Aspects of the May 13/14 th northern high plains Derecho
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Transcript of Aspects of the May 13/14 th northern high plains Derecho
Aspects of the May 13/14th northern high plains Derecho
Jeffry S. Evans
Storm Prediction Center
10/10/07
Overview
• Derecho-producing MCS- 66 severe wind reports/wind damage along with 6 significant wind reports measured up to 75 mph.
• Severe and near severe winds extended swd for nearly 100 mi south of main convection.
Quick OverviewQuick Overview
• Strong, progressive shortwave trough moving across nrn Rockies.
• E-W surface cold front moving swd across ern MT through the day.
• Moderate instability and strong effective bulk-shear develop ahead of and just behind front.– Low and deep layer shear strengthens in E-
NE surface flow behind front.
GOES-W IR12z (5/13) – 08z (5/14)
SHR- 45G55 0145z
BYG- 40G54 0232z
RAWS site M60 mph 0350z
E60 mph 0430z
RAP- 35G48 0652z
Environment
21z
23z
01z
03z
2150z
2153z BIL 04020G26
2223z
2253z
2323z
2353z
2340z BIL PK WND 36043
0030z
0053z
0123z
0148z SHR 31037G520153z SHR 31045G55
0150z
Conclusions/QuestionsConclusions/Questions
• Appears convective cold pool enhanced cold front, surging front ssewd.
• Strong capping limited new thunderstorm development into MT, but not into ND.
• Measured wind gusts were amplified along eastern slopes of Big Horn mountains and Black Hills.– Blocking effect enhanced frontal surge?
Conclusions/QuestionsConclusions/Questions
• WFOs Billings and Riverton both addressed wind threat with short term forecasts.
• WFO Rapid City used severe thunderstorm warnings.
• How should the NWS handle these events with current product suite?
The EndThe End