Winter Storm Impact Index (WSII)
Andy Nash, NOAA/NWS Burlington
Michael Muccilli, NOAA/NWS Burlington
Nathan Foster, NOAA/NWS Las Vegas
WFO BGM Sub-Regional Workshop
It’s an impact severity index…
2
2015 WFO BGM Sub-Regional Workshop
What/Why?
3
 NDFD + GIS Winter Index
 Uses our own Forecast Data
 Non-meteorological data-sets opens up many
possibilities
 IDSS is growing focus of NWS (winter weather is
high impact)
 Not every 6” snowstorm is the same
 Goes Beyond “Watch”, “Warning”, “Advisory”
 What does a Winter Storm Warning mean?
2015 WFO BGM Sub-Regional Workshop
The Goal: Weather Ready Nation
4
 Deliver Impact Based/Severity Weather
Information
 Enhance Decision Support Services
 Simplify Hazard Messaging
2015 WFO BGM Sub-Regional Workshop
Identified Service Gap
5
 Current WWA Paradigm – Black & White
 Does Forecast Exceed Threshold? (Yes/No)
 Mother Nature – Shades Of Gray
 4 inches of wet snow vs. 8 inches of
upslope fluff
2015 WFO BGM Sub-Regional Workshop
Example
6
2015 WFO BGM Sub-Regional Workshop
Example
7
2015 WFO BGM Sub-Regional Workshop
What Can It Do?
8
 Able to show Severity
 Where is the Worst?
 Better convey levels of warning
 What kind of storm? Run of the mill or
something crippling?
 Warning vs. “Super Warning”
 May Catch things you’re not thinking of
 Snow Loading?
2015 WFO BGM Sub-Regional Workshop
Risk Is Severity/Impact Based
9
 Historic/Rare/Common/Very Common
2015 WFO BGM Sub-Regional Workshop
Winter Storm Impact Index (WSII) Project
10
 Began Winter 2013-2014
 Posting to a password-restricted web page
 Updated Hourly
 Running in an ArcGIS environment
 Enlisted a few offices to review output and
provide comments/verification
2015 WFO BGM Sub-Regional Workshop
Meteorological Inputs
11
 Total Snowfall
 Snowfall Accumulation Rate
 Snow-Liquid Ratio
 Blowing/Drifting Snow
 Ice Accumulation
 *Flash Freeze (NEW)
 **Snow Loading (In progress)
2015 WFO BGM Sub-Regional Workshop
Non-Meteorological Inputs
12
 Land Use / Land Cover Type
 Climatology (Resources available)
 ***Population (Future)
 ***Time of Day / Day of Week (Future)
2015 WFO BGM Sub-Regional Workshop
Snow
Amount
Snow
Accum
Rate
Components
13
From NDFD
Normalized Based on Climatology
Blowing
Snow
Snow
Loading
Derived from NDFD/NOHRSC
Normalized Based on Land Cover/Use
Flash
Freeze
Ice / SPIA
NonForecast
Same as Experimental Product in CR/SR
(Wind/Ice Accumulation)
Land Use, Climatology, Forest/Plains Cover
2015 WFO BGM Sub-Regional Workshop
Climatology
14
2015 WFO BGM Sub-Regional Workshop
Normalizing for Climatology
15
2015 WFO BGM Sub-Regional Workshop
Normalizing for Climatology
16
2015 WFO BGM Sub-Regional Workshop
Verification Input From…
17
2015 WFO BGM Sub-Regional Workshop
Verification
18
 2013/2014- Majority +/- 1 Category Difference
 2013/2014- 0.77 correlation (assumes perfect
forecasts)
 2014/2015- WSII Slight High Bias
 2014/2015- 56% were +/- 1 Category
 2014/2015- Events Skewed Larger
2015 WFO BGM Sub-Regional Workshop
Other Efforts – Grand Rapids
19
Being used in
operational IDSS
briefings
Considerable Customer
Feedback (positive
and helped to
evolve/fine tune the
service)
2015 WFO BGM Sub-Regional Workshop
Similar Methods/Results
20
2015 WFO BGM Sub-Regional Workshop
Benefits
21

Allows Forecasters to Concentrate on Forecast

Map-Based (Improves Granularity and levels of impact)

Ability to Show Details beyond the current “WWA” Map

Ties into the HazSimp Project

Can leverage information from the Impacts Catalog Project

Differing Severity/Impacts within same Warning

Possible Concerns Outside of Initial Forecast


Snow-Loading on Trees/Roofs
Push Model Data through the Algorithms

Real Time Ensemble of Risk/Potential Impact
2015 WFO BGM Sub-Regional Workshop
Weaknesses
22
 Is built upon a level of subjectivity
 Only as good as the forecast
 Not a forecast of specific impacts (i.e. closing
schools)
2015 WFO BGM Sub-Regional Workshop
Next Steps

Determine how to “model” other factors
 Population, timing (rush hour vs. overnight vs.
weekend)

Conduct Usability Studies
 Actions to be taken greatly different for ice vs.
blowing snow, even if both show up “Red” on the


23
Map
Better temporal resolution (currently limited by NDFD
6 Hour)
National Goal for Winter Weather Program (test
offices)
2015 WFO BGM Sub-Regional Workshop
Additional Materials
24
 More Info on WSII:
 http://goo.gl/I1UCTm
2015 WFO BGM Sub-Regional Workshop
25
Thank You!
Questions?
2015 WFO BGM Sub-Regional Workshop
26
Extra slides / cases
2015 WFO BGM Sub-Regional Workshop
Atlanta “Carmageddon”
27
2015 WFO BGM Sub-Regional Workshop
SE Ice Storm 02/12/14
28
2015 WFO BGM Sub-Regional Workshop
Blizzard of 2015 – DSS Example
29
Potential Level of Impacts (Experimental)
Depicts potential societal
disruption due to
combination of all aspects
of a winter storm (Total
snow accumulation,
blowing/ drifting snow &
rate of snow accumulation)
Minor: minor disruption to
those not prepared. Recovery
time less than 1 day.
Moderate: definite impacts to
primarily those not prepared.
Recovery time about a day.
Major: Impacts to even those
who prepared. Recovery time up
to several days
Crippling: Widespread
significant impacts. Recovery
time of many days to a week.
2015 WFO BGM Sub-Regional Workshop