Tuesday, October 23, 2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 230549
SWODY2
SPC AC 230547

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1247 AM CDT TUE OCT 23 2007

VALID 241200Z - 251200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
A LARGE CUT-OFF LOW WILL BEGIN TO UNDERGO SLOW RETROGRADE MOTION
OVER THE LOWER MS VALLEY ON WEDNESDAY. AS THIS OCCURS...
STRENGTHENING MID LEVEL CONFLUENCE DOWNSTREAM FROM THE CUT-OFF AND
WITHIN THE BASE OF A STRONG TROUGH EXITING NEW ENGLAND WILL
CONTRIBUTE TO ANTICYCLOGENESIS ACROSS THE MID ATLANTIC REGION. AS
HIGH PRESSURE BUILDS OVER THE GREAT LAKES AND NORTHEAST...A LOW
LEVEL BACK DOOR/WEDGE FRONT IS FORECAST TO SPREAD SWD/SWWD FROM VA
TO THE CAROLINAS LATE IN THE PERIOD. MOIST ONSHORE FLOW WILL PERSIST
ACROSS THE SOUTHEAST AND FL BETWEEN THE HIGH TO THE NORTH AND THE
LARGE DEEP-LAYER OCCLUDED LOW OVER THE LOWER MS VALLEY.

THERE CONTINUE TO BE TIMING/PLACEMENT DIFFERENCES IN THE LATEST
DETERMINISTIC MODEL RUNS REGARDING THE CUT-OFF LOW AND ASSOCIATED
STRONGER WIND FIELDS. NAM-WRF/NAM-KF AND SREF BEGIN TO RETROGRADE
THE LOW CENTER EARLY AND INDICATE STRONGER FLOW/SHEAR WILL REMAIN
PRIMARILY WEST OF THE WARM SECTOR. LATEST GFS IS FORECASTING A MORE
EWD POSITION TO THE LOW WHICH RESULTS IN STRONGER SHEAR AND FORCING
SPREADING ACROSS THE WARM SECTOR TO THE SOUTHEAST COAST THROUGH
THURSDAY MORNING.

..SOUTHEAST...
AIR PARCEL TRAJECTORIES WITHIN EXTENSIVE WARM CONVEYOR BELT WRAPPING
CYCLONICALLY AROUND THE CLOSED LOW WILL ORIGINATE IN VERY MOIST
MARITIME TROPICAL AIR MASS RESIDING ACROSS THE GULF AND WRN
ATLANTIC. WEAK CAP AND DIURNAL HEATING WILL CONTRIBUTE TO AN
INCREASE IN CONVECTION FROM PARTS OF THE CAROLINAS SWD ACROSS GA AND
FL. CONFLUENT LOW LEVEL FLOW AND PRESENCE OF RESIDUAL
FRONTAL/OUTFLOW AND SEA/GULF BREEZES MAY ACT TO FOCUS SOME OF THIS
TSTM ACTIVITY. BASED ON NAM-WRF AND SREF OUTPUT...SHEAR AND LARGE
SCALE FORCING ACROSS MUCH OF THE REGION WILL BE MARGINAL FOR MORE
WIDESPREAD SEVERE POTENTIAL BUT ISOLATED STORMS...OR STORM CLUSTERS
MAY BRIEFLY POSE WIND/TORNADO THREATS GIVEN POTENTIAL FOR LOCALLY
ENHANCED SHEAR AND DESTABILIZATION NEAR THE BOUNDARIES. GFS FORECAST
WOULD SUGGEST GREATER POTENTIAL FOR ORGANIZED STORMS TO THE
SOUTHEAST COAST AND FL AS LIFT AND SHEAR IN THE ERN QUADRANT OF THE
LOW SPREADS OVER THESE AREAS. LOW SEVERE PROBABILITIES APPEAR
WARRANTED FOR THIS FORECAST GIVEN CONTINUING WIDE DISCREPANCIES IN
MODEL GUIDANCE AND UNCERTAINTIES REGARDING MAGNITUDE OF INSTABILITY
AND SHEAR.

.CARBIN.. 10/23/2007

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