Forecaster Awareness and Expressing Uncertainty in Banded Snowfall
Transcript of Forecaster Awareness and Expressing Uncertainty in Banded Snowfall
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
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
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.
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?
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
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”
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
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
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
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
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
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
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