There's More To High Pressure Than You Think
May 13, 2012 8:49 PM
High pressure and low pressure are two fundamentals when it comes to meteorology. Oftentimes when you think of high pressure you think of lots of sunshine and warm temperatures, and vice versa when it comes to low pressure. Lots of sunshine is in the forecast over the next several days with temperatures expected to be well above average. On Saturday temperatures were closer to average with highs in the upper 60’s and on Sunday temperatures were at least 5 degrees warmer than normal, with temperatures in the mid to upper 70’s. Our winds have been light as well, making it feel extra comfortable outside. The closer you have an area of high pressure to an area of low pressure, the stronger the wind speed. Right now we have high pressure over top of us, and as a result our winds are fairly light. Wind speeds also play a huge role in temperatures. Even though they can make it feel colder, strong winds can actually make the temperature warmer, depending on its direction and the amount of dry air in place. On Sunday our winds started coming out of the west, ushering in warmer air.
Speaking of dry air…. you can think of a ridge of high pressure as a big dome of dry air, with very low dewpoints. Remember when the dewpoint gets above 60’s degrees it feels pretty humid out there. Over the next several days’ dewpoints are forecasted to be less than 40 degrees. Dry air cools off and heats up faster than warm air. With dry air in place you typically get a bell curve in temperatures throughout the day…. overnight lows met in the morning around 6am and highs met in the afternoon around 5pm. However, this is not always the case, if warm air moves in overnight it can override the amount of dry air in place allowing temperatures to warm through the overnight instead of drop off. The image below is from Sunday; notice the nice curve to the graph with our low temperature met in the morning and high in the afternoon. Sometimes if we get stuck with clouds and then a cold front moves through temperatures struggle to climb…in that case the graph would look more like a straight line or slide instead of a curve.
Sunday morning...dry air + light winds + clear skies = lower temperatures
With high pressure in place temperatures may differ more so from day and night rather than each day throughout the week…meaning highs and lows won’t vary too much from day to day. However as the ridge continues to strengthen highs may rise a degree or two each day before reaching their peak.
Monday afternoon...highs in the 80's....warm air moving west to east
By the later half of the week the ridge will slowly begin to break down, allowing for a trough to move into the region, as it does so moisture will begin surging up from the south. With more moisture in place overnight lows will also be a little bit warmer. In the mean time clear skies and warm temperatures will prevail, which for some of us is a nice break from last weekends active weather.