and height of pressure surface On the top right corner of the model for a surface weather map is the pressure, showing the last two integer digits of the pressure in millibars, or hectopascals, along with the first decimal. For instance, if the pressure at a certain location is 999.7 hPa, the pressure portion of the station model will read 997. Although the first digit or two of the pressure is left off, other nearby stations give away whether the pressure starts with a 10 or a 9. Most of the time, choosing first digits that would lead to a value nearest to 1000 works out best. The plotting of this value within the station model allows for the analysis of isobars on weather maps. Within maps which plot data on constant pressure surfaces, the pressure is replaced with the height of the pressure surface. Pressure tendency Below the pressure will lie the pressure tendency figure, which indicates the pressure change over the past three hours. The number depicting the pressure change will usually have two digits and indicate the pressure change in 0.1 millibar increments. There are nine different figures which represent the pressure change. A slant angled up and right indicates a steady rise, while a downward slant to the lower right indicates a steady fall. Steady rises can indicate improving conditions and approaching high pressure, and normally occur in the wake of a cold front. Steady falls can indicate deteriorating conditions and an approaching low pressure area, with the largest falls occurring in advance of a surface cyclone and its attendant warm front. The time of the day must be considered, as there are two natural rises per day (locally around 10 am and 10 pm) and two natural falls per day (locally around 4 am and 4 pm). These daily changes in pressure can mask the movement of pressure systems and fronts past a location. The lowest natural dip in the pressure, in a stagnant weather pattern, occurs around 4 pm while the highest natural peak in pressure occurs around 10 am. Once plotted on a map, the analysis of isallobars (lines of equal pressure change) can be plotted on a map, which can indicate the direction of motion of high and low pressures systems across the map domain. Past weather Station models can have past weather plotted within them, which would be located just under