000
FXUS62 KMFL 220539
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
139 AM EDT MON SEP 22 2008

.AVIATION...MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.
A FEW SHOWERS CAN BE EXPECTED ALONG THE EAST COAST TONIGHT AND
TOMORROW WITH MOST TSRA EXPECTED ALONG THE WEST COAST WITH THE SEA
BREEZE. WINDS WILL GENERALLY REMAIN EASTERLY AT ALL EAST COAST
SITES AND AT APF... EASTERLY IN THE AM BUT WESTERLY IN THE
AFTERNOON AND EVENING WITH THE SEA BREEZE. /TINGLER


&&

.PREV DISCUSSION... /ISSUED 913 PM EDT SUN SEP 21 2008/

UPDATE...
THE EAST AND WEST COAST SEA BREEZES COLLIDED OVER THE WESTERN
INTERIOR AREAS OF SOUTH FLORIDA LATE THIS AFTERNOON AND EARLY THIS
EVENING...WITH SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPING
ALONG THE BOUNDARY. THE SHOWERS AND THUNDERSTORMS ARE SLOWLY
DISSIPATING OVER WESTERN INTERIOR AREAS OF THE CWA THIS
EVENING...AND SHOULD CONTINUE TO SLOWLY DISSIPATE THROUGH REST OF
THE EVENING HOURS. SO WILL REMOVE THE POPS OVER THE INTERIOR AND
WEST COAST METRO AREAS BY MIDNIGHT.

THERE HAS ALSO BEEN A FEW SHOWERS DEVELOPING OVER THE EAST COAST
ATLANTIC WATERS THIS EVENING. THESE SHOWERS SHOULD CONTINUE TO
DEVELOP AND MOVE TO THE WEST INTO THE EAST COAST METRO AREAS
BEFORE DISSIPATING...AS THE STEERING FLOW WILL REMAIN FROM THE
EASTERLY DIRECTION AROUND HIGH PRESSURE OVER THE SOUTHEAST UNITED
STATES. SO HAVE KEPT A 20 PERCENT POPS FOR THE EAST COAST METRO
AREAS FOR THE OVERNIGHT HOURS.

THE 00Z MIA SOUNDING ALSO SHOWED THAT THERE WAS STILL SOME DRY AIR
IN THE LOWER TO MID LEVELS OF THE ATMOSPHERE. SO HAVE REMOVE THE
THUNDER WORDING FOR THE EAST COAST METRO AREAS AND THE ATLANTIC
WATERS FOR THE OVERNIGHT HOURS.

THE 00Z MIA SOUNDING WAS ALSO SHOWING 10 TO 15 KNOTS BETWEEN 900
AND 1000 MB. THIS WIND SPEED SHOULD MIX DOWN TO THE ATLANTIC AND
BISCAYNE BAY WATER SURFACE TONIGHT. SO HAVE INCREASE THE WIND
SPEED UP A LITTLE BIT FOR THESE WATERS TONIGHT.

REST OF THE FORECAST LOOKS GOOD AT THIS TIME AND NO OTHER CHANGES
ARE PLAN.

UPDATE...54/BNB

AVIATION... /ISSUED 731 PM EDT SUN SEP 21 2008/

AVIATION...VFR CONDITIONS ARE EXPECTED OVER ALL TERMINALS
OVERNIGHT. SHWRS/STORMS OVER INTERIOR SECTIONS ARE EXPECTED TO
DISSIPATE BEFORE GETTING NEAR KAPF. DECIDED TO INDICATE VCSH OVER
THE ERN TERMINALS THROUGH EARLY MORNING HOURS OF MONDAY BUT NOT
SIGNIFICANT IMPACT EXPECTED. VCTS WILL BE INDICATED FOR KAPF AFT
18Z MON AS THE WEST COAST SEA BREEZE DEVELOPS.

PREV DISCUSSION... /ISSUED 321 PM EDT SUN SEP 21 2008/

DISCUSSION...
THE CURRENT WATER VAPOR SATELLITE ANIMATION CONTINUES TO INDICATE
AN INCREASING TREND IN MID AND HIGH-LEVEL MOISTURE ACROSS SOUTH
FLORIDA...WITH THIS CONFIRMED BY DATA FROM RECENT UPPER AIR
OBSERVATIONS ACROSS THE AREA. THUS...DESPITE WEAK MID-LEVEL
SUBSIDENCE PROVIDED BY RIDGE AXIS ALOFT...EXPECT AT LEAST WIDELY
SCATTERED SHOWERS/THUNDERSTORMS TO DEVELOP ALONG COASTAL
CONVERGENCE BOUNDARIES AND AFFECT MUCH OF THE CENTRAL/WESTERN
PORTIONS OF THE FORECAST AREA THIS AFTERNOON. SHORT TERM MODEL
SOLUTIONS INDICATE THAT MODERATE EASTERLY FLOW WILL PERSIST IN THE
BOUNDARY LAYER OVERNIGHT...NECESSITATING SLIGHT CHANCE POPS OVER
THE ATLANTIC WATERS AND ADJACENT PORTIONS OF THE MAINLAND.
HOWEVER...SUBSIDENT EFFECTS OF MID-LEVEL RIDGE WILL LIKELY LIMIT
COVERAGE COMPARED TO WHAT WAS SEEN SUNDAY MORNING...AS INDICATED
BY RUC/WRF-NMM MODEL SOLUTIONS.

THE GLOBAL MODELS UNANIMOUSLY SUGGEST THAT A LARGE MID-
TROPOSPHERIC HIGH OVER THE CENTRAL NORTH ATLANTIC WILL WEAKEN
AND SHIFT EASTWARD THROUGH THE REMAINDER OF THE SHORT TERM
PERIOD...AS A POTENT VORT MAX TRANSLATES THROUGH BASE OF LONG WAVE
TROUGH CURRENTLY POSITIONED OVER THE DAVIS STRAIT. THIS WILL
SLOWLY ERODE THE RIDGE CENTERED ACROSS SOUTH FLORIDA ON
MONDAY...AND THIS...WHEN COMBINED WITH GRADUALLY INCREASING DEEP-
LAYER MOISTURE...SHOULD RESULT IN A SLIGHTLY GREATER COVERAGE OF
AFTERNOON CONVECTION OVER THE MAINLAND. WILL STILL CARRY HIGHEST
POPS ALONG THE CORRIDOR FROM WEST PALM BEACH SOUTHWESTWARD TO
NAPLES...WITH LOWEST CHANCES ALONG THE IMMEDIATE SOUTHEAST COAST.
EXPECT THE COVERAGE OF NOCTURNAL SHOWERS AND THUNDERSTORMS TO
INCREASE OVER THE ATLANTIC WATERS ON MONDAY NIGHT...AS WELL.
HOWEVER...THE HIGHEST CHANCES FOR RAIN WILL LIKELY COME ON
TUESDAY...AS MODELS REMAIN VERY CONSISTENT IN FORECASTING A WEAK
UPPER LOW CURRENTLY CENTERED OVER WESTERN ILLINOIS TO DRIFT EAST-
SOUTHEASTWARD OVER THE NEXT 48 HOURS...IN RESPONSE TO RISING MID-
LEVEL HEIGHTS OVER THE SOUTHERN PLAINS. THIS FEATURE IS PROGGED TO
DRIFT SLOWLY SOUTHWARD OVER THE CAROLINAS ON TUESDAY...AND DEEPEN
INTO A CUTOFF LOW...AS A BLOCKING SHORTWAVE RIDGE AXIS BUILDS
ACROSS THE GREAT LAKES AND NORTHEAST U.S. AS THIS OCCURS...THE
COMBINATION OF STRENGTHENING MID-LEVEL DIVERGENCE...STEEPENING
LAPSE RATES...AND INCREASING DEEP-LAYER MOISTURE WILL LEAD TO A
VERY FAVORABLE ENVIRONMENT FOR SHOWERS/THUNDERSTORMS TO DEVELOP.
REGARDING TEMPERATURES...WILL MAINTAIN A PERSISTENCE FORECAST FOR
THE NEXT 48 HOURS...AND COOL BOTH MAXIMUM/MINIMUM VALUES BY A 1-3
DEGREES ON TUESDAY/TUESDAY NIGHT...WITH EXPECTATIONS OF A HIGHER
COVERAGE OF CLOUDS AND PRECIPITATION...AS WELL AS NORTHEAST FLOW
OFF THE ATLANTIC.

THE PRIMARY FEATURE OF INTEREST IN THE EXTENDED FORECAST WILL BE
THE CUTOFF LOW...WHICH MODELS INDICATE WILL REMAIN LOCATED
EITHER OVER COASTAL PORTIONS OF GEORGIA/S.C./N.C. OR JUST OFF
SHORE THROUGH THE END OF THE WEEK. THE INFLUENCE OF THIS FEATURE
ON THE WEATHER ACROSS SOUTH FLORIDA WILL BE DIRECTLY RELATED TO
HOW DEEP THE SYSTEM BECOMES...AND HOW CLOSE IT ACTUALLY COMES TO
THE LOCAL AREA. THE LATEST ECMWF MAINTAINS THE CORE OF THE CYCLONE
OVER WATER...ALLOWING IT TO INITIALLY BECOME SIGNIFICANTLY DEEPER
THAN THE GFS WOULD SUGGEST...AND DEEPENS THE SYSTEM EVEN FURTHER
AS ENERGY FROM A POTENT MID-LATITUDE TROUGH BEGINS TO PHASE WITH
IT LATE NEXT WEEKEND. AS A RESULT OF THIS...THE ECMWF ALSO
INDICATES A MUCH DRIER PATTERN FOR SOUTH FLORIDA...AND WITH THIS
AMOUNT OF UNCERTAINTY...WILL MAKE NO CHANGES TO THE EXTENDED
FORECAST AT THIS TIME.

MARINE...
THERE ARE NO MARINE WEATHER CONCERNS THROUGH THE FIRST 24-36 HOURS
OF THIS FORECAST...WITH EAST TO NORTHEAST WINDS EXPECTED TO
REMAIN IN THE 10-15 KNOT RANGE OVER THE SOUTHERN LEG OF THE
ATLANTIC WATERS...AND SLIGHTLY LOWER ACROSS THE REMAINDER OF THE
COASTAL ZONES. A SMALL RESIDUAL SWELL IN THE PALM BEACH COUNTY
WATERS WILL RESULT IN SLIGHTLY HIGHER COMBINED SEAS IN THIS
REGION. MARINE WEATHER CONDITIONS ACROSS THE ATLANTIC WILL LIKELY
DETERIORATE BY TUESDAY AFTERNOON...AS NORTHEAST FLOW INCREASES IN
RESPONSE TO DEVELOPING LOW PRESSURE OFF THE COAST OF NORTH/CENTRAL
FLORIDA. NORTH/NORTHEAST WINDS WILL LIKELY INCREASE INTO THE 15-20
KNOT RANGE...WITH SEAS IN THE GULF STREAM APPROACHING MARGINAL SCA
CRITERIA. WINDS/SEAS ARE FORECAST TO RELAX LATER IN THE WEEK...BUT
THE DEVELOPMENT OF A DEEPER CYCLONE OFF THE COAST OF THE CAROLINAS
WILL GENERATE NORTH/NORTHEAST SWELL WHICH WILL AFFECT THE ATLANTIC
WATERS BY NEXT WEEKEND.

FIRE WEATHER...
THERE ARE NO FIRE WEATHER CONCERNS THROUGHOUT THE FORECAST
PERIOD...AS MINIMUM AFTERNOON RH VALUES WILL REMAIN SUFFICIENTLY
HIGH.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  88  76  87  72 / 50 40 60 30
FORT LAUDERDALE  90  79  88  75 / 40 40 50 30
MIAMI            90  79  88  75 / 40 40 50 30
NAPLES           90  74  87  72 / 50 40 60 30

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
GM...NONE.
&&

$$