NCEP Newsletter

About 48 Hr Surface Forecast

These surface forecast products generated twice each day at 00Z and 12Z for each ocean based on the 00Z and 12Z GFS forecast model run outputs with additional guidance from variety of sources such as the NAVYs Navy Operational Global Atmospheric Prediction System (NOGAPS).  The use of several numerical models allows adjustments to be made to the final forecast product. The products show surface isobars every 4 mb with labeling of 2 digits in increments of 8 mb. The central pressure millibar values of synoptic scale lows and highs in bold 3 or 4 digits are underlined adjacent to or under the "L" or "H". The 24-hour forecast position and future 72-hour forecast position of lows and highs have vector arrows with an "X" for low centers and a "circle with an X inside" by the head for high centers. An underlined bold two digit mb central pressure value will be placed under or adjacent to the 24/72 hour position label (e.g.,1050 mb high would be written as a 50 and a 960 mb low would have 60). The 48-hour surface forecast depicts wind speeds in knots (wind barbs in increments of 5 or 10 knots) for areas of wind in excess of 33 knots, and frontal systems (occluded, warm, and cold). Significant systems have labels depicting whether the system is expected to have "gale" , "storm", or hurricane force conditions. If 72 hour forecast gale, storm, or hurricane force conditions are expected, the appropriate area has the label "developing gale" , "developing storm", or "hurricane force".

A 48-hour tropical cyclone symbol forecast position will be depicted on the forecast chart. Both 24-hour and 72-hour tropical cyclone positions will appear on the 48-hour surface forecasts. The forecast positions and strength of the systems wind speeds will be based on the latest warnings from the Tropical Prediction Center's (TPC) National Hurricane Center (NHC) , which covers the Atlantic and the Eastern Pacific Oceans east of 140W, and the Central Pacific Hurricane Warning Center (PHNL) covering the Eastern and Central Pacific Ocean west of 140W to the international dateline (180), and the Joint Typhoon Warning Center (JTWC), covering the Western Pacific west of 180.