Verification of the RWFS (Road Weather Forecast System)
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Transcript of Verification of the RWFS (Road Weather Forecast System)
Verification of the RWFS(Road Weather Forecast System)
Ben C. Bernstein
Jamie Wolff, Seth Linden
NCAR/RAP
Boulder, CO
Purpose and Presentations• Take a close look at key aspects
– Quality, performance…
• Case studies– What did the forecasts look like before events
• Heavy event: 2/15/03• Light event: 2/4/03
– How did the case evolve• Key factors
– Recommended vs actual treatments (two I-35 segments)
• Bulk statistics– Individual sites and all Iowa sites combined– Weather parameters– Road temperature
• Thanks to IA DOT & CTRE – data collection
Road Segments
A heavy snow event:Feb 14-16, 2003
2/14/03 – 6Z (midnight)A classic storm was setting up…
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NWS Forecasts, 4am (9Z) Feb 14IAZ047>050-061-062-142157-
BOONE-JASPER-MARSHALL-POWESHIEK-STORY-TAMA-
INCLUDING THE CITIES OF...AMES...BOONE...GRINNELL...MARSHALLTOWN... NEWTON
357 AM CST FRI FEB 14 2003
...WINTER STORM WARNING FOR TODAY AND TONIGHT...
.TODAY...WIDESPREAD FREEZING RAIN...SNOW...OR SLEET. ACCUMULATION 2 TO 3 INCHES. TEMPERATURES STEADY IN THE UPPER 20S. EAST WINDS 10 TO 20 MPH. CHANCE OF PRECIPITATION 90 PERCENT.
.TONIGHT...WIDESPREAD SNOW. TOTAL ACCUMULATION 4 TO 6 INCHES. BRISK WITH BLOWING AND DRIFTING SNOW. LOW IN THE MID TEENS. NORTHEAST WINDS 15 TO 25 MPH...GUSTING TO 30 MPH. CHANCE OF SNOW 80 PERCENT.
.SATURDAY...CLOUDY WITH A CHANCE OF SNOW. HIGH IN THE LOWER 20S. NORTHEAST WINDS 10 TO 20 MPH. CHANCE OF SNOW 50 PERCENT.
.SATURDAY NIGHT...PARTLY CLOUDY. LOW NEAR 10.
IAZ044-057>060-142157-
AUDUBON-CRAWFORD-DALLAS-GUTHRIE-POLK-
INCLUDING THE CITIES OF...DENISON...DES MOINES
357 AM CST FRI FEB 14 2003
...WINTER STORM WARNING FOR TODAY AND TONIGHT...
.TODAY...WIDESPREAD FREEZING RAIN...RAIN...OR SLEET. ACCUMULATION 1 TO 2 INCHES. HIGH IN THE LOWER 30S. EAST WINDS 10 TO 20 MPH. CHANCE OF PRECIPITATION 90 PERCENT.
.TONIGHT...WIDESPREAD SNOW. TOTAL ACCUMULATION...4 TO 7 INCHES. BRISK WITH BLOWING AND DRIFTING SNOW. LOW IN THE MID TEENS. NORTHEAST WINDS 15 TO 25 MPH...GUSTING TO 30 MPH. CHANCE OF SNOW 80 PERCENT.
.SATURDAY...CLOUDY WITH A CHANCE OF SNOW. HIGH IN THE LOWER 20S. NORTHEAST WINDS 10 TO 20 MPH. CHANCE OF SNOW 50 PERCENT.
.SATURDAY NIGHT...PARTLY CLOUDY. LOW NEAR 10 ABOVE.
RWFS Forecast3Z – 14 Feb 2003 RUN
RWFS – predicted storm totals
QPF (inches) Snowfall (inches)
Storm totals – much of QPF expected to fall as freezing rain
Forecast at Ames (reprocessed)
Forecast at Des Moines (rep.)
The event – 2/14/03, 6am-12pm
AMW: -1oC, BKN
DSM: 0oC, OVC
AMW: 0oC, OVC
DSM: 2oC, -RA
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2/14/03, 11a.m. (17Z)Changes: NWS & RWFS
DES MOINES IA-HENDERSON IL-HENRY IA-JEFFERSON IA-KEOKUK IA-LOUISA IA-
MERCER IL-WARREN IL-WASHINGTON IA-
INCLUDING THE CITIES OF...ALEDO...BURLINGTON...FAIRFIELD...MONMOUTH...
MOUNT PLEASANT...OQUAWKA...SIGOURNEY...WAPELLO...WASHINGTON
1137 AM CST FRI FEB 14 2003
UPDATED TO ADJUST TIMING OF WATCH AND MAKE TWEAKS TO PCPN/TEMPS
...WINTER STORM WARNING LATE THIS AFTERNOON THROUGH SATURDAY...
.THIS AFTERNOON...OCCASIONAL LIGHT RAIN OR DRIZZLE...POSSIBLY MIXED WITH SLEET. PRECIPITATION CHANGING TO ALL SNOW LATE. HIGH IN THE UPPER 30S. EAST WIND 10 TO 20 MPH. CHANCE OF PRECIPITATION 80 PERCENT.
.TONIGHT...SNOW AND BLOWING SNOW. ACCUMULATIONS 3 TO 5 INCHES. WINDY WITH A NORTHEAST WIND 20 TO 30 MPH. LOW IN THE LOWER 20S. CHANCE OF SNOW 90 PERCENT.
.SATURDAY...SNOW TAPERING TO FLURRIES. CONTINUED WINDY WITH BLOWING SNOW. TOTAL ACCUMULATIONS...5 TO 9 INCHES. TEMPERATURES STEADY IN THE MID 20S. NORTHEAST WIND 20 TO 30 MPH...DIMINISHING TO 15 TO 25 MPH. CHANCE OF SNOW 80 PERCENT.
BOONE-MARSHALL-STORY-TAMA-
INCLUDING THE CITIES OF...AMES...BOONE...MARSHALLTOWN
350 PM CST FRI FEB 14 2003
...WINTER STORM WARNING FOR TONIGHT...
.TONIGHT...FREEZING RAIN...RAIN...OR SLEET THIS EVENING…THEN CHANGING TO ALL SNOW...HEAVY AT TIMES. TOTAL ACCUMULATION...4 TO 8
INCHES. WINDY WITH BLOWING AND DRIFTING SNOW. LOW IN THE MID TEENS. NORTHEAST WINDS 15 TO 30 MPH...GUSTING TO 40 MPH.
.SATURDAY...CLOUDY WITH A CHANCE OF SNOW. BRISK. HIGH IN THE LOWER 20S. NORTHEAST WINDS 15 TO 25 MPH...GUSTING TO 30 MPH. CHANCE OF SNOW
50 PERCENT.
The event – 2/14/03, 6pm-12am
AMW: 0oC, OVC
DSM: 1oC, -RA
AMW: -3oC, -SN
DSM: -2oC, +SN
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The event – 2/15/03, 6am-12pm
AMW: -6oC, -SN
DSM: -6oC, +SN
AMW: -7oC, -SN
DSM: -7oC, -SN
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The event – 2/16/03, 6pm
AMW: -7oC, BKN, SNE1803
DSM: -7oC, OVC, SNE2030
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A closer look – important features
Forecast vs. Observed 2/14/03 – 3Z RUN
QPF
SNOW
10.9
Temperature forecast: Ames
-12
-10
-8
-6
-4
-2
0
2
4
3 5 7 9 11 13 15 17 19 21 23 1 3 5 7 9 11 13 15 17 19 21 23 1
Time (UTC)
Tem
p (
°C)
METAR w/o FSL
METAR w/ FSL
AMW_METAR_OB
Precip Type
RWIS w/o FSL
RWIS w/ FSL
AMW_RWIS_OB
noon 6pm mid 6am noon 6pm
Treatment comparison: Ames
6am noon 6pm mid 6am noon 6pm
-20
-15
-10
-5
0
5
10
3 5 7 9 11 13 15 17 19 21 23 1 3 5 7 9 11 13 15 17 19 21 23 1
Time (UTC)
Tem
p (
°C)
METAR w/o FSL
METAR w/ FSL
DSM_METAR_OB
Precip Type
RWIS w/o FSL
RWIS w/ FSL
DSM_RWIS_OB
Temperature forecast: Des Moines
noon 6pm mid 6am noon 6pm
Treatment comparison: Des Moines
6am noon 6pm mid 6am noon 6pm
Heavy Event Summary• RWFS forecast
– Temperature: CRITICAL– Precipitation: location, timing, amount– PRECIPITATION TYPE– Improved later on 2/14, ditto for others
• Treatment– Reasonable given forecast– Matched reality?
• Lessons– Value of COND probability info for precipitation type– Forward error correction (TEMP)