[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 18 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1722 UTC.

...SPECIAL FEATURES...
TROPICAL DEPRESSION ERIN IS CENTERED NEAR 20.5N 39.3W AT 18/1500
UTC OR ABOUT 912 NM W-NW OF THE CAPE VERDE ISLANDS MOVING WEST
AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. MAXIMUM
SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. SAHARAN DRY
AIR ENTRAINMENT TO THE SYSTEM ENVIRONMENT CONTINUES TO HINDER
DEEP CONVECTION AND ERIN COULD BECOME A REMNANT LOW SOON. PLEASE
SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT5/WTNT35 AND THE FULL FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...
A TROPICAL WAVE CAME OFF THE WEST AFRICAN COASTLINE AND EXTENDS
AN AXIS FROM 15N16W TO A 1009 MB LOW CENTER EMBEDDED WITHIN THE
MONSOON TROUGH NEAR 12N17W TO 04N18W. THE WAVE IS POSITIONED
WITHIN THE HIGH MOIST ENVIRONMENT OF THE MONSOON TROUGH WHICH IS
ENHANCING SCATTERED MODERATE CONVECTION WITHIN AN AREA BOUNDED
BY 07N12W TO 01S26W TO 08N30W TO 15N17W.

A TROPICAL WAVE IS MOVING ACROSS THE LESSER ANTILLES WITH AN
AXIS EXTENDING FROM 20N60W TO 10N61W AND MOVING WEST NEAR 5 KT.
THE WAVE REMAINS EMBEDDED WITHIN A MODERATE MOIST ENVIRONMENT N
OF 12N WHILE SOUTH OF THAT LATITUDE IT IS WITHIN A MOISTER
ENVIRONMENT. MOST OF THE LESSER ANTILLES HAS REPORTED
RAINSHOWERS WITHIN THE LAST COUPLE OF HOURS.

A TROPICAL WAVE IS MOVING ACROSS THE WESTERN CARIBBEAN SEA WITH
AXIS EXTENDING FROM 22N78W TO 10N79W AND MOVING W NEAR 10 KT.
EXCEPT FOR THE NORTHERN AND SOUTHERN ENDS OF THE ITS AXIS...THE
REMAINDER WAVE IS EMBEDDED IN A LOW TO MODERATE MOIST
ENVIRONMENT. A CLUSTER OF MODERATE CONVECTION AND TSTMS IS S OF
13N BETWEEN 77W-81W ASSOCIATED WITH THE MONSOON TROUGH AXIS.
SIMILAR CONVECTION IS FROM 21N-24N BETWEEN 75W-83W BEING
ENHANCED BY UPPER LEVEL DIFFLUENCE FROM A CYCLONIC CIRCULATION IN
THE WESTERN CARIBBEAN AND AN ANTICYCLONIC CIRCULATION OVER THE W
ATLC EXTENDING A RIDGE ACROSS FLORIDA AND THE EASTERN GULF.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E ATLC OVER
THE 1009 MB LOW/TROPICAL WAVE NEAR 12N17W CONTINUING ALONG
06N25W TO 07N34W. THE ITCZ BEGINS NEAR 07N35W AND CONTINUES TO
10N47W...THEN RESUMES WEST OF A 1012 MB LOW NEAR 12N53W AND
CONTINUES TO 11N60W. BESIDES THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE ALREADY DISCUSSED...ISOLATED MODERATE CONVECTION
AND TSTMS ARE FROM 08N-14N BETWEEN 45W-61W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM THE GREAT
LAKES SW TO THE WESTERN GULF CONTINUE TO SUPPORT A FRONTAL
SYSTEM ACROSS THE GULF. AS OF 1500 UTC...A WARM FROM EXTENDS
FROM A 1014 MB LOW OVER SE LOUISIANA NEAR 29N89W TO 30N85W TO SE
GEORGIA. A DISSIPATING STATIONARY FRONT EXTENDS SW FROM THE LOW
ALONG 27N91W 24N95W 21N97W. A SURFACE PRE-FRONTAL TROUGH ALSO
EXTENDS SW FROM THE LOW ALONG 27N89W 24N92W 21N94W 18N95W. A
CONTINUOUS LINE OF RAINSHOWERS AND TSTMS IS WITHIN 100 NM EITHER
SIDE OF THE TROUGH AXIS. FAIR WEATHER IS ACROSS THE REMAINDER
BASIN SUPPORTED BY DRY AIR SUBSIDENCE. THE FRONTAL BOUNDARY AND
ASSOCIATED LOW ARE EXPECTED TO BE INLAND BY VERY LATE MONDAY
WHILE THE PRE-FRONTAL TROUGH WILL BE OVER THE WESTERN BASIN
ENHANCING MORE RAINSHOWERS.

CARIBBEAN SEA...
A TROPICAL WAVE IS MOVING ACROSS THE WESTERN CARIBBEAN SEA WITH
AXIS EXTENDING FROM 22N78W TO 10N79W. EXCEPT FOR THE NORTHERN
AND SOUTHERN ENDS OF THE ITS AXIS...THE REMAINDER WAVE IS
EMBEDDED IN A LOW TO MODERATE MOIST ENVIRONMENT. A CLUSTER OF
MODERATE CONVECTION AND TSTMS IS S OF 13N BETWEEN 77W-81W
ASSOCIATED WITH THE MONSOON TROUGH AXIS. SIMILAR CONVECTION IS
FROM 21N-24N BETWEEN 75W-83W BEING ENHANCED BY UPPER LEVEL
DIFFLUENCE FROM A CYCLONIC CIRCULATION IN THE WESTERN CARIBBEAN
AND AN ANTICYCLONIC CIRCULATION OVER THE W ATLC EXTENDING A
RIDGE ACROSS FLORIDA AND THE EASTERN GULF. AN UPPER LEVEL HIGH
IS CENTERED S OF THE MONA PASSAGE BETWEEN 65W-76W WHICH IS
PROVIDING UPPER LEVEL DIFFLUENCE ACROSS THE HISPANIOLA AND THE
WINDWARD PASSAGE. THIS DIFFLUENCE IS ENHANCING SCATTERED SHOWERS
AND TSTMS ACROSS HISPANIOLA AND ADJACENT WATERS. FURTHER
EAST...A TROPICAL WAVE MOVES ACROSS THE LESSER ANTILLES WITH AN
AXIS EXTENDING FROM 20N60W TO 10N61W. THE WAVE REMAINS EMBEDDED
WITHIN A MODERATE MOIST ENVIRONMENT N OF 12N WHILE SOUTH OF THAT
LATITUDE IT IS WITHIN A MOISTER ENVIRONMENT. MOST OF THE LESSER
ANTILLES HAS REPORTED RAINSHOWERS WITHIN THE LAST COUPLE OF
HOURS.

THE WAVE OVER THE WESTERN BASIN IS EXPECTED TO MOVE ACROSS THE
YUCATAN PENINSULA MONDAY AFTERNOON WHILE THE SECOND WAVE WILL
START MOVING ACROSS HISPANIOLA.

HISPANIOLA...
AN UPPER LEVEL HIGH CENTERED S OF THE MONA PASSAGE BETWEEN 65W-
76W ALONG WITH AN UPPER LOW IN THE NW CARIBBEAN SEA PROVIDES
UPPER LEVEL DIFFLUENCE ACROSS THE HISPANIOLA AND THE WINDWARD
PASSAGE. THIS DIFFLUENCE IS ENHANCING SCATTERED SHOWERS AND
TSTMS ACROSS THE ISLAND AND ADJACENT WATERS. IF THE UPPER LEVEL
PATTERN PERSISTS RAINSHOWERS MAY CONTINUE THROUGHOUT THE DAY.
HOWEVER IF THERE IS A BREAK IN RAINSHOWER ACTIVITY DUE TO A
WESTWARD SHIFT OF THE UPPER LEVEL PATTERN...THIS ACTIVITY IS
EXPECTED TO RESUME AGAIN MONDAY AFTERNOON AS A TROPICAL
WAVE WILL START MOVING ACROSS THE ISLAND.

ATLANTIC OCEAN...
THERE ARE SCATTERED SHOWERS AND TSTMS S OF THE BAHAMAS BETWEEN
73W-81W ASSOCIATED WITH THE TROPICAL WAVE MOVING ACROSS THE
WESTERN CARIBBEAN AND AN UPPER LEVEL DIFFLUENCE PATTERN FROM A
CYLONIC CIRCULATION IN THE NW CARIBBEAN AND AN ANTICYCLONIC
CIRCULATION OVER THE W ATLC EXTENDING A RIDGE ACROSS FLORIDA AND
THE EASTERN GULF. FURTHER EAST...THE CONVECTION OVER HISPANIOLA
EXTENDS AS ISOLATED SHOWERS S OF 23N BETWEEN 65W-70W. MIDDLE
LEVEL DIFFLUENCE SUPPORTS ISOLATED SHOWERS AND TSTMS N OF 27N
BETWEEN 54W-63W. OTHERWISE...BESIDES THE SPECIAL FEATURE/ERIN
AND THE TROPICAL WAVES ALREADY DISCUSSED...FAIR WEATHER AND
SURFACE RIDGING ANCHORED BY A SET OF HIGH PRESSURE CENTERS NORTH
OF THE AREA DOMINATES THE REMAINDER BASIN.

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

$$
RAMOS


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