Model: GFS (Global Forecast System) Global Model from the "National Centers for Environmental Prediction" (NCEP)
Update: 4 times per day, from 3:30, 09:30, 15:30 und 21:30 GMT
Greenwich Mean Time: 12:00 GMT = 13:00 BST
Parameter: Geopotential in 500 hPa (solid, black lines) and Temperature advection across the Pacific in K/6h (colored lines)
Description: The map "T-Adv 500" shows the advection of cold or warm air at 500 hPa level. Negative values indicate cold advection, while positive values indicate warm air advection. Advection of warm or cold air causes the geopotential height to respectively rise or drop, producing vertical rising and sinking motion of air. There is, however, not a direct relationship between temperature advection and resultant vertical motion in the atmosphere since other lifting and sinking mechanisms can complicate the picture, e.g. vorticity advection (see "V-Adv maps").
In weather forecasting, temperature advection maps are often used to locate the postion of wam and cold fronts. Cold advection is common behind cold fronts, while warm advection is common behind warm fronts and ahead of cold fronts. Higher in the atmosphere temperature advection is getting less pronounced, as horizontal much more uniform in temperature and the flow is more zonal.