Damaging Wind in Florida, April 5, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
855 PM EDT SAT APR 5 2008

.UPDATE...THE CURRENT MIMIC TOTAL PRECIP WATER LOOP SHOWS PWS
INCREASING AS EXPECTED OVER SOUTH FLORIDA AND THE SOUTHEAST GOMEX
IN ADVANCE OF THE LINE OF CONVECTION. RECENT TRENDS IN LIGHTNING
DATA SHOWS A LARGE DECREASE IN STRIKES OVER THE NORTHERN PART
MOVING INTO TAMPA BAY AND AN INCREASE OVER THE SOUTHERN LEG OVER
THE FAR GOMEX WATERS. BELIEVE THIS TREND WILL CONTINUE AND MOST OF
THE LIGHTNING WILL STAY OVER THE GULF. THE LINE OF SHOWERS WILL
REACH THE NORTHWEST AREAS WEST OF THE LAKE AROUND MIDNIGHT AND
WONT PENETRATE TOO FAR SOUTHEAST. SOME SHOWER ACTIVITY MAY DEVELOP
OVER THE STRAITS AND OVER THE INLAND AREAS SOUTH OF THE LAKE AND
WILL MOVE NORTH. THE MAIN CONVECTIVE ACTIVITY WILL START IN THE MID
SUNDAY MORNING HOURS. ONLY SLIGHT CHANCES WERE MADE TO THE FORECAST
MAINLY WITH KEEPING THE EAST COASTAL AREAS PRECIP FREE UNTIL MIDNIGHT.

.AVIATION...VFR CONDITIONS ARE EXPECTED TO CONTINUE ACROSS S FL
FOR THE REMAINDER OF THE EVENING... HOWEVER MOISTURE WILL INCREASE
TONIGHT. A LINE OF CONVECTION MOVING ACROSS THE GOMEX IS EXPECTED
TO MOVE INTO THE APF AREA AROUND MIDNIGHT... IF IT HOLDS TOGETHER...
THIS MAY SPREAD SHRA INTO THE WEST COAST, BUT ATTM DO NOT EXPECT
THE LINE TO BE TOO ROBUST AND MOVE ACROSS THE PENINSULA, AND EVEN
OPTED TO LEAVE OUT TS MENTION UNTIL MORNING FOR APF. SHRA AND TS
WILL INCREASE AREA WIDE DURING SUNDAY MORNING AND VCTS HAVE BEEN
ADDED. WIND DIRECTION WILL STAY MOSTLY SE DURING SUN ALONG THE
EAST BUT START SE AT APF AND GO SW BY AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 254 PM EDT SAT APR 5 2008/

DISCUSSION...
LATEST WATER VAPOR AND VISIBLE SATELLITE IMAGERY SHOW A WELL
DEFINED UPPER TROUGH AXIS FROM THE MISSISSIPPI RIVER VALLEY SOUTH
INTO THE NORTHERN GULF OF MEXICO...WHERE A SOLID SQUALL LINE HAS
DEVELOPED TODAY. LOCALLY...SOUTH FLORIDA IS STILL BEING INFLUENCED
SOME BY THE LOW-MID LEVEL RIDGE AXIS NOSING IN FROM OUR EAST,
WHICH HAS LIKELY LIMITED CONVECTIVE COVERAGE SO FAR TODAY.
NEVERTHELESS, VISIBLE IMAGERY SHOWS A CONVERGENCE LINE FROM
WESTERN GLADES COUNTY SOUTH THROUGH CENTRAL COLLIER COUNTY WITH A
FEW SHOWERS TRYING TO DEVELOP ALONG IT. WILL TAILOR CHANCE POPS TO
SUIT A SCENARIO OF CONTINUED SCATTERED DEVELOPMENT ALONG THIS BAND
MOVING NE TOWARDS THE LAKE OKEE. REGION INTO THE EARLY EVENING.

NAM AND GFS DIFFER QUITE A BIT ON POPS FOR TONIGHT...AS THE NAM
RACES THE AFOREMENTIONED SQUALL LINE RIGHT UP TO THE WEST COAST
BEFORE WEAKENING JUST AFTER 00Z...WHILE THE GFS SPLITS THE LINE
AND LINGERS THE SOUTHERN PIECE OVER THE NE GULF INSTEAD, THUS
HAVING LOWER POPS. MODEL GUIDANCE CONSTANTLY HAS DIFFICULTY
HANDLING THESE SITUATIONS, BUT WITH TROUGH AXIS LIFTING NE UP THE
ATLANTIC COAST THINK THAT THE LINE WILL BREAK UP AS IT APPROACHES,
BUT WITH UPPER LEVEL ENERGY AND MOISTURE TRANSPORT IN PLACE, THINK
SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM IS POSSIBLE
OVERNIGHT...BUT WILL LEAN TOWARDS LOWER POPS.

WHILE THE SURFACE COLD FRONT LAGS OVER NORTH FL SUNDAY, BOTH THE
NAM AND GFS AGREE THAT A PRE-FRONTAL TROUGH OR OUTFLOW BOUNDARY
FROM THE SQUALL LINE WILL STALL IN VICINITY OF LAKE OKEE. SUNDAY
MORNING AND WILL BE THE FOCUS FOR THUNDERSTORM DEVELOPMENT
THROUGHOUT THE DAY...WITH THE NAM TAKING THINGS OFF FIRST THING IN
THE MORNING. SOUTH OF THE BOUNDARY...SSW SFC FLOW WILL FINALLY
DEVELOP AND SOME SUN SHOULD OCCUR IN THE MORNING...AND IN TURN
DEVELOP DECENT INSTABILITY ACROSS THE SOUTHERN HALF OF THE
CWA...WITH UPWARD MOTION INCREASING REGION-WIDE AS A SHORTWAVE
MOVES ACROSS CENTRAL FL. THUS EXPECT FAIRLY WIDESPREAD
THUNDERSTORMS TO DEVELOP ALONG THE SW COASTAL CONVERGENCE AND MOVE
NE TOWARDS AND THROUGH THE EAST COAST METRO AREAS DURING THE DAY
GIVEN SW FLOW IN THE MID-LEVELS. PWATS CLIMB TO 1.75 INCHES SO
HEAVY RAIN IS LIKELY WITH ANY STORM...AND WITH THE DEEP-LAYERED
UNIDIRECTIONAL FLOW MAY HAVE TO WORRY ABOUT TRAINING OF
CELLS/BACKBUILDING IN SOME AREAS. CONVERGENCE WILL ALSO BE
ENHANCED ALONG THE EAST COAST METRO AREAS AS MODELS DEVELOP A WEAK
SEA BREEZE. OVERALL SITUATION DOES NOT FAVOR MORE THAN PULSE
SEVERE STORMS GIVEN WEAK MID-LEVEL LAPSE RATES AND OVERALL LACK OF
SIGNIFICANT WIND SHEAR...BUT ANY STORM CROSSING THE EAST COAST SEA
BREEZE WOULD NEED TO BE WATCHED DESPITE WEAK LOW-LEVEL FLOW.

SEVERAL IMPULSES MAY WORK PARALLEL TO THE COLD FRONT OR WHATS LEFT
OF IT AS IT SETTLES SLOWLY SOUTH INTO THE REGION SUNDAY
NIGHT/MONDAY. BOUNDARY WILL BE PARALLEL TO STEERING FLOW AT THIS
POINT...WITH WSW FLOW SOUTH OF IT AND NOT MUCH CONVERGENCE. STILL
EXPECT MID-LEVEL ENERGY MOVING JUST NORTH OF THE REGION WOULD BE
ENOUGH TO PRODUCE SCATTERED THUNDERSTORMS THIS PERIOD ONCE AGAIN.

MODELS TRY TO DEVELOP A WEAK SFC LOW OFF THE CAROLINA COAST AND
DRAG THE FRONT THROUGH FINALLY MONDAY EVENING AS THE UPPER TROUGH
AXIS PASSES THROUGH. INSTABILITY LINGERS HOWEVER DESPITE
DEVELOPING NE FLOW TUESDAY AND WEDNESDAY, SO SCATTERED STORMS
COULD STILL OCCUR BUT MAINLY WESTERN AREAS. BY WEDNESDAY, HOWEVER
..MID-LEVEL RIDGING BEGINS TO BUILD OVERHEAD WHICH COULD LIMIT
CONVECTIVE POTENTIAL.

AVIATION...
VFR CONDS WILL CONTINUE ACROSS MOST OF THE ERN TERMINALS THROUGH AT
LEAST 06Z TONIGHT. HOWEVER...CLOUDS AND PRECIP SHOULD START
INCREASING AFTER 06Z, ESPECIALLY SUN MORNING AND AFTERNOON. DEEP
MODERATE SE-S FLOW WILL KEEP ANY SHWR/TSTM THAT DEVELOP THIS
AFTERNOON AND EVENING INLAND AND WEST OF THE ERN TERMINALS. WL
EXPECT A MORE SW RESULTANT (FROM SEA BREEZE AND MEAN FLOW) FLOW WL
KEEP MOST PRECIP ACTIVITY INLAND AND AWAY FROM KAPF THIS
EVENING...HOWEVER WILL NOT RULE OUT THE POSSIBILITY OF A FEW
SHOWERS IN THE VICINITY OF KAPF. SHOWERS AND POSSIBLY TSTMS WILL
DEVELOP OVR GULF OF MEX WATERS AND MOVE NE POSSIBLY AFFECTING KAPF
AFTER 06Z. WL KEEP VCSH/VCTS OVR ALL TERMINALS SUN THROUGH 18Z BUT
THIS MAY HAVE TO BE CHANGED TO TEMPO GROUPS LATER ON IF CONVECTION
BECOMES MORE WIDESPREAD.

MARINE...
WINDS SHOULD DECREASE A BIT SUNDAY AHEAD OF THE COLD FRONT AS THE
PRESSURE GRADIENT WEAKENS SOME. WINDS WILL BECOME SOUTHERLY ACROSS
THE ATLANTIC AND BAY WATERS WITH SSW ELSEWHERE SUNDAY. SW FLOW
DEVELOPS ALL WATERS SUNDAY NIGHT THROUGH MONDAY UNTIL COLD FRONT
PASSES AND WINDS SHIFT NORTHERLY. AFTER TOMORROW, SPEEDS SHOULD
REMAIN 15 KTS OR LESS. GUIDANCE INDICATES A LONG-PERIOD SWELL FROM
THE NORTHEAST POSSIBLE BY LATE WEDNESDAY...BUT GIVEN UNCERTAINTIES
IN SFC LOW DEVELOPMENT OFF THE CAROLINA COAST WILL LEAVE OUT OF
THE FORECAST FOR NOW.

FIRE WEATHER...
NO CONCERNS THIS PERIOD AS LOW-LEVEL MOISTURE REMAINS ABUNDANT.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  72  83  71  85 / 30 70 40 50
FORT LAUDERDALE  74  84  72  85 / 30 70 40 50
MIAMI            75  85  72  86 / 30 60 40 50
NAPLES           72  84  71  84 / 40 50 40 40

&&

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

LONG TERM UPDATE...18/GR
SHORT TERM/AVIATION UPDATE...04/AT

HAZARDOUS WEATHER OUTLOOK FOR SOUTH FLORIDA
NATIONAL WEATHER SERVICE MIAMI FL
635 PM EDT SAT APR 5 2008

FLZ063-066>075-168-172>174-061000-
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-
635 PM EDT SAT APR 5 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TONIGHT

THUNDERSTORMS: THERE IS A CHANCE FOR ISOLATED THUNDERSTORMS TO MOVE
INTO THE REGION LATER TONIGHT...ESPECIALLY OVER THE NORTHWEST
SECTIONS. THE GREATEST THREAT WITH THE STORMS WILL BE CLOUD OF
GROUND LIGHTNING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS A CHANCE OF THUNDERSTORMS ACROSS THE REGION FROM SUNDAY
THROUGH TUESDAY, WITH THE HIGHEST CHANCES DURING THE AFTERNOON
HOURS. STRONG THUNDERSTORMS WILL ALSO BE POSSIBLE EACH AFTERNOON,
WITH GUSTY WINDS, SMALL HAIL, AND FREQUENT LIGHTNING STRIKES BEING
THE PRIMARY HAZARDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH SUNDAY MORNING.

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