Marine Interpretation Message
Issued by NWS

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000
AGXX40 KNHC 311954
MIMATS

MARINE WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
354 PM EDT THU JUL 31 2014

MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN
SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND
64W...AND THE SW N ATLANTIC INCLUDING THE BAHAMAS.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

...GULF OF MEXICO...
MODEL PREFERENCE: GFS/ECMWF BLENDED WITH OFFICIAL FOR WIND.
MWW3/NWPS BLENDED WITH OFFICIAL FOR WAVES. HIGH CONFIDENCE.

NO SIGNIFICANT CHANGES FROM THE PREVIOUS THINKING. THE PREVIOUS
DISCUSSION CAN BE FOUND BELOW.

WEAK FRONTAL BOUNDARY HAS SHIFTED SLOWLY S ACROSS E PORTIONS OF
GULF PAST 6-8 HOURS...NOW EXTENDING FROM JUST N OF NAPLES...SW TO
NEAR 24.5N86W THEN NW TO UPPER TEXAS COASTAL WATERS...WITH BROAD
AND WEAK CYCLONIC FLOW ABOUT THE BOUNDARY E OF 90W...AND YIELDING
W-SW WINDS ACROSS THE W STRAITS AND INTO THE KEYS ATTM. BOUNDARY
TO DRIFT SSE TODAY ACROSS SE PORTIONS...THEN BEGIN TO DRIFT BACK
TOWARDS THE NW FRI AND SAT AND GRADUALLY DISSIPATE. NW ATLC RIDGE
TO SHIFT NW AND BUILD MODESTLY ACROSS NW PORTIONS OF SW N ATLC AND
TO E COAST OF FLORIDA THU NIGHT AND FRI...AIDING FRONTAL
MOVEMENT...WITH WEAK HIGH PREVAILING BETWEEN MOUTH OF MS AND BIG
BEND REGION...YIELDING LIGHT TO MODERATE ANTICYCLONIC FLOW ACROSS
THE BASIN. MODERATE S TO SE WINDS ACROSS UPPER MEXICAN AND TEXAS
COASTAL WATERS LIKELY TO BECOME ENHANCED BY DIURNAL HEATING EACH
AFTERNOON AND REACH 15-20 KT FOR A FEW HOURS...INCREASING SEAS
LOCALLY TO 4 FT...AND VERY ISOLATED SPOTS TO 5 FT. LIKEWISE...
LATE AFTERNOON/EVENING THERMAL TROUGH ALSO EXPECTED TO YIELD NEAR
20 KT WINDS OFF NW AND W COASTS OF YUCATAN EACH DAY...YIELDING
SEAS PEAKING BRIEFLY AT 3-5 FT EACH DAY. OTHERWISE...TRANQUIL
CONDITIONS EXPECTED THROUGH THE WEEKEND.

...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 64W...

MODEL PREFERENCE: ECMWF BLENDED WITH OFFICIAL FOR WIND. NWPS
BLENDED WITH OFFICIAL FOR WAVES. MEDIUM CONFIDENCE.

THE 12Z GFS CONTINUES TO BE A HAIR FASTER THAN THE MEDR FORECAST
AGREED ON DURING THE WPC/NHC CONCALL...WITH THAT TRACK CLOSER TO
THE 00Z ECMWF THROUGH THE CARIB. THE ECMWF WAS USED TO ADJUST THE
BACKGROUND WINDS. HOWEVER...BOTH MODELS CARRY THE SYSTEM AS AN
OPEN WAVE THROUGH THE NE CARIB. MAJOR ADJUSTMENTS TO THE GRIDDED
FORECAST WERE NECESSARY TO ACCOMMODATE THE AGREED POINTS.
ELSEWHERE...THE GFS IS SIGNIFICANTLY STRONGER WITH THE WINDS ALONG
THE COAST OF COLOMBIA MON NIGHT/TUE MORNING THAN THE ECMWF. WITH
THE THE ECMWF GENERALLY PREFERRED OVER THE GFS WITH THE POSSIBLE
TROPICAL CYCLONE...WILL TONE DOWN WINDS ALONG THE COAST HERE TO 25
KT LIKE THE ECMWF. FEAR THE GFS MAY BUILD TOO MUCH RIDGING AS IT
WEAKENS THE POSSIBLE TC MORE RAPIDLY THAN THE ECMWF.

...SW N ATLANTIC INCLUDING THE BAHAMAS...

MODEL PREFERENCE: ECMWF BLENDED WITH OFFICIAL FOR WIND. MWW3/NWPS
BLENDED WITH OFFICIAL FOR WAVES. HIGH CONFIDENCE THROUGH FRI
NIGHT THEN MEDIUM-LOW CONFIDENCE.

UPDATED...RECON DATA HAS MEASURED GALE FORCE WINDS IN THE N
QUADRANT OF THE TROPICAL LOW...THEREFORE A GALE WARNING WILL
BE ISSUED AT THE 530 PM PACKAGE CONTINUING THROUGH 24 HOURS.

PREVIOUS DEISCUSSION...
WHILE THERE IS PLENTY OF ACTIVE TSTMS OVER THE NW WATERS
ASSOCIATED WITH A LINGERING FRONTAL BOUNDARY AS WELL AS OVER SE
WATERS ASSOCIATED WITH A TUTT LOW...THERE ARE NO WINDS/SEAS NEAR
ADVISORY CRITERIA OVER THE FORECAST AREA. THE FRONTAL BOUNDARY AND
TSTMS WILL RETROGRADE NW TO THE COAST OVER THE NEXT 24 HOURS. THE
TUTT WILL GRADUALLY BREAKDOWN THROUGH SAT. THEN...THE LOW PRES
SYSTEM CURRENTLY IN THE TROPICAL ATLC BEGINS TO INFLUENCE THE
FORECAST AS IT EMERGES INTO SE WATERS...POSSIBLY AS A TROPICAL
CYCLONE. THE 12Z GFS WASHES OUT THIS SYSTEM ONCE IT PASSES THE
TURKS AND CAICOS. THE ECMWF IS CLOSER TO THE TRACK AGREED ON
DURING THE MEDR CONCALL WITH WPC AND HOLDS ONTO A DISTINCT SYSTEM
LONGER THAN THE GFS. THE ECMWF BECOMES FASTER THAN THE AGREED
POINTS AFTER MON...AND THE SYSTEM MAY WELL BE AN OPEN WAVE AT THAT
TIME. THE GRIDS WILL REFLECT WEAKENING. THE ECMWF WAS USED FOR THE
BACKGROUND WINDS...BUT MAJOR ADJUSTMENTS TO WINDS/SEAS WERE
REQUIRED WITH THE POTENTIAL TC FROM THE WEEKEND ONWARD. THE NWPS
WAS RELIED ON FOR THE SEAS AROUND THE TC WITH THE MWW3 USED MORE
FOR THE SURROUNDING WAVE FIELD AS IT WAS BETTER INITIALIZED.

$$

.WARNINGS...ANY CHANGES IMPACTING COASTAL NWS OFFICES WILL BE
COORDINATED THROUGH AWIPS 12 PLANET CHAT OR BY TELEPHONE:

.GULF OF MEXICO...
     NONE.

.CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN
55W AND 64W...
.AMZ035...OFFSHORE WATERS WINDWARD ISLANDS INCLUDING TRINIDAD AND TOBAGO...
     GALE WARNING FRI NIGHT.
.AMZ037...TROPICAL N ATLANTIC FROM 07N TO 15N BETWEEN 55W AND 65W...
     GALE WARNING TONIGHT INTO FRI.

.SW N ATLANTIC INCLUDING THE BAHAMAS...
     NONE.

$$

*FOR DETAILED ZONE DESCRIPTIONS PLEASE VISIT:
HTTP://WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF

NOTE: GRIDDED MARINE FORECASTS ARE AVAILABLE IN THE
NATIONAL DIGITAL FORECAST DATABASE (NDFD) AT:
HTTP://WWW.NHC.NOAA.GOV/MARINE/GRIDS.PHP

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

$$

.FORECASTER NELSON/SCHAUER. NATIONAL HURRICANE CENTER.


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