[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 262352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT SEP 26 2015

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.

...SPECIAL FEATURES...
TROPICAL DEPRESSION IDA IS CENTERED NEAR 24.4N 47.1W AT 26/2100
UTC OR ABOUT 970 NM E-NE OF THE NORTHERN LEEWARD ISLANDS MOVING
NW AT 7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB.
MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT.
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 23N-
26N BETWEEN 44W-46W. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS.

A MIDDLE TO UPPER LEVEL SHORTWAVE TROUGH IS NOTED ON WATER VAPOR
IMAGERY OVER THE NE CORNER OF THE YUCATAN PENINSULA THAT
SUPPORTS A 1008 MB LOW CENTERED NEAR 19N88W. THE SURFACE LOW...
PARTIALLY EXPOSED DUE TO SOUTHWESTERLY WIND SHEAR...IS
GENERATING SCATTERED MODERATE CONVECTION MAINLY NE OF THE LOW
CENTER FROM 18N-25N BETWEEN 82W-88W ACROSS PORTIONS OF THE NW
CARIBBEAN SEA AND SE GULF OF MEXICO. WHILE THE LOW IS EXPECTED
TO MOVE NORTH AT 10 KT DURING THE NEXT 24 TO 36 HOURS...IT WILL
BEGIN TO INTERACT WITH A STRONGER MIDDLE TO UPPER LEVEL LOW
CENTERED OVER THE TEXAS COAST. ASIDE FROM THE MEDIUM POTENTIAL
TO BECOME A TROPICAL CYCLONE...THE PRIMARY IMPACT FROM THIS
SYSTEM WILL REMAIN HEAVY RAINFALL AS IT TRACKS NORTHWARD ACROSS
THE EASTERN GULF OF MEXICO THROUGH MONDAY.

MID-LEVEL ENERGY IS NOTED ON WATER VAPOR IMAGERY IN THE VICINITY
OF 26N67W THAT SUPPORTS A 1011 MB SURFACE LOW CENTERED NEAR
27N69W. A SURFACE TROUGH AXIS EXTENDS S-SW TO 22N71W WITH
SCATTERED MODERATE CONVECTION OCCURRING GENERALLY WITHIN THE
EASTERN SEMICIRCLE OF THE LOW WITHIN 210 NM OF CENTER. THE
SYSTEM HOLDS A MEDIUM CHANCE FOR TROPICAL CYCLONE DEVELOPMENT
DURING THE NEXT 48 HOURS AS IT MOVES NORTHWARD AT 5-10 KT.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 09N34W TO 17N32W MOVING W AT 5 KT.
THE WAVE COINCIDES WITH BROAD 700 MB TROUGHING ALOFT BETWEEN 25W-
38W. ISOLATED MODERATE CONVECTION REMAINS LIMITED AND GENERALLY
OCCURRING WITHIN 120 NM EITHER SIDE OF A LINE FROM 16N25W TO
10N36W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 10N14W TO
09N18W TO 11N28W TO 06N40W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 06N40W TO 01N50W. NUMEROUS MODERATE AND
SCATTERED STRONG CONVECTION IS FROM 07N-15N BETWEEN 10W-17W.
WIDELY SCATTERED MODERATE CONVECTION IS ELSEWHERE FROM 08N-14N
BETWEEN 17W-21W. WIDELY SCATTERED MODERATE CONVECTION IS FROM
03N-10N BETWEEN 32N-43W.

...DISCUSSION...

GULF OF MEXICO...
AN ELONGATED AND BROAD UPPER LEVEL LOW IS NOTED ON WATER VAPOR
IMAGERY CENTERED OVER SOUTH-CENTRAL TEXAS THIS EVENING PROVIDING
MUCH OF THE GULF WITH SOUTH-SOUTHWESTERLY DIFFLUENT FLOW ALOFT.
THE MID-LEVEL LOW IS SLIGHTLY OFFSET TO THE EAST FROM THE UPPER
LEVEL LOW OVER THE NW GULF WITH PLENTY OF RELATIVE VORTICITY AND
DIFFLUENCE GENERATING WIDELY SCATTERED SHOWERS AND TSTMS ACROSS
MUCH OF THE GULF BASIN. GIVEN THE RELATIVE STRENGTH OF THE UPPER
LEVEL DYNAMICS...LOW PRESSURE REMAINS FOCUSED ON A 1009 MB LOW
CENTERED NEAR 24N94W WITH A SURFACE TROUGH EXTENDING N-NE TO
28N89W AND S-SE TO 19N92W. THE GENERAL SYNOPTIC-SCALE LOW
PRESSURE AREA REACHES SE TO ANOTHER LOW...THE 1008 MB SPECIAL
FEATURE...CENTERED ACROSS THE SE YUCATAN PENINSULA NEAR 19N88W.
BOTH OF THESE LOW PRESSURE AREAS ARE EXPECTED TO DRIFT NORTHWARD
DURING THE NEXT 24-36 HOURS WITH PLENTY OF PRECIPITATION
OCCURRING AS A RESULT ACROSS THE EASTERN GULF WATERS AND
PORTIONS OF THE FLORIDA PENINSULA.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE AXIS EXTENDS NORTH-SOUTH ALONG 80W OVER THE
WESTERN CARIBBEAN. ON THE WESTERN PERIPHERY OF THE RIDGING
ALOFT...SOUTHWESTERLY FLOW AND OVERALL DIFFLUENCE PREVAIL
GENERATING AREAS OF SCATTERED SHOWERS AND ISOLATED TSTMS N OF
17N W OF 75W...AND S OF 17N W OF 82W. THE CLOSE PROXIMITY OF THE
MONSOON TROUGH AXIS ALONG 10N BETWEEN NORTHERN COLOMBIA AND
COSTA RICA IS ALSO PROVIDING FOCUS FOR SCATTERED SHOWERS AND
TSTMS ACROSS INTERIOR PORTIONS OF CENTRAL AMERICA THIS EVENING.
ON THE EASTERN PERIPHERY OF THE UPPER LEVEL RIDGING...
RELATIVELY DRY NORTHERLY FLOW DOMINATES PROVIDING GENERALLY
CLEAR SKIES AND FAIR CONDITIONS E OF 75W. THIS NORTHERLY FLOW
ALOFT IS ALSO FOUND ON THE WESTERN PERIPHERY OF A BROAD UPPER
LEVEL LOW CENTERED NEAR 18N62W WHICH RETAINS VERY LITTLE IMPACT
ON THE BASIN AT THIS TIME. OTHERWISE...MAINLY FRESH TO
OCCASIONAL STRONG TRADES PERSIST WITH THE STRONGEST WINDS NOTED
ACROSS SOUTH-CENTRAL PORTIONS. BY MID-WEEK...THE TRADES ARE
EXPECTED TO RELAX SOMEWHAT INTO MODERATE TO FRESH BREEZE LEVELS.

...HISPANIOLA...
CURRENTLY LINGERING LATE AFTERNOON AND EARLY EVENING ISOLATED
SHOWERS CONTINUE TO GRADUALLY DIMINISH WITH MOSTLY FAIR SKIES
EXPECTED FOR THE OVERNIGHT HOURS INTO EARLY SUNDAY. NORTHERLY
FLOW ALOFT PREVAILS OVER THE ISLAND PROVIDING MOSTLY STABLE
CONDITIONS AT THIS TIME.

ATLANTIC OCEAN...
ASIDE FROM THE SPECIAL FEATURES LOW CENTERED NEAR 27N69W...THE
REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF WEAK
SURFACE RIDGING WITH ONLY A FEW ISOLATED SHOWERS AND TSTMS
OCCURRING ACROSS THE FLORIDA PENINSULA AND NEAR SHORE WATERS W OF
79W THIS EVENING. THIS CONVECTION IS LARGELY DUE TO UPPER LEVEL
DIFFLUENCE IN ASSOCIATION WITH THE SPECIAL FEATURES LOW PRESSURE
AREA ACROSS THE YUCATAN PENINSULA. FARTHER EAST ACROSS THE
CENTRAL ATLC IS TROPICAL DEPRESSION IDA...WITH A FRONTAL
BOUNDARY ANALYZED NORTH OF THE DISCUSSION AREA ALONG 34N BETWEEN
40W AND 75W. OTHERWISE...THE EASTERN ATLC IS UNDER THE INFLUENCE
OF A SURFACE RIDGE ANCHORED BY A 1019 MB HIGH CENTERED NEAR
30N32W.

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

$$
HUFFMAN
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