Tropical Weather Discussion
Issued by NWS

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000
AXNT20 KNHC 210520
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE APR 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL
ATLANTIC NEAR 11N15W TO 05N13W WHERE THE ITCZ BEGINS AND
CONTINUES ALONG 01N25W THEN S OF THE EQUATOR NEAR 37W. SCATTERED
MODERATE CONVECTION IS FROM 03N TO S OF THE EQUATOR BETWEEN 17W-
38W.

...DISCUSSION...

GULF OF MEXICO...

A BROAD UPPER-LEVEL RIDGE ANCHORED IN THE EPAC EXTENDS E
REACHING THE WESTERN HALF OF THE GULF. AN UPPER-LEVEL TROUGH
COVERS THE E CONUS SUPPORTING A FRONTAL SYSTEM THAT PREVAILS
ACROSS THE NORTHERN GULF. IT BEGINS AS A STATIONARY FRONT FROM
25N98W TO 26N92W THEN IT TRANSITIONS INTO A COLD FRONT THROUGH
30N87W. ISOLATED CONVECTION IS OBSERVED IN THE VICINITY OF THE
FRONTS MAINLY N OF 28N. A SURFACE TROUGH IS AHEAD OF THE COLD
FRONT FROM 25N90W TO 27N83W. ISOLATED CONVECTION IS ALONG THIS
BOUNDARY. LIGHT TO GENTLE NE FLOW PREVAILS ACROSS THE BASIN W OF
90W WHILE A GENTLE NW FLOW IS OBSERVED IN SCATTEROMETER DATA AND
CURRENT OBSERVATIONS E OF 90W AND N OF THE COLD FRONT. EXPECT
OVER THE NEXT 24-48 HOURS FOR THE STATIONARY FRONT TO WEAKEN
ACROSS THE NW GULF. THE COLD FRONT WILL CONTINUE MOVING SE
ENHANCING CONVECTION. THE SURFACE TROUGH ACROSS THE SE GULF WILL
DISSIPATE. A WEAK HIGH PRESSURE WILL BUILD IN THE WAKE OF THE
COLD FRONT.

CARIBBEAN SEA...

THE UPPER-LEVEL RIDGE THAT EXTENDS FROM THE EPAC INTO THE GULF
ALSO REACHES THE W CARIBBEAN. TO THE E OF THIS...AN UPPER-LEVEL
TROUGH EXTENDS ITS AXIS FROM HISPANIOLA TO 10N83W. SATELLITE
WATER VAPOR IMAGERY SHOWS STRONG SUBSIDENCE AND DRY STABLE AIR
ACROSS THE CARIBBEAN IN THE AREA DOMINATED BY THE UPPER-LEVEL
TROUGH. DESPITE THIS...LOW-LEVEL MOISTURE IS ALSO PRESENT ACROSS
THE BASIN GENERATING ISOLATED CONVECTION. LIGHT TO GENTLE TRADES
PREVAIL ACROSS THE BASIN EXCEPT N OF COLOMBIA FROM 12N-16N
BETWEEN 69W-76W WHERE GENTLE TO MODERATE FLOW IS OBSERVED IN
SCATTEROMETER DATA. THERE IS ALSO A SMALL AREA N OF HONDURAS
MAINLY S OF 17N WHERE A MODERATE FLOW IS DEPICTED. EXPECT
A SIMILAR WEATHER PATTERN OVER THE NEXT 24-48 HOURS.

HISPANIOLA...

CLEAR SKIES AND FAIR WEATHER PREVAILS ACROSS THE AREA OVERNIGHT.
LOW-LEVEL MOISTURE COUPLED WITH THE EASTERLY TRADE WINDS WILL
CONTINUE TO GENERATE ISOLATED CONVECTION ACROSS THE ISLAND
MAINLY IN THE AFTERNOON OVER THE NEXT IN 24 HOURS.

ATLANTIC OCEAN...

A 1012 MB SURFACE LOW IS CENTERED OVER THE W ATLANTIC NEAR
30N78W. A SURFACE TROUGH EXTENDS FROM THE LOW TO 27N81W. A
SQUALL LINE IS E OF THE LOW AND TROUGH EXTENDING FROM 30N77W TO
26N79W. SCATTERED MODERATE CONVECTION IS N OF 26N BETWEEN 71W-
77W. A FRONTAL SYSTEM CONTINUES ACROSS THE CENTRAL
ATLANTIC...BEGINNING AS A STATIONARY FRONT FROM 28N57W TO 29N45W
THEN TRANSITIONING INTO A COLD FRONT TO 31N40W. ISOLATED
CONVECTION PREVAILS ALONG THE COLD FRONT MAINLY N OF 30N. A PAIR
OF SURFACE HIGH PRESSURES CENTERED NEAR 24N48W AND 38N24W EXTEND
ACROSS THE REMAINDER OF THE BASIN WITH FAIR WEATHER. EXPECT OVER
THE NEXT 24-48 HOURS FOR A COLD FRONT TO REACH THE W ATLANTIC
WITH CONVECTION. THE FRONTAL SYSTEM OVER THE CENTRAL ATLANTIC
WILL WEAKEN.

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

$$

ERA



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