Guide to the Tropical Forecasts and Analyses


We describe and display the results from the Medium-Range Forecast (MRF) model of the U.S. National Center for Environmental Prediction (NCEP). This guide is not meant to be a thorough and complete description, but to give an overview of the forecasts and their presentation.

The view for the forecasts and analyses in the tropics consists of two overlaping longitudinal bands between 30ēN-30ēS, one centered on the Pacific basin, and the other centered over Africa. There is an analysis, and a series of forecast maps. The forecasts are presented at 12 hour intervals out to three three days, then at 24 hour intervals to five days. There are five different panels for each period. The contents and meaning of the five panels is described below in detail.

The analyses represent the initial state for the integration of the various forecast models. The analyses are produced from observations at weather stations around the world, as well as ship and buoy reports at sea, reports from aircraft, radiosonde balloons, and even satellite data. These data are merged after quality control procedures have been applied. Even with all of the data sources, there are still tremendous gaps in coverage over remote areas. An optimal interpolation (OI) procedure is performed using the previous model forecasts to fill these gaps and create a complete picture of the state of the atmosphere at the forecast time T=0. The model is then integrated forward in time to produce the forecasts which are displayed here.

At the bottom of each map is a bar telling the date and time for which the analysis or forecast is valid, the number of hours after the analysis for which the forecast is valid, the fields displayed, and their units. The five types of maps are described below.

Panels 1 and 2

Winds at 850mb and 200mb

Panel 3

Vertical Velocity and Precipitation

Panel 4

Temperature of the Sea Surface, and 2 Meter Air Temperature

Panel 5

Cloud Cover and Precipitable Water

last update: 23 August 1995
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