351 
FXUS62 KILM 232032
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
432 PM EDT TUE OCT 23 2012

.SYNOPSIS...
HIGH PRESSURE AND DRY CONDITIONS WILL AFFECT THE EASTERN CAROLINAS
THROUGH THURSDAY...WITH THE HIGH ITSELF SLIDING OFFSHORE FRIDAY.
TEMPERATURES WILL RUN 5 TO 10 DEGREES ABOVE NORMAL THROUGH THE END
OF THE WEEK. TROPICAL CYCLONE SANDY IN THE CARIBBEAN SEA TONIGHT...
IS EXPECTED TO INTENSIFY TO A HURRICANE AS SHE MOVES NORTH INTO
THE BAHAMAS LATER THIS WEEK. SANDY WILL REMAIN IN CLOSE PROXIMITY
THIS WEEKEND BEFORE FINALLY MOVING AWAY FROM THE AREA BY EARLY
NEXT WEEK. THE RISK OF HIGH SURF AND DANGEROUS RIP CURRENTS WILL
DEFINITELY AFFECT LOCAL BEACHES THIS WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 130 PM TUESDAY...THE BIG QUESTIONS FOR TONIGHT WILL BE HOW
LOW WILL TEMPERATURES DROP AND HOW MUCH FOG WILL DEVELOP. EASTERN
END OF ELONGATED SURFACE HIGH WILL BREAK OFF LATER TONIGHT AND
SLIP OFF THE COAST...PROVIDING A PERIOD OF LIGHT SOUTHERLY FLOW
AND INCREASING LOW LEVEL MOISTURE. IN FACT FORECAST SOUNDINGS
SHOW A 24 HOUR SURFACE DEWPOINT CHANGE FROM TUE TO WED MORNING ON
THE ORDER OF 10 DEGREES F. THIS INCREASE IN LOW LEVEL MOISTURE
COMBINED WITH EXCELLENT RADIATIONAL COOLING CONDITIONS SUGGESTS
WIDESPREAD FOG DEVELOPMENT IS A GOOD BET. AT THIS POINT NOT READY
TO SAY THAT WIDESPREAD DENSE FOG WILL DEVELOP AS WARM SOIL
TEMPERATURES WOULD WORK TO LIMIT DURATION OF DENSE FOG. ALTHOUGH
850 TEMPS OF 14C SUGGEST LOWS IN THE MID TO UPPER 50S FORECAST
SOUNDINGS ALONG WITH THIS MORNINGS DATA SHOW THERE IS SHALLOW
LAYER OF COOLER AIR WHICH HAS BEEN CAUSING LOWS TO RUN COOLER THAN
850 TEMPS OR THICKNESS WOULD SUGGEST. USING PARTIAL THICKNESS
SCHEMES AND LOOKING AT 1K FT TEMPS UPPER 40S TO LOW 50S SEEMS TO
BE MORE REASONABLE FOR MUCH OF THE AREA.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...LOOK FOR A CONTINUED QUOTE...INDIAN
SUMMER...UNQUOTE ACROSS THE ILM CWA DURING THIS SHORT TERM PERIOD.
LOOK FOR AMPLIFIED RIDGING ALOFT TO AFFECT THE FA...WITH THE N-S
RIDGE AXIS JUST REACHING THE ILM CWA LATE THURSDAY. THIS PERIOD
WILL BE HIGHLIGHTED BY CONTINUED DRY CONDITIONS...NO POPS AND
LIMITED CLOUDS...AS WELL AS ABOVE NORMAL TEMPS. MAX TEMPS FOR
WED/THU WILL BE WELL INTO THE 70S NEAR THE COAST...AND 80S
INLAND ESPECIALLY ACROSS THE SW PORTIONS OF THE ILM CWA. FOR MIN
TEMPS...HAVE GONE WITH WIDESPREAD 50S...TO 60+ ALONG THE
IMMEDIATE COAST EACH NIGHT DUE TO THE WEAK ONSHORE FLOW
PUSHING/ADVECTING HIGHER ATLANTIC DEWPOINTS ACROSS THE FA. THIS
WILL RESULT WITH AVAILABLE LOW LEVEL MOISTURE FOR POSSIBLE
PATCHY/AREAS OF FOG THU MORNING. GFS MOS GUIDANCE TEMPS LOOK LIKE
THE WAY TO GO THIS ROUND. THE LATEST GFS MOS GUIDANCE NOW
IDENTIFYING THIS AIRMASS MUCH BETTER THEN ITS MOS
COUNTERPARTS...VIA LOCAL VERIFICATION. OVERALL...LOOK FOR MAX/MIN
TEMPS 5 TO 10+ DEGREES ABOVE NORMAL THRU THIS FCST PERIOD.

OF NOTE...A WEAK BACK-DOOR COLD FRONT IS IDENTIFIED BY THE NAM/GFS
AS WELL AS HP...AND IS PROGGED TO APPROACH THE FA FROM THE NE
LATE IN THIS SHORT TERM. AT THIS POINT...MODELS PREVENT IT FROM
REACHING THE ILM CWA DUE TO SANDYS INCREASING AND EXPANDING
CIRCULATION AS IT TREKS NORTHWARD. BAROCLINICITY ASSOCIATED WITH
THE APPROACH OF A VIGOROUS UPPER S/W TROF FROM THE NORTH CENTRAL
U.S. ALONG WITH ITS ASSOCIATED COLD FRONT...WILL EVENTUALLY INTERACT
WITH SANDY AND FURTHER EXPAND HER WIND FIELD. BUT THIS WILL LIKELY
OCCUR DURING THE LONG TERM PERIOD AS SHE POSSIBLY BEGINS HER
TRANSITION TO EXTRA-TROPICAL.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...TRANSITIONAL DAY ON FRIDAY AS TROPICAL STORM 
SANDY MAKES ITS WAY NORTH. DRY AND CALM WEATHER WILL BE REPLACED BY 
MORE UNSETTLED WEATHER WITH GUSTY NORTHERLY WINDS FOR MUCH OF THE 
WEEKEND. THE CENTER OF SANDY SHOULD BE RIDING UP THROUGH THE BAHAMAS 
FRI BUT THE OUTER INFLUENCE OF CLOUDS AND GUSTY WINDS SHOULD BE FELT 
OVER THE COASTAL CAROLINAS LATE FRI THROUGH SATURDAY.

THE HIGH PRESSURE RESPONSIBLE FOR OUR DRY WEATHER WILL CONTINUE TO 
RIDGE BACK INTO THE CAROLINAS FROM THE PARENT HIGH LOCATED JUST OFF 
THE NEW ENGLAND EARLY FRI...BUT TIGHTLY WOUND TROPICAL STORM SANDY 
WILL MOVE UP THE SPINE OF THE BAHAMAS WITH AN INCREASING NE GRADIENT 
FLOW BETWEEN THESE TWO SYSTEMS. THESE GUSTY NORTHEAST WINDS WILL 
SPREAD CLOUDS AND SHOWERS OVER MAINLY THE COASTAL AREAS FRI 
AFTERNOON BUT DEPENDING ON THE EXACT TRACK OF SANDY...COULD SEE 
CLOUDS AND SHOWERS SPREAD FURTHER INLAND FRI NIGHT INTO EARLY 
SATURDAY. 

GFS/ECMWF AND CMC ALL IN VERY GOOD AGREEMENT UP THROUGH FRI EVNG 
BRINGING THE CENTER OF SANDY UP THROUGH THE BAHAMAS. IT IS AT THAT 
TIME THAT MODEL SOLUTIONS DEVIATE WITH THE ECMWF STAYING ON A MORE 
NORTHWARD TRACK HEADING TOWARD THE NORTH ENDING UP GETTING PULLED 
INTO NEW ENGLAND BY NEGATIVELY TILTED UPPER TROUGH ON TUES. THE GFS 
AND CANADIAN MODELS HAVE SANDY MOVING OUT TO SEA SATURDAY THROUGH 
TUES. THE TRACK IS VERY DEPENDENT ON MID TO UPPER TROUGH DIGGING 
DOWN FROM CANADA IN WHICH THE GFS/CMC KEEP FARTHER EAST WHILE ECMWF 
HANGS BACK TO THE WEST AND BECOMES MORE NEGATIVELY TILTED DRAGGING 
SANDY OVER NEW ENGLAND.

OVERALL FOR OUR AREA IT LOOKS LIKE GREATEST THREAT FROM SANDY WILL 
BE GUSTY WINDS...SOME HEAVIER SHOWERS IN OUTER RAINBANDS...HIGH 
SURF...STRONG RIP CURRENTS THROUGH THE FIRST HALF OF THE WEEKEND. 
GREATEST CHC OF PCP WILL COME LATE FRI INTO SAT WITH GREATEST WINDS 
AND CHC FOR HEAVIER PCP CLOSER TO THE COAST SAT MORNING. SKIES 
SHOULD CLEAR WITH DRY AIR AND SUBSIDENCE BUILDING IN ON THE BACK END 
OF SANDY AS IT MOVES AWAY FROM LOCAL AREA SAT NIGHT INTO SUN AND 
COLD FRONT MOVES THROUGH FROM THE NW. COOL AND DRY CANADIAN HIGH 
PRESSURE WILL BUILD IN BEHIND IT THROUGH MID WEEK IF SANDY DOES MOVE 
OUT TO SEA. GUSTY NORTHERLY WINDS WILL DIMINISH IN INTENSITY AS HIGH 
MOVES CLOSER AND SANDY MOVES FARTHER OUT TO SEA. WILL HAVE TO 
MONITOR CLOSELY TO SEE HOW MODELS PLAY OUT IN TERMS OF TRACK AND 
INTENSITY ESPECIALLY FOR THE LATTER HALF OF THE WEEKEND INTO EARLY 
NEXT WEEK.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AS OF 18Z...EXPECT VFR THROUGH THE VALID PERIOD WITH EXCEPTION OF 
MVFR DUE TO FOG OVERNIGHT INTO EARLY WEDNESDAY MORNING. 

VFR CONTINUES THIS AFTERNOON WITH GENERALLY SOUTHEAST WINDS AOB 8 
KTS. MAY SEE A FEW HIGH CLOUDS...BUT OTHERWISE EXPECT NEARLY CLEAR 
SKIES. WINDS WILL BECOME LIGHT AND VARIABLE INTO THE OVERNIGHT HOURS 
WITH FAVORABLE CONDITIONS FOR FOG DEVELOPING. THUS HAVE INTRODUCED 
MVFR DUE TO FOG INTO THE EARLY MORNING HOURS. AFTER DAYBREAK...ANY 
FOG WILL DISSIPATE...GIVING WAY TO VFR WITH LIGHT WINDS BECOMING 
SOUTH-SOUTHEAST IN THE EARLY AFTERNOON.

EXTENDED OUTLOOK...VSBY RESTRICTIONS POSSIBLE THROUGH 
FRIDAY MORNINGS FROM GROUND FOG...OTHERWISE VFR.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM TUESDAY...NORTHEAST WINDS MAY DEVELOP A SOUTHERLY
COMPONENT OVERNIGHT AS EASTERN EDGE OF ELONGATED HIGH SLIDES
NORTHEAST OF THE WATERS. HOWEVER...WEAK GRADIENT LIMITS THE IMPACT
DIRECTION WILL HAVE ON THE WATERS. BENIGN WINDS AND SEAS WILL
CONTINUE THROUGH THE END OF THE PERIOD.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...WEDNESDAY AND FOR THE MOST PART OF 
THURSDAY...WILL EXPERIENCE THE CALM BEFORE THE STORM SO TO SPEAK.
THESE 2 DAYS SHOULD BE PERFECT FOR THE MARINE COMMUNITY 
TO TRAVERSE THE ATLANTIC WATERS AND WINYAH BAY PRIOR TO THE
EFFECTS FROM TROPICAL CYCLONE SANDY ARRIVING. THE CENTER OF THE
SFC HIGH ACROSS THE EASTERN CAROLINAS WILL PUSH ACROSS THE LOCAL
WATERS AND BASICALLY MERGE WITH THE HIGH RIDGING FROM SE CANADA.
THE SFC PRESSURE PATTERN WILL YIELD A NE TO E WIND
DIRECTION...WITH SPEEDS MAINLY 10 KT OR LESS DURING WED...SLOWLY
INCREASING TO 15 TO 20 KT BY THU AFTERNOON FOR THE ILM SC
WATERS...AND 15 TO 20 KT THU NIGHT FOR THE ILM NC WATERS.

LEFTOVER ESE 1 TO 2 FOOT GROUND SWELL AT 8-9 SECOND PERIODS AND
LOCALLY PRODUCED 3-4 SECOND PERIOD WIND DRIVEN CHOP ...WILL BOTH 
AFFECT THE LOCAL WATERS THROUGH EARLY THU. SWELL FROM SANDY LATER
THU THROUGH THU NIGHT WILL SLOWLY BECOME THE DOMINANT PRODUCER OF
SIGNIFICANT SEAS. SANDYS WIND FIELD WILL NEED TO EMERGE FROM THE
CARIBBEAN SEA AND INTERACT WITH THE DECENT FETCH ACROSS THE ATLANTIC
OFF THE SE U.S. COAST FOR A PERIOD OF TIME. SANDYS SWELL IS
EXPECTED TO EXHIBIT THE HIGHER POWER WITHIN SPECTRAL DENSITY
CHARTS BY OR AFTER THU NIGHT. 

LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 300 PM WEDNESDAY...MARINE CONDITIONS WILL DETERIORATE AS
SWELLS AND STRONG GUSTY WINDS FROM TROPICAL STORM SANDY AFFECT THE
LOCAL COASTAL WATERS FRIDAY THROUGH THE WEEKEND. THE ON SHORE NE
FLOW WILL BACK TO THE NORTH AND INCREASE THROUGH FRI AS SANDY
MOVES UP FROM THE BAHAMAS IN THE OFF SHORE ATLANTIC WATERS. EXPECT
AN EXTENDED PERIOD OF ENHANCED NORTHERLY WINDS OF 20 KTS OR
MORE...GUSTING TO 30 KTS...POSSIBLY HIGHER. E-SE SWELLS FROM SANDY
WILL INCREASE THROUGH THE FRIDAY WITH LATEST WNA SHOWING AN UP TO
14 SECOND LONG PERIOD SWELL PERSISTING OVER THE WATERS FRI EVENING
THROUGH EARLY NEXT WEEK. WNA ALSO SHOWS SEAS INCREASING UP TO 16
FT OUT OVER FRYING PAN SHOALS PEAKING SAT MORNING IN NORTHERLY
WINDS UP TO 40 KTS. WINDS WILL BECOME MORE OFF SHORE THROUGH THE
WEEKEND AND WEAKEN ON BACK END OF SANDY AS IT MOVES OFF TO THE
NORTH AWAY FROM AREA. WINDS AND SEAS WILL BE HIGHLY DEPENDENT ON
EXACT TRACK AND INTENSITY OF SANDY AS IT MAKES ITS WAY NORTH FROM
THE BAHAMAS FRI THROUGH SATURDAY. DEFINITELY EXPECT PERIOD OF SCA
CONDITIONS BEGINNING AS EARLY AS THURS NIGHT AND CONTINUING
THROUGH THE WEEKEND.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...DCH
NEAR TERM...III
SHORT TERM...DCH
LONG TERM...RGZ
AVIATION...III/SGL