In addition to using guidance from the Storm Prediction Center's Convective Outlooks, Mesoscale Discussions, and Watches to decide when and where to chase, VUSIT members also make use of various weather data available free on the Internet, such as model data, surface and upper-air observations, and satellite and radar imagery. Here are some valuable links for forecasting and tracking severe weather:

Storm Prediction Center

• Surface and upper-air maps updated twice daily, at 0Z and 12Z, for looking at synoptic features that could produce severe weather
• Sounding analysis for various locations, for looking at vertical temperature, dew point, and wind profiles, hodographs, instability, and cap strength
• Mesoanalysis graphics for looking at mesoscale features over an area at risk for severe weather, such as surface observations, satellite and radar imagery, analysis of instability, various convective parameters, and much more

NCEP Model data

• NAM, GFS, HRW, and RUC model data
  

National Weather Service

• Radar and satellite imagery, watches, warnings and advisories
  

University of Oklahoma Weather Lab

• Surface and upper-air observations and analysis, radar and satellite imagery, and model data, including model predicitions of instability and helicity

TwisterData.com

• Model data, including model predictions of instability, wind shear, and other forecast ingredients, as well as forecast soundings for any particular point

College of Dupage Weather Lab

• Model data, including the RUC, WRF-NMM, GFS, ECMWF, and UKMET models 
• Surface observations and radar and satellite imagery
• National Weather Service Text Products, including links to products from various Weather Forecast Offices including Area Forecast Discussions, as well as SPC Convective Outlooks, Watches, and Mesoscale Discussions.

Earl Barker's Current Weather Page

• Model data, observations, radar and satellite imagery, and analysis products 

Weather Underground

• Model data, radar and satellite imagery, and watches, warnings and advisories
  

Unisys Weather

• Model data, surface and upper observations and analysis, and radar and satellite imagery

RAP Real-Time Weather

• Radar and satellite imagery, and surface and upper-air observations and analysis