1. Improving the Understanding and Prediction of Lake-Effect Snowstorms in the Eastern Great Lakes Region A NWS BUF and SUNY Oswego COMET Partners project David Zaff Science and Operations Officer Buffalo, NY Weather Forecast Office November 1, 2006

2. But first… WHAT HAPPENED IN BUFFALO THE OTHER DAY???

3. Here’s some examples of what 2 feet of heavy wet snow can do to trees…

4. The NWS is America’s “no surprise” weather service Only 383 Hits for “BUFFALO SURPRISE SNOW STORM”

5. Storm names and ranking Since the late 90s BUF has been naming lake effect events, kind of like naming hurricanes Each year has a theme –last year we had “cats” (Abyssinian, Bengal, Chartreux etc) –This year it will be insects or battles This Storm a will be either: –“Aphid” (devastating to trees) or –“Antietam” (the bloodiest battle in American history (Civil War)) All storms are also subjectively ranked –On a “flake” scale from 1 to 5 flakes –Idea similar to Kocin and Uccellini (Population, snow amount, impact) –This storm will be a 5+ flakes!

6. Storm Names Arborgeddon Oc-timber Snowpocalypse '06 Snow-nami Blizzacane The Baby Maker Octsnowberfest Super Freak' storm In memory of the King of Funk, Rick James, a Buffalo Native

8. Monday Afternoon Discussion IT IS PRETTY EARLY FOR SNOW BUT THE MREF ENSEMBLES ARE INDICATING 500 MB HEIGHTS ABOUT 3 STANDARD DEVIATIONS BELOW NORMAL AND 850 MB TEMPS ABOUT 2 STANDARD DEVIATIONS BELOW NORMAL. THIS COULD BE A VERY INTERESTING PERIOD. Tuesday 00Z NAM Snow Forecast (Based on Max Temp in Profile) Tuesday Afternoon Discussion AS THE COLDER AIR DEEPENS THURSDAY NIGHT AND FRIDAY...RAIN SHOWERS WILL MIX WITH SNOW SHOWERS...ESPECIALLY FOR AREAS EAST AND NORTHEAST OF THE LAKES WHERE MODERATE TO EXTREME INSTABILITY WILL SET UP AS 850 MB TEMPS WILL DIP TO ABOUT -7C. Wednesday 00Z NAM Snow Forecast (Based on Max Temp in Profile) Wednesday Morning Discussion HAVING A HARD TIME VISUALIZING WHAT 850MB LAKE SFC TEMP DIFFERENCE OF 20-25C SO EARLY IN THE SEASON WILL PRODUCE. IS -7C AT 850 COLD ENOUGH? CAN THE LAKE BE TOO WARM? Thursday 00Z NAM Snow Forecast (Based on Max Temp in Profile) Thursday Morning Discussion THERE IS LOW CONFIDENCE IN THE SNOW AMOUNT FORECAST AT THIS TIME. (A Special Weather Statement was issued on the previous evening with minor accumulations) Friday 00Z NAM Snow Forecast (Based on Max Temp in Profile) Warning already issued at 230PM Headline:...HISTORIC SNOWFALL MAY BE IN STORE OVERNIGHT... MOST OF THIS AREA COULD EASILY SEE 1 TO 3 INCHES OF WET SNOW WITH ISOLATED AMOUNTS OF 6 INCHES OR MORE NOT OUT OF THE QUESTION 6.5 Day Confidence Forecast (based on 2 Meter Temps

9. This was a historic storm –Never has this much snow fallen this early! –Temperatures aloft were marginal (rules of thumb) 850mb marginal at -5C to -7C –(depending on model, model time and forecast time) –Some forecasters questioned a moderating effect due to the +16C Lake Erie water temperature There was no doubt about the extreme instability! Note 5 out of 6 Events took place in Oct-Dec (Lake clearly has an Influence (often freezing over mid winter)) Greatest 24hr Snow 1 37.9 Dec 9-10 1995 2 35.4 Dec 27-28 2001 3 25.3 Jan 10-11 1982 4 24.9 Nov 20 2000 5 24.3 Dec 15-16 1945 6 22.6 Oct 12-13 2006

11. Latent heating plays a role Melting snow requires heat –this can have a cooling effect on the atmosphere –Melt a lot of snow…cool the airmass From Kain, et al (2000) You only need about.08” of precip to cool a 20mb layer 2C

12. Melting snow aloft and at the surface Every snowflake that melts aloft cools the column –you get an isothermal layer Every snowflake that hits the warm ground melts and cools the ground

13. 15Z and 18Z sounding comparison 15Z T Sounding (Aqua) 18Z Td Sounding (blue) 18Z T Sounding (yellow)

14. Melting snow aloft?? Another Latent Heat example Albany - Oct 1987 (Another memorable event –Massachusetts May 9-10 1977)

15. Evaporative Cooling Dewpoints in the upper 20s to near 30 Dewpoints near 30 Dewpoints in the mid 20s Dewpoints in the teens

16. Latent Heat plays a critical role SolidVapor Sublimation Deposition Melting Freezing Liquid Evaporation Condensation LATENT HEAT ABSORBED FROM ENVIRONMENT LATENT HEAT RELEASED TO ENVIRONMENT

17. Other possibilities? Could Cold air aloft be brought down to the surface with convection? –You could cool the lower levels a few degrees

18. And now back to the original presentation…

19. Lake Effect Snow! Lake-effect snowstorms are intense, banded mesoscale phenomena that occur in late fall and winter downwind of the Great Lakes Reinking et al. (1993) and Kristovich et al. (2000) This one produced over 18” under the band an an inch at the BUF airport! Wed – 10PM  Thurs 730AM 16-17 November 2005:

20. Research and Forecasting Lake Effect Snow We’ve come a long way! –Many studies/research done in the past 20 years (Snyder, Waldstreicher, Niziol etc) –Relatively coarse models to high resolution models 80km resolution 2x per day to 5km resolution 4x per day or better There is still much to learn! –Timing –Intensity –Location –Inland extent

21. Mesoscale Modeling and Lake Effect Mesoscale Models have been used for a number of years in an attempt to simulate some band formation –Some notes/experience with MM5: Intensity handled well Placement not so good –Southward error of 10-30 km for Lake Ontario bands Ballentine (personal communication) For a classic single band (“Type I”) event, this could mean the difference between raking leaves and shovelling snow!

22. BUF and SUNY Oswego COMET Project Test Weather Research and Forecast (WRF) model –Choose several past events –Run a series of simulations on each case Examples –Core (ARW vs NMM) –Horiziontal Resolution –Modify Boundary Conditions (frequency) –Domain –Background model –Vertical Resolution

23. Cases DateLocationType of Event AmountsComments Nov 20 2000BuffaloSouthwest flow28”Under forecast amounts paralyzing (24hr extreme) Dec 4 2002Wayne County“Tea Kettle”6-8”Hard to forecast these small scale events! Jan 28-31 2004OswegoWesterly flow80”Well forecast Jan 16-18 2005RochesterNorthwest flow12-24”Lake Huron connection Dec 6-7 2005OswegoWesterly flow17-29”Lots of lightning and recent Dec 15-17 2005BuffaloBust0-2”Too much wind?

24. Preliminary Results Case study: Dec 5-7, 2005: –What how does horizontal model resolution affect the forecast? –Project plans: Test at 4km 6km, 8km, and 10km –This is a big question for a separate project Mike Evans (SOO BGM) –WRF Ensemble for Eastern Great Lakes Region »Can/should we run at 12km?

25. Dec 5-7, 2005 Event over Oswego 12km 24hr NAM Forecast from NCEP (solid lines) 6km 24hr WRF Forecast (dashed) Will a locally run WRF at 12km look different than a 12km NCEP run?

26. Dec 5-7, 2005 Event over Oswego 12km 24hr WRF Forecast (solid lines) 6km 24hr WRF Forecast (dashed) Will a locally run WRF at 12km look different than a 12km NCEP run? How much smoothing is being done by the 12km NCEP run? Quite A bit! (12km NCEP run)

27. Summary So far: –Even a mesoscale model with a “relatively low” horizontal resolution (12km) can pick up a lake band –Goal: How low should we go? Which dynamic core to use Boundary conditions, and background model Is there a best fit configuration for all the different types of lake events?