Erin Strengthens to a Hurricane; Heavy Rainfall Possible in Puerto Rico and the Virgin Islands, the Upper Midwest, South Texas

Hurricane Erin may bring isolated flash and urban flooding, landslides or mudslides, and possible tropical storm conditions to Puerto Rico and the U.S. Virgin Islands this weekend. Scattered thunderstorms and heavy rainfall may bring areas of flooding this weekend over the Upper Midwest. A tropical disturbance will bring locally heavy rain and mainly urban flash flooding to far southern Texas. Read More >

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	15^oC	59^oF
1000 mb	100 m	300 ft	15^oC	59^oF
850 mb	1,500 m	5,000 ft	5^oC	41^oF
700 mb	3,000 m	10,000 ft	-5^oC	23^oF
500 mb	5,000 m	18,000 ft	-20^oC	-4^oF
300 mb	9,000 m	30,000 ft	-45^oC	-49^oF
200 mb	12,000 m	40,000 ft	-55^oC	-67^oF
100 mb	16,000 m	53,000 ft	-56^oC	-69^oF

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

Environmental Modeling Center
U.S. Navy
UCAR
Institute of Global Environment and Society
The Ohio State University
University of Michigan
University of Wisconsin
Texas A & M
University of Wyoming
University of Utah
UCAR MM5 model
Navy's NOGAPS model
Canadian Global Spectral model
United Kingdom UKMET model
European Centre for Medium-Range Weather Forecasting ECMWF model
Daily Maps

NAM Forecast Model

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.

NAM MOS Numerical Guidance:

GFS (Global Forecast System) Forecast Model

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.

GFS Short Range Numerical Guidance:

GFS Medium Range Numerical Guidance:

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