASING THE TRADE WIND FLOW THROUGH THE CARIBBEAN
TO 20-25 KT...WITH UP TO 30 KT ALONG THE COLOMBIAN COAST.
UPPER-LEVEL MOISTURE/HIGH CLOUDS ASSOCIATED WITH STRONG UPPER
LEVEL ELY WINDS ARE AFFECTING THE WINDWARD ISLANDS AND THE FAR
SE CARIBBEAN.

ATLANTIC...
AS PREVIOUSLY MENTIONED...A BROAD AREA OF SHOWERS AND TSTMS IS
AFFECTING FROM WESTERN CUBA TO THE NW BAHAMAS...INCLUDING ALSO
SE FLORIDA. THIS CONVECTIVE ACTIVITY IS DRIVEN BY UPPER-LEVEL
DIFFLUENCE BETWEEN A TROUGH OVER THE GULF OF MEXICO AND A RIDGE
OVER THE CARIBBEAN SEA. A COLD FRONT IS EXPECTED TO MOVE OFF THE
EAST COAST OF THE CONUS TODAY BRINGING ADDITIONAL CONVECTION TO
THE AREA. MOSTLY ZONAL UPPER FLOW DOMINATES THE WEST AND CENTRAL
ATLC WITH A SHORTWAVE TROUGH NEAR 57W/58W N OF 21N. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE JUST AHEAD OF THE TROUGH AXIS
FROM 21N-26N. AN UPPER-LEVEL LOW IS OVER THE E ATLC NEAR 28N21W.
AN UPPER TROUGH EXTENDS FROM THE LOW TO THE CAPE VERDE ISLANDS.
THIS TROUGH SUPPORTS A TROUGH...REMNANTS OF A FRONTAL BOUNDARY
THAT RUNS FROM 31N38W TO 25N52W. A BAND OF MULTI-LAYERED CLOUDS
AND SCATTERED SHOWERS ARE ASSOCIATED WITH THE TROUGH. THIS
FEATURE SPLITS A PAIR OF SFC HIGH PRESSURE SYSTEMS. ONE IS
LOCATED NEAR 29N33W WITH CENTRAL PRESSURE OF 1024 MB. THE SECOND
ONE IS FURTHER WEST NEAR 29N50W WITH 1023 MB. THE PRESSURE
GRADIENT BETWEEN THE STRONGER HIGH AND LOWER PRES OVER AFRICA
WILL CONTINUE TO PRODUCE MODERATE NLY WINDS MAINLY N OF 16N AND
E OF 25W.

$$
GR/CW






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