NOAA HMT-WPC Flash Flood and Intense Rainfall Experiment

In collaboration with the National Severe Storms Laboratory (NSSL) and the Earth Systems Research Laboratory (ESRL), HMT-WPC is planning a Flash Flood and Intense Rainfall Experiment for July 2013. This experiment will focus on improving short term quantitative precipitation (QPF) and flash flood forecasts through the use of high resolution models and ensembles and rapidly updating hydrologic information.

 

 

Rossby Wave Packet Tool for Medium Range Forecasting (CSTAR)

A Rossby Wave Packet Tool is being tested by WPC medium range forecasters during the 2012-13 cold season. Rossby Wave Packets are a quantitative way to depict the group velocity of a train of multiple troughs and ridges, and their propagation. The development of the tool is the result of a CSTAR funded collaborative effort between WPC and Stony Brook University. Extreme weather events have been found to be associated with wave packets, and one of the main goals of this work is to identify and forecast wave packet episodes using output from multiple global models. Introductory training was provided to HPC forecasters in August 2011.

 

Object-Oriented Verification

In collaboration with NOAA-HMT and the Developmental Testbed Center (DTC), HMT-WPC is exploring the use of object-oriented verification. The goal of this type of verification is to better account for spatial discontinuities between the forecast and observed precipitation. HMT-WPC is using the Method for Object-Based Diagnostic Evaluation (MODE) tool for the verification of model and WPC forecaster QPF. The MODE tool is part of the Model Evaluation Tools (MET) verification package developed by DTC.

 

Model Displacement Biases (COMET Partners)

HPC collaborated with researchers from Texas A&M University as part of a COMET Partners project that focused on determining whether operational numerical weather prediction (NWP) models have a consistent displacement bias in the predicted location of elevated warm season convective systems. Using the Method for Object-Based Diagnostic Evaluation (MODE) tool, Texas A&M researchers objectively confirmed forecasters' subjective impression that there is a north bias in the location of elevated convection systems in both the NAM and the GFS. A report detailing the project's findings can be found here.  

 

Probabilistic QPF

WPC is experimenting with probabilisitc QPF products. The products consist of both the probability of exceeding a given precipitation threshold as well as precipitation amounts by percentile. The products are generated automatically using the WPC deterministic QPF and uncertainty information from an ensemble. A binormal probability distribution (density) function (PDF), which allows skewness, is constructed such that the mode is the WPC QPF and the variance is that of the ensemble. The skewness is based on the position of the WPC QPF in the ensemble distribution. This approach to estimating the three parameters for the binormal PDF is a variation on the method of moments. Here is a realtime depiction of probabilisitc QPF.  

 

Predecessor Rainfall Events

HMT-WPC is investigating the diagnosis and identification of predecessor rainfall events (PREs). A comparison of model performance between the NAM and the GFS as well as an evaluation of WPC QPF is being looked at to help improve WPC QPF forecasts. The application of a meridional moisture flux tool is being investigated to identify transport of deep tropical moisture into the mid-latitude heavy rainfall system. 

 

 

 

Snow/Ice Accumulation Tool

HMT-WPC collaborated with EMC cloud physicist Brad Ferrier to develop an algorithm to estimate hourly snowfall accumulation. The algorithm utilizes a parameter in the Ferrier microphysics scheme called the "rime factor" to estimate one-hour instantaneous snow/ice accumulation from NCEP's NAM 12km model. This data was made available to WPC forecasters in NAWIPS. (Fall 2009)

 

Training was provided to WPC Forecasters during November 2009.

 

In November 2012, an updated algorithm was delivered to NAWIPS. The update used the rime-facter data from the NAM12 to modify the Roebber Snow to Liquid Ratio (SLR) computed for the NAM. This modified SLR was then multiplied by the percent of frozen precipitation output from the NAM12, and the NAM12 post processed precipitation to arrive at a snow accumulation forecast. This data set was tested in the 2013 Winter Weather Experiment.

and implemented into WPC winter weather operations in February 2013.

 

WPC Heavy Rainfall Forecasting Manual

Wes Junker developed a forecasting manual for forecasters preparing QPFs. This training material is available online and contains a wealth of information on warm season precipitation forecasting. (Summer 2008)

 

 

Whitaker-Hamill Reforecast Technique

The HMT-WPC evaluated the Whitaker-Hamill reforecast technique and migrated it to NCEP computers. This data is now available for WPC forecasters in NAWIPS to aid in precipitation forecasting. (Winter 2006-2007)

 

Normalized Anomalies

The use of normalized anomalies has been successfully migrated into WPC operations. Model forecasts of normalized anomalies for both mass fields and mositure diagnostics (precipitable water and moisture flux) are available both in NAWIPS and online. (Winter 2005-2006)