A GIS application for weather analysis and forecasting
The observations coming from the observing stations, through several processing steps are transferred into weather forecasts. First step in this process is to plot the observations over a base map of the region, global or regional according to the area of interest, after removing possible observational and communication errors.
Figure 2: Wind analysis for 500 hPa on 17th Dec. 2000 at 5.30 A. M. over India and neighborhood areas.
Figure 3: Geoptoential height analysis at 850 hPa level on 17th Dec. 2000 at 5.30 A. M. over India and neighborhood areas.
The plotted maps are analyzed to bring out different weather systems in action in the atmosphere at that particular instant of observation. Fig. 2. shows, such an analyzed chart generated using ArcView GIS at NCMRWF for 5.30 A.M. observation time on 17th December 2000. In the figure, the red arrows represent the wind at 500-hPa level of the atmosphere. The hollow head of the arrow represents the direction towards which the wind is blowing. Fig. 3. presents the geopotential height analysis at 850 hPa on the same day and time.
The forecaster draws contours or isobars of pressure and marks the fronts, lows highs etc. on the chart. The contouring can be done by Arc View plotted map using the necessary analysis tools. In this application, Troughs, ridges, highs and lows can be drawn on the chart in appropriate color and style, and saved as a part of the chart or a separate view. The successive movement of these systems also can be drawn on the same chart by super imposing the successive charts. The trends and rate of movement of the systems can be studied either directly from the charts or using the theme attribute table.
Fig. 4. Wind flow pattern over India and neighborhood at 500 hPa on 17th Dec. 2000 at 5.30 A.M (IST). The green line represents the low pressure troughs. The same trough as manifested at 850 hPa is also marked in the chart.