Flash Flood in Florida, May 29, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
646 AM EDT WED MAY 29 2013

.AVIATION...
NOT TOO MUCH CHANGE FROM YESTERDAY WEATHER. BERMUDA HIGH CONTINUES
TO BRING GUSTY WINDS IN A EASTERLY FLOW. THIS FLOW IS ALSO
BRINGING PERIODS OF SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM TO
SOUTH FLORIDA. SOME OF THE SHOWERS MAY BE HEAVY, WHICH WOULD
BRIEFLY REDUCE VSBYS AND CIGS TO MVFR AND POSSIBLY IFR LEVELS.
HOWEVER, THESE PERIOD OF REDUCED FLIGHT CATEGORIES WILL BE VERY
BRIEF, LASTING ONLY 10 TO 20 MINUTES, THUS, NOT IN THE TAFS AT THIS
TIME. WIND GUSTS MAY REACH AROUND 25 KTS, OR EVEN LOCALLY HIGHER
THIS AFTERNOON. SHORT RANGE MODELS ARE SHOWING THAT THERE MAY BE
SOME TAPERING OFF OF SHOWER COVERAGE THIS AFTERNOON. THUS, HAVE
ONLY VCSH AFTER 17Z ALONG ATLANTIC COAST TAF SITES. FOR KAPF, RAIN
WILL MOVE INTO THE AREA THIS MORNING, AND LAST INTO THE LATE AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 234 AM EDT WED MAY 29 2013/

SHORT TERM (TODAY THROUGH FRIDAY)...
THE FORECAST FOR SOUTH FLORIDA HAS BECOME INCREASINGLY UNCERTAIN.
DEEP TROPICAL MOISTURE REMAINS ACROSS SOUTH FLORIDA THIS MORNING
WITH PWAT FROM THE 00Z MFL SOUNDING AT JUST UNDER TWO INCHES AND
CURRENT SATELLITE ESTIMATES RANGING FROM OVER TWO INCHES ALONG THE
SOUTHEAST COAST TO 1.8-1.9 INCHES NEAR THE LAKE. GLOBAL MODELS IN
GOOD AGREEMENT WITH SHOWING A VERY WEAK PRESSURE PATTERN AT MID
LEVELS WITH LITTLE CHANGE IN THIS PATTERN THROUGH THIS PERIOD.
HOWEVER, THIS IS WHERE THE AGREEMENT ENDS. THE MODELS DO AGREE
THAT THERE IS CURRENTLY A TIGHT SURFACE PRESSURE GRADIENT ACROSS
SOUTH FLORIDA WITH STRONG HIGH PRESSURE OVER THE SOUTHEAST STATES
RESULTING IN A BREEZY ONSHORE FLOW ALONG THE SOUTHEAST COAST WHICH
IN TURN IS PREVENTING A SEA BREEZE ALONG COASTAL COLLIER COUNTY.
THE FIRST PROBLEM ARISES WITH THE GFS SHOWING AN INVERTED SURFACE
TROUGH DEVELOPING ACROSS SOUTH FLORIDA EARLY FRIDAY WITH THE
EASTERLY FLOW GETTING SHUT OFF. THE SECOND PROBLEM IS THAT THE NAM
KEEPS THE EASTERLY FLOW IN TACT BUT BRINGS IN MUCH DRIER AIR ALOFT
FROM THE ATLANTIC ON THURSDAY AND THURSDAY NIGHT LOWERING THE PWAT
TO UNDER 1.5 INCHES. THERE IS DRIER AIR AS SEEN FROM WATER VAPOR
IMAGERY OVER THE ATLANTIC NEAR 30N BUT IT DOES NOT APPEAR THAT THE
FLOW OF AIR WOULD BE SUFFICIENT IN FILTERING THIS DRYING SOUTHWARD
AND NEITHER THE GFS NOR THE ECMWF SHOW THIS OCCURRING. SO GIVEN
THE UNCERTAINTY OF WHICH MODELS WIN OUT AT THE MID LEVELS AND AT
THE SURFACE, WILL LEAN TOWARDS THE HIGHER POPS FROM THE MAV WITH
THE ECMWF ALSO SHOWING HIGH MOISTURE CONTENT CONTINUING AND THE
SURFACE WIND GUIDANCE FROM THE NAM/ECMWF. THE GFS HAS BEEN CHANGING ITS
TUNE TOO MANY TIMES OVER THE PAST FEW RUNS TO PLACE MUCH FAITH IN
ITS POSITION OF A TROUGH IF IT EVEN DEVELOPS.

IN ADDITION, DEPENDING ON WHICH MODEL IS CORRECT AS WITH DEEP
MOISTURE CONTENT WILL DETERMINE THE QUANTITY OF RAINFALL ACROSS
SOUTH FLORIDA THROUGH THE END OF THIS WEEK. BUT GOING WITH THE
IDEA OF PWAT REMAINING AROUND TWO INCHES WILL CONTINUE THE
POSSIBLE TOTALS APPROACHING TWO TO THREE INCHES BY LATE FRIDAY AND
LOCALLY HIGHER AMOUNTS OF AROUND FOUR INCHES OVER THE FAR SOUTHERN
PENINSULA.

LONG TERM (FRIDAY NIGHT THROUGH TUESDAY)...
THE GFS AND ECMWF CONTINUE WITH A WEAK MID LEVEL PRESSURE PATTERN
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK WITH HIGH PWAT VALUES
AROUND TWO INCHES. THE GFS HOWEVER CONTINUES THE SURFACE TROUGH
INTO EARLY NEXT WEEK ALTHOUGH IN A WEAKER STATE BUT THIS STILL
GIVES A SOUTHWEST WIND FOR THE GULF WATERS WHILE THE ECMWF
CONTINUES WITH A SOUTHEAST WIND. SO THAT BEING SAID, WILL GO WITH
THE ECMWF SURFACE WIND GUIDANCE IN THE EXTENDED PERIOD WITH NEAR
CLIMATOLOGICAL CHANCES FOR RAINFALL.

MARINE...
EAST TO SOUTHEAST WIND HAS DIMINISHED TO 20 KNOTS OR LESS AS
INDICATED FROM THE FOWEY ROCKS C-MAN STATION ALONG WITH SOME
COASTAL MESONET SITES. FOWEY ROCKS DID SHOW A PEAK GUST THIS PAST
HOUR AT 22 KNOTS BUT IT IS AN ELEVATE SITE AT ALMOST 50 METERS.
SETTLEMENT ALSO INDICATED A HIGHER GUST BUT THAT APPEARS TO BE
SHOWER INDUCED. TWO MESONETS THAT ARE IN BISCAYNE BAY SHOWED GUSTS
TO 15 AND 18 KNOTS. IN ADDITION ALL MODEL GUIDANCE IN THE SHORT
TERM THROUGH TONIGHT IS SHOWING AN EAST WIND OF 15 TO 20 KNOTS. SO
THEREFORE, WILL CANCEL THE SCA AND GO WITH SCEC FOR ALL WATERS.
THIS TREND WILL CONTINUE THROUGH THE END OF THE WEEK AT WHICH TIME
IT APPEARS THE GRADIENT MAY RELAX OVER THE WEEKEND WITH WIND AND
SEAS DIMINISHING AT THAT TIME.

FIRE WEATHER...
NO PROBLEMS OR CONCERNS WITH AMPLE TROPICAL MOISTURE.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  83  75  85  77 / 60 40 40 20
FORT LAUDERDALE  84  75  85  75 / 70 50 40 30
MIAMI            85  75  85  75 / 70 50 50 30
NAPLES           86  71  89  74 / 70 40 40 20

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...RIP CURRENT RISK THROUGH FRIDAY AFTERNOON FOR COASTAL BROWARD-
     COASTAL MIAMI DADE-COASTAL PALM BEACH.

AM...NONE.
GM...NONE.
&&

DISCUSSION/MARINE/FIRE...30/KOB
AVIATION/RADAR...13/SI

HAZARDOUS WEATHER OUTLOOK FOR SOUTH FLORIDA
NATIONAL WEATHER SERVICE MIAMI FL
351 AM EDT WED MAY 29 2013

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
292300-
LAKE OKEECHOBEE-BISCAYNE BAY-
COASTAL WATERS FROM JUPITER INLET TO DEERFIELD BEACH, FL OUT 20 NM-
COASTAL WATERS FROM DEERFIELD BEACH TO OCEAN REEF, FL OUT 20 NM-
WATERS FROM JUPITER INLET TO DEERFIELD BEACH, FL EXTENDING FROM
20 NM TO 60 NM-
WATERS FROM DEERFIELD BEACH TO OCEAN REEF, FL EXTENDING FROM 20 NM
TO THE TERRITORIAL WATERS OF THE BAHAMAS-GLADES-HENDRY-
INLAND PALM BEACH-METRO PALM BEACH-COASTAL COLLIER-INLAND COLLIER-
INLAND BROWARD-METRO BROWARD-INLAND MIAMI DADE-METRO MIAMI DADE-
MAINLAND MONROE-COASTAL PALM BEACH-COASTAL BROWARD-
COASTAL MIAMI DADE-FAR SOUTH MIAMI DADE-
COASTAL WATERS FROM CHOKOLOSKEE TO BONITA BEACH, FL OUT 20 NM-
COASTAL WATERS FROM EAST CAPE SABLE TO CHOKOLOSKEE, FL OUT 20 NM-
GULF WATERS FROM CHOKOLOSKEE TO BONITA BEACH, FL EXTENDING FROM
20 TO 60 NM-
351 AM EDT WED MAY 29 2013

...HIGH RISK OF RIP CURRENTS FOR ATLANTIC BEACHES...
...ISOLATED THUNDERSTORMS POSSIBLE TODAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TODAY AND TONIGHT

RIP CURRENTS: THERE IS A HIGH RISK OF RIP CURRENTS ALONG THE
ATLANTIC BEACHES.

THUNDERSTORMS: THERE IS A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
THE OVERNIGHT HOURS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A HIGH RISK OF RIP CURRENTS WILL CONTINUE ALONG THE ATLANTIC
BEACHES THROUGH AT LEAST FRIDAY. STRONG RIP CURRENTS ARE LIKELY,
MAKING CONDITIONS VERY DANGEROUS FOR SWIMMING.

THUNDERSTORMS WITH GUSTY WINDS AND LOCALLY HEAVY RAINFALL ARE POSSIBLE
ACROSS SOUTHEAST FLORIDA THROUGH AT LEAST THE BEGINNING OF NEXT WEEK.
ALTHOUGH SEVERE THUNDERSTORMS ARE NOT ANTICIPATED, THERE IS ALWAYS
A SLIGHT CHANCE OF A THUNDERSTORM BECOMING SEVERE IF CONDITIONS
BECOME CONDUCIVE TO ENHANCED DEVELOPMENT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

FOR MORE INFORMATION...VISIT THE NATIONAL WEATHER SERVICE IN MIAMI
WEBSITE AT WWW.WEATHER.GOV/MIAMI.