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 OfficerBuffalo, NY Weather Forecast Office

November 1, 2006

But first…

• WHAT HAPPENED IN BUFFALO THE OTHER DAY???

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

• The NWS is America’s“no surprise” weather service

Only 383 Hits for “BUFFALO SURPRISE SNOW STORM”

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!

Storm Names

Arborgeddon

Oc-timber

Snowpocalypse '06

Snow-nami

Blizzacane The Baby Maker

Octsnowberfest Super Freak' stormIn memory of the King of Funk, Rick James, a Buffalo Native

• 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

• 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 6Events took place in Oct-Dec

(Lake clearly has anInfluence (often freezing over mid winter))

Greatest 24hr Snow1 37.9 Dec 9-10 19952 35.4 Dec 27-28 20013 25.3 Jan 10-11 19824 24.9 Nov 20 20005 24.3 Dec 15-16 19456 22.6 Oct 12-13 2006

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

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

15Z and 18Z sounding comparison

15Z T Sounding (Aqua)

18Z Td Sounding (blue) 18Z T Sounding (yellow)

Melting snow aloft??Another Latent Heat example

• Albany - Oct 1987• (Another memorable event

– Massachusetts May 9-10 1977)

Evaporative CoolingDewpoints in the upper 20s to near 30

Dewpoints near 30

Dewpoints in the mid 20s

Dewpoints in the teens

Latent Heat plays a critical role

Solid Vapor

Sublimation

Deposition

Melting

FreezingLiquid

Evaporation

Condensation

LATENT HEAT ABSORBED FROM ENVIRONMENT

LATENT HEAT RELEASED TO ENVIRONMENT

Other possibilities?

• Could Cold air aloft be brought down to the surface with convection?

– You could cool the lower levels a few degrees

• And now back to the original presentation…

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 – 10PMThurs 730AM

16-17 November 2005:

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

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 bandsBallentine (personal communication)

• For a classic single band (“Type I”) event, this could mean the difference between raking leaves and shovelling snow!

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

CasesDate Location Type of

EventAmounts Comments

Nov 20 2000 Buffalo Southwest flow 28” Under forecast amounts

paralyzing (24hr extreme)

Dec 4 2002 Wayne County “Tea Kettle” 6-8” Hard to forecast these small scale events!

Jan 28-31 2004 Oswego Westerly flow 80” Well forecast

Jan 16-18 2005 Rochester Northwest flow 12-24” Lake Huron connection

Dec 6-7 2005 Oswego Westerly flow 17-29” Lots of lightning and recent

Dec 15-17 2005 Buffalo Bust 0-2” Too much wind?

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?

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?

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)

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?