CREEPING AUTUMN

Every once-in-awhile I like to throw a little more detail out about our weather situations. During the next two weeks colder air is expected to overspread much of the northwestern and northcentral part of the United States. The beginning of that change is underway now.

The first map below shows the upper level winds near 35,000 feet above the ground. The green shaded areas includes wind speeds greater than 50 knots (58 mph). The red area is greater than 100 knots (115 mph). In the magenta areas winds are approaching 150 mph. Again, keep in mind this is at about 35,000 feet.

The strongest winds are found across the northern one-half of the United States. Notice the curvature in the flow as it drops out of western Canada and turns east across the Northern Rockies and Northern Plains to the Great Lakes. The northerly flow will become established further south as the colder air slides south into the northern United States.

Next we use the same basic map above but instead of showing the flow aloft we super-impose the surface fronts and surface weather reports. Your station model decoding skills will come in handy on this map but if you don’t know how here is how to find the current temperatures in degrees Fahrenheit.

In north central Oklahoma you will see 94 plotted to the upper left of the station circle. That is the current temperature at Enid, Oklahoma, 94 degrees. Now look for the temperatures at individual stations across the map. It is colder in the north with 40s in the northern Plains. The colder air is sinking south behind two surface cold fronts; one from Iowa to Nevada/northern California and the other from Minnesota to Montana. Let’s just say that cold air is creeping into the United States and it’s a sign of things to come.

Here is a map showing the surface temperatures contoured in color. Notice the temperature plots on the station models.

The maps are plotting using Digital Atmosphere software. If you are interested in trying it out go to www.weathergraphics.com. (I receive no money for recommending the software. I just think it is a great tool if you like to plot your own maps.