SWOD48
SPC AC 260850
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0350 AM CDT WED SEP 26 2007
VALID 291200Z - 041200Z
..DISCUSSION...
ECMWF CONTINUES TO TREND SLOWER IN THE MEDIUM RANGE...WHILE THE GFS
-- SIMILAR TO THE NAM THROUGH 84 HOURS -- CONTINUES TO DEPICT A
SEVERE WEATHER EVENT CENTERED OVER THE CENTRAL PLAINS FOR SAT. SEPT.
29 /I.E. DAY 4/. WHILE THE GFS DEPICTS A NEGATIVELY-TILTED TROUGH
OVER THE ERN DAKOTAS/THE MID MO VALLEY REGION AT THE END OF THE DAY
4 PERIOD...THE ECMWF DEPICTS THE FEATURE EXITING ERN WY/ERN CO AT
THAT TIME. AS A RESULT...THE ECMWF WOULD SUGGEST A MORE LIMITED
SEVERE POTENTIAL OVER THE CENTRAL/NRN HIGH PLAINS REGION DAY 4...AND
THEN PERHAPS A THREAT FROM THE MID MO VALLEY TO THE UPPER MS VALLEY
REGION DAY 5.
ATTM...WILL MAINTAIN CONTINUITY WITH A FORECAST FOR A CENTRAL CONUS
SEVERE EVENT DAY 4...THOUGH DIFFERENCES BETWEEN THESE TWO MODELS --
AND FURTHER REVEALED IN NCEP MEDIUM-RANGE ENSEMBLE DATA -- CAST A
SUBSTANTIAL DEGREE OF UNCERTAINTY ON THIS SCENARIO.
MODEL DIFFERENCES CONTINUE TO INCREASE BEYOND DAY 4...WITH THE GFS
DEPICTING A SECOND SUBSTANTIAL UPPER TROUGH AFFECTING THE PLAINS DAY
6...WHILE THE ECMWF DEPICTS A SIMILAR TROUGH BUT A FULL 24 HOURS
LATER. GIVEN THESE UNCERTAINTIES...WILL NOT ISSUE ANY AREAS BEYOND
DAY 4 ATTM.
.GOSS.. 09/26/2007
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