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Forecast Models
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 |
-69oC |
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.
Model Data Servers
NAM Forecast Model
This table contains contour plots of data from
the NAM forecast model. This model will replace the NGM model
at some time in the future. The output fields are the same as
the NGM so that results of the two models can be compared so
you can make the best estimate of the true forecast. 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.
NAM MOS Numerical Guidance:
NGM Forecast Model
This model gives forecast information out to
48 hours and plots are sorted into 5 directories for the initial
observed fields (00), 12, 24, 36, and 48 hour forecast fields.
These plots are updated once every 12 hours at roughly 08:00
PST.
NGM MOS Numerical Guidance:
GFS (Global Forecast System) Forecast Model
This is a global model run by NCEP whereas the NGM and NAM are regional models. 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.
GFS Short Range Numerical Guidance:
GFS Medium Range Numerical Guidance:
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