Description:
The Lifted Index (LI) is defined as a rising parcel's temperature when it reaches
the 500 millibars level (at about 5,500m or 18,000 feet asl), subtracted from
the actual temperature of the environmental air at 500 mbar. If the Lifted
Index is a large negative number, then the parcel will be much warmer than its
surroundings, and will continue to rise. Thunderstorms are fueled by strong rising air, thus the
Lifted Index is a good measurement of the atmosphere's potential to produce
severe thunderstorms.
| The Lifted Index (LI) |
| RANGE IN K |
COLOR |
AMOUNT OF INSTABILITY |
THUNDERSTORM PROBABILITY |
| more than 11 |
BLUE |
Extremely stable conditions |
Thunderstorms unlikely |
| 8 to 11 |
LIGHT BLUE |
Very stable conditions |
Thunderstorms unlikely |
| 4 to 7 |
GREEN |
Stable conditions |
Thunderstorms unlikely |
| 0 to 3 |
LIGHT GREEN |
Mostly stable conditions |
Thunderstorm unlikely |
| -3 to -1 |
YELLOW |
Slightly unstable |
Thunderstorms possible |
| -5 to -4 |
ORANGE |
Unstable |
Thunderstorms probable |
| -7 to -6 |
RED |
Highly unstable |
Severe thunderstorms possible |
| less than -7 |
VIOLET |
Extremely unstable |
Violent thunderstorms, tornadoes possible |
COAMPS:®
The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) has been developed by the Marine Meteorology Division (MMD) of the Naval Research Laboratory (NRL). The atmospheric components of COAMPS®, described below, are used operationally by the U.S. Navy for short-term numerical weather prediction for various regions around the world.
The atmospheric portion of COAMPS® represents a complete three-dimensional data assimilation system comprised of data quality control, analysis, initialization, and forecast model components. Features include a globally relocatable grid, user-defined grid resolutions and dimensions, nested grids, an option for idealized or real-time simulations, and code that allows for portability between mainframes and workstations. The nonhydrostatic atmospheric model includes predictive equations for the momentum, the non-dimensional pressure perturbation, the potential temperature, the turbulent kinetic energy, and the mixing ratios of water vapor, clouds, rain, ice, grauple, and snow, and contains advanced parameterizations for boundary layer processes, precipitation, and radiation.
NWP:
Numerical weather prediction uses current weather conditions as input into mathematical models of the atmosphere to predict the weather. Although the first efforts to accomplish this were done in the 1920s, it wasn't until the advent of the computer and computer simulation that it was feasible to do in real-time. Manipulating the huge datasets and performing the complex calculations necessary to do this on a resolution fine enough to make the results useful requires the use of some of the most powerful supercomputers in the world. A number of forecast models, both global and regional in scale, are run to help create forecasts for nations worldwide. Use of model ensemble forecasts helps to define the forecast uncertainty and extend weather forecasting farther into the future than would otherwise be possible.
Wikipedia, Numerical weather prediction,
http://en.wikipedia.org/wiki/Numerical_weather_prediction(as of Feb. 9, 2010, 20:50 UTC).