240
FXUS64 KJAN 081604 AAA
AFDJAN
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON MS
1004 AM CST SUN NOV 8 2009
UPDATE
THE MAIN FORECAST ELEMENTS ARE ON TRACK FOR TODAY AND NO
ADJ WERE NEEDED TO THOSE. HOWEVER...THE WARM UP THIS MORNING WAS MUCH
FASTER THAN ANTICIPATED AND I HAD TO ADJ HOURLY TEMPS QUITE A BIT.
THIS WARMING SHOULD SLOW AS WE ARE MIXING TO THE INVERSION AND WE
SHOULD SEE THICKER HIGH CLOUDS SPREAD OVER DURING THE AFTERNOON.
AS FOR THE EVOLUTION OF IDA AND ANY IMPACTS IN OUR AREA FOR MON
THROUGH EARLY TUE. THE SITUATION REMAINS QUITE COMPLICATED AS IDA
WILL INTERACT WITH A LOW PRESSURE FEATURE IN THE WESTERN GULF AND
THEY WILL ALL INTERACT WITH THE EASTWARD MOVING DISTURBANCE CURRENTLY
OVER THE BIG BEND OF TX. ITS THIS ENTIRE INTERACTION THAT SHOULD
CAUSE IDA TO WEAKEN SOME AND TAKE ON MORE EXTRATROPICAL
CHARACTERISTICS. IT WILL ALSO HAVE SOME IMPACT ON FORWARD SPEED WHICH
ULTIMATELY WILL DETERMINE IF THERE WILL BE A LANDFALL AND WHERE THAT
MAY OCCUR. THE OFFICIAL NHC FORECAST HAS STEADILY TRENDED FASTER EACH
ADV AND NOW HAS IDA MAKING LANDFALL SOMEWHERE IN THE WESTERN FL
PANHANDLE TUE AFTERNOON. ON THE OTHER HAND...THE OPERATIONAL
EURO/GFS/NAM ARE ALL AT LEAST 12HRS FASTER AND HAVE A LANDFALL FURTHER
WEST BETWEEN THE SE LA COAST AND MOBILE BAY LATE MON AFTERNOON/MON
EVE. ALL THE FORECASTS HAVE MERIT AND THE GOING FORECASTS HANDLES THE
SITUATION. IF THE EVENTUAL TRACK IS FASTER AND CLOSER TO THE MS
COAST...THEN THERE WILL BE MORE OF A WIND IMPACT ACROSS A PORTION OF
THE SE CWA. STILL WINDS DON'T APPEAR TO BE TOO STRONG BUT WOULD
LIKELY FIT INTO SOME SORT OF WIND ADV CRITERIA WITH SUSTAINED WINDS
25-30 MPH AND GUSTS 30-40 MPH. THE PRESSURE GRADIENT ACROSS THE REST
OF THE CWA WILL BE TIGHT AND RESULT IN BREEZY CONDITIONS AND
SUSTAINED WINDS 15-20 MPH WITH SOME HIGHER GUSTS. IF THE TRACK IS
SLOWER AND FURTHER E...THEN JUST THE PLAIN BREEZY CONDITIONS SHOULD
APPLY FOR ALL...MAIN THE SE/E PORTION OF THE AREA. NEW MODEL GUID IS
ARRIVING THIS MORNING AND WE WILL SORT THROUGH THAT FOR THE AFTERNOON
FORECAST PACKAGE.
THE RAINFALL SITUATION STILL SEEMS ON TARGET FROM PREV FORECASTS.
STEADY RAIN IS EXPECTED AS SOME SORT OF DEFORMATION AXIS SETS UP.
LOOK FOR MULTIPLE HOURS OF STEADY RAIN WITH ACCUMULATIONS BETWEEN 2-4
INCHES SE OF THE TRACE. THERE WILL LIKELY BE A STRONG GRADIENT WITH
HOW THE PRECIP AXIS SETS UP AND AREAS TO THE W/NW OF THAT AXIS WILL
LIKELY SEE LITTLE TO NO PRECIP. /CME/
AVIATION
VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH THE
REMAINDER OF THE DAY AND INTO TONIGHT. LOOK FOR EAST TO SOUTHEAST
WINDS TODAY TO AGAIN BE BETWEEN 5-10 KNOTS WITH A FEW HIGHER GUSTS
UP AROUND 15 KNOTS POSSIBLE AS HIGH CLOUDS CONTINUE TO THICKEN AND
SPREAD NORTHWARD THROUGH THE AFTERNOON. THE PRESSURE GRADIENT WILL
BEGIN TO TIGHTEN ACROSS THE AREA LATE TONIGHT INTO MONDAY
MORNING...ESPECIALLY ACROSS SOUTHEAST MISSISSIPPI. LOOK FOR
EASTERLY WINDS ON MONDAY TO INCREASE TO BETWEEN 10-15 KNOTS WITH
SOME HIGHER GUSTS AROUND 20 KNOTS POSSIBLE DURING THIS TIME. WHILE
MID AND HIGH CLOUDS WILL BE ON THE INCREASE THROUGH MONDAY MORNING
HOURS...VFR CONDITIONS ARE STILL EXPECTED TO PREVAIL. HOWEVER...AS
RAIN CHANCES INCREASE DURING THIS TIME...PERIODS OF AT LEAST MVFR
VISIBILITIES WILL BE POSSIBLE THROUGH THE MORNING HOURS MONDAY AT
SITES THAT OBSERVE ANY RAINFALL. /19/
PREV DISCUSSION
/ISSUED 455 AM CST SUN NOV 8 2009/
DISCUSSION...
SHORT TERM...TODAY THROUGH MONDAY NIGHT...PRIMARY FOCUS CONTINUES TO
BE HURRICANE IDA AND ASSOCIATED HEAVY RAINFALL POTENTIAL ACROSS THE
ARKLAMISS.
FOR TODAY...CLOUD COVER WILL BE ON THE INCREASE AS THE UPPER LEVEL
FLOW HAS SHIFTED SOUTHERLY WITH THE ADVANCE OF THE UPPER HIGH
LOCATED TO OUR EAST. THIS WILL KEEP AFTERNOON HIGHS SLIGHTLY LOWER
THAN WE SAW YESTERDAY...MID TO LOWER 70S AREAWIDE. MAV GUIDANCE
SEEMED TO HANDLE THIS WELL.
FOCUS SUNDAY NIGHT SHIFTS TO THE INCREASING ATMOSPHERIC MOISTURE
CONTENT AHEAD OF TWO FEATURES...AN UPPER LEVEL S/WV MOVING EAST
CURRENTLY LOCATED OVER SW TEXAS...AND THE MORE OBVIOUS HURRICANE IDA
CURRENTLY LOCATED NEAR THE YUCATAN PENINSULA. THE EVENTUAL IMPACT
THESE FEATURES WILL HAVE ON OUR CWA IS SURPRISINGLY QUITE UNCERTAIN
AT THIS TIME. NHC IS KEEPING THE CENTER OF IDA OFFSHORE IN THEIR
LATEST FORECAST AND WELL SOUTHEAST OF THE ARKLAMISS...AND THIS
TRACK IS SLOWER AND FARTHER EAST THAN THE 00Z GFS/ECMWF SOLNS. AS
FOR THE TX S/WV...BOTH MODELS AGREE WITH THE DEEP LAYER LIFT AHEAD
OF THIS FEATURE MOVING OVER THE ARKLAMISS STARTING SUNDAY NIGHT AND
EXITING TUESDAY MORNING. SO THE DILEMMA REMAINS...IF IDA TRACKS
CLOSER TO OUR CWA...HOW MUCH LOW LEVEL MOISTURE WILL STREAM INTO
CENTRAL MS AHEAD OF IT. THIS WILL ULTIMATELY DETERMINE HOW MUCH RAIN
WE SEE ACROSS OUR AREA AS THIS MOISTURE INTERACTS WITH THE S/WV.
THE FORECAST FOR THIS PACKAGE IS BASED ON A BLEND OF THE NHC
FORECAST TRACK OF HURRICANE IDA...AND THE FASTER/WWD SOLUTIONS OF
THE GFS/ECMWF. LUCKILY...NO SIGNIFICANT CHANGES TO THE GOING
FORECAST WERE NEEDED. THE BIGGEST DIFFERENCE WAS A REDUCTION POPS
TO NEAR MAV GUIDANCE ACROSS THE NORTHERN TIER COUNTIES MONDAY
AFTERNOON AND NIGHT AS CONFIDENCE IS NOT TERRIBLY HIGH IN ANY SIG
PRECIP MAKING IT THAT FAR NORTH. MAINTAINED ABOVE GUIDANCE POPS
ACROSS SOUTHERN AND MORE PROMINENTLY SOUTHEASTERN COUNTIES WHERE
PRECIP IS ALMOST CERTAIN. AS THIS EVENT EVOLVES...IF AN INCREASE IN
MOISTURE OVER OUR AREA IS EXPECTED AHEAD OF IDA DUE TO A MORE
NORTHERLY TRACK, POPS WILL LIKELY NEED TO BE BUMPED BACK UP ABOVE
GUIDANCE. ANOTHER IMPACT TO THE GOING FORECAST WAS THE REDUCTION IN
QPF AMOUNTS BASED ON LATEST HPC GUIDANCE. AN IDA TRACK FURTHER
OFFSHORE WOULD MEAN LOWER QPF TOTALS OVER OUR SOUTHEASTERN COUNTIES.
AGAIN...THIS WILL NEED TO BE RAISED BACK UP IF IDA TAKES A CLOSER
TRACK TO THE ARKLAMISS.
DUE TO THE LARGE AMOUNT OF UNCERTAINTY HERE...WILL MAINTAIN THE
HEAVY RAIN POTENTIAL ACROSS SOUTHEASTERN COUNTIES IN THE HWO. THE
ONE THING THAT HAS NOT CHANGED OVER THE PAST SEVERAL DAYS IS THE
POSSIBILITY OF HEAVY RAINFALL SOUTHEAST OF THE NATCHEZ TRACE.
THE WIND FORECAST DUE TO THE IDA TRACK IS PROBLEMATIC AS WELL AS A
CLOSER TRACK TO THE COAST WILL MEAN MUCH STRONGER NORTHEAST WINDS ON
MONDAY. FOR NOW...WILL KEEP 15-20 MPH WINDS IN THE FORECAST AS THIS
SEEMS TO BE A GOOD COMPROMISE. MAY BE A LITTLE HIGH BUT WILL KEEP IT
GOING FOR NOW. MAV LOWS LOOKED REASONABLE MON AND TUES MORNING BUT
DID BUMP HIGHS MON A TAD BASED ON A LITTLE LESS RAIN THAT IS
EXPECTED. SHAPING UP TO BE AN INTERESTING START TO THE WORK WEEK.
/BK/
TUESDAY THROUGH FRIDAY...MODEL GUIDANCE IS IN GOOD AGREEMENT THAT A
PROGRESSIVE PATTERN WILL ALLOW THE SOUTH ATLANTIC COAST RIDGE TO
BREAK DOWN QUICKLY TUESDAY WITH OUR SHORTWAVE TROUGH AND ASSOCIATED
RAINFALL ZIPPING BY TO THE EAST. ANY LINGERING RAINFALL EARLY
TUESDAY MORNING WILL BE LIGHT. A BUILDING RIDGE OVER THE ARKLAMISS
WILL BRING DRY WEATHER FOR THE MID TO LATE WEEK WITH TEMPERATURES A
LITTLE ABOVE CLIMATIC AVERAGE.
FRIDAY NIGHT THROUGH NEXT SUNDAY...GLOBAL MODELS CONTINUE TO
INDICATE THAT A LONGWAVE TROUGH POSITION WILL SET UP OVER THE PLAINS
NEXT WEEKEND AND THIS WOULD PLACE THE ARKLAMISS UNDER SOUTHWEST FLOW
ALOFT. THE MODELS ARE VERY CHAOTIC WITH SHORTWAVE DETAILS IN
THIS PERIOD...SO IT SEEMS MOST REASONABLE TO ACCEPT THE LOW-END MEX
MOS POPS FOR NOW. IN ANY CASE...IT LOOKS LIKE INSTABILITY WILL BE
LACKING AND TSTM ACTIVITY WOULD BE LIMITED. CAN IMAGINE THAT
ANOTHER ROUND OF SUBSTANTIAL RAINFALL WILL NOT BE OUT OT THE
QUESTION IN THIS PATTERN AND THAT WOULD BE THE MAIN CONCERN AS WE GO
THROUGH NEXT WEEKEND INTO EARLY NEXT WEEK. /EC/
PRELIMINARY POINT TEMPS/POPS
JACKSON 74 56 68 57 / 0 17 69 75
MERIDIAN 74 52 68 55 / 0 10 71 89
VICKSBURG 74 56 69 57 / 0 20 63 61
HATTIESBURG 74 57 70 59 / 3 30 91 82
NATCHEZ 73 58 68 57 / 4 35 76 63
GREENVILLE 73 55 68 55 / 0 7 33 39
GREENWOOD 76 54 70 56 / 0 6 35 48
JAN WATCHES/WARNINGS/ADVISORIES
MS...NONE.
LA...NONE.
AR...NONE.
CME/19
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