Area Forecast Discussion
Issued by NWS Miami, FL

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000
FXUS62 KMFL 211143
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
743 AM EDT THU AUG 21 2014

.AVIATION...
GENERALLY EASTERLY FLOW WILL PREVAIL THROUGH THE DAY ACROSS THE
EAST COAST SITES WITH A GULF BREEZE AT KAPF AFTER 17Z. A FEW SHRAS
COULD BRIEFLY AFFECT THE EAST COAST SITES LATE THIS MORNING WITH
THE EASTERLY FLOW AS DEPICTED BY THE LATEST HRRR. MOST OF THE
AFTERNOON CONVECTION SHOULD REMAIN ACROSS THE INTERIOR AND GULF
COAST AS THE GULF BREEZE PENETRATES INLAND. THEREFORE PLACED A
TEMPO GROUP IN FOR KAPF.

&&

.PREV DISCUSSION... /ISSUED 349 AM EDT THU AUG 21 2014/

DISCUSSION...

CURRENTLY A LARGE AREA OF HIGH PRESSURE COVERS THE SUBTROPICS
EXTENDING FROM NORTH AFRICA TO MEXICO. A TROUGH OF LOW PRESSURE OVER
THE PACIFIC COAST OF THE US INTERRUPTS THE SUBTROPICAL HIGH. AS THIS
TROUGH CONTINUES TO AMPLIFY IN THE WEST, A PORTION OF THE
SUBTROPICAL HIGH IS DRAWN INTO THE SOUTHEASTERN US EXPANDING AND
REACHING 595 DAM BETWEEN FRIDAY AND SATURDAY AT 500MB. AS THIS
AMPLIFICATION OCCURS, A TROUGH OF LOW PRESSURE MOVES SOUTHWARD
ALONG THE EASTERN SEABOARD WITH THE HIGH EXTENDING FROM NORTHERN
MEXICO TO THE NORTHEAST US FOR EARLY NEXT WEEK. SLOWLY, THE HIGH
MOVES EASTWARD NEXT WEEK.

THE SOLUTIONS OF THE GFS AND ECMWF MODELS ARE VERY SIMILAR, EXCEPT
THAT THE ECMWF HAS A MORE PRONOUNCED TROUGH OF LOW PRESSURE,
EXTENDING FURTHER SOUTH, FOR THE ATLANTIC OCEAN EAST OF THE HIGH FOR
NEXT WEEK. THIS VOID IN PRESSURES IS WHAT COULD CHANNEL NORTHWARD
THE AREA OF DISTURBED WEATHER CURRENTLY LOCATED NE OF SOUTH AMERICA.
THE GFS MODEL IS BECOMING MORE IN LINE WITH THE ECMWF ON THE
DEPICTION OF THIS FEATURE.

THE AREA OF INCREASED MOISTURE THAT AFFECTED OUR REGION TODAY IS
NOW MOVING INTO THE GULF OF MEXICO. HOWEVER, AN AREA OF RESIDUAL
MOISTURE LINGERS BETWEEN NOW AND FRIDAY ALONG THE SOUTHERN PORTION
OF THE HIGH PRESSURE. DRIER AIR IS FORECAST TO AFFECT SOUTH
FLORIDA BEGINNING ON SATURDAY. HOWEVER, AS THE HIGH PRESSURE
DESCRIBED ABOVE OVER THE SOUTHEASTERN US GETS ELONGATED, IT WRAPS
AROUND AN AREA OF MOISTURE THAT ROTATES ALONG THE NORTHERN
PERIPHERY OF THE HIGH POSSIBLY TAKING THIS MOISTURE TO CENTRAL
FLORIDA. DUE TO THE AMPLIFIED PATTERN, DETAILS OF THIS SORT HAVE A
LOW CONFIDENCE IN TIMING. IT IS IMPORTANT TO NOTE THAT THE ECMWF
SHOWS RELATIVELY HIGH SURFACE PRESSURE STANDARD DEVIATIONS FOR
EARLY NEXT WEEK, WHICH IS INDICATIVE OF A LOW CONFIDENCE
FORECAST. IT IS VERY DIFFICULT TO KNOW WHERE THE AREA OF DISTURBED
WEATHER COULD END SINCE IT DEPENDS ON THE EASTWARD DISPLACEMENT OF
THE HIGH AND THE POSITION OF THE TROUGH IN THE WESTERN ATLANTIC.
AT THIS TIME THE UNCERTAINTY IS JUST TOO LARGE. SOUTH FLORIDA
RESIDENTS ARE ADVISED TO STAY TUNED OVER THE WEEKEND. NOTHING TO
WORRY ABOUT AT THIS TIME OTHER THAN CHECKING OUR PREPAREDNESS
PLANS. AFTER ALL, WE ARE HEADING INTO THE PEAK OF THE HURRICANE
SEASON.

THE DRY AIR THAT IS FORECAST TO AFFECT SOUTH FLORIDA THIS WEEKEND MAY
STILL HAVE A LITTLE BIT OF SAHARAN DUST IN IT SINCE BOTH THE
NRL/MONTERREY NAAPS AND THE NASA/GMAO SHOW SOME DUST MIXED IN AT
700 MB. ALL MODELS SHOW THE VISIBILITY RETURNING TO NORMAL
BACKGROUND LEVELS BY MONDAY OF THIS COMING WEEK.

DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS ARE FORECAST BETWEEN
NOW AND THE WEEKEND WITH LESS COVERAGE ON SAT/SUN BECAUSE OF THE
INCREASE IN DRY AIR. THE EASTERLY FLOW WILL CONCENTRATE THESE
STORMS OVER THE INTERIOR AND WEST COAST.

A SLIGHT RISK OF RIP CURRENTS IS POSSIBLE BEGINNING ON FRIDAY
EVENING FOR THE EAST COAST BEACHES, ESPECIALLY FOR MIAMI-DADE AND
BROWARD.

MARINE...

WINDS ARE FORECAST TO REMAIN SOUTHEASTERLY TO EASTERLY ACROSS THE
ATLANTIC WATERS AROUND OR BELOW 10 KNOTS AND PERSISTING THROUGH
THE WEEKEND. AS A RESULT, SEAS ARE FORECAST TO BE 2 FEET OR LESS
THROUGH THIS TIME FRAME. THERE IS LARGE UNCERTAINTY FOR THE WIND
FORECAST FOR MONDAY AND TUESDAY DEPENDING ON THE TRACK AND
INTENSITY OF THE ATLANTIC LOW.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  79  91  77  90 /  10  30   0  10
FORT LAUDERDALE  81  91  80  91 /  20  20   0  10
MIAMI            80  91  80  91 /  10  20   0  20
NAPLES           78  91  79  91 /  20  40  20  30

&&

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

$$


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