SNOWIN’ TO BEAT THE BAND Using Satellite and Local Analysis and Prediction System Output to Diagnose the Rapid Development of a Mesoscale Snow Band Eleanor Vallier-Talbot and David R. Vallee NOAA/NWS Taunton, MA

Fast Hitting Snowstorm Fast moving storm produced swath of snows across major metro areas of Southern New England

Methodology “Anticipating Mesoscale Band Formation” WFO Taunton has incorporated the method outlined in Novak, D.R., 2002, for anticipating band formation. Critical Elements: –Upper Level Divergence –Mid Level Frontogenesis/Instability –Snow Growth and CSI Potential

Methodology “Anticipating Mesoscale Band Formation” Day shift forecasters used the same approach incorporating an updated version of the Local Analysis and Prediction System Output (LAPS) in real time along with Satellite signatures. Helped diagnose the northwest displacement and resulted in dramatically higher snowfall forecast.

Methodology- “Why LocalLAPS” WFO BOX had obtained a newer version of the LAPS software from FSL in 2002 (for unrelated reasons) –LocalLaps domain was the Northeast region and was being run at 10 km horizontal resolution. –The “LocalLAPS” was being run on a separate LINUX workstation This allowed for a larger analysis domain and earlier receipt of data. –Version being run back on Feb ’03 is basically the version currently in AWIPS OB 2.0 Allowed the office to utilize several unique datasets that were not available in AWIPS –Including local mesonets such as AWS, NOS PORTS, boundary layer profilers and ACARS Data. WFO BOX is now running LocalLAPS at 5km

Eta Model Guidance NWP/Eta Model was forecasting cyclogenesis along mid Atlantic coast Low to pass well south and east of Cape Cod –A track far enough off shore which doesn’t often produce heavy snows far inland

Eta Model Guidance Co-location and placement of upper level divergence, mid level frontogenesis and max upward motion and potential for efficient snow growth were poised to occur along or just off the coast of Southern New England

Composite 4-panel - 24 hr fcst valid 12 UTC 7 Feb 03

Composite 4-panel - 30 hr fcst valid 18 UTC 7 Feb 03

Composite 4-panel - 36 hr fcst valid 00 UTC 8 Feb 03

Cross Section – 30 hr fcst valid 18 UTC 7 Feb 03 Lebanon, NH to 150 nm south of Martha’s Vineyard, MA

Time Height Cross Sections 12 UTC Run for Eta at Norwood, MA -8°C -18°C -12°C -16°C

Time Height Cross Section 12 UTC Run for Eta at Nantucket, MA -8°C -18°C -12°C -16°C

Composite 4-panel - 12 hr fcst, valid 12 UTC 7 Feb 03

Composite 4-panel - 18 hr fcst, valid 18 UTC 7 Feb 03

Composite 4-panel - 24 hr fcst, valid 00 UTC 8 Feb 03

Cross Section – 18 hr fcst valid 18 UTC 7 Feb 03 Lebanon, NH to 150 nm south of Martha’s Vineyard, MA

Time Height Cross Sections 00 UTC Run for Eta at Norwood, MA -18°C -8°C -16°C -12°C

Time Height Cross Sections 00 UTC Run for Eta at Nantucket Island, MA -18°C -8°C -16°C -12°C

RUC40 Model Guidance 06Z Run of the Eta continued to present a similar solution to the 12z/6 th and 00z/6 th runs Winter Weather Experience (WWE) collaborative efforts also placed axis of heaviest snows along the immediate south coast of New England RUC40 guidance from the 09Z run began to at least hint at a northwest displacement to the major forcing mechanisms

Composite 4-panel – 09 UTC RUC40 Valid 12 UTC 7 Feb 03

Composite 4-panel – 09Z RUC40 Valid 15 UTC 7 Feb 03

Composite 4-panel – 09Z RUC40 Valid 18 UTC 7 Feb 03

Reality Check…. Satellite and LocalLAPS Data tell the tale! Major Corridor of very heavy snow did develop across the CWA But did it occur along the south shore where we all thought it would?????

Water Vapor Image 06 UTC, 7 Feb 03

Water Vapor Image 12 UTC, 7 Feb 03

Composite 4-panel - LocalLAPS Valid 12 UTC 7 Feb 03 Frontogenesis is displaced to the northwest!

Composite 4-panel - LocalLAPS Valid 16 UTC 7 Feb 03 Corridor moving right across the CWA!

16Z Visible Image Note the “Convective” look to the cloud pattern!

WSR-88D Base Reflectivity WFO BOX Valid Time: 14 UTC through 17 UTC

Visible Satellite Loop Valid Time: 14 UTC through 20 UTC

18Z Visible Image Note the “Convective” look to the cloud pattern!

Water Vapor Image 18Z, 7 Feb 03

Composite 4-panel – LocalLAPS Valid 18 UTC 7 Feb 03 Corridor moving right across the CWA!

LAPS Cross Section valid 16 UTC 7 Feb 03 Lebanon, NH to 150 nm south of Martha’s Vineyard, MA

LAPS Time Height over Norwood, MA Again…quite productive! -18°C -8°C -16°C -12°C

18 UTC Base Reflectivity and Surface Weather, Ceiling and Visilbiites Vsby ¼ to ½ mile in moderate/heavy snow

Observed Snowfall Analysis - February 7 th, 2003 Snowstorm

WFO Taunton Performance WFO Taunton lead times: –45 hours on Outlook Statement –36 hours for the watch –24 hours for warning South Coast, Cape Cod and the Islands But: very short lead time Providence to Boston Metro Corridor! –Just 1 to 4 hours!

Using Satellite and LAPS Data to Diagnose the Evolution of a Heavy Snow Band Appreciate your time! Comments? Questions?