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


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.


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?


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


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”


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


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


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


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


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


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


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

forecaster awareness and expressing uncertainty in banded snowfall

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