[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201041
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1022 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLC EXTENDING FROM
19N42W TO 08N47W 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 ENGULFED BY SAL DRY AIR WITH SOME OF IT
SPREADING OVER THE ITS ENVIRONMENT WHICH IS SUPPRESSING DEEP
CONVECTION.

TROPICAL WAVE EXTENDS FROM 19N78W TO 09N78W MOVING W NEAR 10 KT.
THE WAVE AXIS LIES WITHIN A MODERATE MOIST ENVIRONMENT DEPICTED
IN TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED SHOWERS ARE WITHIN
150 NM W OF THE AXIS FROM 16N-19N AND WITHIN 60 NM EITHER SIDE
OF THE AXIS S OF 10N.

TROPICAL WAVE IS MOVING ALONG BELIZE...GUATEMALA AND EL SALVADOR
EXTENDING FROM 18N88W TO 10N89W AND MOVING W NEAR 15 KT KT. THE
WAVE IS EMBEDDED WITHIN A MODERATE MOIST ENVIRONMENT IN BELIZE
AND THE EAST PACIFIC WHILE THE REMAINING WAVE OVER LAND IS
WITHIN DRY AIR. SCATTERED MODERATED CONVECTION WITH ISOLATED
THUNDERSTORMS ARE OVER SOUTHERN BELIZE AND EASTERN GUATEMALA.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE WEST COAST OF AFRICA NEAR
12N16W TO 09N21W 06N26W. THE ITCZ BEGINS NEAR 06N26W AND
CONTINUES ALONG 04N33W TO 08N41W THEN IT RESUMES WEST OF A
TROPICAL WAVE ALONG 08N49W TO 06N57W. SCATTERED MODERATE
CONVECTION IS WITHIN 100 NM EITHER SIDE OF THE AXES E OF 31W AS
WELL AS FROM 07N-10N BETWEEN 53W-60W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LOW CENTERED OVER LOUISIANA CONTINUES TO EXTEND A
TROUGH INTO THE GULF W OF 87W. THIS IS SUPPORTING A SURFACE
TROUGH THAT EXTENDS FROM THE FLORIDA PANHANDLE TO 30N87W 28N90W
TO 25N94W. SMALL CLUSTERS OF MODERATE CONVECTION WITH ISOLATED
THUNDERSTORMS ARE WITHIN 200 NM SE OF THE TROUGH AXIS. DIVERGENT
FLOW ALOFT RESULTING FROM AN UPPER LEVEL HIGH WEST OF MEXICO AND
THE TROUGH OVER THE WESTERN GULF IS ENHANCING SCATTERED MODERATE
CONVECTION AND ISOLATED THUNDERSTORMS S OF 20N W OF 92W. ANOTHER
AREA OF DIVERGENT FLOW ALOFT DUE TO A RIDGE AXIS E OF 87W IS
ENHANCING SCATTERED SHOWERS IN THE YUCATAN CHANNEL. RETURN FLOW
WITH WINDS RANGING FROM 5-15 KT SPREADS ACROSS THE BASIN.

RAINSHOWERS ARE EXPECTED TO CONTINUE OVER THE GULF UNTIL SUNDAY
NIGHT WHILE THE SURFACE TROUGH ACROSS THE GULF CONTINUES TO MOVE
NW. RETURN FLOW IS ALSO EXPECTED TO PREVAIL DURING THAT TIME.

CARIBBEAN SEA...
UPPER LEVEL RIDGING COVERS MUCH OF THE WESTERN CARIBBEAN WHICH
IS PROVIDING NORTHERLY FLOW ALOFT THAT IS DRAWING MOISTURE SOUTH
FROM THE GULF OF MEXICO. THE REMNANTS OF A TROPICAL WAVE THAT IS
MOVING ACROSS CENTRAL AMERICA AS WELL AS DIFFLUENT FLOW ALOFT
FROM THE UPPER LEVEL LOW OVER THE WESTERN GULF AND THE HIGH TO
THE EAST ARE SUPPORTING SCATTERED MODERATE CONVECTION AND
ISOLATED THUNDERSTORMS N OF 16N W OF 83W. A TROPICAL WAVE IS
MOVING ACROSS THE WESTERN CARIBBEAN JUST WEST OF JAMAICA
EXTENDING FROM 19N78W TO 09N78W. ISOLATED SHOWERS ARE WITHIN 140
NM W OF THE AXIS FROM 16N-19N AS WELL AS EITHER SIDE OF THE AXIS
S OF 10N. ISOLATED SHOWERS AND THUNDERSTORMS ARE WITHIN 90 NM OF
THE COASTLINES OF NICARAGUA...COSTA RICA AND PANAMA. THE
REMAINDER OF THE BASIN IS UNDER MOSTLY FAIR CONDITIONS DUE TO
DRY AIR AT THE LOWER AND MIDDLE LEVELS ACTING TO SUPPRESS DEEP
CONVECTION. TRADEWINDS FROM 15 TO 25 KT SPREAD ACROSS THE BASIN
WITH THE MAXIMUM VALUES BEING ACROSS THE CENTRAL CARIBBEAN DUE
TO A TIGHTER PRESSURE GRADIENT.

THE WAVE OVER CENTRAL AMERICA IS EXPECTED TO BE COMPLETELY OVER
THE E PACIFIC EARLY ON SATURDAY WHILE THE SECOND TRAILING WAVE
IS EXPECTED TO DISSIPATE DUE TO INTERACTION WITH VERY 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 FOR THE
DOMINICAN REPUBLIC DUE TO A SURGE OF LOW LEVEL MOISTURE. THIS
MOISTURE WILL DRIFT WESTWARD TOWARD HAITI LATE ON SUNDAY AND
SHOWERS MAY BE EXPECTED.

ATLANTIC OCEAN...
A SURFACE TROUGH IS MOVING ACROSS THE BAHAMAS EXTENDING FROM
26N73W TO 23N79W. CONVECTION ASSOCIATED WITH IT HAS AUGMENTED TO
A CLUSTER OF MODERATE CONVECTION WITH EMBEDDED THUNDERSTORMS
FROM 22N-25N BETWEEN 76W-80W. N OF THAT CONVECTION...SCATTERED
SHOWERS ARE W OF 75W. SURFACE RIDGING IS ACROSS THE REMAINDER
BASIN ANCHORED BY A PAIR OF 1022 MB HIGHS...ONE NEAR 28N64W AND
THE OTHER NEAR 29N32W. BESIDES THE REGIONS FORMERLY
MENTIONED...FAIR WEATHER IS ACROSS THE ATLC SUPPORTED BY DRY AIR
AT THE LOWER AND MIDDLE LEVELS.

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

$$
NR


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