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Mesoscale Discussion 1997 |
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MESOSCALE DISCUSSION 1997
NWS STORM PREDICTION CENTER NORMAN OK
1119 PM CDT MON SEP 07 2009
AREAS AFFECTED...PORTIONS NC OUTER BANKS.
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 080419Z - 080645Z
CONDITIONAL POTENTIAL FOR BRIEF TORNADO IS SHIFTING NEWD UP NC
COAST...PRIMARILY FROM CAPE LOOKOUT TO CAPE HATTERAS DURING NEXT
SEVERAL HOURS. WW NOT PLANNED ATTM BECAUSE OF MRGL NATURE OF THREAT
AND VERY LIMITED LAND AREA INVOLVED.
SFC MESOANALYSIS SHOWS LOW JUST OFFSHORE ILM INVOF BUOY
41037...DRIFTING NNE TO NE...WITH WARM FRONT NEWD TO JUST OFFSHORE
CAPE LOOKOUT AND STILL S OF BUOY 41025. WARM FRONT SHOULD DRIFT NWD
AHEAD OF LOW. REFLECTIVITY IMAGERY INDICATES PRIMARY ASSOCIATED
BAND OF CONVECTION FROM ERN CARTERET COUNTY SSEWD OVER
ATLANTIC...WITH NET NEWD MOTION 8-10 KT. DRY SLOTTING AND LACK OF
LOW LEVEL CONVERGENCE SHOULD CONTINUE W OF THIS BAND...MAKING IT WRN
BOUND OF ANY SVR POTENTIAL. THROUGHOUT EVENING SO FAR...A FEW
SHORT-LIVED...SMALL...LOW-LEVEL CIRCULATIONS HAVE SPUN UP FROM TIME
TO TIME OFFSHORE WITHIN BAND...AND IN CLUSTERS OF CONVECTION AHEAD
OF BAND. CAUSATIVE ENVIRONMENT MAY SHIFT SHOREWARD JUST ENOUGH TO
AFFECT OUTER BANKS. THERMODYNAMIC AND LOW-LEVEL SHEAR
CHARACTERISTICS -- WHILE OCCURRING IN CONJUNCTION WITH A
NON-TROPICAL LOW -- STRONGLY APPROXIMATE THAT COMMON TO SOME
IMMATURE TROPICAL CYCLONES OVER SMALL AREA NE THROUGH E OF CENTER.
VWP...MODIFIED MHX RAOB AND RUC SOUNDINGS EACH SUGGEST SUFFICIENT
LOW LEVEL SHEAR FOR ADDITIONAL/TRANSIENT MINI-SUPERCELLS TO FORM.
MHX VWP -- WHEN SAMPLING SECTOR OF CYCLONE AND WARM FRONTAL ZONE NOW
LOCATED FARTHER E OVER OUTER BANKS...YIELDED 0-1 KM SRH AROUND 150
J/KG...WITH SIMILAR VALUES DERIVED FROM FCST SOUNDINGS. PRESENCE OF
LARGE AREAS OF PRECIP AND SUBTLE DIABATIC COOLING TO ITS N SHOULD
HELP TO KEEP STABLE BOUNDARY LAYER INLAND WITH WARM FRONT NEAR
SHORE. HOWEVER...HIGH-THETAE MARINE AIR OFFSETS WEAK LAPSE RATES
ALOFT JUST ENOUGH TO PRODUCE MRGL BUOYANCY NEAR WARM FRONT...I.E.
MLCAPE AROUND 250 J/KG...WITH EFFECTIVE PARCELS ROOTED AT SFC.
..EDWARDS.. 09/08/2009
ATTN...WFO...MHX...
LAT...LON 34827644 34947631 35217587 35307553 35587547 35587543
35197550 35197561 35097592 34917617 34757632 34757645
34827644
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