February 6, 2012 Verification Western California Dan Tomaso, Tyler Roys, & Brian Clavier

HPC Analysis, Monday 2/6 12z

Forecast Concerns- Timing

Forecast Concerns- Terrain/P-Type

Forecast Concerns- Previous Day Warming due to compression with easterly, downsloping winds, Plot valid 2/5 2343z

FORECAST PERIOD BEGINS!

Forecast Concerns- High Wind Potential Will 850 mb winds mix to the surface? 850 mb observations valid at 2/6 12z

Forecast Concerns- Freeze Possibility? Plot valid 2/6 1243z <= 32°F for 3 hours is need for Freeze/Frost to verify

Forecast Concerns- 2/6 12z Easterly winds at the onset?

HPC Analysis, Monday 2/6 12z

HPC Analysis, Tuesday 2/7 00z

HPC Analysis, Tuesday 2/7 12z

Regional Radar- 2/7 0201z

Regional Radar- 2/7 0800z

Regional Radar- 2/7 1159z

Eliminating Categories “All-zero categories” – All winter precipitation events (Categories 1-11) Used Redding observations and other cold sites to rule these out. Temperatures increased through our period. Also used NOHRSC database:

Eliminating Categories No snow=no blowing & drifting snow (Cat. 15) No blowing dust reports (Cat. 14) No smoke reported in ASOS/AWOS obs. (Cat. 16) – Note: We did read through every ASOS/AWOS ob. Visibilities from reports > 0.5 mile (No to Cat. 17) Wind chill and extreme chill ruled out from coldest sites and wind chill chart (Cat. 18 & Cat. 19) Flood categories (Cat ) ruled out via ASOS/AWOS obs and Mesonet obs found at

Eliminating Categories Lightning (Cat. 25) ruled out based on PSU eWall lightning data (next slide) Thunderstorm and severe thunderstorm (Cat. 26 & 27) ruled out based on ASOS/AWOS reports and lack of lightning

Verifying High Winds/Severe Winds Checked each ASOS/AWOS ob in our zones Example: KSNS Z AUTO 11031G38KT 10SM FEW120 16/01 A2973 RMK AO2 PK WND 11038/1153 SLP T TSNO Also used max wind reports from NWS Mesonet – Checked data quality by using surrounding reports

High Wind Verification Zones 1-4, 505, 508, 510, 512, 513, 517, 518, 528

Severe Wind Verification Zones 1 and 510 Gusts exceeded 50 knots

Verifying Temperatures Again ASOS/AWOS, Mesonet reports were used. Every zone examined in this way

Freeze Verification Zones 4 & 15 Highest elevation sites P-type again was not an issue as warm air pushed temperatures above freezing

Temperature ≥ 68°F Verification

Zones 1, 3, 508, , , and 528 Easterly winds the culprit!

Verifying Precip Used ASOS/AWOS and Mesonet reports Different format for Mesonet reports: Radar imagery (as seen before) Radar estimated rainfall:

Mesonet Reports

Precipitation Ending 2/7 12z

≥0.25” Precip Verification Zones 2, 17, 18, 63, 64, 76, , 510

3 hours of Precip Verification Same zones verified as ≥0.25” precip category Zones 2, 17, 18, 63, 64, 76, , 510 Used radar, ASOS/AWOS, and mesonet reports

Verification Summary No zones verified for Cat. 1-11, 14-19, & Zones that verified for high winds: 1-4, 505, 508, 510, 512, 513, 517, 518, 528 Zones that verified for severe winds: 1 & 510 Zones that verified for freeze/frost: 4 & 15 Zones that verified for T ≥ 68°F: 1, 3, 508, , , and 528 Zones that verified for Precip. Total ≥0.25” and 3 hours of precip: 2, 17, 18, 63, 64, 76, , 510

Lessons Learned Beware of downsloping winds! Timing of precip- GFS more on target than NAM – Progression of storm system faster over water? Look at observations first while forecasting – Leads to “gimme” points Overlay terrain map on zone map, where is terrain an issue? For verifying out west: Mesonet data!