Modelo:

Actualização:

4 times per day, from 3:30, 09:30, 15:30 and 21:30 UTC

Greenwich Mean Time:

12:00 UTC = 12:00 WET

Resolution:

0.5° x 0.5° for forecast time <= 384 hrs

parâmetro:

CAPE and vertical velocity at 700 hPa

Descrição:

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

GFS:

The Global Forecast System (GFS) is a global numerical weather prediction computer model run by NOAA. This mathematical model is run four times a day and produces forecasts up to 16 days in advance, but with decreasing spatial and temporal resolution over time it is widely accepted that beyond 7 days the forecast is very general and not very accurate.

The model is run in two parts: the first part has a higher resolution and goes out to 180 hours (7 days) in the future, the second part runs from 180 to 384 hours (16 days) at a lower resolution. The resolution of the model varies in each part of the model: horizontally, it divides the surface of the earth into 35 or 70 kilometre grid squares; vertically, it divides the atmosphere into 64 layers and temporally, it produces a forecast for every 3rd hour for the first 180 hours, after that they are produced for every 12th hour.

NWP:

A previsão numérica do tempo usa o estado instantâneo da atmosfera como dados de entrada para modelos matemáticos da atmosfera, com vista à previsão do estado do tempo.
Apesar dos primeiros esforços para conseguir prever o tempo tivessem sido dados na década de 1920, foi apenas com o advento da era dos computadores que foi possível realizá-lo em tempo real. A manipulação de grandes conjuntos de dados e a realização de cálculos complexos para o conseguir com uma resolução suficientemente elevada para produzir resultados úteis requer o uso dos supercomputadores mais potentes do mundo. Um conjunto de modelos de previsão, quer à escala global quer à escala regional, são executados para criar previsões do tempo nacionais. O uso de previsões com modelos semelhantes ("model ensembles") ajuda a definir a incerteza da previsão e estender a previsão do tempo bastante mais no futuro, o que não seria possível conseguir de outro modo.

Contribuidores da Wikipédia, "Previsão numérica do tempo," Wikipédia, a enciclopédia livre, http://pt.wikipedia.org/w/index.php?title=Previs%C3%A3o_num%C3%A9rica_do_tempo&oldid=17351675 (accessed fevereiro 9, 2010).