[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 162350
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUL 16 2012

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...

TROPICAL WAVE IS ADDED OFF THE COAST OF AFRICA ALONG 19N20W TO
13N17W MOVING W AT 10-15 KT. THE WAVE LIES ON THE E SIDE OF A
SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER
IMAGERY. THERE IS ALSO A CLEARING IN THE SAHARAN DUST LAYER WITH
AN AREA OF DENSE DUST DIRECTLY BEHIND THE WAVE. DUE TO THIS AREA
OF DUST...NO DEEP CONVECTION IS CURRENTLY NEAR THE AXIS.

TROPICAL WAVE IS ALONG 18N42W TO 10N46W MOVING W AT 15-20 KT.
THE WAVE LIES ON THE W SIDE OF A SURFACE OF DEEP LAYER MOISTURE
PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. IT ALSO COINCIDES
WITH 700 MB MODEL DATA THAT INDICATES A MID-LEVEL TROUGH...OFTEN
THE STRONGEST INDICATION OF THE WAVE...NEAR THE SURFACE
LOCATION. SCATTERED MODERATE CONVECTION IS NEAR THE SRN TIP OF
THE WAVE WITHIN THE ITCZ REGION FROM 8N-10N BETWEEN 43W-48W.

TROPICAL WAVE MOVES ACROSS THE N CENTRAL CARIBBEAN AND SW
BAHAMAS ALONG 23N75W TO 15N76W MOVING W AT 10-15 KT. THE WAVE IS
EMBEDDED WITHIN AN AREA OF ENHANCED MOISTURE PRESENT ACROSS MUCH
OF THE NRN CARIBBEAN. UPPER LEVEL RIDGE IS DRAWING SOME OF THE
MOISTURE TOWARDS THE SE INTO THE SE CARIBBEAN. DAYTIME HEATING
HAS HELPED FORM CLUSTER OF STRONG CONVECTION NEAR THE WAVE AXIS.
ONE CLUSTER IS ACROSS HAITI FROM 18N-21N BETWEEN 72W-74W. OTHERS
ARE OVER JAMAICA FROM 18N-19N BETWEEN 77W-80W...AND ACROSS ERN
CUBA FROM 20N-21N BETWEEN 75W-77W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
GUINEA-BISSAU AT 13N17W CONTINUING S OF THE TROPICAL WAVE TO
NEAR 9N30W TO S OF ANOTHER TROPICAL WAVE ALONG 11N40W 9N47W. THE
ITCZ BEGINS AT 9N47W CONTINUING ALONG 8N52W TO 9N61W. SCATTERED
MODERATE CONVECTION IS FROM 8N-10N BETWEEN 31W-34W...AND FROM
7N-9N BETWEEN 48W-53W.

...DISCUSSION...

GULF OF MEXICO...
A PAIR OF UPPER LEVEL LOWS IS IMPACTING THE GULF OF MEXICO AND
IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM THE BIG BEND OF
FLORIDA NEAR 30N83W TO THE CENTRAL GULF AT 25N89W TO THE SW GULF
NEAR 19N93W. ONE OF THE UPPER LOWS IS CENTERED JUST OFFSHORE OF
NE FLORIDA NEAR 30N81W...WHILE THE SECOND COVERS THE SE GULF
CENTERED NEAR 23N86W. THE FIRST UPPER LOW IN COMBINATION WITH
THE SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS
ALL UP THE FLORIDA PENINSULA ALONG WITH A FEW ISOLATED SHOWERS
OVER THE GULF WATERS NEAR THE TROUGH AXIS. THE SECOND UPPER LOW
IS SUPPORTING SHOWERS/THUNDERSTORMS OVER PORTIONS OF THE YUCATAN
PENINSULA AND WRN CUBA. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO
ALONG THE REMAINDER OF THE SURFACE TROUGH. DESPITE THE EXPANSIVE
SURFACE TROUGH...SURFACE RIDGING COVERS MUCH OF THE NRN GULF
EXTENDING FROM A 1018 MB HIGH OVER ALABAMA. THE HIGH IS
SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED OVER ARKANSAS THAT
EXTENDS INTO THE NRN GULF. MODEL GUIDANCE INDICATES THAT THE
SURFACE TROUGH WILL SPLIT LEAVING THE NRN PORTION MAINLY
STATIONARY...WHILE THE SRN PORTION DRIFTS W. SURFACE RIDGING
WILL REMAIN DOMINANT ACROSS THE REST OF THE BASIN. THE UPPER
TROUGH/LOWS WILL ALSO REMAIN OVER THE ERN HALF OF THE
BASIN...AND WILL LIKELY CAUSE MOIST CONDITIONS TO STAY OVER THIS
AREA.

CARIBBEAN SEA...
THE UPPER LEVEL LOW OVER THE SE GULF OF MEXICO EXTENDS INTO THE
NW CARIBBEAN SUPPORTING SHOWERS/THUNDERSTORMS NEAR THE COAST OF
THE YUCATAN PENINSULA...NICARAGUA...AS WELL AS OVER WRN CUBA.
SHOWERS/THUNDERSTORMS ARE ALSO OVER COSTA RICA AND PANAMA
ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS S OF COSTA RICA
AND PANAMA TO NRN COLOMBIA. A TROPICAL WAVE APPROACHING JAMAICA
AND ERN CUBA IS HELPING PRODUCE SHOWERS/THUNDERSTORMS OVER BOTH
THESE AREAS ALONG WITH HAITI. SEE TROPICAL WAVE SECTION ABOVE
FOR MORE DETAILS. AN UPPER LEVEL RIDGE COVERS THE CENTRAL
CARIBBEAN EXTENDING FROM THE WINDWARD PASSAGE TO COSTA RICA. THE
ERN SIDE OF THE RIDGE IS ACCOMPANIED BY DRY AIR WHICH IS HELPING
MAINTAIN FAIR CONDITIONS BESIDES NEAR THE WAVE. THE ERN
CARIBBEAN IS COVERED BY A DRY UPPER LEVEL TROUGH EXTENDING FROM
THE CENTRAL ATLC TO THE VIRGIN ISLANDS TO NW VENEZUELA. VISIBLE
SATELLITE IMAGERY ALONG WITH SURFACE OBSERVATIONS INDICATE THAT
AN AREA OF SAHARAN DUST COVERS MUCH OF THE ERN CARIBBEAN FURTHER
SUPPORTING FAIR CONDITIONS. TRADEWIND FLOW OF 20-25 KTS IS
PRESENT OVER THE CENTRAL CARIBBEAN WITH LIGHTER WINDS TO EITHER
SIDE. EXPECT THE WAVE TO CONTINUE MOVING WWD DRAWING MOISTURE
OVER THE NW CARIBBEAN.

ATLANTIC OCEAN...
AN UPPER LEVEL LOW CENTERED OFF THE NE COAST OF FLORIDA NEAR
30N81W IS SUPPORTING SHOWERS/THUNDERSTORMS FROM 26N-31N BETWEEN
73W-76W...AS WELL AS FROM 23N-26N BETWEEN 76W-79W. THE REMAINDER
OF THE W ATLC IS DOMINATED BY SURFACE RIDGING AROUND A 1020 MB
HIGH NEAR 28N67W. THE HIGH IS SUPPORTED BY AN UPPER LEVEL RIDGE
E OF THE UPPER LOW. A SECOND UPPER LEVEL TROUGH EXTENDS FROM
NEAR 30N47W TO THE VIRGIN ISLANDS IN THE CARIBBEAN. THIS TROUGH
SUPPORTS A SURFACE TROUGH ALONG 31N54W TO 27N55W. ISOLATED
SHOWERS ARE WITHIN 120 NM E OF THE AXIS. THE ERN ATLC IS COVERED
BY SURFACE RIDGING ANCHORED BY A 1030 MB HIGH NEAR
43N16W...WHICH IS PROVIDING FAIR WEATHER ACROSS THE REMAINDER OF
THE BASIN. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE
EXTENDING FROM NEAR 19N39W TO 32N12W. VISIBLE SATELLITE IMAGERY
INDICATES AN INTENSE SURGE OF SAHARAN DUST HAS EMERGED OFF THE
COAST OF AFRICA BEHIND A TROPICAL WAVE. DUST ALSO EXTENDS
BETWEEN THE TWO ATLC WAVES.

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

$$
WALTON




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