[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 071720
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON SEP 07 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
1715 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM GRACE AT 07/1500 UTC IS NEAR 13.7N
35.9W. GRACE IS MOVING TOWARD THE W AT 15 KT. THE MINIMUM
CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 40
KT WITH GUSTS TO 50 KT. ISOLATED CONVECTION IS FROM 11N-16N
BETWEEN 33W-37W. PUBLIC ADVISORIES ABOUT GRACE ARE BEING ISSUED
UNDER THE WMO HEADER WTNT32 KNHC...AND UNDER THE AWIPS HEADER
MIATCPAT2. FORECAST/ADVISORIES ARE BEING ISSUED UNDER THE WMO
HEADER WTNT22 KNHC...AND UNDER THE AWIPS HEADER MIATCMAT2.
SCATTERED MODERATE FROM 12N-14N BETWEEN 30W-32W.

...TROPICAL WAVES...

A TROPICAL WAVE IS MOVING ACROSS THE E ATLANTIC WITH AXIS FROM
19N19W TO A 1012 MB LOW CENTERED NEAR 13N20W TO 09N20W...MOVING
W AT AROUND 15 KT. 700 MB STREAMLINES DEPICT A WELL DEFINED
INVERTED TROUGH FROM 13W-23W AND TPW IMAGERY SHOWS A MOISTURE
MAXIMA PREVAILING E OF THE WAVE AXIS. SCATTERED MODERATE
CONVECTION IS FROM 09N-20N AND E OF 25W.

A TROPICAL WAVE IS OVER THE CENTRAL ATLANTIC WITH AXIS ALONG 45W
FROM 07N-17N MOVING W AT APPROXIMATELY 15 KT OVER THE PAST 24
HOURS. DESPITE THE FACT THAT TPW IMAGERY SHOWS A MOIST
ENVIRONMENT SURROUNDING THIS WAVE...NO CONVECTION IS OBSERVED AT
THIS TIME DUE TO SAHARAN DUST PREVAILING ACROSS THE AREA
INHIBITING ANY SIGNIFICANT ACTIVITY.

A TROPICAL WAVE IS AT ABOUT 200 NM E OF THE LESSER ANTILLES WITH
AXIS EXTENDING FROM 17N57W TO 08N57W...MOVING W AT AROUND 10-15
KT. THIS WAVE IS DEPICTED IN SATELLITE IMAGERY WITH THE
CHARACTERISTIC INVERTED V AND A WEAK CYCLONIC SWIRL NEAR THE
SURFACE. TPW IMAGERY SHOWS MODERATE MOISTURE ASSOCIATED WITH
THIS WAVE MAINLY S OF 14N WHERE SCATTERED CONVECTION IS OBSERVED
BETWEEN 57W-60W.

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN WITH AXIS
EXTENDING FROM 20N73W TO 11N75W...MOVING W AT AROUND 10 KT OVER
THE PAST 24 HOURS. THE WAVE IS ASSOCIATED MAINLY WITH LIGHT TO
MODERATE MOISTURE AS DEPICTED IN TPW IMAGERY. HOWEVER...STRONG
DEEP LAYER WIND SHEAR AND SUBSIDENCE THAT PREVAILS ACROSS THE
CARIBBEAN IS LIMITING THE CONVECTION TO THE NORTHERN PORTION OF
THE WAVE THAT EXTENDS ACROSS THE WINDWARD PASSAGE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH PASSES OVER COASTAL SECTIONS OF AFRICA NEAR
13N17W TO 14N30W. THE ITCZ BEGINS NEAR 09N47W AND CONTINUES TO
08N56W. ASIDE FROM THE CONVECTION ASSOCIATED WITH GRACE AND THE
TROPICAL WAVES...ISOLATED MODERATE CONVECTION IS FROM 06N-09N
BETWEEN 49W-53W.

...DISCUSSION...

GULF OF MEXICO...

A BROAD SURFACE RIDGE COVERS THE EASTERN CONUS AND EXTENDS A
RIDGE AXIS ACROSS THE NORTHERN GULF WATERS. A WEAKNESS IN THIS
RIDGE IS ANALYZED AS A 1012 MB LOW LOCATED NEAR 28N85W.
ALOFT...A BROAD ANTICYCLONE IS CENTERED OVER NORTHERN MEXICO AND
EXTENDS E ACROSS THE WESTERN GULF WHILE AN ELONGATED UPPER-LEVEL
LOW IS CENTERED OVER THE NE GULF NEAR 28N87W AND EXTENDS ACROSS
THE REMAINDER OF THE BASIN. THIS UPPER-LEVEL FEATURES ARE
SUPPORTING SCATTERED MODERATE CONVECTION ACROSS MOST OF THE
AREA...MAINLY E OF 93W. SCATTEROMETER DATA DEPICTS LIGHT AND
VARIABLE WINDS ACROSS THE GULF. WEAK RIDGING WILL CONTINUE
ACROSS THE BASIN OVER THE NEXT 24-48 HOURS WHILE THE SURFACE LOW
WILL MOVE NORTHWARD WITH CONVECTION.

CARIBBEAN SEA...

A TROPICAL WAVE IS OVER THE BASIN. SEE THE TROPICAL WAVES
SECTION FOR MORE DETAILS. THE EASTERN PORTION OF AN UPPER-LEVEL
TROUGH EXTENDS FROM THE GULF OF MEXICO ACROSS THE W CARIBBEAN.
THE CENTRAL CARIBBEAN BETWEEN 72W-83W IS UNDER THE INFLUENCE OF
AN UPPER-LEVEL HIGH CENTERED NEAR 12N79W. TO THE E...AN UPPER-
LEVEL LOW EXTENDS FROM SOUTH AMERICA ACROSS THE E CARIBBEAN E OF
72W. THE ONLY CONVECTION OBSERVED ACROSS THE BASIN IS DUE TO THE
PROXIMITY OF THE MONSOON TROUGH ACROSS THE SOUTHERN CARIBBEAN S
OF 12N BETWEEN 77W-83W. SCATTEROMETER DATA DEPICTS GENTLE TO
MODERATE TRADES ACROSS THE AREA BECOMING FRESH S OF 13N BETWEEN
72W-78W. OVER THE NEXT 24 HOURS...THE WAVE WILL CONTINUE MOVING
W. CONVECTION IS EXPECTED ACROSS THE W CARIBBEAN IN THE
AFTERNOON AND EVENING HOURS AS THE UPPER-LEVEL TROUGH PREVAILS
ACROSS THE GULF OF MEXICO. THE NEXT TROPICAL WAVE WILL ENTER THE
E CARIBBEAN WITH CONVECTION.

...HISPANIOLA...

A TROPICAL WAVE IS MOVING ACROSS THE WINDWARD PASSAGE WITH
CONVECTION ACROSS THE AREA AFFECTING PORTIONS OF HAITI. FAIR
WEATHER WILL PREVAIL AS THIS WAVE CONTINUES MOVING W.

ATLANTIC OCEAN...

THE MAIN FEATURE IN THE BASIN IS TROPICAL STORM GRACE...WHICH IS
DISCUSSED IN THE SPECIAL FEATURES SECTION. THREE TROPICAL WAVES
ARE ALSO MOVING ACROSS THE TROPICAL ATLANTIC. PLEASE REFER TO
THE TROPICAL WAVES SECTION FOR MORE DETAILS. A SURFACE TROUGH
WAS ANALYZED ACROSS THE W ATLANTIC FROM 28N80W TO 32N80W. TO THE
E...ANOTHER SURFACE TROUGH EXTENDS FROM 26N78W TO 28N70W.
ISOLATED CONVECTION IS OBSERVED ALONG THESE FEATURES AFFECTING
THE BAHAMAS AND ADJACENT WATERS W OF 72W. A MID TO UPPER-LEVEL
TROUGH OVER THE CENTRAL ATLANTIC WITH BASE REACHING NEARLY 30N
SUPPORTS A STATIONARY FRONT THAT EXTENDS FROM 31N64W TO 30N46W
THEN BECOMES A COLD FRONT FROM THAT POINT ON ACROSS THE WATERS N
OF OUR AREA OF RESPONSIBILITY. SCATTERED MODERATE CONVECTION
PREVAILS IN THE VICINITY OF THESE BOUNDARIES MAINLY N OF 28N AND
BETWEEN 42W-61W. ANOTHER SURFACE TROUGH...REMNANTS OF
FRED...EXTENDS FROM 27N42W TO 31N38W WITH SCATTERED MODERATE
CONVECTION. A SURFACE RIDGE AND FAIR WEATHER PREVAILS ACROSS THE
E ATLANTIC E OF 34W.

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

$$

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