1. Using Standardized Anomalies to Identify Significant Heavy Rain Events Jason Krekeler And Richard H. Grumm National Weather Service State College, PA

3. 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

4. Bloomsburg PA

5. City Island in Harrisburg

6. Swatara Creek in Hersey

7. Hersheypark, Comet Hollow

8. Rainfall from remnants of TS Lee

9. Rainfall totals from 9/29-10/2 2010

10. Lee 500 hPa pattern

11. Surface

12. Precipitable water

13. Sep 29-Oct 2 500 hPa Pattern

14. Surface pattern

15. Precipitable water

16. 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

17. Persistance Both events featured a 24 hour period of intense rainfall – Deep southerly flow – High precipitable water – Jet entrance regions – Downstream blocking ridge

18. Heaviest 24 hour period Sep 30 th 2010

19. Heaviest 24 hour period Sep 7 th 2011

20. Sep 30 2010

21. TC Lee remnants and Katia

22. Sep 7 2011

23. The resulting Rainfall Patterns

24. 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

25. PW Plume Comparisions

26. Comparison with LLJ

27. 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

28. Bloomsburg PA