Tropical Weather Discussion
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000
AXNT20 KNHC 222343
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED JUL 22 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
2330 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS IN THE EASTERN TROPICAL ATLANTIC WITH AXIS
EXTENDING ALONG 30W FROM 10N-19N AND MOVING W NEAR 15 KT OVER
THE PAST 24 HOURS. THE POSITION OF THIS WAVE WAS IDENTIFIED
USING 700 MB STREAMLINE ANALYSIS AND THE GFS-BASED TROUGH
DIAGNOSTICS. THE TOTAL PRECIPITABLE WATER IMAGERY SHOWS THE WAVE
IS N OF SIGNIFICANT MOISTURE WHERE ISOLATED CONVECTION IS
EVIDENT...S OF 10N. THE WAVE IS EMBEDDED IN A DUSTY SAHARAN AIR
LAYER THEREFORE NO SIGNIFICANT CONVECTION IS PRESENT AT THIS
TIME.

A TROPICAL WAVE IS MOVING OVER PUERTO RICO AND THE E CARIBBEAN
WITH AXIS EXTENDING ALONG 67W FROM 08N-20N...MOVING W NEAR 20 KT
OVER THE PAST 24 HOURS. A LARGE PLUME OF MOIST AIR IS DEPICTED
ON TPW IMAGERY MAINLY E OF THE WAVE AXIS EXTENDING ACROSS PUERTO
RICO AND THE LESSER ANTILLES. AN UPPER-LEVEL LOW CENTERED OVER
THE SOUTHERN ATLANTIC WATERS N OF PUERTO RICO IS INTERACTING
WITH THIS WAVE GENERATING CLOUDINESS AND ISOLATED CONVECTION
MAINLY N OF 66N AND E OF 69W. THIS WAVE WILL CONTINUE MOVING W
ACROSS THE CARIBBEAN INCREASING THE MOISTURE AND HENCE
SUPPORTING CONVECTION ACROSS THE GREATER ANTILLES AND
ADJACENT CARIBBEAN WATERS.

A TROPICAL WAVE IS MOVING OVER THE W CARIBBEAN WITH AXIS
EXTENDING ALONG 81W FROM 08N-21N...MOVING W NEAR 20 KT OVER THE
PAST 24 HOURS. THE WAVE HAS A NEGLIGIBLE SURFACE COMPONENT...BUT
IT IS OBSERVABLE VIA THE TOTAL PRECIPITABLE WATER IMAGERY AND
CARIBBEAN RAWINDSONDES. SCATTERED MODERATE CONVECTION IS
CURRENTLY IN THE SOUTHERN PORTION OF THE WAVE S OF 10N MOSTLY
RELATED TO UPPER-LEVEL DIVERGENCE PREVAILING ACROSS CENTRAL
AMERICA AND EPAC AND ALSO THE PROXIMITY OF THE MONSOON TROUGH
AXIS.

THE TROPICAL WAVE PREVIOUSLY ANALYZED OVER NICARAGUA AND THE W
CARIBBEAN HAS LOST ITS DEFINITION AND NO EVIDENCE OF ITS
EXISTENCE CAN BE FOUND. THEREFORE...IT IS BELIEVED THAT THIS
WAVE HAS DISSIPATED.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS ACROSS AFRICA INTO THE EASTERN
TROPICAL ATLANTIC NEAR 13N17W TO NEAR 10N28W. THE ITCZ BEGINS W
OF A TROPICAL WAVE NEAR 09N32W TO THE COAST OF SOUTH AMERICA AT
05N53W. SCATTERED MODERATE CONVECTION IS LOCATED FROM 05N-09N
BETWEEN 20W-42W.

...DISCUSSION...

GULF OF MEXICO...

A SURFACE RIDGE EXTENDS W FROM THE ATLANTIC INTO THE GULF WATERS
ANCHORED BY A WEAK 1017 MB HIGH CENTERED NEAR 25N86W. UPPER-
LEVEL DIFFLUENCE AND DAYTIME HEATING COMBINED TO GENERATE
SCATTERED MODERATE CONVECTION ACROSS THE FLORIDA PENINSULA
AFFECTING THE FAR E GULF WATERS E OF 83W. THE REMAINDER OF THE
BASIN REMAINS CONVECTION-FREE. SCATTEROMETER DATA DEPICTS A
LIGHT ANTICYCLONIC FLOW PREVAILING ACROSS THE BASIN. LITTLE
CHANGE IS EXPECTED DURING THE NEXT TWO DAYS.

CARIBBEAN SEA...

TWO TROPICAL WAVES ARE MOVING ACROSS THE BASIN. FOR MORE DETAILS
PLEASE REFER TO THE SECTION ABOVE. A MODERATE PRESSURE GRADIENT
PRODUCED BY THE SURFACE HIGH OVER THE SUBTROPICAL ATLANTIC AND
LOWER PRESSURES PREVAILING OVER CENTRAL AND SOUTH AMERICA IS
SUPPORTING GENTLE TO MODERATE TRADES ACROSS THE CENTRAL
CARIBBEAN BETWEEN 70W-80W. LIGHT TO GENTLE TRADES PREVAIL
ELSEWHERE. ASIDE FROM THE CONVECTION IN THE VICINITY OF THE
TROPICAL WAVES...FAIR WEATHER PREVAILS OVER THE REMAINDER OF THE
CARIBBEAN. THE PRESSURE GRADIENT WILL TIGHTEN OVER THE NEXT TWO
DAYS INDUCING AN INCREASE IN WIND SPEEDS ACROSS THE CENTRAL
CARIBBEAN.

...HISPANIOLA...

SCATTERED MODERATE CONVECTION IS OBSERVED ACROSS THE ISLAND AS
THE TROPICAL WAVE CURRENTLY OVER PUERTO RICO APPROACHES
INCREASING MOISTURE AND INSTABILITY. THIS WAVE IS INTERACTING
WITH AN UPPER-LEVEL LOW CENTERED OVER THE ATLANTIC WATERS N OF
PUERTO RICO NEAR 21N66W. SIMILAR ACTIVITY IS EXPECTED THROUGH
THURSDAY. OVER THE NEXT 48 HOURS...THE TROPICAL WAVE ITS
ASSOCIATED MOISTURE SHOULD BE WEST OF HISPANIOLA...REDUCING
PRECIPITATION POTENTIAL THEN.

ATLANTIC OCEAN...

A TROPICAL WAVE IS OVER THE TROPICAL ATLANTIC. REFER TO THE
SECTION ABOVE FOR MORE DETAILS. A 1023 MB BERMUDA HIGH CENTERED
NEAR 29N47W AND A 1024 MB AZORES HIGH CENTERED NEAR 34N27W ARE
DOMINATING THE SUBTROPICAL ATLANTIC. A SURFACE TROUGH IS BETWEEN
THESE HIGH CENTERS EXTENDING FROM 30N41W TO 23N40W. ISOLATED
CONVECTION IS OBSERVED ALONG THIS BOUNDARY. SCATTEROMETER DATA
DEPICTS A LIGHT TO GENTLE ANTICYCLONIC FLOW ACROSS THE BASIN. NO
SIGNIFICANT CHANGES ARE EXPECTED DURING THE NEXT TWO DAYS.

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

$$

ERA



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