Wednesday Morning Tropical Weather Discussion

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.


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