Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 021324
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
924 AM EDT THU JUL 2 2015

.UPDATE (REST OF TODAY THROUGH FRIDAY)...
12Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS AN AMPLIFIED UPPER LEVEL
PATTERN ACROSS THE CONUS CONSISTING OF LONGWAVE RIDGING OVER THE
PACIFIC COAST/INTER-MOUNTAIN WEST...AND DOWNSTREAM TROUGHING
CARVED OUT ACROSS THE EASTERN HALF OF THE NATION. ALTHOUGH THESE
FEATURES WILL EVOLVE WITH TIME...THIS GENERAL UPPER LEVEL FLOW
PATTERN WILL REMAIN IN PLACE THROUGH AT LEAST THE FIRST HALF OF
THE UPCOMING HOLIDAY WEEKEND. THE EASTERN CONUS TROUGH EXTENDS
DOWN TO JUST ABOUT THE NORTHERN GULF COAST...LEAVING OUR FORECAST
AREA UNDER A MORE ILL-DEFINED PATTERN. THIS CAN BE SEEN ON THE
KTBW 02/12Z SOUNDING PROFILE WHICH SHOWS LIGHT AND ALMOST
VARIABLE WINDS ABOVE 500MB.

AT THE SURFACE...SUBTROPICAL RIDGE AXIS EXTENDS FROM THE NORTHERN
BAHAMAS...ACROSS THE CENTRAL FL PENINSULA AND INTO THE EASTERN
GULF OF MEXICO. ONE OF THE THINGS I ALWAYS TAKE NOTE OF ON MY WAY
DOWN I-75 INTO THE OFFICE IN THE MORNING...IS THE DIRECTION OF
MOVEMENT OF THE STEAM PLUMES FROM THE POWER PLANT IN APOLLO BEACH.
THESE PLUMES CAN GIVE YOU A GOOD INDICATION OF THE LOWER LEVEL
FLOW AND HENCE THE POSITION OF THE SUBTROPICAL RIDGE AXIS THAT
WILL DRIVE CONVECTION THAT DAY (AT LEAST ACROSS THE CENTRAL
FORECAST ZONES). THIS MORNING...THESE STEAM PLUMES WERE ALMOST
STRAIGHT VERTICAL...MEANING THE LOW LEVEL FLOW IS LIGHT...OFTEN
INDICITIVE OF WHEN THE RIDGE AXIS IS NEARBY.

THE FORECAST FOR THE REMAINDER OF THE DAY WILL FOLLOW A SIMILAR
PHILOSOPHY TO WHAT OCCURRED WEDNESDAY. NOW...THAT DOES NOT MEAN IF
YOU SAW RAIN YESTERDAY THAT YOU WILL NECESSARY SEE IT AGAIN. SUCH
IS THE REALITY WITH THE SCATTERED NATURE OF OUR CONVECTION...AND
THE RANDOM NATURE OF OUTFLOW BOUNDARIES. HOWEVER...MANY OF THE
VARIABLES THAT DROVE THE WEATHER ON WEDNESDAY ARE STILL IN PLACE.

WEAK SHORTWAVE ENERGY WILL BE SLOWLY MOVING ALONG THE NORTHEAST
GULF COAST TODAY HELPING TO ENHANCE THE CONVECTIVE POTENTIAL OVER
THE PANHANDLE/BIG BEND REGION. SOME OF THIS ENHANCEMENT WILL
LIKELY EXTEND DOWN INTO THE NE GULF WITH SCT STORMS MIGRATING
ONSHORE ACROSS THE NATURE COAST LATER THIS MORNING/MIDDAY.
OUTFLOW FROM THESE CELLS ALONG WITH SLOW SEA-BREEZE FORMATION WILL
LIKELY THEN RESULT IN SCT CONVECTION EVOLVING DOWN INTO THE TAMPA
BAY AREA AROUND MIDDAY/EARLY AFTERNOON THAT WILL MIGRATE EASTWARD
WITH TIME. LATER IN THE DAY...THE HIGHEST COVERAGE OF STORMS WILL
END UP OVER THE INTERIOR SOUTH-CENTRAL ZONES
(HIGHLANDS/POLK/HARDEE/DESOTO)...AND EXTEND SOUTHWEST TO THE FORT
MYERS AREA.

LOOKING AT OUR SOUNDING PROFILE...THE SAME THREAT FOR SOME LARGER
HAIL (SIMILAR TO WHAT WAS SEEN ON WEDNESDAY) IS STILL IN THE
FORECAST. THE 500MB TEMP IS UP A DEGREE OR SO FROM WEDNESDAY...BUT
THE -10C MARK IS STILL LOW. LAPSE RATES THROUGH SEVERAL DIFFERENT
LEVELS ARE FAIRLY IMPRESSIVE AS WELL. IN FACT...THE CAPE IN THE
-10C TO -30C RANGE (OR HAIL GROWTH ZONE) IS CERTAINLY MORE
IMPRESSIVE THAN WE WOULD USUALLY SEE IN EARLY JULY.
THEREFORE...ESPECIALLY SOME THE LATER DAY STORMS WILL HAVE A
HAIL/DOWNBURST WIND THREAT. IT IS INTERESTING TO SEE THAT THE HRRR
SEEMS TO BE PICKING UP ON THIS THREAT WITH SOME IMPRESSIVE WARM
SEASON SIMULATED UPDRAFT VELOCITIES LATE TODAY APPROACHING 20M/S.

STORMS WILL SLOWLY SUBSIDE AFTER SUNSET INTO THE LATER EVENING
OVER THE SOUTHERN/SOUTH-CENTRAL ZONES...AND END UP WITH A MOSTLY
DRY OVERNIGHT PERIOD FOR THE LANDMASS AFTER AROUND 03Z. LATE AT
NIGHT...WE MAY SEE AN ISOLATED SHOWER OR STORM APPROACH THE
LEVY/CITRUS COUNTY COASTS WITHIN THE WEAK SOUTHWEST FLOW REGIME
JUST NORTH OF THE SURFACE RIDGE AXIS...BUT WOULD NOT BE SURPRISED
IF THIS ACTIVITY HOLDS OFF UNTIL AS LATE AS 12Z.

MORE OF THE SAME FOR FRIDAY WITH THE RIDGE AXIS ACROSS THE CENTRAL
PENINSULA AND AN ILL-DEFINED UPPER LEVEL PATTERN. WITH THE RIDGE
AXIS ALONG OR JUST SOUTH OF THE I-4 CORRIDOR...THE SEA-BREEZE AND
ANY CONVECTION WILL MIGRATE INLAND FASTEST OVER THE NATURE
COAST...A BIT SLOWER ACROSS THE TAMPA BAY AREA...AND SLOWEST ALONG
THE SUN COAST. DOWN TOWARD CHARLOTTE/LEE COUNTIES...A WEAK
SOUTHEAST LOW LEVEL FLOW FURTHEST REMOVED SOUTH OF THE RIDGE AXIS
WILL LIKELY RESULT IN THE BEST EAST/WEST SEA BREEZE CLASH AND THE
GREATEST LATE DAY CONVECTIVE COVERAGE/INTENSITY. WILL SEE HOW
THINGS EVOLVE WITH THE 12Z GUIDANCE CYCLE...BUT HIGHER POPS MAY
NEED TO BE EXTENDED NORTHWARD INTO POLK COUNTY AFTER 21Z TOMORROW
IF IT APPEARS THAT THE EAST/WEST SEA-BREEZE COLLISION MAY REACH
THAT FAR NORTH BEFORE SUNSET.

&&

.AVIATION...
VFR CONDITIONS PREVAIL ACROSS WEST-CENTRAL FLORIDA THIS MORNING.
THESE QUIET CONDITIONS SHOULD CONTINUE FOR SEVERAL MORE HOURS AT
THE TERMINALS BEFORE WE BEGIN TO SEE DIURNAL CONVECTION DEVELOP.
WOULD EXPECT THE FIRST CHANCE OF SCT STORMS TO BE AROUND
KPIE/KTPA/KLAL AS WE APPROACH MIDDAY...WITH STORMS THEN MAINLY
PUSHING INLAND FROM THE I-4 TERMINALS BY MID AFTERNOON. FURTHER
SOUTH...BEST STORM CHANCES WILL BE LATER IN THE AFTERNOON AND INTO
THE EARLY EVENING HOURS.

&&

.MARINE...
SUBTROPICAL SURFACE RIDGE WILL REMAIN IN PLACE OVER THE EASTERN
GULF OF MEXICO THROUGH THE UPCOMING HOLIDAY WEEKEND. WITH THE
RIDGE IN PLACE...WIND AND SEAS ARE ANTICIPATED TO REMAIN BELOW
HEADLINE CRITERIA AWAY FROM TYPICAL SCATTERED THUNDERSTORM
ACTIVITY. BEST CHANCES FOR STORMS OVER THE MARINE ZONES THE NEXT
SEVERAL DAYS WILL BE DURING THE MORNING HOURS...AS ACTIVITY MOSTLY
PUSHES OVER THE LANDMASS FOR THE AFTERNOON AND EVENING HOURS.

&&

.PRELIMINARY POINT TEMPS/POPS...
TPA  93  78  90  78 /  40  10  40  20
FMY  94  76  91  76 /  60  40  60  20
GIF  94  75  91  75 /  50  20  60  40
SRQ  92  76  89  77 /  30  10  30  20
BKV  93  72  90  72 /  40  10  40  30
SPG  92  80  89  80 /  40  10  40  20

&&

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

&&

$$

UPDATE/AVIATION/MARINE...MROCZKA
DECISION SUPPORT...MCKAUGHAN/GUSACK


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