Area Forecast Discussion
Issued by NWS Miami, FL

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000
FXUS62 KMFL 031354
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
954 AM EDT SUN MAY 3 2015

.UPDATE...
THE CURRENT MODEL ANALYSIS SHOWS MOSTLY ZONAL FLOW ACROSS THE
FLORIDA PENINSULA WITH A VERY WEAK MID LEVEL TROUGH OVER SOUTH
FLORIDA. AT THE SURFACE, A BROAD AREA OF HIGH PRESSURE EXISTS
ACROSS THE SOUTHEAST STATES CENTERED FROM WEST VIRGINIA TO
NORTHERN GEORGIA. THE MID LEVEL TROUGH IS REFLECTED WELL ON THE
12Z MFL SOUNDING SHOWING A NORTH-NORTHEAST WIND IN THE LAYER FROM
600MB TO 450MB WITH WESTERLY FLOW ABOVE AND BELOW THAT. LOW LEVEL
FLOW IS EAST-NORTHEAST WITH THE HIGH PRESSURE CENTERED TO THE
NORTH. THE SURFACE HIGH WILL RAPIDLY SHIFT EAST TODAY IN RESPONSE
TO A COLD FRONT THAT WILL MOVE INTO THE CENTRAL PORTION OF THE
CONTINENTAL U.S. WITH THE PRESSURE GRADIENT TIGHTENING ACROSS
SOUTH FLORIDA BY EARLY THIS AFTERNOON. THIS WILL KEEP THE HIGH
RISK OF RIP CURRENTS AT THE ATLANTIC BEACHES WITH MIAMI BEACH
OCEAN RESCUE ALREADY REPORTING STRONG CURRENTS THIS MORNING. THE
12Z SOUNDING ALSO SHOWS A VERY STABLE AIRMASS LAYER BETWEEN 850MB
AND 750MB SO THIS WILL CONTINUE TO KEEP RAIN CHANCES OUT OF THE
FORECAST ALTHOUGH THE HRRR IS INDICATING THE POSSIBILITY OF A
COUPLE OF QUICK PASSING SHOWERS. HOWEVER, IT IS ONLY DEPICTING
20-25 DBZ INTENSITY SO NOT WORTH MENTIONING AT THIS TIME AND THE
HRRR OFTEN TIMES OVER EMPHASIZES SHOWERS IN A DRY EASTERLY FLOW
REGIME. BUT STILL, SOMETHING TO MONITOR.

FOR THE MARINE FORECAST, DO NOT PLAN ANY CHANGES AT THIS TIME.
HOWEVER, THE LATEST GFS MODEL GUIDANCE IS SHOWING A TAD BIT
STRONGER WINDS OVER THE ATLANTIC WATERS THIS AFTERNOON THAN IS
CURRENTLY DEPICTED. DUE TO THIS BEING FROM THE INTERMEDIATE RUN AT
06Z AND ONLY ONE UPDATE SHOWING THIS, WILL WAIT FOR THE 12Z RUN TO
MAKE ANY DECISIONS BUT MAY NEED TO BUMP UP THE WIND TO 20 KNOTS
FROM THE CURRENT 15-20 KNOTS WHICH COULD AFFECT THE SIGNIFICANT
WAVE HEIGHTS AS WELL AND MAY NEED TO BEGIN THE SCA FOR THOSE
WATERS EARLIER THAN THE 00Z START NOW.

KOB

&&

.PREV DISCUSSION... /ISSUED 744 AM EDT SUN MAY 3 2015/

AVIATION...
MAINLY VFR CONDITIONS EXPECTED TO PREVAIL THROUGH THE EARLY MORNING
HOURS AND THROUGH THE AFTERNOON WITH MAINLY STABLE WEATHER CONDITIONS
ANTICIPATED. AS HIGH PRESSURE BUILDS...EAST NORTHEAST WINDS FORECAST
TO INCREASE TO THE 15 TO 20 KNOTS RANGE BY LATE MORNING WITH
HIGHER GUSTS POSSIBLE AND SUBSIDING OVERNIGHT BUT STILL REMAINING
AROUND 10-15 KTS EXCEPT AROUND 10 KNOTS AT APF AND TMB.

PREV DISCUSSION... /ISSUED 433 AM EDT SUN MAY 3 2015/

DISCUSSION...

THE REGIONAL SYNOPTIC FEATURES EARLY THIS MORNING INCLUDE A WEAK SURFACE
TROUGH JUST WEST OF THE KEYS AND EXTENDING NORTHWARD...A MID TO
UPPER LEVEL TROUGH EXTENDING INTO THE CENTRAL TO EASTERN GULF AND
A COLD FRONT ACROSS EASTERN CUBA THAT EXTENDS NORTHWARD TO A
SURFACE LOW NORTHEAST OF THE MID-ATLANTIC STATES.

FOR TODAY...HIGH PRESSURE WILL SLOWLY DEVELOP OFF THE
GEORGIA/CAROLINAS COAST WITH THE AFOREMENTIONED SURFACE TROUGH
ERODING. IN ADDITION DEEPER LAYERED MOISTURE WILL LIKELY REMAIN
ACROSS THE KEYS TODAY. WITH HIGHER PRESSURE BUILDING INTO THE
REGION THE WEST COAST SEA BREEZE WILL BE SUPPRESSED AND WITH PWAT
EXPECTED TO BE AROUND ONLY AN INCH CONVECTION IS NOT LIKELY TODAY
ALTHOUGH SOME ISOLATED SHOWER ACTIVITY IS POSSIBLE ACROSS THE
SOUTHERN TIP OF THE PENINSULA.

THERE WILL BE A HIGH RISK OF RIP CURRENTS ALONG THE ATLANTIC COAST
BEACHES TODAY AND TONIGHT WITH A LONG PERIOD NORTHEASTERLY SWELL
IN THE 2 TO 4 FOOT RANGE FORECAST TO ENTER THE ATLANTIC WATERS
EAST OF PALM BEACH COUNTY THIS MORNING...WITH THE GREATEST IMPACT
EXPECTED ACROSS THE WATERS TO THE EAST OF PALM BEACH COUNTY.

FOR MONDAY...MOISTURE AND CLOUDINESS WILL BEGIN TO RETURN TO THE
REGION. THE MID TO UPPER LEVEL TROUGH ACROSS THE GULF IS FORECAST
TO DEEPEN WITH THE FLORIDA PENINSULA TO THE EAST OF THE TROUGH
AXIS. THE LOW LEVEL FLOW WILL BECOME SOUTHERLY BRINGING DEEP
MOISTURE ACROSS CUBA NORTHWARD INTO THE REGION. MODERATE EASTERLY
WINDS WILL FAVOR SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS
MAINLY ALONG THE EASTERN THIRD OF THE PENINSULA AND THE ADJACENT
ATLANTIC WATERS.

FOR TUESDAY...PREVIOUS DISCUSSIONS HAVE ALREADY INDICATED THAT
DEEP TROPICAL MOISTURE IS FORECAST TO ENTER ON TUESDAY WITH THE MID
TO UPPER LEVEL TROUGH AXIS JUST WEST OF FLORIDA AND A BROAD LOW
LEVEL TROUGH DEVELOPING ACROSS THE FLORIDA STRAITS AND EXTENDING
INTO THE NORTHWEST BAHAMAS. THE PWAT IS FORECAST TO BE ABOUT 1.7
INCHES AND MID LEVEL TEMPERATURES FORECAST TO BE SIGNIFICANTLY
COOL FOR THIS TIME OF YEAR...ABOUT 3 DEGREES COOLER. ALL THESE
FACTORS ARE FORECAST TO BRING SCATTERED TO NUMEROUS
SHOWERS/THUNDERSTORMS TO THE REGION ON TUESDAY WITH A SYNOPTIC
PATTERN SUPPORTIVE OF LOCALLY HEAVY RAINFALL WITH FLOODING
POTENTIAL POSSIBLE IN ISOLATED AREAS.

BY WEDNESDAY THE GLOBAL MODELS START TO DIVERGE SOME IN THEIR
SOLUTIONS BUT THE GFS ENSEMBLE SHOWS BROAD FEATURES THAT SEEM LIKE
A GENERAL CONSENSUS BETWEEN THE GFS AND THE ECMWF. THE ENSEMBLE INDICATES THAT
THE UPPER LEVEL TROUGH AXIS IS FORECAST TO SHIFT EAST ACROSS THE FLORIDA
PENINSULA WITH A BROAD LOW LEVEL AND SURFACE TROUGH OFF THE EAST
CENTRAL FLORIDA COAST WITH DEEP MOISTURE EXTENDING ACROSS SOUTH
FLORIDA. SCATTERED TO NUMEROUS SHOWERS/THUNDERSTORMS ARE FORECAST
WITH A SYNOPTIC PATTERN AGAIN SUPPORTIVE OF LOCALLY HEAVY
RAINFALL.

FOR THE EXTENDED FORECAST...BY THURSDAY THE ECMWF...GFS AND THE
GFS ENSEMBLE HAVE BROAD AGREEMENT THAT THE UPPER LEVEL TROUGH
WILL PERSIST NEAR THE FLORIDA PENINSULA WITH A CLOSED SURFACE LOW
FORECAST OFF THE NORTHEAST FLORIDA COAST. THE GUIDANCE GENERALLY
SUGGESTS THAT THE LOW COULD SLOWLY DRIFT TO THE NORTHWEST INTO
NEXT WEEKEND. OBVIOUSLY ITS TOO EARLY TO SPECULATE ON THIS
SCENARIO AND WHAT IF ANY IMPACT IT MIGHT HAVE FOR SOUTH FLORIDA
AND WILL HAVE TO WAIT AND SEE WHAT CONSENSUS THE GUIDANCE HAS
DURING THIS WEEK.

MARINE...

A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE GULF WATERS FOR
WINDS TO NEAR 20 KNOTS OR JUST ABOVE THROUGH 10 AM. WINDS ARE
FORECAST TO SLOWLY DECREASE TODAY THEN INCREASE AGAIN TO 20 KNOTS
OR JUST ABOVE MAINLY ACROSS THE OFF SHORE WATERS. THEREFORE THE
SMALL CRAFT ADVISORY WILL BE ALLOWED TO EXPIRE THIS MORNING BUT A
NEW ONE WILL BE ISSUED FOR TONIGHT...STARTING AT 00Z FOR THE OFF
SHORE GULF WATERS.

WITH THE COMBINATION OF NORTHEASTERLY WINDS IN THE 15 TO 20
KNOT RANGE ACROSS THE ATLANTIC WATERS AND A LONG PERIOD
NORTHEASTERLY SWELL IN THE 2 TO 4 FOOT RANGE FORECAST TO ENTER
THE ATLANTIC WATERS EAST OF PALM BEACH COUNTY LATER THIS MORNING...HAZARDOUS
SEAS TO NEAR 7 FEET ARE FORECAST ACROSS THE ATLANTIC WATERS WITH A
SMALL CRAFT ADVISORY IN EFFECT TODAY STARTING AT 18Z THROUGH 00Z
TUESDAY BUT MAY HAVE TO BE EXTENDED WITH LATER GUIDANCE.

THERE IS A LOT OF UNCERTAINTY IN THE EXTENDED FORECAST GIVEN THE
UNCERTAINTIES OUTLINED IN THE DISCUSSION ABOVE. SO THERE COULD BE
CONSIDERABLE CHANGES TO THE WIND AND WAVES FORECAST IN THE
EXTENDED PERIODS IN THE NEXT FEW DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  79  69  82  73 /  10   0  20  60
FORT LAUDERDALE  80  71  82  73 /  10  10  20  70
MIAMI            81  70  82  72 /  10  10  20  70
NAPLES           87  63  86  67 /  10  10  10  20

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR FLZ168-172-173.

AM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM EDT THIS MORNING FOR
     AMZ651-671.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM THIS AFTERNOON
     TO 8 PM EDT MONDAY FOR AMZ650-651-670-671.

GM...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM EDT THIS MORNING FOR
     GMZ656-657-676.

     SMALL CRAFT ADVISORY FOR WINDS FROM 8 PM THIS EVENING TO 8 AM
     EDT MONDAY FOR GMZ676.

&&

$$


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