Wednesday Morning Tropical Weather Discussion


Atlantic Tropical Weather Discussion

000
AXNT20 KNHC 181037
TWDAT

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

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 41W S OF 18N MOVING W 15-20 KT. A BROAD
MID LEVEL CYCLONIC TURNING IS APPARENT JUST AHEAD OF THE WAVE
AXIS NEAR 12N44W. DURING THE NIGHT...CONVECTION HAS FLARE UP
NEAR THE SOUTHERN END OF THE WAVE AXIS. CLUSTERS OF MODERATE TO
ISOLATED STRONG CONVECTION ARE NOTED FROM 6N-10N BETWEEN
40W-45W. THE TPW PRODUCT FROM CIMSS SHOWS A VERY GOOD SURGE OF
MOISTURE ASSOCIATED WITH THIS WAVE. 850 MB RELATIVE VORTICITY
ALSO SUPPORTS THE WAVE POSITION. MOISTURE FROM THIS TROPICAL
WAVE IS EXPECTED TO REACH THE LESSER ANTILLES LATE THURSDAY.

A WEAK TROPICAL WAVE IS ALONG 57W S OF 14N MOVING W 15-20 KT.
THE WAVE SHOWS SOME INVERTED-V CLOUD PATTERN AND CONVECTION IS
MAINLY CONFINED TO THE ITCZ. MIMIC-TPW SHOWS ONLY 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 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
89W/90W S OF 22N MOVING W NEAR 10 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 SE MEXICO...THE YUCATAN PENINSULA AND NORTHERN CENTRAL
AMERICA.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N14W 4N24W 5N37W 8N46W 6N54W.
CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE MOVING
OFF THE AFRICAN COAST COVERING THE AREA FROM 5N-9N E OF 17W TO
THE AFRICAN COAST. THIS CONVECTIVE ACTIVITY MAY BE ASSOCIATED
WITH A NEW TROPICAL WAVE. HOWEVER...AWAITING FOR NEW DATA AND
VIS SAT IMAGERY TO HAVE MORE EVIDENCE.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER-LEVEL TROUGH EXTENDS ACROSS THE GULF REGION WITH ITS
AXIS STRETCHING FROM THE SE CONUS TO THE YUCATAN PENINSULA. A
DIFFLUENT PATTERN BETWEEN THE LEADING EDGE OF THE TROUGH AND AN
UPPER-LEVEL HIGH LOCATED OVER THE CARIBBEAN...JUST SOUTH OF
JAMAICA...IS HELPING TO INDUCE A WIDE AREA OF SHOWERS AND
THUNDERSTORMS ACROSS THE NW CARIBBEAN...WESTERN CUBA...SOUTH
FLORIDA AND THE NW BAHAMAS. ADDITIONAL SHOWERS AND TSTMS ARE
INVADING THE NORTHERN GULF WATERS AHEAD OF A FRONTAL BOUNDARY
THAT CURRENTLY LIES MAINLY ALONG 30N...FROM SE GEORGIA TO THE
UPPER TEXAS COAST. THE REMAINDER OF THE GULF IS RATHER TRANQUIL
UNDER THE INFLUENCE OF A WEAK SFC HIGH ANCHORED IN THE NW GULF
NEAR 27N92W AT 09Z. THE WEAK PRESSURE GRADIENT AROUND THE HIGH
IS PRODUCING MAINLY LIGHT WINDS ACROSS THE BASIN. EXPECT THE
COLD FRONT TO MOVE INTO THE NE GULF WATERS TODAY AND STALL
TONIGHT LIFTING OUT TO THE NE OF AREA THU NIGHT.

CARIBBEAN...
A BROAD UPPER-LEVEL RIDGE AROUND A HIGH NEAR 16N78W DOMINATES
THE WEATHER PATTERN IN THE CARIBBEAN WITH MODERATE TO STRONG
SUBSIDENCE S OF 17N KEEPING THE CENTRAL AND EASTERN CARIBBEAN
MOSTLY CLEAR WITH ONLY PATCHY LOW CLOUDS MOVING THROUGH THE
AREA. DIFFLUENCE ALOFT BETWEEN THIS RIDGE AND THE AFOREMENTIONED
TROUGH OVER THE GULF OF MEXICO IS GENERATING AN AREA OF SHOWERS
AND THUNDERSTORMS ACROSS THE NW CARIBBEAN AND WESTERN CUBA. A
BUILDING HIGH PRESSURE IN THE ATLANTIC IS KEEPING THE TRADE WIND
FLOW THROUGH THE CARIBBEAN TO 20-25 KT. UPPER-LEVEL MOISTURE AND
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 AND THE W ATLC W OF 72W. THIS CONVECTIVE ACTIVITY IS
DRIVEN BY UPPER-LEVEL DIFFLUENCE BETWEEN A TROUGH OVER THE GULF
OF MEXICO AND A RIDGE OVER THE CARIBBEAN SEA. LIGHTNING DATA
REVEALS THAT TSTMS ARE MORE CONCENTRATED OVER THE NW BAHAMAS AND
N REGIONAL WATERS. A COLD FRONT IS EXPECTED TO MOVE OFF THE SE
CONUS TODAY BRINGING ADDITIONAL CONVECTION TO THE AREA. MOSTLY
ZONAL UPPER FLOW DOMINATES THE WEST AND CENTRAL ATLC WITH A
SHORTWAVE TROUGH NEAR 56W/57W N OF 20N. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE JUST AHEAD OF THE TROUGH AXIS FROM 21N-26N. A
SFC TROUGH IS ANALYZED IN THIS AREA AND STRETCHES FROM 31N38W TO
24N52W. THIS TROUGH SEPARATES A COUPLE OF SFC HIGH PRESSURE
SYSTEMS. ONE IS LOCATED NEAR 29N33W WITH CENTRAL PRESSURE OF
1023 MB. THE SECOND ONE IS FURTHER WEST NEAR 31N47W 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. AN UPPER-LEVEL LOW IS OVER THE E
ATLC NEAR 28N21W WITH AN UPPER-LEVEL TROUGH EXTENDING FROM THE
LOW TO THE CAPE VERDE ISLANDS.

$$
GR/CW


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