THE 2011 GROUNDHOG DAY BLIZZARD: A

SYNOPTIC AND MESOSCALE OVERVIEW

Stephen Rodriguez, Jr.National Weather Service Chicago, IL

Introduction Brief background. Purpose of Study. Synoptic background and forcing

mechanisms. Synoptic/Mesoscale features: Moisture,

Forcing, Instability. Conclusions.

Radar Storm Evolution

http://www.crh.noaa.gov/images/ilx/events/02feb11/us_warnings.png

Observed Snowfall Totals

CHICAGO

Wind Gusts/Visbys/Lightning

1/4 MILEVISBYS.

65 STRIKES!

Purpose of Study Synoptic/Mesoscale Overview. Pattern Recognition/Conceptual Models. “How to Forecast” Blizzards? What are we forecasting?

Purpose - NWS Blizzard Definition Sustained wind or frequent gusts to 35

miles an hour or greater; and Considerable falling and/or blowing

snow (i.e., reducing visibility frequently to less than ¼ mile).

For a period of 3 hours or longer.

Purpose - Blizzard Elements Heavy snowfall. Snow efficiency. Strong winds.

Synoptic Overview

300 MB02/02/1100Z

Synoptic Overview

700 MB02/02/1100Z

Synoptic Overview

850 MB02/02/1100Z

Synoptic Overview

SFC02/02/1100Z

Synoptic Overview

02/02/00 00ZROAB KDVN

00Z

Low/Isallobaric Component

03Z06Z

Well-Mixed Environment

04Z RUCSounding

Moisture

850 MBMoistureTransport

Moisture

TROWAL structureidentifiable by02Z-3Z.

CHICAGO

Forcing - Deformation

Forcing - Isentropic Lift22Z/00Z/02ZRUC 290K

Persistent isentropiclift from lateafternoon throughlate evening.

CHICAGO

Forcing - Frontogenesis

RUC 02Z

ORDMSN EVV

Instability - EPV

ORD EVVMSN

RUC 02Z

Instability – CAPE/Lapse Rates

04Z RUCSounding

NORTHCENTRALILLINOIS

Snow Efficiency

NORTHCENTRALILLINOIS

00Z-03Z

Conclusions - Review Copious amounts of moisture. Persistent strong forcing due to both

synoptic/meso forcing mechanisms. Instability – an added benefit. Snow efficiency.

Conclusions – Key Factors Heavy Snowfall – Yes! Snow efficiency – Yes! Strong winds – Yes! Yes! Yes!!!

Blizzard Climatology

Conclusions – Lessons Learned Stick to “base” data. Pattern Recognition of three elements. All come together – Blizzard.

Questions? References: NOAA/NWS/Storm Prediction Center Schwartz, 2001.