using standardized anomalies to identify significant heavy rain events
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Using Standardized Anomalies to Identify Significant Heavy Rain Events. Jason Krekeler And Richard H. Grumm National Weather Service State College, PA. Motivation. Record rainfall with remnants of TS Lee Look at key features of this event Pattern and persistence of the pattern - PowerPoint PPT PresentationTRANSCRIPT
Using Standardized Anomalies to Identify Significant Heavy Rain Events
Jason KrekelerAnd
Richard H. GrummNational Weather Service State College, PA
Motivation
• Record rainfall with remnants of TS Lee– Look at key features of this event– Pattern and persistence of the pattern
• Pattern similar 9/30 – 10/1 2010 event and others– Compare these events
Bloomsburg PA
City Island in Harrisburg
Swatara Creek in Hersey
Hersheypark, Comet Hollow
Rainfall from remnants of TS Lee
Rainfall totals from 9/29-10/2 2010
Lee 500 hPa pattern
Surface
Precipitable water
Sep 29-Oct 2 500 hPa Pattern
Surface pattern
Precipitable water
How do these events compare?
• Similarities– Deep trough in eastern US– Anticyclone in North Atlantic– Surge of tropical moisture along frontal boundary
• Differences– Deepening surface low vs cut off upper level low– T bone vs north/south bands– duration
Persistance
• Both events featured a 24 hour period of intense rainfall– Deep southerly flow– High precipitable water– Jet entrance regions– Downstream blocking ridge
Heaviest 24 hour periodSep 30th 2010
Heaviest 24 hour periodSep 7th 2011
Sep 30 2010
TC Lee remnants and Katia
Sep 7 2011
The resulting Rainfall Patterns
Comparison
• Similar rainfall pattern- north/south bands• Sep 7, 2011-– Higher rainfall totals– Stronger frontal boundary– More focused band of high pw
• Sep 30,2010 – broader area of heavy rain– Stronger southerly flow– Ridge further off the coast
PW Plume Comparisions
Comparison with LLJ
Conclusions
• Large scale patterns similar but differences in the details
• Persistence of the pattern• Similar pattern of rainfall but differences in
magnitude and scale• If TC Katia was not there…?– Would the LLJ been broader/stronger with
broader area of high PW and heavy rain
Bloomsburg PA