Sunday, September 6, 2009

DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 060820
SWOD48
SPC AC 060819

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0319 AM CDT SUN SEP 06 2009

VALID 091200Z - 141200Z

...DISCUSSION...

THREAT FOR AN ORGANIZED SEVERE EVENT SHOULD REMAIN RELATIVELY LOW
FROM DAY 4 THROUGH ABOUT DAY 5 AS THE BELT OF STRONGER WLYS STAY
NORTH OF THE U.S. BORDER.

BEYOND DAY 5 DETERMINISTIC MODELS AND MREF ENSEMBLE MEMBERS HAVE
TRENDED TOWARD A SIGNIFICANT AMPLIFICATION OF THE UPPER PATTERN AS A
TROUGH EVOLVES OVER THE ERN HALF OF THE COUNTRY...RESULTING IN A
HIGH AMPLITUDE POSITIVE-NEGATIVE ANOMALY BECOMING ESTABLISHED BY DAY
7. HOWEVER...MODELS HAVE NOT DEMONSTRATED RUN TO RUN CONTINUITY
BEYOND DAY 5 WITH WIDELY VARYING SOLUTIONS BETWEEN THE 12Z AND 00Z
RUNS. THE MREF MEMBERS ALSO BEGIN TO SHOW CONSIDERABLE DISPERSION BY
DAY 7. SOME THREAT FOR SEVERE STORMS COULD DEVELOP FROM THE MID MS
VALLEY INTO THE OH VALLEY BY DAY 6-7 AS THE TROUGH BEGINS TO
AMPLIFY. AT THIS TIME...TOO MUCH UNCERTAINTY EXISTS REGARDING HOW
THE UPPER PATTERN WILL EVOLVE TO INTRODUCE A RISK AREA.

..DIAL.. 09/06/2009

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