[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 262348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 26 2014

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 67W FROM 12N TO 22N
CROSSING WESTERN PUERTO RICO. THE WAVE IS INTERACTING WITH AN
UPPER-LEVEL LOW AND IS PRODUCING A LARGE AREA OF MODERATE
CONVECTION PARTICULARLY S OF PUERTO RICO TO ABOUT 15N AND JUST
NE OF THE LEEWARD ISLANDS COVERING THE REGION FROM 16N TO 20N
BETWEEN 58W AND 63W. THE WAVE WILL CONTINUE TO MOVE WESTWARD...
REACHING THE CENTRAL CARIBBEAN TONIGHT AND THE WESTERN CARIBBEAN
SAT NIGHT. HOWEVER THE UPPER-LOW IS FORECAST TO REMAIN NEAR
PUERTO RICO AND THE UK/US VIRGIN ISLANDS THROUGH THE WEEKEND
KEEPING THE ATMOSPHERE VERY UNSTABLE WITH THE POTENTIAL OF MORE
SHOWERS AND TSTMS.

A TROPICAL WAVE IS OVER THE YUCATAN PENINSULA GENERATING SOME
SHOWER AND TSTMS MAINLY ON THE EAST SIDE OF THE WAVE AXIS. THIS
WAVE WILL MOVE ACROSS THE SW GULF OF MEXICO TONIGHT AND SAT.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS OVER AFRICA INTO THE TROPICAL ATLC
NEAR 12N16W AND CONTINUES TO NEAR 13N37W. THE ITCZ EXTENDS FROM
12N45W TO JUST EAST OF TRINIDAD AND TOBAGO NEAR 10N60W. A
CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION IS ALONG THE
COAST OF AFRICA FROM 11N TO 14N LIKELY ASSOCIATED WITH THE NEXT
TROPICAL WAVE. NO SIGNIFICANT CONVECTION IS NOTED ELSEWHERE.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER TROUGH IS OVER THE CENTRAL PLAIN STATES FROM THE
UPPER MISSISSIPPI VALLEY TO W TEXAS GIVING THE GULF W-SW FLOW
ALOFT. UPPER DIFFLUENCE BETWEEN THIS TROUGH AND A RIDGE OVER THE
NW CARIBBEAN IS HELPING TO INDUCE SCATTERED MODERATE CONVECTION
ACROSS THE NORTHERN HALF OF THE GULF. THIS ACTIVITY IS FURTHER
ENHANCED BY A WEAKENING STATIONARY FRONT THAT EXTENDS FROM THE
TAMPA BAY AREA ACROSS THE CENTRAL GULF TO NEAR 25N94W AT 26/2100
UTC. A TROUGH EXTENDS FROM THIS POINT TO 22N95W TO 19N94W. THIS
FRONTAL BOUNDARY COMBINED WITH DIURNAL HEATING IS HELPING TO
GENERATE SHOWERS AND THUNDERSTORMS ACROSS PARTS OF THE FLORIDA
PENINSULA AND COASTAL WATERS MORE CONCENTRATED OVER CENTRAL
FLORIDA BASED ON THE MOSAIC DOPPLER RADAR FROM THE SE U.S.. NE
WINDS OF 15-20 KT ARE NOTED OVER THE NW PART OF THE GULF BY AN
EARLIER ASCAT PASS. THE SAME SCATTEROMETER PASS SHOWED VERY WELL
THE WIND SHIFT ASSOCIATED WITH THE AFOREMENTIONED TROUGH. THE
FRONT WILL DRIFT N AND DISSIPATE THROUGH TONIGHT. THE FRONTAL
REMNANTS WILL MOVE W AS A TROUGH WITH WEAK LOW PRES FORMING
ALONG IT OVER THE N CENTRAL GULF BY SUN NIGHT.

CARIBBEAN SEA...
AS PREVIOUSLY MENTIONED...AN UPPER-LEVEL RIDGE IS OVER THE NW
CARIBBEAN. A DIFFLUENT PATTERN ALOFT ASSOCIATED WITH THIS SYSTEM
IS SUPPORTING THE DEVELOPMENT OF SCATTERED SHOWERS AND TSTMS
OVER THE YUCATAN PENINSULA AND WESTERN CUBA. AN UPPER-LEVEL LOW
IS CENTERED OVER PUERTO RICO WITH A TROUGH EXTENDING FROM THE
LOW CENTER TO THE SW CARIBBEAN. SOUTHWESTERLY FLOW AHEAD OF THIS
TROUGH IS TRANSPORTING ABUNDANT TROPICAL MOISTURE FROM NORTHERN
SOUTH AMERICA INTO THE EASTERN CARIBBEAN. A TROPICAL WAVE IS
ALSO OVER PUERTO RICO. SEE TROPICAL WAVES SECTION FOR DETAILS.
GENTLE TO MODERATE TRADES WILL CONTINUE TO PREVAIL ACROSS THE
BASIN THROUGH THE WEEKEND AS HIGH PRES REMAINS WEAK N OF AREA.

...HISPANIOLA...
SCATTERED SHOWERS AND TSTMS FLARED UP ACROSS THE ISLAND THIS
AFTERNOON UNDER THE INFLUENCE OF AN UPPER-LEVEL LOW CURRENTLY
CENTERED NEAR THE SW PART OF PUERTO RICO. THE ABUNDANCE OF
MOISTURE ACCOMPANYING THE TROPICAL WAVE AND THE UPPER LOW OVER
PUERTO RICO WILL CONTINUE TO SPREAD ACROSS HISPANIOLA DURING THE
WEEKEND. AS A RESULT...EXPECT AN INCREASE IN SHOWER AND TSTM
ACTIVITY.

ATLANTIC OCEAN...
A STATIONARY FRONT EXTENDS FROM 31N78W TO CENTRAL FLORIDA. THIS
FRONT IS FORECAST TO LIFT NORTHWARD ALONG THE FLORIDA COAST AND
GRADUALLY DISSIPATE THROUGH SAT. THE ATLANTIC HIGH PRES REMAINS
WEAK ACROSS THE FORECAST AREA. SEVERAL WEAK LOW PRES AREAS ARE
NOTED INSTEAD. ONE IS NEAR 28N45W WITH A CENTRAL PRES OF 1012
MB. A TROUGH EXTENDS FROM THE LOW CENTER TO NEAR 24N50W. THIS
SYSTEM IS GENERATING SOME SHOWER ACTIVITY. THE MOST RECENT ASCAT
PASS SHOWED FRESH TO STRONG WINDS ON THE NE QUADRANT OF THE LOW.
ANOTHER SURFACE TROUGH IS ANALYZED ACROSS THE ATLANTIC AND
STRETCHES FROM 29N30W TO A 1011 MB LOW PRES NEAR 17N76W FORECAST
TO DISSIPATE IN ABOUT 24 HOURS. AN EARLIER SCATTEROMETER PASS
CONFIRMED THE PRESENCE OF THESE TWO FEATURES. THE THIRD LOW PRES
OF 1011 MB IS EMBEDDED WITHIN THE ITCZ NEAR 13N43W AND IS
FORECAST TO REMAIN NEARLY STATIONARY DURING THE NEXT 24 HOURS.
NONE OF THESE LOWS HAVE THE POTENTIAL OF TROPICAL CYCLONE
DEVELOPMENT. IN FACT...TROPICAL CYCLONE FORMATION IS NOT
EXPECTED DURING THE NEXT 5 DAYS ACCORDING WITH THE LATEST
TROPICAL WEATHER OUTLOOK ISSUED BY THE NATIONAL HURRICANE
CENTER. THE NORTHERN EXTENT OF THE TROPICAL WAVE NOW LOCATED
OVER PUERTO RICO WILL MOVE ACROSS THE FAR SOUTHERN WATERS OF THE
SW N ATLANTIC THROUGH SUN.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
GR


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