Usage of Satellite Precipitation Estimates by

HAS Forecasters at the West Gulf RFC

Greg StoryNWS/WGRFC HAS Forecaster

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Introduction

The WGRFC needs accurate mean areal precipitation in real time to make good flood forecasts.

The WGRFC uses the Multisensor Precipitation Estimator (MPE) program to derive mean areal precipitation

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Introduction (cont.)

Problem: On the map on the left, we are responsible for deriving basin averaged areal precipitation for every location inside the red outline. As you can see, this is outside the range of the WSR-88D, and there are roughly 15 real-time rain gauges over this region. 3

Introduction (cont.)

Problem: The HAS forecasters at the WGRFC must arrive at a 24 hour rainfall estimate for Mexican basins every day.

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Satellite QPE is used where there is no dependable radar estimates or rain gauge data

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Introduction (cont.)

The primary source of rainfall for this region is the satellite precipitation estimates (the hydroestimator) from NESDIS.

Problem: It is difficult to determine how accurate these estimates are!

Raw radar estimate from MPE program6

Incorporating Satellite Estimates

Multi-sensor Mosaic Multi-sensor Mosaic and Satellite Estimates

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Satellite Precipitation Estimates

The WGRFC uses the Hydro-Estimator, which is NESDIS’ operational algorithm for estimating rainfall rate from infrared (IR) window.

Estimates arrive via AWIPS and can be used in MPE (with or without local biasing).

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Satellite Precipitation Estimates

IR Satellite Image SPE from Hydroestimator9

In MPE we use a polygon edit to replace the default field with

any other field (like SPE)

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We can insert Satellite QPE using polygons and it becomes our “best estimate field” there

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There are times when the SPE’s are not good

Note the wave affects

of the SPE’s

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Lack of SPE’s when there are lightning strikes

Note the lightning over

northeast New Mexico

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Lack of SPE’s when there are lightning strikes

The lightning and associated precipitation is in a location of poor radar coverage

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Lack of SPE’s when there are lightning strikes

The associated precipitation on the hydro-estimator is blank where the lightning was noted

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A Case Study

A flood of record occurred on the Rio Grande at Presidio, Texas in September,

2008. The flood waters started in

Mexico and moved downstream to

points including Big Bend National Park.

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What set the Stage for Rio Grande Flooding?

First, there was hurricane Dolly which dissipated near Presidio July 24, 2008.

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What set the Stage for Rio Grande Flooding?

Rainfall ending 12Z 26 July 2008 18

What set the Stage for Rio Grande Flooding?

Rainfall for July 200819

What set the Stage for Rio Grande Flooding?

Next came rain from tropical storm Julio from the Pacific in late August.

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What set the Stage for Rio Grande Flooding?

Rainfall ending 12Z 31 August 200821

What set the Stage for Rio Grande Flooding?

Rainfall for August 200822

What set the Stage for Rio Grande Flooding?

Lastly, as Lake Luis Leon was starting to discharge, came rain from tropical storm Lowell from the Pacific in September.

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What set the Stage for Rio Grande Flooding?

Rainfall ending 12Z 12 September 200824

What set the Stage for Rio Grande Flooding?

Rainfall for September 200825

The End Result

Using satellite precipitation estimates in the MPE software, we estimated between 5 and 12 inches of rain for the 30 day period ending on 17 September 2008

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Problem: Due to data constraints, we didn’t know

what affect the rain was having!

Lake Luis Leon in mid September 27

Discharge from Lake Luis Leon

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The Flood Wave hit Presidio Texas and Ojinaga Mexico producing the flood

of record

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1. The WGRFC HAS forecasters still don’t know exactly how much rain fell over Mexico. Only 15 rain gauges exist over that part of Mexico. 2. We look forward to the government of Mexico’s addition of new radars (by 2014).3. Best solution would be for improved satellite-based precipitation estimates. Could lightning data assist this effort?

Lessons Learned

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Satellite Precipitation Estimates will likely remain the primary source of QPE over most of the Rio Conchos basin near Chihuahua and most of the Rio Grande tributaries in Mexico. We need to work more closely with the NESDIS meteorologists who are refining and working to improve satellite QPE.

Satellite QPE can also supplement hourly precipitation estimates in other locations where radar QPE is limited (far Southwest Texas, Southern Colorado and New Mexico)

Conclusion

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Acknowledgements

• Billy Finn, Chief, Water Accounting Division, U.S. International Boundary & Water Commission, El Paso TX

• Lora Mueller, Hydrologic Focal Point, NWS WFO Midland TX (now with the NWS Headquarters)

• Jason Johnson, Senior Service Hydrologist, NWS WFO San Angelo TX

• Cary Carman, USGS, San Angelo TX

• NPS, Big Bend National Park TX

• Sheldon Kusselson, NESDIS, College Park MD.

• Fellow staff members of WGRFC 32

Questions or Comments?

MPE Precipitation products are available on the web from the WGRFC:

http://water.weather.gov/precip

E-Mail: Greg.Story@noaa.gov

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