Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 230755
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
355 AM EDT SAT AUG 23 2014

.SHORT TERM (TODAY - SUNDAY)...
WE WILL SEE MORE HEAT AND HUMIDITY FOR THE WEEKEND AS A LARGE
MID-LEVEL RIDGE OF HIGH PRESSURE STRETCHES FROM MICHIGAN
SOUTHWARD TO THE NORTHERN GULF COAST WHILE A MID-LEVEL TROUGH
REMAINS OVER THE ATLANTIC. DEEP EASTERLY WIND FLOW BETWEEN THESE
SYSTEMS WILL STEER ANY AFTERNOON STORMS TOWARD THE WEST...WITH
SEA BREEZE COLLISIONS EVENTUALLY PUSHING BACK TOWARD THE COAST.

THE WRINKLE IN THE FORECAST IS THE POSSIBILITY OF A WEAK BACK-DOOR
COLD FRONT THAT IS FORECAST TO PUSH SOUTHWARD DOWN THE BACK SIDE
OF THE MID-LEVEL TROUGH OVER THE ATLANTIC ON SUNDAY. MODELS HAVE
BEEN SHOWING THIS FEATURE FOR SEVERAL DAYS NOW WITH VARYING
DEGREES OF IMPACT AND TIMING. THE DEVELOPING DISTURBANCE NEAR
HISPANIOLA MAY ALSO PLAY AN EVENTUAL ROLE IN HOW FAR THIS COLD
FRONT GETS...BUT REGARDLESS WE WILL SEE AN INCREASING PRESSURE
GRADIENT AND A STRENGTHENING OF THE LOW-LEVEL EASTERLIES BY THE
END OF THE WEEKEND. THE GFS SHOWS A MODEST INCREASE IN
PRECIPITABLE WATERS ON SUNDAY DUE TO THE BOUNDARY...AND THIS
COMBINED WITH STRONGER LOW-LEVEL CONVERGENCE SHOULD LEAD TO AT
LEAST HIGH END SCATTERED IF NOT MORE NUMEROUS SHOWERS AND STORMS
DURING THE AFTERNOON.

TEMPERATURES EACH DAY WILL BE IN THE MID TO UPPER 90S JUST AWAY
FROM THE COAST WITH HEAT INDICES GETTING CLOSE TO OUR HEAT
ADVISORY CRITERIA OF 108 DEGREES. STILL THINK MOST LOCATIONS WILL
NOT QUITE REACH THIS MARK SO NO HEAT ADVISORIES PLANNED AT THIS
TIME.

.LONG TERM (MONDAY THROUGH NEXT FRIDAY)...
WELL...A CHALLENGING LONG RANGE FORECAST TO SAY THE LEAST. ALL EYES
ARE ON A VIGOROUS TROPICAL DISTURBANCE NEAR HISPANIOLA EARLY THIS
MORNING. MOST NWP GUIDANCE MEMBERS WANT TO BEGIN DEVELOPING THIS
SYSTEM (TO VARYING DEGREES) ONCE IT IS FREE FROM THE HOSTILE
HIGHER TERRAIN OF HISPANIOLA LATER TODAY...AND SLOWLY MOVING THE
SYSTEM TOWARD THE BAHAMAS OVER THE WEEKEND.

HERE IS THE DEAL WITH NWP AND TROPICAL CYCLONES. OVERALL NWP IS NOT
SO GOOD AT DEALING WITH STORMS THAT HAVE NOT BECOME WELL-DEFINED
(AND THIS ONE IS NOT WELL DEFINED AS OF NOW). SO...YOU NEED TO TAKE
ANY OF THE VARIOUS SOLUTIONS WITH SOME SKEPTICISM...SOMEWHAT WITH
THE TRACK OF THE POTENTIAL STORMS...AND VERY MUCH SO WITH THE
STRENGTH. WHAT WE CAN SAY IS THAT THE RELIABLE GLOBAL GUIDANCE KEEP
"THE SYSTEM" TO THE EAST OF THE FLORIDA PENINSULA AS IT IS DRAGGED
NORTH INTO AN AMPLIFYING LONGWAVE TROUGH OFF THE
NORTHEAST/MID-ATLANTIC COAST EARLY NEXT WEEK. EVEN THE GEM WHICH HAD
BEEN MUCH FURTHER WEST HAS TRENDED BACK TO THE EAST AND KEEPS THIS
POTENTIAL SYSTEM WELL EAST OF THE FL PENINSULA. WE STILL NEED TO
KEEP A VERY CLOSE EYE ON THIS SYSTEM REGARDLESS...BUT FOR NOW...THE
FORECAST WILL REFLECT A SCENARIO TAKING A CIRCULATION NEAR THE
BAHAMAS AND THEN NORTHWARD OFF THE SOUTHEAST CONUS COAST THROUGH THE
EARLY/MIDDLE PORTION OF NEXT WEEK. WILL NOT GO OVERLY DETAILED WITH
ANY PORTION OF THE FORECAST AS SO MANY POTENTIAL SCENARIOS ARE STILL
IN PLAY.

FOR INSTANCE...A STRONGER/MORE ORGANIZED SYSTEM OFF THE SOUTHEAST
COAST EARLY NEXT WEEK COULD ACTUALLY RESULT IN LARGE SCALE
SUBSIDENCE OVER OUR REGION AND LOWER RAIN CHANCES...BUT WOULD
TIGHTEN THE SYNOPTIC GRADIENT OVER THE EASTERN GULF OF MEXICO
BETWEEN THE SYSTEM AND RIDGING TO OUR NORTH...PRODUCING STRONGER
WINDS ACROSS THE COASTAL WATERS. HOWEVER...AS WAS SAID
ABOVE...FORECASTING STRENGTH OF TROPICAL CYCLONES IN THE EARLY
STAGES OF DEVELOPMENT IS NOT SOMETHING NWP DOES A PARTICULARLY GOOD
JOB AT. WILL DO MY BEST TO COME UP WITH A MOST LIKELY SCENARIO FOR
THE EXTENDED PORTION OF THE FORECAST AS IT STANDS NOW...AND WE WILL
SIMPLY ADJUST AS EVENTS UNFOLD.

KEEPING WITH THE IDEAS OF AN TROPICAL SYSTEM TO OUR EAST MOVING
NORTHWARD OFF THE SOUTHEAST CONUS COAST...WILL HAVE EAST/NORTHEAST
FLOW THROUGH THE EARLY AND MIDDLE PORTION OF THE WEEK. BASED ON THE
LIKELIHOOD OF SOME DRIER AIR ARRIVING FROM THE NORTHEAST ABOVE THE
SURFACE (ESPECIALLY OVER THE NORTHERN HALF OF THE STATE)...WILL HAVE
GENERALLY NEAR CLIMO RAIN CHANCES FOR OUR SOUTHERN ZONES AND BELOW
CLIMO FOR THE NORTH.

TOWARD THE END OF NEXT WEEK...THE SUBTROPICAL RIDGE IS SHOWN BY BOTH
THE GFS/ECMWF TO REBUILD INTO THE SOUTHERN HALF OF THE PENINSULA AND
PROVIDE A LIGHT SW LOW LEVEL FLOW. THIS PATTERN SUGGEST MORNING
SHOWERS OVER THE GULF AND COASTAL LAND ZONES...WITH BEST CHANCES FOR
SHOWERS AND STORMS MIGRATING INLAND FOR THE AFTERNOON/EVENING
HOURS.

&&

.AVIATION...
VFR THROUGH 18Z. CONVECTIVE INITIATION WILL LIKELY BE LATE SO BEST
CHANCE OF STORMS WILL BE AFTER 20Z OR SO...AND THEN MORE LIKELY
NEAR THE COASTAL TAF SITES.

&&

.MARINE...
MAIN CONCERN WILL BE WITH INCREASING PRESSURE GRADIENT BETWEEN
HIGH PRESSURE TO OUR NORTH AND THE DEVELOPING TROPICAL DISTURBANCE
TO OUR SOUTHEAST. THE WINDS SHOULD REMAIN MOSTLY BELOW 15 KNOTS
THROUGH THE WEEKEND...THEN BEGIN TO INCREASE MONDAY AND MONDAY
NIGHT. THE ACTUAL TIMING AND EXTENT OF STRONGER WINDS WILL DEPEND
ON THE TRACK AND STRENGTH OF THE DISTURBANCE...BUT FOR NOW EXPECT
WINDS TO APPROACH 20 KNOTS FOR THE FIRST PART OF NEXT WEEK MAKING
FOR SOME UNUSUALLY ROUGH BOATING CONDITIONS FOR SUMMER.

&&

.FIRE WEATHER...
NO FIRE WEATHER CONCERNS NEXT COUPLE OF DAYS. GUSTY WINDS MAY
DEVELOP EARLY NEXT WEEK DEPENDING ON THE STRENGTH AND EVENTUAL
TRACK OF THE DISTURBANCE NEAR HISPANIOLA.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  93  79  94  79 /  50  30  50  40
FMY  96  77  96  78 /  30  20  30  20
GIF  96  77  96  76 /  40  20  50  20
SRQ  95  78  95  78 /  40  20  40  30
BKV  95  73  96  76 /  40  20  50  30
SPG  93  82  93  81 /  40  20  40  40

&&

.TBW WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GULF WATERS...NONE.

&&

$$

SHORT TERM/AVIATION/MARINE/FIRE WEATHER...JILLSON
LONG TERM/DECISION SUPPORT...MROCZKA




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