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Gridded Warnings The next generation of NWS warning product?

Gridded Warnings The next generation of NWS warning product?. Contributions: David Andra Harold Brooks Don Burgess Charles Kerr Jim LaDue Mike Magsig Kiel Ortega Kevin Scharfenberg Travis Smith Greg Stumpf Lou Wicker. HWT/EWP Participants: Brad Grant Les Lemon Dan Miller

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Gridded Warnings The next generation of NWS warning product?

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  1. Gridded WarningsThe next generation of NWS warning product? Contributions: David Andra Harold Brooks Don Burgess Charles Kerr Jim LaDue Mike Magsig Kiel Ortega Kevin Scharfenberg Travis Smith Greg Stumpf Lou Wicker HWT/EWP Participants: Brad Grant Les Lemon Dan Miller Steve Nelson Patrick Burke Liz Quoetone Dave Sharp Steve Zubrick

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

  3. 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

  4. 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

  5. Area-Based WarningShortcomings • 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

  6. 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

  7. 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

  8. Polygon Slivers This storm produced a damaging tornado that went nearly down the unwarned “sliver” that the arrow points to!

  9. Was this really intended?

  10. 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.

  11. A t=0

  12. A t=0

  13. No Warning for User B A B t=0

  14. No Warning for User B A B t=5

  15. No Warning for User B A B t=10

  16. No Warning for User B A B t=15

  17. No Warning for User B A B t=20

  18. No Warning for User B A B t=25

  19. No Warning for User B A B t=30

  20. No Warning for User B A B t=35

  21. No Warning for User B A B t=40

  22. No Warning for User B A B t=45

  23. < 5 min lead time for User B A B t=50

  24. < 5 min lead time for User B A B t=55

  25. Area-Based WarningShortcomings • 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

  26. 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

  27. 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)

  28. Deriving Swath User defines: Initial Threat Area at time=0 time = 0

  29. Method User: Drag Me To Storm Use cursor to reposition threat area time = -20

  30. Method User: Drag Me To Storm Use cursor to reposition threat area time = -20

  31. Method Motion Vector Calculated time = 0, 15, 30, 45, 60

  32. Method Threat Area Advected

  33. Method User Defines: Motion Uncertainty ± 5 m s-1 ±15°

  34. Method Speed uncertainty stretches threat along motion vector ± 5 m s-1 ±15°

  35. Method Direction uncertainty stretches threat perpendicular to motion vector ± 5 m s-1 ±15°

  36. Method Integrated threat area across warning time provides swath

  37. 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.

  38. 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

  39. Advecting Threat Area x A B t=0 TOA TOD NOTE: No warning (yet) For User B 1 Warn? 0 A B Time 

  40. Advecting Threat Area x A B t=5 TOA TOD TOA TOD NOTE: > 40 min lead time For User B 1 Warn? 0 A B Time 

  41. Advecting Threat Area x A B t=10 TOA TOD TOA TOD 1 Warn? 0 A B Time 

  42. Advecting Threat Area x A B t=15 TOA TOD TOA TOD 1 Warn? 0 A B Time 

  43. Advecting Threat Area x A B t=20 TOA TOD TOA TOD 1 Warn? 0 A B Time 

  44. Advecting Threat Area x A B t=25 TOA TOD TOA TOD 1 Warn? 0 A B Time 

  45. Advecting Threat Area x A B t=30 TOA TOD TOA TOD 1 Warn? 0 A B Time 

  46. Advecting Threat Area x A B t=35 TOA TOD TOA TOD NOTE: Point A already In “all clear” 1 Warn? 0 A B Time 

  47. Advecting Threat Area x A B t=40 TOA TOD TOA TOD NOTE: Point A already In “all clear” 1 Warn? 0 A B Time 

  48. Advecting Threat Area x A B t=35 TOA TOD TOA TOD NOTE: Point A already In “all clear” 1 Warn? 0 A B Time 

  49. Advecting Threat Area x A B t=50 TOA TOD TOA TOD NOTE: Point A already In “all clear” 1 Warn? 0 A B Time 

  50. 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

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