#98 Postby cycloneye » Wed Aug 09, 2006 6:21 am
000
FXCA62 TJSJ 091035
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
635 AM AST WED AUG 9 2006
.DISCUSSION...
BACK SIDE OF TUTT LOW TO OUR NE DROPPING IN ON THE LOCAL AREA
THIS MORNING...PROMOTING SINKING MOTION...AND COMBINING WITH THE
DOMINANT SAL CONTINUING TO STREAM THROUGH THE REGION TO PRODUCE A
DRY AND STABLE ATMOSPHERE. PW VALUES CONTINUE TO PLUMMET BELOW 1.5
INCHES OVERNIGHT PER SOUNDER OBSERVATIONS. LITTLE MOISTURE APPEARS
UPSTREAM IN THE SHORT TERM...AND GFS FORECASTING A DRYING TREND IN
THE LOW LEVELS TODAY. A DRY HAZY AND BREEZY FORECAST IS THUS IN
ORDER FOR THE DAY AS THE MID SUMMER DROUGHT CONTINUES.
MONSOONAL TROUGH SEGMENT AND EMBEDDED LOW CONTINUE TO PROPAGATE
WWD ACROSS THE TROPICAL ATLANTIC THIS MORNING...WITH A SW TO NE
TILT OF AXIS ROUGHLY CENTERED ALONG 54 WEST. DRY AIR ENTRAINMENT
OF SAL FROM THE NW AND W...AND UNTIL RECENTLY...STABLE SOUTH
ATLANTIC AIR INGESTED INTO SOUTH SIDE OF MONSOON TROUGH...CONTINUE
TO DENY ANY SIGNIFICANT CONVECTIVE DEVELOPMENT OF THIS SYSTEM.
NO TROPICAL DEVELOPMENT OF THIS SYSTEM IS THEREFORE EXPECTED FOR
THE NEXT FEW DAYS. A SIGNIFICANT ACCUMULATION OF WARM DEEP WATER
FROM NBC RING EDDIES IS SCATTERED ABOUT THE EXTREME EAST CARIB AND
TROPICAL ATLANTIC EAST OF THE WINDWARDS...AND THIS MAY OFFER SOME
MOISTURE INFLUX FOR THIS SYSTEM AS IT PASSES OVER TODAY THROUGH
THURSDAY MORNING. ALTHOUGH THIS IS CERTAINLY NOT A CLASSIC
AEW...WE ARE CALLING THIS A TROPICAL WAVE FOR PUBLIC
CONSUMPTION...TO AVOID A LONG DETAILED DESCRIPTION OF THE
EVOLUTION OF THIS FEATURE. THIS "WAVE-LIKE" FEATURE IS FORECAST TO
MOVE MOSTLY SOUTH OF THE LOCAL AREA THURSDAY THROUGH THURSDAY
NIGHT...WITH AEJ SEGMENT ACROSS THE TOP TO MOVE ACROSS THE LOCAL
AREA FOR ANOTHER SURGE IN WINDS...AND LIKELY A BRIEF BREAK IN THE
SEEMINGLY ENDLESS STREAM OF SAL AND ASSOCIATED AFRICAN DUST.
SYNPOTIC PATTERN ACROSS THE TROPICAL AND SUBTROPICAL ATLANTIC PAST
TWO WEEKS HAS ALLOWED FOR STRONG POSITIVE TILTING OF AEW AND
STRETCHING AND SHEARING OF NV WAVE ENERGY...YIELDING NON CLASSIC
WAVE STRUCTURE. WE HAVE FELT SOMEWHAT FORCED TO REFER TO THESE
SHEARED VORT LOBES OR PIECES OF THE WAVES AS TROPICAL WAVES IN
LOCAL PRODUCTS TO SIMPLIFY EXPLANATION.
&&
.MARINE...
STRONG MID LEVEL RIDGING E TO W ACROSS ATLC MAINTAIN A
RELATIVELY ZONAL AEJ ACROSS THE TROPICAL ATLC...AND COMBINING
WITH PERSISTENT BERMUDA HIGH TO MAINTAIN A STRONGER THAN NORMAL
TRADE WIND FLOW ACROSS THE LOCAL REGION. RECENT SSMI AND QUIKSCAT
PASSES...A VERY FEW LOCAL OBSERVATIONS...AND MY OBS FROM IN THE
WATER SUGGEST THAT WE HAVE BEEN UNDERFORECASTING LOCAL MARINE
CONDITIONS TFOR PORTIONS OF THE PAST FEW DAYS. I HAVE DECIDED TO
USE GFS90 WINDS AS OPPOSED TO GFS40 FOR MARINE FORECAST AS THIS
HIGHER SIGMA LEVEL FORECAST FROM GFS90 SEEMS TO BE MORE ACCURATE.
A BRIEF DECREASE IN WIND AND SEAS WILL BE SEEN ACROSS THE AREA
TODAY...DOWN AROUND 5 KNOTS FROM YESTERDAY... BEFORE ANOTHER SURGE
IS SEEN WITH NEXT APPROACHING "WAVE" ON TUESDAY. THIS WIND SURGE
AND ASSOCIATED INCREASE IN SEAS ARE EXPECTED TO AFFECT THE LOCAL
CARIB WATERS MORE SIGNIFICANTLY THAN THE ATLC...AS "WAVE" PASSES
SOUTH OF THE LOCAL ISLANDS. A MORE TYPICAL 15 TO 20 KNOT TRADE
WIND FLOW IS THEN EXPECTED TO PREVAIL THROUGH THE WEEKEND...
ALLOWING LOCAL SEAS TO DECREASE TO MORE NORMAL LEVELS. SEA YOU IN
THE WATER.
Above is the discussion from the NWS San Juan about this system.
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