NAVY OPERATIONAL REGIONAL AT-MOSPHERIC PREDICTION SYSTEM. As of this writing, NORAPS is used in operational data runs to provide 36-hour fine-mesh forecasts for four geographical regions: the Mediterranean Sea, western Pacific Ocean, Indian Ocean, and the northwestern Atlantic Ocean. The Med and WestPac regions are run at approximately 03Z and 15Z, while the Indian Ocean and NW Atlantic regions are run at 07Z and 19Z. Data from two other regions are also run through the NORAPS program: the Eastern Pacific and the North Pole.

However, these two regions are available to the Fleet only upon request. The number and time of NORAPS model runs changes with changing Fleet requirements.

FINE MESH ANALYSIS AND PROG-NOSIS. Fine-mesh products incorporate a terrain disassociation parameter so that values and their gradients do not unduly influence each other on opposite sides of mountains or land features. For example, cold air that piles up on the north side of the Alps does not carry over to the south side.

SST analyses for selected regions of the Gulf Stream, Labrador, and Kuroshio currents are conducted using 1/8 size fine-mesh grids. The disassociation parameter is also applied to these analyses, because the temperature structure on opposite sides of peninsulas, etc., can be markedly different.

SPHERICAL SURFACE PRESSURE AND WIND ANALYSIS. FIB is also used in the construction of the spherical surface pressure and wind analysis. This analysis is produced on a spherical grid every 6 hours. It is a combination of a surface pressure analysis and a wind analysis. The input data include ship reports up to 6 hours old; land reports, with islands receiving more relative weight; low-level satellite winds decreased by 20% of their estimated value (satellite-derived winds are used in the area between 20N and 20S only); and coded isobaric analysis messages from various Southern Hemisphere meteorological organizations.

The FIB-produced Northern and Southern hemispheres sea-level pressure analyses are interpolated onto a spherical grid, and a first-guess analysis is produced for the regions poleward of 20N and S. The first-guess pressure analysis is then blended with climatology and the previous spherical pressure analysis to produce a pressure analysis of the region equatorward of 20N and S.

The first-guess wind analysis for mid-latitudes is derived from the surface-pressure analysis; the first-guess wind analysis for the tropics is obtained by blending the previous wind analysis with climatology. A global marine wind analysis is performed to blend the mid latitude and tropical wind fields together.

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