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Analysis of Radar-Rain Rate Relations During the Southeast Texas Flood Event of 18 April 2009 Steve Vasiloff, NOAA/National Severe Storms Laboratory Jeffrey.

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Presentation on theme: "Analysis of Radar-Rain Rate Relations During the Southeast Texas Flood Event of 18 April 2009 Steve Vasiloff, NOAA/National Severe Storms Laboratory Jeffrey."— Presentation transcript:

1 Analysis of Radar-Rain Rate Relations During the Southeast Texas Flood Event of 18 April 2009 Steve Vasiloff, NOAA/National Severe Storms Laboratory Jeffrey Lindner, Harris County Flood Control District Lance Wood, NOAA/National Weather Service, Houston 2010 National Flood Workshop, Houston, TX

2 Outline Radar reflectivity rainrate (Z-R) relations Radar resolution impacts Heavy rain and wind impacts on gauges 5 and 1-min radar and gauge comparisons Examples of radar and gauge uncertainties Concluding remarks

3 Harris County Flood Control District gauges

4 NSSL Q2 system Next-generation quantitative precipitation estimation (QPE) system 1 km resolution CONUS every 5 min Multisensor products Dynamic Z-R Q2 radar-based used as base field for West Gulf RFC operations (with local gauge correction) Other RFCs “cut and paste” Q2 into their systems

5 Q2 main page

6 TS Nicole example Q2 Z-Rs

7 TS Nicole example Q2 reflectivity

8 Radar reflectivity-rainrate relations

9 Radar data resolution

10 KHGX super-res

11 Q2 1-km res 180 * * 130

12 5-min Q2 dBZ; gauge data convective & tropical Z-Rs 5 min data are aggregated from 1 st to 5 th min past top of the hour Gauge Convective QPE Tropical QPE Q2 5-min reflectivity

13 5-min Q2 dBZ & gauge data convective & tropical Z-Rs Q2 5-min reflectivity Gauge Hi-res reflectivity

14 1-min hi-res KHGX & gauge Gauge Hi-res reflectivity

15 5-min Q2 dBZ; gauge data convective & tropical Z-Rs 5 min data are aggregated from 1 st to 5 th min past top of the hour Q2 5-min reflectivity Gauge Convective QPE Tropical QPE

16 1-min hi-res KHGX & gauge Gauge Hi-res reflectivity

17 Radar clutter filter “zero isodop” line

18 Radar clutter filtering Radar echo minima due to filter?

19 5 min sampling – constant rainrate for QPE Echo motion

20 Gauge networks

21

22 Summary Urban FF warnings require hi-res data 1 –min data too noisy? High rainrates and winds reduce confidence in gauge data – difficult to quantify undercatch – 15-30%???? Clutter filter causes uncertainty in radar data Need better gauge-radar metadata – Know which gauges are in clutter, zero isodop Gauge QC is an ongoing issue

23 Q2 future Higher resolution – 2.5 min radar (NEXGEN) – min gauge MADIS/additional gauge networks (HCFCD) Gauge quality control algorithm – Using temporal analysis of radar-gauge bias – Spatial checks – Gauge Quality Index


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