|David Reed, Hydrologist In Charge||Vol. 3No. 4, Summer 2000||Ethan A. Jolly, Editor|
|New Quantitative Precipitation Procedures||SHEF Code Explained|
|From the HIC|
Drought conditions continue over much of the LMRFC area and we are entering the most active portion of the hurricane season. LMRFC has been busy with procedure development efforts to improve our forecast models and to bring new products online.
LMRFC has been active in working with our cooperators participating in coordination meetings with the US Geological Survey, US Army Corps of Engineers, and Tennessee Valley Authority. Our procedure development efforts continue with model calibration, product development with geographic information
systems (GIS), and changes in the way quantitative precipitation forecasts (QPF) are prepared and used by the NWS taking a large portion of our efforts. To help everyone understand the major changes that have taken place in the preparation of QPF, much of this issue will be devoted to documenting this change.
We will continue to improve our forecast techniques and work with our cooperators to provide better products and services. Any comments and ideas are greatly appreciated.
|New Quantitative Precipitation Procedures|
|The National Weather Service (NWS) created a Quantitative Precipitation Forecast (QPF) Assessment Team in 1998 to review the QPF process. The team was charged with determining if the current process to generate QPF in support of the NWS hydrology program was effective and beneficial. The team concluded that the old QPF process needed to be simplified and consistent nationally. The recommendation from the team consisted of relieving the Weather Forecast Office (WFO) from producing QPF east of the Continental Divide and reorganizing existing resources at the Hydrologic Prediction Center (HPC) to enhance and reformat QPF guidance for direct use by HAS forecasters at the River Forecast Center (RFC). A QPF Implementation Working Group was formed to help in the transition over a one year period from the old QPF process to the new QPF process.
The old QPF process at the River Forecast Centers consisted of HPC providing graphical guidance to the WFO. The WFO would use the program WinQPF to make a 24 hour QPF in six hour
increments using the graphical guidance from HPC and other meteorological tools. The WFO would send the output from WinQPF to the RFC. The HAS forecaster at the RFC would combine QPF from each WFO using a program called HASQPF and create a mosaic of QPF over the entire RFC area. The QPF output from HASQPF was used as input for the hydrologic models at the RFC.
The new QPF process started at the LMRFC during the winter/spring of 2000. HPC started to provide gridded QPF forecasts to the RFC to supplement the graphical QPF forecast. To be able to use the gridded QPF forecasts directly, new software was needed at the RFC. A new software program called NMAP (see figure 1) was installed at the LMRFC and HPC provided NMAP training to the LMRFC staff on 4/13/00. The NMAP software inputs QPF from HPC directly and allows the LMRFC forecaster to manipulate/modify the gridded QPF. After the HAS forecaster modifies the QPF, output from NMAP is formatted for input into the LMRFC hydrologic models.
The NMAP program contains several post processing scripts which are used by the LMRFC. One script produces a text file of six hourly QPF for each sub-basin in the LMRFC area. Another script produces 6 and 24 hour gif files of QPF and sends the files to the web site http://www.srh.noaa.gov/lmrfc/qpfpage.shtml. Finally, NMAP post processing scripts create LMRFC modified gridded QPF files and transmits them through the wide area network for distribution through the NWS.
Before converting officially to the new QPF process, a test and evaluation of the procedures were conducted from 5/15/00 thru 7/31/00. LMRFC forecasters were able to get accustom to the new procedures and use QPF from NMAP for input into the hydrologic models.
WFO's continued to send QPF during the test and evaluation period in the event problems were encountered using the new QPF procedures. On 8/1/00, LMRFC began officially using the new QPF process for daily QPF operations and WFO's were no longer required to issue QPF forecasts.
The new QPF process will continue to evolve over time. In the future, gridded 6 and 24 hour QPF from each RFC will be combined to generate one national mosaic product. The new QPF process will expand to include RFC's west of the continental divide and the National Precipitation Verification Unit (NPVU) will verify QPF using precipitation estimates from NWS radars across the country.
|SHEF Code Explained|
As was stated in the 1999 Spring issue of Crawfish Tales, there are three formats that make up SHEF. Through the use of parameter code characters to identify the data, these three message formats have the flexibility to transmit a wide range of hydrometeorological information. The formats are as follows:
The current version, 1.3, of the SHEF decoder is Y2K compatible and allows for the extension of input beyond 80 characters. The .E1 format continuation line .E1 in the above example was inserted for visual readability. Any agency or cooperator can download a complete copy of the SHEF documentation and/or a copy of the SHEF decoder from the following web site: http://hsp.nws.noaa.gov/oh/tt/soft/hsoft.shtml