[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT MAY 16 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 10N14W TO
06N19W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
06N19W TO 05N32W TO THE COAST OF S AMERICA NEAR 03N51W.
SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 180 NM S OF
THE MONSOON AND ITCZ 15W-21W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 120 NM N OF THE MONSOON TROUGH AND ITCZ
BETWEEN 17W-21W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM
N OF THE ITCZ BETWEEN 50W-51W...AND ALSO N OF THE ITCZ WITHIN 30
NM OF LINE FROM 35W-37W.

...DISCUSSION...

GULF OF MEXICO...

BOTH MODEL GUIDANCE AND WATER VAPOR IMAGERY SHOW AN UPPER TROUGH
OVER FAR EASTERN TEXAS APPROACHING THE BORDER OF LOUISIANA...AND
EXTENDING S TO NEAR 24N92W. AHEAD AND SE OF THIS TROUGH...
MOISTURE IN THE FORM OF MID/UPPER LEVEL CLOUDS IS PRESENT. AT
THE SURFACE...A RIDGE EXTENDS SW FROM THE FLORIDA BIG BEND AREA
TO THE NE COAST OF MEXICO. LOW-LEVEL MOIST SE FLOW AROUND THE
WESTERN PERIPHERY IS ALLOWING FOR SCATTERED TO LOCALLY BROKEN
LOW CLOUDS WITH ISOLATED SHOWERS TO MOVE IN A NW DIRECTION E OF
ABOUT 91W. THE RIDGE IS ALLOWING FOR GENERALLY GENTLE TO
MODERATE SW WINDS TO CONTINUE OVER THE AREA.

THE UPPER TROUGH IS FORECAST TO SHIFT EASTWARD TO THE EASTERN
GULF BY MON...WITH ASSOCIATED UPPER DIFFLUENCE EXPECTED TO MORE
NOTICEABLE THERE. WITH THIS IN MIND...EXPECT ISOLATED SHOWERS
AND TSTMS OVER THAT PART OF THE GULF WITH SCATTERED SHOWERS AND
TSTMS EXPECTED TO DEVELOP CLOSER THE NE GULF COAST SUN AND MON
MAINLY FROM INFLUENCES RELATED TO SURFACE BOUNDARIES THERE. THE
GENTLE TO MODERATE SE WINDS WILL CONTINUE THROUGH MON UNDER THE
INFLUENCE OF THE RIDGE...WITH THE EXCEPTION OF THE NW COAST OF
THE YUCATAN PENINSULA WHERE A TIGHT PRES GRADIENT WILL
MATERIALIZE THERE AT NIGHT RESULTING IN STRONG E-SE WINDS THAT
SHIFT FROM THAT WESTWARD ACROSS THE EASTERN PART IF THE SW GULF
THAT THE LATE NIGHT HOURS.

CARIBBEAN SEA...

A WEAK AND SMALL UPPER LOW IS NOTED OVER THE FAR WESTERN TIP OF
CUBA WITH A TROUGH EXTENDING S TO NE HONDURAS. UPPER-LEVEL SW
FLOW E OF THE TROUGH CONTINUES TO ADVECT DEEP ATMOSPHERIC
MOISTURE...THAT ORIGINATES FROM THE EASTERN PACIFIC...ACROSS
JUST ABOUT THE ENTIRE BASIN. SATELLITE IMAGERY SHOWS CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION CONFINED TO THE SW
CARIBBEAN S OF ABOUT 12N AND W OF 78W TO INLAND PORTIONS OF
COSTA RICA AND PANAMA. DEBRIS UPPER LEVEL CLOUDS...IN THE FORM OF
BROKEN CIRRUS...IS BEING ADVECTED IN THE SW FLOW ALOFT NEWD
TOWARDS JAMAICA...HISPANIOLA...AND EASTWARD TO PUERTO RICO...AND
THE LEEWARD ISLANDS.

THE SURFACE HIGH CENTERED OVER THE W ATLANTIC THAT EXTENDS SW
ACROSS THE GULF ALSO REACHES THE WESTERN CARIBBEAN. THE
ASSOCIATED PRES GRADIENT BETWEEN IT AND BROAD LOW PRES OVER THE
SW CARIBBEAN AND NW COLOMBIA IS ALLOWING FOR FRESH TO STRONG
TRADES TO PERSIST OVER THE S CENTRAL CARIBBEAN AS SEEN IN THE
ASCAT PASS FROM THIS MORNING. MODERATE TO FRESH TRADES ARE
ELSEWHERE S OF 17N...AND MODERATE TRADES N OF 17N EXCEPT FOR
GENTLE TO MODERATE TRADES OVER THE NW CARIBBEAN. THE FRESH TO
STRONG TRADES OVER THE S CENTRAL CARIBBEAN ARE FORECAST TO
CONTINUE THROUGH SUN NIGHT.

CURRENT AND LATEST NWS DOPPLER RADAR IMAGERY FROM SAN JUAN
PUERTO RICO INDICATES LIGHT TO MODERATE SHOWERS MOVING QUICKLY
WESTWARD N OF 17N E OF 69W. SIMILAR ACTIVITY IS INFERRED ON
SATELLITE IMAGERY TO BE OCCURRING ACROSS THE REMAINDER OF THE
SEA...EXCEPT TO THE N OF 12N E OF 73W. ISOLATED TSTMS ARE
POSSIBLE S OF 15N BETWEEN 73W AND 78W. SHOWER AND TSTM ACTIVITY
IS EXPECTED TO BECOME ACTIVE IN COVERAGE OVER THE ISLANDS IN THE
AFTERNOON DUE TO OROGRAPHIC LIFTING AND DAYTIME HEATING. LATEST
MOISTURE GUIDANCE FROM THE GFS SHOWS AN INCREASE IN LOW-LEVEL
MOISTURE ACROSS THE EASTERN PART OF THE CARIBBEAN OVER THE NEXT
24-48 HRS WITH PRECIPITABLE WATER VALUES IN THE 1.25 TO 1.75
INCH RANGE OVER THAT PORTION OF THE SEA MOST PROBABLE LEADING TO
MORE CONCENTRATED PATCHES OF CONVECTION THERE.

...HISPANIOLA...

LOW CLOUDS ARE BEGINNING TO DEVELOP OVER THE INTERIOR PORTIONS
OF THE ISLAND...WITH THE MOST CONCENTRATION OVER THE S CENTRAL
PART OF THE DOMINICAN REPUBLIC. THE UPPER LEVEL DEBRIS
CLOUDINESS DESCRIBED UNDER CARIBBEAN SEA ARE MOVING ACROSS THE
ISLAND...BUT VISIBLE IMAGERY INDICATES THAT THEY ARE RATHER
THIN. EXPECT DAYTIME HEATING AND OROGRAPHIC LIFTING ALONG WITH
SUPPORT OF A NEARBY UPPER JET FOUND TO THE E OF THE CARIBBEAN
UPPER TROUGH MENTIONED ABOVE TO ENHANCE SHOWER ACTIVITY EVERY
AFTERNOON AND INTO THE EVENING HOURS THROUGH THE NEXT 48 HRS.

ATLANTIC OCEAN...

UPPER LEVELS...A TROUGH STRETCHES FROM NEAR 32N55W SW TO
24N67W...AND WEAKENS AS IT CONTINUES SW TO THE UPPER LOW OVER
THE WESTERN TIP OF CUBA. A SHARPER UPPER TROUGH EXTENDS FROM
A WELL DEFINED LOW LOCATED N OF THE AREA NEAR 35N54W SSW TO NEAR
26N53W. WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE
S OF 26N BETWEEN 51W AND 68W...AND ALSO FROM 16N TO 24N BETWEEN
41W AND 51W.

A THE SURFACE...A COLD FRONT ASSOCIATED WITH THE LOW N OF THE
AREA AND THE SHARP UPPER TROUGH ENTERS THE AREA THROUGH
32N49W...AND CONTINUES SW TO 26N55W TO 24N59W WHERE IT BECOMES A
WEAKENING COLD FRONT TO 24N63W...AND WEAKENING STATIONARY TO
24N68W. A PRE-FRONTAL TROUGH EXTEND FROM 25N57W SW TO NEAR
20N64W. ISOLATED SHOWERS AND TSTMS ARE WITHIN 30-60 NM OF THE
FRONT AND TROUGH. A SWIRL OF LOW-LEVEL MOISTURE SPUN OFF THE
FROM THE WESTERN PART OF THE STATIONARY IS IDENTIFIED TO BE NEAR
25N70W. THE ASCAT PASS FROM THIS MORNING SHOWED AN ENHANCED
GRADIENT SUPPORTING NE 15-20 KT WITHIN ABOUT 60 NM TO ITS N.
ANOTHER SIMILAR AREA OF LOW-LEVEL MOISTURE MOVING WESTWARD JUST
N OF THE NW BAHAMAS FROM 26N-28N. NWS DOPPLER RADAR SHOWS
SCATTERED SHOWERS AND ISOLATED TSTMS WITH THIS AREA OF LOW-LEVEL
MOISTURE. TPW IMAGERY AND UPPER LEVEL PV DIAGNOSTICS SUGGEST
THAT A WEAK TROUGH IS AT THE WESTERN MOST PORTION OF THE ITCZ
NEAR 51W. THIS FEATURE IS HELPING TO ENHANCE ITCZ-RELATED
CONVECTION AS DESCRIBED ABOVE. THE TROUGH IS FORECAST TO WEAKEN
AS IT APPROACHES S AMERICA MON AND MON NIGHT.

STRONG HIGH PRES RIDGING EXTENDS FROM A 1028 HIGH N OF THE AREA
AT 35N71W SE TO NEAR 25N63W ALLOWING FOR MAINLY SCATTERED LOW
CLOUDS AND O PREVAIL W OF THE FRONT. SCATTERED HIGH CLOUDS ARE
SEEN THERE AS WELL. THE REMAINDER OF THE BASIN IS UNDER THE
INFLUENCE OF RATHER STRONG HIGH PRES. BROKEN HIGH CLOUDS
STREAMING NE ARE SEEN WITHIN 60 NM OF A LINE FROM 13N60W TO
16N45W TO 21N36W RELATE TO A SUBTROPICAL JET STREAM BRANCH
PRESENT THERE. LITTLE CHANGE IS EXPECTED WITH THIS PATTERN OVER
THE NEXT 48 HRS.

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

$$

AGUIRRE
This weather bulletin was brought to you by:
www.nashvilleweather.net