Forecaster Awareness and Expressing Uncertainty in Banded Snowfall
Transcript of Forecaster Awareness and Expressing Uncertainty in Banded Snowfall
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Maintaining Situational Awareness and Communicating Uncertainty Associated with Banded Snowfall
Matthew A. Dux*Philip N. Schumacher*
Ray Wolf+
* National Weather Service – Sioux Falls, SD+ National Weather Service – Quad Cities, IA/IL
October 21, 2015, National Weather Association
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Mesoscale Heavy Snow Bands
Meteorological Challenges:
- High Snowfall Gradients- Significant Snowfall Rates- Rapid and Unpredictable Development- Model Ingredient Variance
NAM – 24 Hour Forecast
Actual Snowfall
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Mesoscale Heavy Snow Bands
Impact/Messaging Challenges
- Short “Lead Time” to Warning- Less Planning Time by Partners
- Can Produce Significant Impacts
- Difficult to Message Uncertainty- Changing Forecast Public Confusion
Many of these events are considered “surprises” by the public.
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Changing Concept of Awareness/Messaging
Prediction and Forecast of Heavy Mesoscale Banded Snow Can Be Similar to That of Summer-Time Convection
Similarities:
- Conceptually Modeled Days in Advance- Highly Depend on Mesoscale Details- Rapidly Evolve as Event Approaches- Share a Localized High-Impact Potential
Why Not Model the Forecast and Messaging Process in Similar Fashions?
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Outlook Stage
Alert Stage
Watch Stage
Warning Stage
Communication/Forecast Model12 to 24+ Hours Ahead
- Focus on Potential- Highlight Broad Area- May Already Have Ongoing
Watch
12 to 24+ Hours AheadFocus on Potential
6 to 12 Hours AheadEvolve the
Forecast
0 to 6 Hours AheadKey on the
Details
Event OngoingPush the
Message
Increased Accuracy
& Certainty
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Example Case
Typical Mid-Winter Snow Event for Northern Plains
Expectations of Widespread Light Snow 3” or Less
Arrival of Snow Late Afternoon/Evening
Models Showing Signs of Banded Precipitation
Huron
Alexandria
Marshall
Chamberlain
Aberdeen
Yankton
Sioux City
Sioux Falls
Brookings
Valentine
Pierre
Watertown
Storm Lake
36 Hour Snow Forecast
Timeline: 36 Hours in Advance
1”- 3”
1”- 3”
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Outlook Stage Timeline: 12 to 24 Hours Prior
Forecast Awareness
- Be Aware of Model Trends
- Address Concerns in the AFD
- WWA in Effect?
Event Messaging
- Focus on Potential
- Highlight Broad Area
- Address Uncertainty
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Alert Stage Timeline: 6 to 12 Hours Prior
Forecast Awareness- In Depth Examination
of Environment
- Use Probabilities to Inspect Heavy Snow Potential
- Change in Headlines Needed?
- Adjust Staffing?
Event Messaging- Narrow Down Risk of
Heavy Snow Area
- Begin to Stress Potential Impacts
- Address Uncertainty
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Watch Stage Timeline: 0 to 6 Hours Prior
Forecast Awareness- Heavy Focus on
Observations
- Begin Mesoscale Interrogation
- Write a Mesoscale Discussion in AFD
- Headline/Staffing Changes?
Event Messaging- Narrow Risk of Heavy
Snow Area
- Begin to Stress Potential Impacts
- Change Tone of Message
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Warning Stage Timeline: Event Ongoing
Forecast Awareness
- Focusing on Incoming Information
- Gather Reports
- Continual Weather Watch and Forecast Adjustments
- Warning Already Issued
- Staffing Adjusted
Strong Emphasis on Social Media and Communications
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Warning Stage Timeline: Event Ongoing
What Types of Messages:
- Live Traffic Cameras
- 30 Second Human Video Updates
- Animated Radar GIFS to Show Motion
- Public Service Announcements
Event Messaging
- Heavy Focus on Impacts
- Continual Flow of Information
- Express Certainty in the Message
- Provide Outlooks into the Night
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Future WorkNWS Sioux Falls Will be Participating:Experimental Probabilistic Snowfall Forecast Products
With Goals:
1.) Better defining categorical term usage for “Low, Moderate, High” based on forecast probabilities.
2.) Targeting Communication Based on NWS Partners
Example from WFO - Sterling
Minimum Most Likely Maximum
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October 21, 2015, National Weather Association Comments: @matthewdux #nwas15
Important Questions for the Future
How Do We Advertise the Worst Case Snow Scenario? Can We?
How Do You Message Extreme Events Without Leading to “Forecast Hype”?
Does “One-Size-Fits-All” Messaging Work? Does Message Need to Vary by User (Public/Schools/Emergency Management/DOT)?
Let’s Keep the Conversation Going!
Contact: [email protected]@MatthewDux