**National Weather Service**

**Statement of Need**

**WSR-88D Data Resolution And Coverage Enhancements**

Approved: Date:

Gregory A. Mandt

Director, Office of Climate, Water

and Weather Services.

NWS Statement of Need (SON)

**1. Title** WSR-88D Data Resolution And Coverage Enhancements

**2. Sponsor** Greg Cate, W/OST11, 405.366.9243 x3510

**3. Description**

v.  The NWS needs increased observational data density, both spatial and
    temporal, to improve tornado and other severe weather warning
    performance. A technological opportunity exists to address this
    need. With the deployment of Open Systems Radar Data Acquisition
    (ORDA), the WSR-88D will be capable of providing 2 degree angular
    resolution and 3 km range resolution, an 8X increase in spatial
    resolution for reflectivity, and 2X for velocity. Additional
    opportunity would be for velocity data during low tilt surveillance
    scans, and a velocity data maximum range of 354 km, measures that
    would increase temporal resolution and velocity coverage.

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b.  This observational data need was identified by a special NWS teams
    chartered to recommend ways to improve severe weather warning
    performance, by the NWS/OST Science Planning Branch in its
    development of the NWS Science and Technology Infusion Plan, and by
    scientific analyses at laboratories such as National Severe Storms
    Laboratory. The ORDA technical opportunity was identified by NWS
    personnel knowledgeable of WSR-88D performance.

**4. Strategic Plan Element**

-   NOAA Strategic Goal 3: Serve Society=s Needs for Weather and Water
    Information

-   NWS Tornado Warning Performance Measures Targets for 2007

-   Probability of Detection: 0.74

-   Lead Time: 15 min

-   False Alarm Rate 0.64

**5. Mission Need Statement**

n.  [Authority]{.underline}

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a.  [Description]{.underline}

> The NWS requires the best possible information on pre-storm
> environments and developing thunderstorms to support tornado, severe
> thunderstorm and flash flood warnings. Weather radars have been
> acknowledged as a primary, critical source of information to support
> NWS tornado and other severe weather operations, from the WSR-57 to
> the current WSR-88D.

c.  [Existing Shortfalls]{.underline}

> The WSR-88D has limitations in its support to severe weather
> operations.

-   **Data Coverage**

> Currently, the WSR-88D provides Doppler data for tornadic circulation
> analyses only to 230 km. When storms move out of this range, or are
> moving into a WFO=s CWA from outside this range, the WFO forecasters
> must rely on data from neighboring WSR-88D units. Problems arise when
> a relevant neighboring WSR-88D unit is out of service or is farther
> away from the storm, and when there is no surrounding WSR-88D
> coverage.
>
> Extending Doppler processing to the end of the second trip would
> increase the range of velocity data from 230 km to as much as 354 km,
> depending on the Pulse Repetition Frequency in use.

-   **Data Timeliness**

> For the first two elevation angles of each WSR-88D volume scan, a
> surveillance cut is made that provides only reflectivity data to the
> forecaster. At each of these angles, the surveillance cut is followed
> by a Doppler cut, a delay of about 20 seconds at each angle. Doppler
> data are collected during the earlier surveillance cuts, but currently
> are not made available to forecasters.
>
> Providing Doppler data collected during surveillance scans would
> provide more timely velocity information to forecasters, and extend
> the velocity information range at the lower elevation angles to 460
> km.

-   **Data Spatial Resolution**

> Tornadic vortex signatures are small, and require high spatial
> resolution data for optimum analysis. The WSR-88D provides
> reflectivity data at 1 km by 1 degree, and velocity data at 1/4 km by
> 1 degree spatial resolution. At longer ranges from the radar, the
> resultant spatial resolution is not sufficient to identify the
> circulation patterns of many tornadoes, especially smaller ones.
>
> Super Resolution data would provide reflectivity data radial
> resolution of 1/4 km, and 0.5^0^ angular resolution for both
> reflectivity and velocity data. Combined, these two enhancements would
> improve tornado detection accuracy and effective range.

d.  [Schedule]{.underline}

> This capability is need as soon as it can be provided. The three
> NEXRAD agencies (DOC, DOT, DOD) have set WSR-88D Build 7 (deployment
> in April 2005) as the goal for this package of ORDA enhancements.

e.  [Mission Importance]{.underline}

> High. Improving severe weather warnings is one of the highest NWS and
> NOAA priorities, as reflected in the Government Performance and
> Results Act goals for NWS tornado and flash flood warning performance.

**6. Non-Program Alternatives**

> Non-program alternatives, e.g. procedural / training / policy changes,
> are not applicable means to address the need for better data to
> improve severe weather operations.

**7. Potential Program Alternatives**

> Other programs, (e.g., Satellite, Wind Profiler, Surface Observations)
> cannot provide the types of data or the temporal and spatial
> resolutions that radar can for severe weather warnings improvements.

**8. Constraints**

> Availability of Super Resolution WSR-88D data will likely lead to
> consideration of central collection and distribution of Super
> Resolution Level II data, and Level III products derived from the
> data. Potential impacts on NWS communications and processing
> infrastructure need to be analyzed and planned for.
>
> There are no additional known or suspected key boundary conditions and
> operational environments (e.g., logistics support, security,
> operational environment, FTEs) that may impact implementing the use of
> Super Resolution data.

**9. Cross Line Office Potential Designator**

> Independent \-- No potential for other LO use of systems interface or
> for cross-LO development or procurement.

**10. Review and Analyses Statement**

Lead Analyst:

Participating Office(s):

Summary of Review and Analyses:

**11. Disposition**

**12. Attachments**

b.  Endorsements

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b.  Diagram Relating 0.5^0^ Data to Tornadic Circulations

c.  Map of Increased Tornado Detection Potential With 0.5^0^ Data

d.  Examples of Improved Severe Weather Weak Echo Region Detection

e.  Example of Better Tornadic Circulation Identification

Attachment A - Endorsements

f.  **(2002) NWS Corporate Board Action Item: ORDA Impact on Tornado
    Warning Performance**

> *One of three ORDA potential capabilities:*

-   *Increase data angular resolution to 0.5^0^ from 1^0^, increase
    reflectivity radial resolution to 0.25 km from 1 km*

> *Projected Impact*

-   *Increase positive lead time tornado detection accuracy to 75% from
    current 50%*

-   *Increase average lead time to 14 min from current 11 min*

b\. **(2003) National Severe Storms Laboratory: AExperimental
High-Resolution WSR-88D Measurements in Severe Storms,@ Final Report**

> Referring to 0.5^0^ and 1/4 km data:
>
> *At all ranges, high-resolution data did a much better job in
> depicting severe storm characteristics. Mean rotational velocities for
> mesocyclones \... were up to 15-20% stronger \... . Similarly, Doppler
> velocity differences across tornado and tornadic vortex signatures
> were up to 15-20% stronger \... . At ranges greater than 100 km,
> high-resolution reflectivity displays revealed severe storm
> signatures, such as bounded weak echo regions and hook echoes, which
> were not readily apparent on current-resolution displays. These
> findings hold great promise for helping to improve severe storm
> warning capabilities for National Weather Service forecast offices.*

Attachment B - Diagram Relating 0.5^0^ Data to Tornadic Circulations

Attachment C - Map of Increased Tornado Detection Potential With 0.5^0^
Data

Attachment D - Examples of Improved Severe Weather Weak Echo Region
Detection![](media/image3.wmf){width="6.503472222222222in"
height="5.563888888888889in"}

Current Resolution Super
Resolution![](media/image4.png){width="6.502083333333333in"
height="6.963888888888889in"}

Attachment E - Example of Better Tornadic Circulation Identification

Current Resolution Super
Resolution![](media/image5.png){width="6.503472222222222in"
height="5.113888888888889in"}