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An assessment of local forecaster’s ability to anticipate convective event
severity using the Hazardous Weather Outlook at WFO Binghamton
Mike Evans NWS / WFO BGM
CSTAR V – Severe convection in scenarios with low-predictive skillSUNY 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 outlineExamine day 1 NWS BGM forecasts issued on the
midnight shift from 2011-August 2014.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 OutlooksExample 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: 5 10 13 17 7 6 1 59Warnings: 7 14 15 24 7 8 1 76
POD and FAR by season
Events: 22 37Warnings: 30 46
Do “dry-spells” bias our forecasts?
Events: 7 of 15 30 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 FARM
LC
AP
E
(J/k
g)
0-3
km
sh
ear
(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, 201322 large hail reports16 damaging wind reports7 days since the previous severe weather
occurrence
Future WorkResults 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.