This is a set of contour plots using data from the GFS model. The output fields are consistent with other models so the models can be compared. This model gives forecast information out to 240 hours and plots are 48 and 96 hour 4 panel plots where each plot has a panel data for a specific forecast time (12-48 and 60-96 hrs) and individual forecast times from initialization to 240 hours in 12 hour increments. These plots are updated every 12 hours at roughly 0500 UTC and 1700 UTC.
Sample 1000 mb Plot
The 1000 mb chart details near surface weather conditions and is plotted since most models don't report surface conditions. The parameters plotted are the same as the surface plot except for the level being 1000 mb. These include temperature in Celsius (in color contours), convergence (black lines, interval=2, shaded > 0), dewpoints in Celsius(colored lines, interval=5) and winds plotted as vectors.
1000 mb temperature field
The temperature field shows the location of warm and cold air near the surface of the earth and can be used to locate surface fronts or predict high and low temperatures. Low level instability can estimated by taking the 1000-850 mb temperature differences. A difference of 12 or greater indicates potential instability.
1000 mb convergence field
The convergence field shows where low level wind conditions are favorable for thunderstorm development. Positive areas (shaded) represent converging winds and result in forced upward movement of air. Thunderstorms can develop in areas where convergence is strongly positive (>2). Negative areas (non-shaded) represent diverging air which is often a result of descending air and indicates areas of clearing weather.
1000 mb dewpoint field
The dewpoint field shows where moisture is significant enough to fuel thunderstorm development. 55 F or 13 Celsius is a cutoff for strong thunderstorm development. Areas of dewpoints greater than 19 C can generate air mass thunderstorms which often aren't reliant on low level convergence for initial development.
1000 mb wind vectors
These are the estimated 1000 mb winds plotted as vectors. This showswhether the low level flow is from the south where warmer more moist air would advect into the region or whether the flow is from the north where cooler drier air would advect in.
NOTE: Most of the western third of the country have surface pressures well below 1000 mb and these charts don't apply to those regions.