[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200558
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT JUL 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0522 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLC EXTENDING FROM
19N41W TO 10N43W AND MOVING W-SW NEAR 10 KT. THE WAVE AXIS LIES
WITHIN A MODERATE MOIST ENVIRONMENT AS DEPICTED IN TOTAL
PRECIPITABLE WATER IMAGERY. THE METEOSAT-9 SAL TRACKING IMAGERY
SHOW THE WAVE IS BEING ENGULFED BY DRY AIR WITH SOME OF IT
SPREADING OVER THE WAVE ENVIRONMENT WHICH IS HINDERING DEEP
CONVECTION.

TROPICAL WAVE EXTENDS FROM 19N76W TO 10N77W MOVING W NEAR 5 KT.
THE WAVE AXIS LIES WITHIN A MODERATE MOIST ENVIRONMENT AS
DEPICTED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE
CONVECTION IS WITHIN 150 NM W OF THE AXIS FROM 15N-17N.

TROPICAL WAVE IS MOVING ACROSS CENTRAL AMERICA EXTENDING FROM
17N86W TO 07N86W MOVING W NEAR 5 KT KT. THE WAVE IS EMBEDDED
WITHIN A HIGH MOIST ENVIRONMENT OVER THE W CARIBBEAN AND THE
EAST PACIFIC WHILE THE PORTION OF THE WAVE OVER LAND IS WITHIN
DRY AIR. SCATTERED MODERATED CONVECTION WITH ISOLATED
THUNDERSTORMS ARE FROM 17N-19N BETWEEN 84W-88W AS WELL AS OVER
NICARAGUA AND ITS COASTAL WATERS S OF 12N.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE WEST COAST OF AFRICA NEAR
18N16W TO 13N20W 06N25W. THE ITCZ BEGINS NEAR 06N25W AND
CONTINUES ALONG 04N34W TO 07N41W THEN IT RESUMES WEST OF A
TROPICAL WAVE ALONG 09N46W TO 06N58W. SCATTERED MODERATE
CONVECTION IS FROM 06N-13N BETWEEN E OF 27W. ISOLATED MODERATE
CONVECTION IS WITHIN 120 NM N OF THE ITCZ W OF 46W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH EXTENDS FROM THE LOWER MISSISSIPPI VALLEY
INTO THE GULF W OF 87W. THIS IS SUPPORTING A SURFACE TROUGH THAT
EXTENDS FROM THE FLORIDA PANHANDLE TO 30N86W 27N90W 25N93W TO
23N96W. AN UPPER LEVEL RIDGE AXIS EXTENDS E OF 87W INTO THE W
CARIBBEAN. MODERATE MOISTURE AT THE LOWER LEVELS AND DIFFLUENCE
ALOFT IS ENHANCING ISOLATED SHOWERS SE OF THE SURFACE TROUGH N
OF 24N E OF 89W. CONTINUOUS RAINSHOWERS HAVE BEEN REPORTED
ACROSS THE FLORIDA PANHANDLE. WINDS ACROSS THE BASIN RANGE FROM
5-15 KT.

THE UPPER LEVEL DIFFLUENT PATTERN IS EXPECTED TO PREVAIL WITHIN
THE NEXT 48 HOURS AND RAINSHOWERS CAN BE EXPECTED ACROSS THE
GULF. MOISTURE ASSOCIATED WITH A SURFACE TROUGH CURRENTLY OVER
THE BAHAMAS WILL ALSO BRING INCREASED ACTIVITY TO THE SE GULF
OVER THE WEEKEND.

CARIBBEAN SEA...
UPPER LEVEL RIDGING COVERS MUCH OF THE WESTERN CARIBBEAN WHICH
IS PROVIDING NORTHERLY FLOW ALOFT OVER THE WESTERN PART OF THE
AREA DRAWING MOISTURE SOUTH FROM THE GULF OF MEXICO. TWO
TROPICAL WAVES ARE ALSO IN THIS AREA...ONE MOVING ACROSS CENTRAL
AMERICA AND THE OTHER ACROSS JAMAICA INTO THE SOUTHERN
CARIBBEAN. THESE WAVES ARE LEADING TO SCATTERED
RAINSHOWERS/ISOLATED THUNDERSTORMS N OF 16N W OF 78W. SIMILAR
ACTIVITY IS ACROSS NICARAGUA AS WELL AS S OF 12N W OF 78W. THE
REMAINDER OF THE BASIN IS UNDER MOSTLY FAIR CONDITIONS DUE TO
DRY AIR ALOFT AROUND A WEAK AND BROAD UPPER LOW NEAR 11N71W.

THE WAVE OVER CENTRAL AMERICA IS EXPECTED TO BE COMPLETELY OVER
THE E PACIFIC WITHIN 24 HOURS WHILE THE SECOND TRAILING WAVE IS
EXPECTED TO VANISH DUE TO INTERACTION WITH DRY AIR AT THE LOWER
LEVELS.

HISPANIOLA...
DRY AIR IS ACROSS LA HISPANIOLA LIMITING ANY CONVECTIVE ACTIVITY
EVEN THAT A DIVERGENT PATTERN IS ALOFT. A DRY AIR MASS WILL
CONTINUE TO BRING FAIR WEATHER TO THE ISLAND UNTIL EARLY SUNDAY
AFTERNOON WHEN CONDITIONS CAN START TO DETERIORATE DUE TO A SURGE
OF LOW LEVEL MOISTURE.

ATLANTIC OCEAN...
A SURFACE TROUGH IS MOVING ACROSS THE BAHAMAS EXTENDING FROM
26N73W TO 22N77W AND GENERATING SLIGHT SHOWERS N OF 22N W OF
75W. SURFACE RIDGING IS ACROSS THE REMAINDER BASIN ANCHORED BY A
1024 MB HIGH NEAR 28N64W AND A 1023 MB HIGH NEAR 29N35W. BESIDES
THE REGIONS FORMERLY MENTIONED...FAIR WEATHER IS ACROSS THE
ATLC SUPPORTED BY DRY AIR AT THE LOWER LEVELS.

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

$$
NR


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