[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 160003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED JUL 15 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
2345 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AXIS
APPROXIMATELY ALONG 32W FROM 06N TO 15N MOVING W AT 20-25 KT.
TPW IMAGERY INDICATED THE WAVE IS EMBEDDED IN A DEEP MOIST
ENVIRONMENT MAINLY E OF THE WAVE AXIS. METEOSAT SAL IMAGERY SHOW
SAHARAN DRY AIR AND DUST ENGULFING THE WAVE. SCATTERED MODERATE
CONVECTION IS FROM 07N TO 10N BETWEEN 24W AND 31W BEING
SUPPORTED BY MIDDLE TO UPPER LEVEL DIVERGENCE.

A LARGE AMPLITUDE TROPICAL WAVE IS APPROACHING THE LESSER
ANTILLES WITH AXIS APPROXIMATELY ALONG 59W AND S OF 20N...MOVING
AT 20 KT. SSMI TPW AND METEOSAT IMAGERY INDICATE DRY AIR
ENTRAINMENT IN THE WAVE ENVIRONMENT WHICH IS HINDERING
CONVECTION. DUST IS ALSO PRESENT IN THE WAVE ENVIRONMENT AS
OBSERVED IN SATELLITE IMAGERY AND IS BEING REPORTED THROUGH THE
LESSER ANTILLES.

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS
APPROXIMATELY ALONG 78W...MOVING W AT 15-20 KT. SSMI TPW IMAGERY
INDICATE THE WAVE IS EMBEDDED IN A MODERATELY MOIST ENVIRONMENT.
DIVERGENT FLOW AHEAD OF THE WAVE IN THE MIDDLE LEVELS SUPPORT
SCATTERED MODERATE CONVECTION ALONG THE WAVE AXIS FROM 15N TO
16N BETWEEN 76W AND 79W. STRONG DEEP LAYER WIND SHEAR HINDER
CONVECTION ELSEWHERE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH ENTERS THE ATLANTIC OCEAN THROUGH GUINEA
BISSAU NEAR 13N17W CONTINUING TO 12N19W. THE ITCZ EXTENDS FROM
THAT POINT TO 10N30W THEN RESUMES W OF A TROPICAL WAVE NEAR
10N33W TO 07N45W TO 08N59W. ASIDE FROM THE CONVECTION ASSOCIATED
WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS
OBSERVED FROM 05N TO 11N BETWEEN 35W AND 55W.

...DISCUSSION...

GULF OF MEXICO...

A BROAD SURFACE RIDGE COVERING LARGE PORTIONS OF THE ATLC BASIN
EXTENDS WESTWARD ACROSS SOUTH FLORIDA AND THE STRAITS OF FLORIDA
TO THE SOUTH-CENTRAL GULF OF MEXICO. A WEAK SURFACE TROUGH IS
OVER THE BAY OF CAMPECHE FROM 24N93W TO 18N95W. ALOFT...AN
ELONGATED UPPER LOW IS CENTERED OVER THE ISTHMUS OF TEHUANTEPEC
INTO THE BAY OF CAMPECHE PROVIDING SUPPORT FOR THE SURFACE TROUGH
NOTED IN THE AREA. A MID-TO UPPER LEVEL ANTICYCLONE OVER E TEXAS
WITH RIDGE AXIS EXTENDING ESE ACROSS THE GULF TO CENTRAL
FLORIDA. A POCKET OF DEEP LAYERED SUBSIDENCE WAS NOTED OVER THE
NW GULF. THE BASE OF A SHARP MID-TO UPPER LEVEL TROUGH ALONG THE
EASTERN CONUS IS SLICING ACROSS THE FAR NE GULF. THIS TROUGH IS
SUPPORTING A SURFACE TROUGH EXTENDING ACROSS NORTHERN FLORIDA TO
29N85W TO 29N88W. THE CONVECTIVE ACTIVITY ALONG THE TROUGH
EARLIER HAS DISSIPATED LEAVING A SWATH OF MULTILAYERED CLOUDS
OVER THE NE GULF AND FLORIDA WITH ISOLATED EMBEDDED SHOWERS AND
THUNDERSTORMS. LIGHT SE TO S SURFACE WINDS PREVAILED OVER THE
GULF S OF 25N...WINDS TURNED MORE TO THE W AND SW OVER THE GULF
N OF 25N AND INCREASED TO 15 KT IN THE VICINITY OF THE SURFACE
TROUGH. SURFACE RIDGING AND LIGHT FLOW WILL BE THE DOMINANT
FEATURE DURING THE NEXT THREE DAYS.

CARIBBEAN SEA...

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 78W IS
ASSOCIATED WITH A BROAD MODERATELY MOIST AIRMASS THAT EXTENDS
ACROSS THE WESTERN PORTION OF THE BASIN INTO THE GULF OF MEXICO.
HOWEVER STRONG DEEP LAYER WIND SHEAR INHIBITS CONVECTION FOR THE
MOST PART. OVER THE SW CARIBBEAN...LOWER PRESSURES ASSOCIATED
WITH A LOW CENTER OVER N COLOMBIA AND THE EPAC MONSOON TROUGH
SUPPORT SCATTERED BUT DIMINISHING MODERATE CONVECTION S OF 12N
BETWEEN 74W AND 83W. SAHARAN AIR AND DUST ENGULFING THE NEXT
TROPICAL WAVE TO ENTER THE BASIN COVERS THE E CARIBBEAN E OF
70W...THUS INHIBITING CONVECTION. REFER TO THE TROPICAL WAVES
SECTION FOR MORE DETAILS. A GENERALLY TIGHT PRESSURE GRADIENT
BETWEEN RIDGE OF HIGH PRESSURE OVER THE ATLC EXTENDING ACROSS
THE NORTHERN BASIN AND LOWER PRESSURE OVER COLOMBIA SUPPORT
TRADE WINDS OF 20-25 KT ACROSS THE CENTRAL CARIBBEAN MAINLY S OF
17N BETWEEN 70W-78W. TRADES OF 15 KT DOMINATE ELSEWHERE. THE
NEXT TROPICAL WAVE WILL ENTER THE E CARIBBEAN TONIGHT POSSIBLY
ENHANCING SHOWERS OVER THE WINDWARD ISLANDS.

HISPANIOLA...

RESIDUAL MOISTURE ASSOCIATED WITH THE PASSAGE OF A TROPICAL WAVE
WITH AXIS CURRENTLY NEAR 78W IS BEGINNING TO MOVE NW AWAY FROM
HISPANIOLA WITH TPW IMAGERY INDICATING A PATCH OF DRIER AIR IN
ITS WAKE OVER PUERTO RICO AND THE DOMINICAN REPUBLIC. AT THE
UPPER LEVELS...THE AREA IS SITUATED IN A DIFFLUENT ZONE BETWEEN
A SMALL UPPER CYCLONE OVER THE CENTRAL BAHAMAS AND AN
ANTICYCLONE OVER THE FAR SW CARIBBEAN. A LARGE UPPER LEVEL
CYCLONE OVER THE TROPICAL ATLC NEAR 16N59W WITH A BAND OF
SUBSIDENCE EXTENDING WWD OVER PUERTO RICO IS FORECAST TO MOVE
WEST WITH SUBSIDENCE SWEEPING WESTWARD ACROSS THE ISLAND
TOMORROW WHICH WILL LIMIT CONVECTIVE ACTIVITY.

ATLANTIC OCEAN...

TWO TROPICAL WAVES ARE OVER THE TROPICAL ATLANTIC ALONG 32W AND
59W. PLEASE SEE THE TROPICAL WAVES SECTION ABOVE FOR MORE
DETAILS. IN KEEPING WITH THE CLIMATOLOGICAL NORM FOR THIS TIME
OF THE YEAR...THE BERMUDA AZORES HIGH EXTENDS A RIDGE ACROSS
LARGE PORTIONS OF THE TROPICAL ATLANTIC SUPPORTING MAINLY FAIR
WEATHER. OVER THE SW N ATLC...THE BASE OF A MIDDLE LEVEL TROUGH
ALONG THE EASTERN CONUS IS GENERATING DIFFLUENT FLOW N OF 27N W
OF 75W. THIS WIND FLOW ALOFT ALONG WITH MOISTURE BEING ADVECTED
FROM THE CARIBBEAN AND SE CONUS SUPPORT SCATTERED SHOWERS AND
TSTMS N OF 29N W OF 77W. FARTHER SOUTH...AN UPPER LOW ANCHORED
NEAR ANDROS ISLAND SUPPORTS SIMILAR CONVECTION FROM 21N TO 28N W
OF 71W. A VERY LARGE CYCLONIC CIRCULATION CENTERED NEAR 16N59W
COVER THE TROPICAL ATLC S OF 25N BETWEEN 45W AND THE CARIBBEAN
IS PROVIDING UNUSUALLY STRONG NW FLOW ALOFT OVER THE DEEP
TROPICS AND STRONG SUBSIDENCE OVER THE E CARIBBEAN.
OTHERWISE...A WEAKENING COLD FRONT EXTENDS OVER THE N-CENTRAL
ATLC FROM 31N46W TO 29N55W WITH NO CONVECTION.

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

$$
COBB
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