February 6, 2012 VerificationWestern California

Dan Tomaso, Tyler Roys,& Brian Clavier

HPC Analysis, Monday 2/6 12z

Forecast Concerns- Timing

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 hoursis 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. 21-24) ruled out via

ASOS/AWOS obs and Mesonet obs found at http://www.wrh.noaa.gov/sgx/gmap/index.php

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 071153Z AUTO 11031G38KT 10SM FEW120

16/01 A2973 RMK AO2 PK WND 11038/1153 SLP077 60000 T01610006 10178 20150 58015 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

Temperature ≥ 68°F Verification

• Zones 1, 3, 508, 510-511, 513-518, and 528

• Easterly winds the culprit!

Verifying Precip

• Used ASOS/AWOS and Mesonet reports• Different format for Mesonet reports:

http://www.cnrfc.noaa.gov/google_precip.php• Radar imagery (as seen before)• Radar estimated rainfall:

http://water.weather.gov/precip/

Mesonet Reports

Precipitation Ending 2/7 12z

≥0.25” Precip Verification

• Zones 2, 17, 18, 63, 64, 76, 505-507, 510

3 hours of Precip Verification

• Same zones verified as ≥0.25” precip category

• Zones 2, 17, 18, 63, 64, 76, 505-507, 510

• Used radar, ASOS/AWOS, and mesonet reports

Verification Summary

• No zones verified for Cat. 1-11, 14-19, & 21-27• 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, 510-511,

513-518, and 528• Zones that verified for Precip. Total ≥0.25” and 3

hours of precip: 2, 17, 18, 63, 64, 76, 505-507, 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!