Mike Evans NWS / WFO BGM

CSTAR V – Severe convection in scenarios with low-predictive skill SUNY Albany researchers are examining SPC forecasts and associated severe weather occurrence to identify events with low-predictive skill. Their project covers the CONUS, with an emphasis on the northeast. Goal will be to identify environments with low predictive skill, and to improve forecasts in those environments.

Local study outline Examine day 1 NWS BGM forecasts issued on the midnight shift from 2011-August Define a “warning” as any time Hazardous Weather Outlook product indicates “severe”, “large hail” or “damaging wind” during the next 24 hours. Define an “event” as a day when at least 5 severe weather reports were received. How good are our warnings? What factors influence the quality of our warnings? Note… Joe Villani in Albany has been working on a similar study for the ALY county warning area.

Hazardous Weather Outlooks Example of a “warning”Example of a “non-warning”

How many severe reports are needed for an “event” to be identified? So… bigger events are more likely to be caught than marginal events. Using a high threshold results in lots of false alarms. For the rest of this study, an event is defined as 5 or more reports.

POD and FAR

POD and FAR by month Events: Warnings:

POD and FAR by season Events: Warnings: 30 46

Do “dry-spells” bias our forecasts? Events: 7 of of 44

What about the large-scale environment? Define – “good forecast” events as events with a warning. Define – “over-achieving” events as events with no warning. Define – “under-achieving” events as a warning issued with no event.

POD and FAR MLCAPE (J/kg) 0-3 km shear (kt)

High CAPE / High shear events

Low CAPE / High shear events

High CAPE / Low shear events

Summary

Example – June 24, 2013

SPC damaging wind outlook

SPC hail outlook

500 mb heights and vorticity

Sea-level pressure and satellite

2 hour RAP Sounding at BGM valid 20z

Radar reflectivity animation

BGM Hazardous Weather Outlook – issued at 422 AM June 24, 2013 “SCATTERED THUNDERSTORMS ARE EXPECTED TODAY WITH THE BEST CHANCES THIS AFTERNOON… SOME MAY CONTAIN HEAVY RAINFALL”.

Severe reports – June 24, large hail reports 16 damaging wind reports 7 days since the previous severe weather occurrence

Future Work Results from this study and work at ALY will be compared to results from the larger study at SUNY ALY. These results will be available next year.