Heavy to excessive rainfall may lead to flooding Wednesday over southwest Pennsylvania into northern West Virginia, and western Maryland. Flood Watches have been issued. An extended period of hot weather will continue for parts of coastal southern California including Los Angeles through Thursday. Heat Advisories remain in effect. Read More >
Meteorology uses pressure as the vertical coordinate and not height. This works out better for thermodynamic computations that are done on a regular basis. Pressure decreases in the atmosphere exponentially as height increases reaching zero pressure in space. The standard unit of pressure is millibars (mb or hectopascals-hPa) of which sea level is around 1013 mb. Standard pressure levels and approximate heights:
Pressure | Approximate Height | Approximate Temp | ||
Sea level | 0 m | 0 ft | 15oC | 59oF |
1000 mb | 100 m | 300 ft | 15oC | 59oF |
850 mb | 1,500 m | 5,000 ft | 5oC | 41oF |
700 mb | 3,000 m | 10,000 ft | -5oC | 23oF |
500 mb | 5,000 m | 18,000 ft | -20oC | -4oF |
300 mb | 9,000 m | 30,000 ft | -45oC | -49oF |
200 mb | 12,000 m | 40,000 ft | -55oC | -67oF |
100 mb | 16,000 m | 53,000 ft | -56oC | -69oF |
The the primary difference between the models is their resolution or grid boxes. The smaller the grid box, the higher the resolution so little nuances in the atmosphere are more easily identified. Below are some of the models used by the National Weather Service.
This table contains contour plots of data from the NAM forecast model. This model gives forecast information out to 84 hours and are updated once every 6 hours at roughly 02:00 PST and 08:00 PST.
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NAM MOS Numerical Guidance:
This is a global model run by NCEP whereas the NAM is a regional model. As a result, the grids from this model are somewhat coarser than the grids from those models and lack some products. This model replaced the AVN and MRF models and gives forecast information out to 384 hours, and are updated once every 6 hours by roughly 04:00 and 10:00 PST.
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GFS Short Range Numerical Guidance:
GFS Medium Range Numerical Guidance: