Warn on Forecast

Warn-on-Forecast is a National Oceanic and Atmospheric Administration (NOAA) research program tasked to increase tornado, severe thunderstorm, and flash flood warning lead times. Increasing the lead time and accuracy for hazardous weather and water warnings and forecasts, in order to reduce loss of life, injury, and damage to the economy, is one of the strategic goals of NOAA. Trends in yearly-averaged tornado warning lead time suggest that the present weather warning process, largely based upon a warn-on-detection approach using National Weather Service (NWS) Doppler radars, is reaching a plateau and further increases in lead time will be difficult to obtain. A new approach is needed to extend warning lead time in which probabilistic hazard guidance is provided by an ensemble of forecasts from convection-resolving numerical weather prediction models. This convective-scale probabilistic hazardous weather forecast system is called Warn-on-Forecast, and research is needed before we can develop of this system.

NEW! 2013 Technical Guidance/Warn on Forecast and High Impact Weather Workshop will be held at the National Weather Center Feb. 5–7. Download the agenda (.pdf, 88 kB) (updated 2 Feb 2013)

Warn-on-Forecast Project Plan (.pdf, 245 kB)

Warn-on-Forecast Backgrounder, a brief overview of the WoF project, in layperson's language (.pdf, 950 kB)

Left: An ensemble of storm-scale NWP models predicts the path of a potentially tornadic supercell during the next hour. The ensemble is used to create probabilistic tornado guidance.

Right: Probabilistic tornado guidance: Forecast look on track, storm circulation (hook echo) is tracking along centerline of highest tornadic probabilities.

larger image

Left: An ensemble of storm-scale NWP models predicts the path of a potentially tornadic supercell during the next hour. The ensemble is used to create probabilistic tornado guidance.

Right: Probabilistic tornado guidance: Forecast look on track, storm circulation (hook echo) is tracking along centerline of highest tornadic probabilities.

Warn on Forecast News Archive »

New System Automatically Detects Supercell Thunderstorms

NWS forecasters will be evaluating a new weather-adaptive three-dimensional variational data assimilation (3DVAR) system from NSSL/CIMMS that automatically detects and analyzes supercell thunderstorms during the 2011 Experimental Warning Program in the Hazardous Weather Testbed. The program runs from May 9-June 10, 2011.

Early identification of supercell thunderstorms is critical to the public severe weather warning process since 90% of supercell thunderstorms produce tornadoes, large hail and damaging winds.

The 3DVAR system uses data from the national WSR-88D radar network and NCEP's North American Mesoscale model product to automatically locate regions of thunderstorm activity. It is able to identify deep rotating updrafts that indicate a supercell thunderstorm at 1 km resolution every five minutes in these regions.

The 3DVAR analyses contain full three-dimensional wind field and precipitation fields, and can provide estimates of storm dynamics such as the strength of the updraft. In addition, by combining observations from multiple radars, the 3DVAR system provides a single information source that can reduce the observational data flow that challenges forecasters every day.

During the 5-week project, 3DVAR products will be available to participating NWS forecasters in near real-time to determine if these high-resolution analyses can improve their awareness of the hazardous weather threat.

The system performed well during the spring of 2010, detecting and analyzing significant severe weather events including tornado outbreaks in Mississippi, Arkansas, Kansas and Oklahoma. More recently, the significant tornadoes in Greensburg, Pa. and Mapleton, IA in early April were also well identified and analyzed.

View a preliminary display of the product »

The Warn-on-Forecast program is led by a project manager and overseen by a science advisory board with members representing the major organizations involved in leading the operational and research efforts. The role of the project leader is to oversee all parts of the project and to ensure that each organization contributes to the success of the project and the team. Working groups will be formed as needed to address each of the major tasks outlined in the project plan and according to the funding schedule. Each working group will select a group leader to interact more closely with project management and be a focal point for information dissemination.

WoF Project Leader

Louis Wicker, NSSL

WoF Science Advisory Board

Stan Benjamin, ESRL/GSD
Mike Foster, MIC Norman NWSFO
Kevin Kelleher, NSSL Deputy Director
Steven Koch, NSSL Director
Russ Schneider, NCEP/SPC
David Stensrud, NSSL
Ming Xue, CAPS Director