# Presentation: 550259

## Gridded WarningsThe next generation of NWS warning product?

**David Andra**
**Harold Brooks**
**Don Burgess**
**Charles Kerr**
**Jim LaDue**
**Mike Magsig**
**Kiel Ortega**
**Kevin Scharfenberg**
**Travis Smith**
**Greg Stumpf**
**Lou Wicker**

- Gridded WarningsThe next generation of NWS warning product?

**HWT/EWP Participants:**
**Brad Grant**
**Les Lemon**
**Dan Miller**
**Steve Nelson**
**Patrick Burke**
**Liz Quoetone**
**Dave Sharp**
**Steve Zubrick**

## Introduction

- This idea and project are nascent.
- This work must consider many intersecting disciplines:
- Meteorology
- Technology
- Sociology
- Human Factors

## Recap from 1st Wkshp

- Warnings (forecasts) are for _areas_
- Reports (events) are _points_
-  Probability of Detection (POD):
- points within polygons / total points
- False Alarm Ratio (FAR):
- polygons without points / total polygons
- Measures of skill (e.g., CSI) cannot be calculated
- These definitions are inconsistent
- No measure of correct null forecasts
- Warning area sizes are inconsistent
- Verification really affects areas, not points

## Storm versus County

- NWS implementing “Storm-based Warnings” for FY08.
- Characterizes the area to be threatened with (supposedly) no regard to geopolitical boundaries
- But there are still issues

## Area-Based WarningShortcomings

- Storm-based warnings are still _area_ forecasts verified by _point_ events.
- The polygons are just “differently shaped”
- The threat information for the polygon remains “monotonic”
- Each location inside polygon is under exact same threat for the exact same time period
- Each location inside (outside) polygon is given 100% (0%) certainty of event

## Vision

- Warnings and Reports are GRIDDED
- Consistency between forecasts and events
- Consistency with other forecast products
- Allows for growth (added detail)
- Can be aggregated to simpler formats

## OB8.1 WarnGen Limitations

- Allow toggling individual counties off/on
- Automatically clip small portions of counties within an area threshold setting
- Not provide for situations when threats straddle adjacent CWAs
- Not match the edges of adjacent warnings where there was manual or automated county clipping
- Not provide a easily-identifiable preview of the _actual_ polygon until the after the warning was transmitted

## Polygon Slivers

- This storm produced a
- damaging tornado that went
- nearly down the unwarned
- “sliver” that the arrow points to!

## Was this really intended?

## Downstream Warnings

- Very little overlap between adjacent warnings
- Many times, a new polygon is issued only when storm is just about to exit the previous polygon.
- This gives inconsistent lead time to all points within each polygon, with some points getting much less and sometimes zero lead time.

## A

- t=0

## A

- t=0

## No Warning for User B

- A

- B

- t=0

## No Warning for User B

- A

- B

- t=5

## No Warning for User B

- A

- B

- t=10

## No Warning for User B

- A

- B

- t=15

## No Warning for User B

- A

- B

- t=20

## No Warning for User B

- A

- B

- t=25

## No Warning for User B

- A

- B

- t=30

## No Warning for User B

- A

- B

- t=35

## No Warning for User B

- A

- B

- t=40

## No Warning for User B

- A

- B

- t=45

## < 5 min lead time for User B

- A

- B

- t=50

## < 5 min lead time for User B

- A

- B

- t=55

## Area-Based WarningShortcomings

- WarnGen has a motion estimator (“Drag Me To Storm”):
- But, once any vertex in the swath polygon is changed, the storm motion and swath become decoupled
- e.g., if swath is lengthened or shortened, it no longer matches the storm speed and warning time.
- Forecaster has no control over initial swath area provided by WarnGen (point and line motion only)
- Forecaster has no control over motion uncertainty values (speed and direction)
- Therefore, the forecaster can only _guess_ the result of these variables when adjusting the swath polygon

## Hypothesis

- Instead of the forecaster guessing at the swath...
- ...we propose that much more robust warning information can be derived if the forecaster instead determines
- the _initial_ threat area at time=0, along with
- the motion vector, and adds
- motion _uncertainty_ information

## Drivers for growth

- This information used to integrate a more accurate swath
- Continuously advecting threat areas
- Meaningful guidance on time of arrival and time of departure
- Allows for the addition of forecaster uncertainty information (e.g., probabilities)

## Deriving Swath

- time = 0

- _User defines_:
- Initial Threat Area at time=0

## Method

- time = -20

*Use cursor to reposition*
*threat area*

- _User_:
- Drag Me To Storm

## Method

- time = -20

*Use cursor to reposition*
*threat area*

- _User_:
- Drag Me To Storm

## Method

- time = 0, 15, 30, 45, 60

- Motion Vector Calculated

## Method

- Threat Area Advected

## Method

- _User Defines_:
- Motion Uncertainty

- ± 5 m s-1  ±15°

## Method

- Speed uncertainty stretches threat along motion vector

- ± 5 m s-1  ±15°

## Method

- Direction uncertainty stretches threat perpendicular to motion vector

- ± 5 m s-1  ±15°

## Method

- Integrated threat area across warning time provides swath

## Swath properties

- Greater (lesser) motion uncertainty leads to wider (more narrow) swath
- Larger (smaller) initial threat area leads to wider (more narrow) swath
- Neither of these factors can be controlled in WarnGen.
- Swaths are truly independent of geopolitical boundaries.

## Advecting threat

- As threat area advects downstream, the area affects different grid points at different times.
- For each grid point in the warning, the intersection of the threat area over time provides information about
- time of arrival
- time of departure

## Advecting Threat Area

**x**

- t=0

- A

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**Warn?**

**Time ******

- NOTE:
- No warning (yet)
- For User B

## Advecting Threat Area

**x**

- A

- t=5

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

- NOTE:
- > 40 min lead time
- For User B

## Advecting Threat Area

**x**

- A

- t=10

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

## Advecting Threat Area

**x**

- A

- t=15

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

## Advecting Threat Area

**x**

- A

- t=20

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

## Advecting Threat Area

**x**

- A

- t=25

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

## Advecting Threat Area

**x**

- A

- t=30

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

## Advecting Threat Area

**x**

- A

- t=35

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

- NOTE:
- Point A already
- In “all clear”

## Advecting Threat Area

**x**

- A

- t=40

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

- NOTE:
- Point A already
- In “all clear”

## Advecting Threat Area

**x**

- A

- t=35

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

- NOTE:
- Point A already
- In “all clear”

## Advecting Threat Area

**x**

- A

- t=50

- B

- A

- B

- 1

- 0

**TOA**

**TOD**

**TOD**

**TOA**

**Warn?**

**Time ******

- NOTE:
- Point A already
- In “all clear”

## Threat Type

- Each severe weather type can be depicted on separate grids
- Hail
- Wind
- Tornado
- Lightning
- Threat subtypes could also be depicted
- Hail size
- Wind speed
- Lightning Density

## Redefining threat areas

- As an analog to the Severe Weather Statement (an update to an issued warning)...
- Regularly redefine threat areas in time intervals (e.g., every 15 min), or when threat begins to deviate from the forecast
- This is a continually evolving process

## A Real Case

- We won’t tell you where or when!

## How is grid produced?

- Isolate current threat area at time=0

## How is grid produced?

- Input:
- Warning type
- Hail
- Wind
- Tornado
- Warning length
- Motion vector
- speed
- direction
- Motion uncertainty
- Speed
- Direction

## Result is warning swath

## WDSSII Rotation Tracks

**Summary of**
**entire event**

## WDSSII Rotation Tracks

**Summary of**
**entire event**

## NOTE:
Very little overlap in some warnings
Some areas never warned
Very few polygons seem to depict the actual swath

- NOTE:
- Very little overlap in some warnings
- Some areas never warned
- Very few polygons seem to depict the actual swath

- NWS Tornado Warnings

**Summary of**
**entire event**

## HWT Gridded

- Tornado Warnings

**Summary of**
**entire event**

## Probabilities

- This method allows for the inclusion of probabilistic information:
- As threat area grows with time, the probability that a grid point will receive severe weather will naturally drop.
- We allow the user to define their initial uncertainty, as well as forecasted uncertainty
- The forecast probabilities are multiplied with the probabilities derived from motion uncertainty.

## Probabilistic Swath

*>50%*

*>25%*

*>10%*

*>0%*

- A

- B

## Probabilistic Swath

*>50%*

*>25%*

*>10%*

*>0%*

- A

- B

## Probabilistic Swath

*>50%*

*>25%*

*>10%*

*>0%*

- A

- B

## Does this look familiar?

## Probabilistic Info

- For each grid point in the warning, the intersection of the threat area over time provides time of arrival and time of departure information, _**and**_** probabilities of the event**.

- A

- B

- 1

- 0

**Warn?**

**Time ******

## Adding probabilities

- Input:
- Initial Probability
- Peak Probability
- Time of Peak Probability
- Decay Method
- By Time
- By Area
- Time and Area

## Result is probabilistic swath

## Sociology

- FAQ:  “Will the public understand probabilistic warnings?”
- Answer:
- 	The Public ≠

*A monolithic mass with equal needs*

## Sociology

- FAQ:  “Will the public understand probabilistic warnings?”
- Answer:
- 	The Public =

*Spectrum of Warning Users with differing needs*

## Sociology

- Risk = Hazard * Exposure

**e.g., Tornado, wind, hail, hazardous materials**

**How to account for this?**

## Sociology

- The NWS cannot anticipate everyone’s exposure
- The NWS can make hazard warnings more adaptable to those that do know their own exposure
- Adaptive warnings allow users to set their threshold criteria
- Adaptive warnings need to exploit digital media

## How this gridded data can be used

- Any high resolution grid (space and time) can be aggregated into simpler and simpler formats across all levels of sophistication
- Even right down to the original county-based warnings (needed for NOAA All-Hazards Radio, some tv crawl software).
- The more-deatiled information can allow users to adapt, and third-party vendors to provide better information to their clients.
- GIS

## Which counties get warned?

## Which counties get warned?

## Which counties get warned?

## But....which users get warned?

- C

- B

- A

- E

- D

## Human Factors

- Tested concept within the HWT/EWP this spring with visiting WFO forecasters, WDTB trainers, and CIMMS/NSSL/MDL scientists.
- Feedback on technological improvements
- Feedback on workload management
- For example, worked best with this team set-up:
- Tech interface (per sector)
- Storm interrogation (per sector)
- Near-storm environment

## Science Questions

- How do we define the initial threat area?
- What do these probabilities mean?
- How do we calibrate the probabilities?
- Storm-type classification study

## Science Questions

- Verification of grids (see Brooks’ 1st Workshop talk)
- Storm reports are still points
- “Splat”?
- High density verification (e.g., SHAVE)
- Probabilistic verification (e.g., radar)
- Will need new metrics!

## Future Considerations

- This is an opportunity, not necessarily “the solution”
- Next-generation warning tool
- C*STAR proposal
- Must be a multi-disciplinary effort

## Questions?

- Greg.Stumpf@noaa.gov
- NWS Meteorological Development Laboratory
- Decision Assistance Branch

## Bonus Slides

## Multiple Threats

- Can provide TOA and TOD for multiple threats affecting same areas (e.g., training storms)

## “Open-ended” warnings

- “Open-ended” warnings

- An “open-ended” warnings is one with a very long expiration time
- Can eventually merge upscale to watch and convective outlook probabilities.
- “Warn on Forecast” can help bridge the gap between these scales.

- A

- B

**1h**

**4h**