Description:
The Convectively Available Potential Energy (CAPE) map - updated every 6 hours - shows the modelled convectively available
potential energy. CAPE represents the amount of buoyant energy (J/kg) available to accelerate a parcel vertically, or the amount of work
a parcel does on the environment. The higher the CAPE value, the more energy available to foster storm growth. The
potential energy can be converted to kinetic energy reflected in upward motion.
It should be remembered that CAPE represents potential energy, and will only be used should a parcel be lifted to the level of free convection.
When values are above 3500 j/kg and storms do develop, they may build rapidly and quickly become severe.
Often these storms are referred to as "explosive storms" by chasers and professionals. In a high CAPE environment
storms that develop can usually be seen by the human eye as rising rapidly.
Higher CAPE typically involves stronger storms with a higher chance of large hail and other severe weather. Note that
CAPE is usually of lesser importance than the vertical shear environment for tornadoes. The probability of large hail increases
with CAPE, given at least moderate shear(values around 500-1000 J/kg are sufficient).
CAPE is very sensitive to small differences in the moisture and temperature profiles. While the maps indicate
1000 J/kg CAPE at some location, a
skew-T thermodynamic diagram at that location may indicate 500-1500 J/kg.
(Source:
The Lightning Wizard)
Table 1: Characteristic values for CAPE
| CAPE value |
Convective potential |
| 0 |
Stable |
| 0-1000 |
Marginally Unstable |
| 1000-2500 |
Moderately Unstable |
| 2500-3500 |
Very Unstable |
| 3500 + |
Extremely Unstable |
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).