Upgrade boosts flood forecasting

Hydrologic models help National Weather Service improve river flood predictions

A recent upgrade has improved the accuracy and prediction capabilities of the Advanced Hydrologic Prediction Service, as the National Weather Service works to field the river flooding prediction tool nationwide.

AHPS provides improved flood warnings and water resource forecasts with advanced hydrologic modeling systems, said officials at the National Oceanic and Atmospheric Administration. The improved hydrologic models allow NWS to make:
  • More-accurate forecasts

  • More-specific and timely forecasts of fast-rising floods

  • Forecasts that emphasize the probabilities of various events

  • Forecasts further into the future

  • Improved graphic presentation of river flow forecasts.

George F. Smith, chief of the NWS hydrology laboratory, said the service first used AHPS in 1993 in the upper Midwest. The system now covers the upper Mississippi River, and parts of the Ohio River basin and Red River.

'More recently we have been expanding it to the upper Connecticut River Valley, and we are moving into North Carolina,' Smith said.

The service is moving AHPS into North Carolina in response to the flooding that Hurricane Floyd caused there in 1997, Smith said.

AHPS benefits from the service's improved computation capability associated with the decade-long systems upgrade known as the Advanced Weather Interactive Processing System, which cost $550 million and at times faced delays.

'The timing of this was good because AWIPS brought increased computing horsepower to the forecasting offices,' Smith said.

The Bush administration has requested $6.3 million to expand AHPS nationwide in the fiscal 2003 budget. The program now gets about $1.5 million, officials said.

Old-fashioned forecasting

AHPS replaces methods used since the 1950s to forecast flood levels, which largely involved tracking flood crests as they moved down a river basin.

Those methods can only predict water levels for a three- to five-day period, according to Thomas Graziano, chief of the Services Branch of NWS' Hydrologic Services Division.

'With AHPS we can forecast out from a few hours to three months,' Graziano said.

The advanced prediction system uses radar and satellite data to buttress rainfall and flood crest information fed into the hydrologic models, officials said.

If it receives full funding, AHPS will be deployed in all 122 NWS offices and 13 river forecast centers nationwide, officials said. AHPS will run on Dell and IBM servers under Red Hat Linux 7.1. In each office, a 100-Mbps Ethernet link using a Hewlett-Packard Procurve switch will connect the servers via an intranet.

Some parts of AHPS are written in Java and C++ while others are written in Fortran, Smith said.

The computing power of the Linux servers allows NWS' staff to run AHPS models repeatedly, generating more-accurate river flow forecasts, Smith said.

While flooding is one of NWS' major concerns, 'droughts can cause as much impact as floods and AHPS will allow better forecasts of them as well,' said Glenn S. Austin, chief of the Hydrologic Services Division of the Office of Climate, Water and Weather Services.

'We have a diverse society,' Austin said. 'We realize that we have to get the forecasting tools for various segments of society, including emergency response, recreation, navigation and water resources.'

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