NSSL Hot Item

Addition to weather model helps forecast precip types more accurately

An NSSL microphysics scheme that will help forecast six different types of precipitation more accurately was included in the most recent update of the Weather Research and Forecasting (WRF) model. The model is used by operational meteorologists and refined by atmospheric researchers to help forecast thunderstorms and other smaller scale weather with greater realism.

The NSSL scheme predicts the development of water and ice particles in clouds. Like other schemes, it categorizes particles into broad classes of liquid (small cloud droplets or larger rain drops) and ice (small crystals, snow particles, graupel, and hail). Both the amount of mass and the number of particles are tracked, so that the average particle size is predicted. The new NSSL scheme adds a prediction of graupel particle density.

Graupel is a type of ice particle that has a lot of small water drops frozen onto it (rime ice), and can vary in widely in density. Graupel that starts as a freezing rain drop will have higher density than graupel that starts as a rimed ice crystal. Typical schemes have a constant density for graupel and a constant fall speed relationship. Predicting the density, however, allows a much greater range of fall speeds and can result in a more realistic distribution of graupel in a storm. This then affects where the rain (melted graupel) falls to ground, and the melting and evaporation cool the air. The cold air outflow is important for storm motion, longevity, and even severity.

NSSL’s Ted Mansell was instrumental in getting the scheme into NCAR WRF and plans to test it in the NOAA Hazardous Weather Testbed during the 2013 Spring Experiment.

Addition to weather model helps forecast precip types more accurately

An NSSL microphysics scheme that will help forecast six different types of precipitation more accurately was included in the most recent update of the Weather Research and Forecasting (WRF) model. The model is used by operational meteorologists and refined by atmospheric researchers to help forecast thunderstorms and other smaller scale weather with greater realism.

The NSSL scheme predicts the development of water and ice particles in clouds. Like other schemes, it categorizes particles into broad classes of liquid (small cloud droplets or larger rain drops) and ice (small crystals, snow particles, graupel, and hail). Both the amount of mass and the number of particles are tracked, so that the average particle size is predicted. The new NSSL scheme adds a prediction of graupel particle density.

Graupel is a type of ice particle that has a lot of small water drops frozen onto it (rime ice), and can vary in widely in density. Graupel that starts as a freezing rain drop will have higher density than graupel that starts as a rimed ice crystal. Typical schemes have a constant density for graupel and a constant fall speed relationship. Predicting the density, however, allows a much greater range of fall speeds and can result in a more realistic distribution of graupel in a storm. This then affects where the rain (melted graupel) falls to ground, and the melting and evaporation cool the air. The cold air outflow is important for storm motion, longevity, and even severity.

NSSL’s Ted Mansell was instrumental in getting the scheme into NCAR WRF and plans to test it in the NOAA Hazardous Weather Testbed during the 2013 Spring Experiment.

Addition to weather model helps forecast precip types more accurately

An NSSL microphysics scheme that will help forecast six different types of precipitation more accurately was included in the most recent update of the Weather Research and Forecasting (WRF) model. The model is used by operational meteorologists and refined by atmospheric researchers to help forecast thunderstorms and other smaller scale weather with greater realism.

The NSSL scheme predicts the development of water and ice particles in clouds. Like other schemes, it categorizes particles into broad classes of liquid (small cloud droplets or larger rain drops) and ice (small crystals, snow particles, graupel, and hail). Both the amount of mass and the number of particles are tracked, so that the average particle size is predicted. The new NSSL scheme adds a prediction of graupel particle density.

Graupel is a type of ice particle that has a lot of small water drops frozen onto it (rime ice), and can vary in widely in density. Graupel that starts as a freezing rain drop will have higher density than graupel that starts as a rimed ice crystal. Typical schemes have a constant density for graupel and a constant fall speed relationship. Predicting the density, however, allows a much greater range of fall speeds and can result in a more realistic distribution of graupel in a storm. This then affects where the rain (melted graupel) falls to ground, and the melting and evaporation cool the air. The cold air outflow is important for storm motion, longevity, and even severity.

NSSL’s Ted Mansell was instrumental in getting the scheme into NCAR WRF and plans to test it in the NOAA Hazardous Weather Testbed during the 2013 Spring Experiment.