Forecast discussion:

The ridge is bearing down on us.  The record high at DIA for today is 95F.  Many forecasts have the high at or above this. Poking into records on my own, the highest September temperature ever for Denver was 97F – this has happened a few times with 1995 being the most recent. Smoke keeps coming down from Montana and the Pacific Northwest.  At times yesterday, the mountains were invisible from I-25.  (See Figure 1)

Figure 1: The 500mb upper level map from Saturday PM.


A look into the near future:

The next trough (red line in Figure 2) is very potent and will drive a strong cold front down the Front Range Monday afternoon and early evening.  The sad thing is… there is little precipitation associated with it.  Some may see a shower or brief storm (more up in the mountains) – but the chances of Longmont seeing significant rain are very low. By Tuesday PM, the trough has pushed further south bringing in much cooler air.  Highs on Tuesday may drop to as low as 68F; 30 degrees lower than Sunday.  Nice!

After Harvey heavily damaged south Texas, everyone is extra aware of the next – very potent already- hurricane Irma far out in the Atlantic. Irma is already a Category 2 storm and will soon be a Category 3 storm. Figure 4 shows a comparison of a ton of different hurricane forecast models all laid together for comparison.  Saturday night’s GFS actually brings this storm into the DC to Baltimore region around next Sunday.  But a lot can happen this week as we watch. It will keep inching in on the far eastern edge of our maps all week.

Figure 2: 500mb upper level map Monday/Labor Day morning.



Figure 3: GFS 500mb forecast upper air map for Tuesday night.



Figure 4: The multi-model comparison graphic.
Previous articleSunset Pool to close for the Summer 2017 Season on Monday, September 4th
Next articleRenewal Work Continues at Garden Acres Park
John Ensworth works from Longmont as the Principle Investigator for the NASA Science Mission Directorate Earth and space science education product review through the IGES (The Institute for Global Environmental Strategies – . He is in his 14th year running this review. He is an astronomer (from the 2nd grade onward) and became a meteorologist (in the 5th grade) when a thunderstorm in Arizona rained on his telescope when the weather service had only forecasted a 10% chance of rain. He has college degrees in physics and astronomy and climatology and a graduate degree in meteorology and earth science. He lectures at the Little Thompson Observatory in Berthoud, the Estes Park Memorial Observatory in Estes Park, and for a number of online universities. He built and runs a backyard observatory near Pace and 17th in northeast Longmont where he has lived for 8 years with his wife, daughter, son, and two cats. Invitations to open house nights at this observatory, LTO, and EPMO will be posted with future discussions when they are scheduled. Forecasting severe weather and snow amounts via text lead to this column. He began texting friends about the weather right after the September 2013 flood. The readers of this column will, hopefully, keep him honest in what he ‘thought’ he had forecasted for ‘the most recent’ storm.