Gis and drought applications
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GIS and Drought Applications. Keith Stellman Senior Hydrologist Lower Mississippi River Forecast Center Slidell, LA. Outline. Overview of CPC products History/Background info/Examples Validity of the Data Gridded Normals? Compositing Possibilities. Normal CPC Drought Graphics.

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GIS and Drought Applications

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Gis and drought applications

GIS and Drought Applications

Keith Stellman

Senior Hydrologist

Lower Mississippi River Forecast Center

Slidell, LA



  • Overview of CPC products

  • History/Background info/Examples

  • Validity of the Data

  • Gridded Normals?

  • Compositing

  • Possibilities

Normal cpc drought graphics

Normal CPC Drought Graphics

Cpc graphics cont

CPC Graphics Cont’

Cpc graphics cont1

CPC Graphics Cont.

Overview history

Overview / History

  • Stage III

    • 4 x 4 km resolution

    • Gridded PRISM data


    • Computed daily average from PRISM data

    • Posted output images to web


    • Converted prism grids to HRAP projection in GIS

    • Computed monthly images on 1st of the month

Cpc percent of normal

CPC Percent of Normal

Rfc graphics 1 month stage iii

RFC Graphics1 Month Stage III

Rfc graphics

RFC Graphics

Wgrfc abrfc ohrfc examples


Detailed rfc images

Detailed RFC Images

Details details

Details, Details

  • County to county rainfall surplus/deficits

  • Grid to grid comparisons

  • Water supply issues from county to county

Rfc observed analysis

RFC Observed Analysis

  • Daily rain gage analysis in GIS using IDW method of interpolation on 4x4 km grid

  • Grids are archived

  • Grids are summed for monthly totals

  • Rain gage analysis can then be used for percent of normal

Observed analysis 1 month totals

Observed Analysis1 Month Totals

Lmrfc observed analysis

LMRFC Observed Analysis




How accurate is the data 1 month totals for october 2002

How Accurate is the Data?1 month totals for October 2002

What is normal

What is Normal?

  • PRISM (Parameter-elevation Regressions on Independent Slopes Model)

  • Knowledge-based system using point data, digital elevation model, & other spatial data sets

  • Generates gridded estimates of climatic parameters (such as precipitation & temperature)

  • Accounts for rain shadows, inversions, coastal proximity, and others

Orographic enhancement

Orographic Enhancement

Prism maps


Where can i find prism data

Where Can I Find PRISM Data?

  • Digital via Web Sites



    Contact Info:

    Christopher Daly


    Spatial Climate Analysis Service

    Oregon State University

    Corvallis, Oregon

How do we get the results

How do we get the results

  • PRISM data is on a 4x4 km grid

  • Stage III data is on a 4x4 km grid

  • ((((StageIII-Prism)/Prism)+1)*100) = % of Normal Precipitation

  • GIS Software does grid calculations and exports result as a JPEG

  • Program is automatically run on 1st of the month for previous 1,2,3 and 6 months

Who is doing what

Who is doing what?


    • Utilize gridded datasets

      • CBRFC lists under water supply in form of pdf document


    • Utilize observed datasets on larger scale

      • MBRFC uses pdf document under water supply



  • Southern Region RFC Web Team

    • Goal is to composite graphics with levels of zoom

  • Each SR RFC (SERFC,WGRFC,LMRFC,ABRFC) sends daily StageIII totals to WGRFC

  • Data is summed into monthly totals and compared to PRISM data

Coming very soon

Coming Very Soon!

Future possibilities

Future Possibilities

  • Providing each monthly calculation as a shapefile or ascii grid

  • Incorporating more than SR RFC’s into the datasets

  • Utilizing gage only datasets across SR

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