[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 122337
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN JUL 12 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
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM ABOUT 09N20W TO 18N18Z MOVING W AT 10
TO 15 KT.  THE WAVE HAS A WEAK CONVECTIVE AND SURFACE
SIGNATURE...BUT IS EVIDENT IN THE TOTAL PRECIPITABLE WATER
IMAGERY...THE SENEGAL RAWINDSONDES...AND THE GFS-BASED 700 MB
TROUGH DIAGNOSTICS.  NO SIGNIFICANT DEEP CONVECTION IS
ASSOCIATED WITH THE WAVE OVER THE ATLANTIC...THOUGH SUBSTANTIAL
CONVECTION IS SEEN OVER SENEGAL...GAMBIA...GUINEA-BISSAU...AND
GUINEA.

TROPICAL WAVE EXTENDS FROM 07N33W TO 17N31W MOVING W AT 10 TO 15
KT.  THE WAVE IS EASILY DISTINGUISHED IN VISIBLE IMAGERY FROM
THE SWIRL OF LOW-LEVEL CLOUDS...A MAXIMUM OF TPW...AND THE
TROUGH DIAGNOSTICS.  JUST TO THE NORTH AND THE WEST OF THE
WAVE...THERE IS A LARGE AREA OF SAHARAN AIR LAYER AS SEEN FROM
THE METEOSAT9 SAL IMAGERY.  NO SIGNIFICANT CONVECTION IS PRESENT
WITH THE WAVE CURRENTLY.

TROPICAL WAVE EXTENDS FROM 06N56W TO 18N52W MOVING W AT AROUND
20 KT. THE WAVE COINCIDES WITH A RELATIVELY BROAD 700 MB GFS
MODEL INDICATED TROUGH BETWEEN 48W AND 58W AND THE BARBADOS
RAWINDSONDE...BUT WITH LITTLE SIGNATURE AT THE SURFACE. THIS
WAVE IS EMBEDDED IN RELATIVELY DRY AIR WITH SAHARAN DUST NORTH
OF 10N. NO SIGNIFICANT CONVECTION IS PRESENT WITH THE WAVE
CURRENTLY.

TROPICAL WAVE EXTENDS FROM 09N77W TO 18N75W MOVING W AT 15 TO 20
KT. THE WAVE IS ONLY OBSERVED WELL FROM THE CARIBBEAN
RAWINDSONDES AND THE TROUGH DIAGNOSTICS...AS IT IS QUITE WEAK AT
THE SURFACE.  THE NORTHERN PORTION OF THIS WAVE IS MOVING UNDER
AN UPPER LEVEL LOW. SCATTERED MODERATE ISOLATED STRONG
CONVECTION EXISTS OVER EASTERN CUBA AS WELL AS IN THE
SOUTHWESTERNMOST CARIBBEAN SEA FROM 09N TO 12N BETWEEN 78W TO
83W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N17W TO
07N30W...WHERE THE ITCZ BEGINS AND CONTINUES THROUGH 06N54W AT
THE SOUTH AMERICA COAST. SCATTERED MODERATE CONVECTION IS FROM
04N TO 10N BETWEEN 12W AND 28W. ISOLATED MODERATE CONVECTION IS
FROM 04N TO 08N BETWEEN 18W AND 25W.

...DISCUSSION...

GULF OF MEXICO...

A 1020 MB HIGH IS CENTERED JUST SOUTH OF THE TEXAS-LOUISIANA
BORDER.  SURFACE WINDS AROUND THE HIGH ARE VERY WEAK...15 KT OR
LESS ACROSS THE WHOLE GULF.  A SURFACE TROUGH EXTENDS THROUGH
THE FLORIDA PENINSULA.  MOST OF THE DEEP CONVECTION OVER THE
EASTERN GULF EARLIER TODAY HAS NEARLY DISSIPATED...WITH ONLY
ISOLATED MODERATE CONVECTION REMAINING NORTH OF 28N EAST OF 85W.
THE SURFACE HIGH IS ANTICIPATED TO REMAIN RELATIVE STATIONARY
DURING THE NEXT TWO DAYS AND ADDITIONAL SHOWERS AND
THUNDERSTORMS MAY OCCUR OVER THE EASTERN GULF OF MEXICO.

CARIBBEAN SEA...

A MODERATE NORTH-SOUTH PRESSURE GRADIENT IS PRODUCING GENERALLY
10-20 KT TRADEWINDS ACROSS THE CARIBBEAN...WITH A 25 KT MAX
OBSERVED JUST NORTH OF COLOMBIA.  A STRONG UPPER LOW IS CENTERED
OVER THE SOUTHERN BAHAMAS NEAR 22N74W.  THE INTERACTION OF THE
UPPER LOW AND A TROPICAL WAVE OVER THE CENTRAL CARIBBEAN
CONTRIBUTED TOWARD SCATTERED MODERATE AND ISOLATES STRONG
CONVECTION OVER EASTERN CUBA.  THE PUERTO RICO RADAR INDICATES
THAT SCATTERED SHOWERS ALSO ARE OVER WESTERN PUERTO RICO AND THE
ADJACENT WATERS.  THE DIFFLUENT ZONE IN THE SOUTHEASTERN
SEMICIRCLE OF THE UPPER LOW IS CAUSING A LARGE AREA OF UPPER
LEVEL DIVERGENCE IN THE NORTHEASTERN CARIBBEAN SEA IN SUPPORT OF
THESE SHOWERS.  DURING THE NEXT TWO DAYS...LITTLE CHANGE IS
EXPECTED TO THE TRADEWINDS.  THE UPPER LOW SHOULD LIFT OUT TO
THE NORTHEAST...WHILE THE TROPICAL WAVE CONTINUES WESTWARD.
THIS LIKELY WILL SHIFT CHANCES FOR DEEP CONVECTION WESTWARD TO
THE WESTERN CARIBBEAN.

...HISPANIOLA...

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OCCURRED EARLIER
TODAY OVER EASTERN DOMINICAN REPUBLIC.  DURING THE
AFTERNOON...THERE WERE ISOLATED THUNDERSTORMS OVER NORTHERN
HAITI.  THE BROAD UPPER LOW OVER THE SOUTHERN BAHAMAS MAY
CONTINUE TO PROMOTE SOME DEEP CONVECTION DURING THE NEXT DAY OR
SO.  THESE COULD RESULT IN HEAVY RAINFALL AND FLASH FLOODING
WITH THE POTENTIAL FOR MUDSLIDES.  AS THE UPPER LOW PULLS
NORTHEASTWARD AND THE TROPICAL WAVE MOVES TO THE WESTERN
CARIBBEAN...THE CHANCES FOR DEEP CONVECTION SHOULD DROP ON
TUESDAY.

ATLANTIC OCEAN...

A 1025 MB SURFACE HIGH IS LOCATED AT 32N38W WITH RIDGING
EXTENDING WEST-SOUTHWESTWARD.  THIS IS RESULTING IN
NORTHEASTERLY TRADEWINDS OF GENERALLY 10-20 KT IN THE EASTERN
ATLANTIC AND 5-15 KT IN THE WESTERN ATLANTIC.  NUMEROUS SHOWERS
WITH SCATTERED MODERATE CONVECTION IS OCCURRING NORTH OF PUERTO
RICO...FROM 18N TO 25N BETWEEN 65W AND 70W.  ISOLATED MODERATE
TO DEEP CONVECTION ALSO IS OCCURRING OVER THE BAHAMAS.  THIS
CONVECTIVE ACTIVITY IS DUE TO THE UPPER LOW CENTERED OVER THE
SOUTHERN BAHAMAS.  SCATTERED MODERATE CONVECTION IS ALSO
OBSERVED FROM 30N TO 32N BETWEEN 76W TO 79W IN ASSOCIATION WITH
A WEAK FRONTAL LOW JUST OFFSHORE OF SOUTH CAROLINA.  THE SURFACE
SYNOPTIC PATTERN DOES NOT CHANGE MUCH DURING THE NEXT TWO DAYS.
HOWEVER...THE UPPER LOW SHOULD MOVE NORTHEASTWARD AND FILL SOME.
AS IT DOES SO...THE LIKELIHOOD FOR DEEP CONVECTION WILL CONTINUE
FOR THE BAHAMAS ON MONDAY BUT DIMINISH ON TUESDAY.

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

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