Storm Force wind events of October and December 2010

1. Kevin Birk, Mike Bardou and Mark Ratzer WFO Chicago Storm Force wind events of October and December 2010

2. Review of Two Storm Force Wind Events across Lake MI • October 26th “Bomb” • December 12th Winter Storm • Both events produced Storm force winds (48+ knots). • However, the strength and the tracks of the two lows were quite different.

3. Motivation • Increase the forecast accuracy for the onset of high impact winds across Lake Michigan. -> Gain a better understanding of the main processes that govern the onset and maintenance of storm force winds across the lake .

4. The October 26th Bomb • Central pressure dropped from 980 mb at 00UTC on the 26th to 955 mb at 00UTC on the 27th as the surface low tracked across MN. • Lake MI remained in the warm sector through the morning of the 26th . • Occluded front pushed across the lake late morning on the 26th. • Following this, the system filled as the low became vertically stacked.

5. 12 UTC Oct 26th 00 UTC Oct 27th 300 MB Jet and Surface 300 MB Jet and Surface

6. 12 UTC Oct 27th 00 UTC Oct 28th 300 MB Jet and Surface 300 MB Jet and Surface

7. 12 UTC October 26th

8. 15 UTC October 26th

9. 18 UTC October 26th

10. 21 UTC October 26th

11. 00 UTC October 27th Adiabatic Lapse Rate

12. Forecasts For Oct 26th Event • Headlines for Gale/Storm watch first issued at 3:42 AM Sun 10/24 • Gale watch from Monday PM – Tuesday AM. • Storm watch from Tuesday PM – Wed evening. • Headlines upgraded to Storm Warning at 4:01 AM Mon 10/25. • Warning from 4 AM Tue -7 PM Wed. • Later forecasts shifted times slightly.

13. North Half Verification • Winds remained below Gale force Until about 10 AM Tue 26th as the cold front passed. • Gusts remained below Storm force at the north buoy (peaked at 47 knots Tue PM). • Port Inland, MI peaked at 56 knots Wed AM. Frontal Passage Frontal Passage

14. South Half Verification • Winds remained below Gale force Until about 7 AM Tue 26th as the cold front passed. • Gusts remained below Storm force at the south buoy (peaked at 45 knots Tue PM). • Chicago Harrison Crib peaked at 65 knots Tues AM. Frontal Passage

15. December 12th Winter Storm • Surface Low tracked across Northern IL/Southern Lake MI during predawn hours on the 12th . • The low deepened to 988 mb during the afternoon on the 12th as the low moved across western New York. • Farther Northwest, Canadian high pressure of 1038 mb moved across eastern Dakotas.

16. 12 UTC Dec 12th 00 UTC Dec 13th 300 MB Jet and Surface 300 MB Jet and Surface

17. 12 UTC December 12th

18. 15 UTC December 12th

19. 21 UTC December 12th

20. 03 UTC December 13th

21. 03 UTC December 13th Super Adiabatic Lapse Rate

22. Forecasts For Dec 12th Event • Headlines for Gale/Storm watch first issued at 8:50 AM December 10th. • Late Saturday the 11th through Monday morning the 13th. • Winds to 55 knots on Sunday/Sunday Night the 12th . • Headlines upgraded to Storm Warning at 2:27 PM on the 11th . • Late Saturday the 11th through Monday morning the 13th. • Winds to 55 knots on Sunday/Sunday Night the 12th .

23. Verification • North Half • Winds increased to Gales around 04 UTC and to Storm by 10 UTC. • Storm force winds ended around 11 UTC on the 13th (25 hours of storm). • South Half • Winds increased to Gales/Storm around 14 UTC. • Storm force winds ended around 05 UTC on the 13th (15 hours of storm).

24. Considerations • Stability over the lake • Boundary layer lapse rates. • Near adiabatic -> gusts = boundary layer winds. • Super adiabatic -> gusts = the max wind in the boundary layer. • The track of the low and time of year. • Strength of cold air advection. • Dynamics • Isallobaricwind component. • Synoptic scale descent following the passage of a mid level vorticity max and dry slot.

25. Questions?