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By John Ensworth
Discussion:
Everything is on track still for a relatively dry Saturday (afternoon storms are possible at any time for a few lucky folks). Thursday saw some beneficial chilly rain then a thunderstorm for Friday. Figure 1 is the CoCoRaHS rainfall report for Thursday (reported at 7am Friday) and shows the city getting just under 0.20” of rain.
Figure 1: CoCoRaHS reported rainfall.
We defiantly notice the milky appearance to the sky, which is from smoke released by fires that have benefited from the west coast ridge that stopped precipitation for western states and created dry and hot conditions out there. A bad combination in August (Figure 2).
Figure 2: Smoke map for August 3rd/4th for the U.S. and Canada. Orange dots are active fires. ( from http://wildfiretoday.com/2017/08/03/wildfire-smoke-produces-unhealthy-conditions-in-some-areas-of-the-us-northwest-and-british-columbia/ ).
Today, shortwave energy will interact with warm and moderately moist air this afternoon and kick off a few thunderstorms, especially in the mountains, then later on the adjacent plains (the is more moisture further east, so things will be more exciting, even severe, well east of I-25).
In a look at the longer range: With the ridge still off the west coast, the upper air flow continues out of the northwest allowing cool fronts and/or short waves to affect the weather every few days with short waves traveling down the flow. (As discussed over the last couple of days.)
Our next stronger front invades Sunday as seen in the forecast map for Sunday (Figure 3). Into next week, the ridge stays nearly stationary for a while with northwest flow aloft over Colorado .The ridge position is marked off the West Coast in dark blue in Figure 4 and the passing shortwaves-of-the-day are marked in red for Tuesday morning.
Figure 3 Forecast map for Sunday morning – surface fronts and expected precipitation.
Figure 4 The Tuesday AM 500mb map with shortwave troughs highlighted with red lines, the big ridge in blue.
*** This feature will run as close to daily as possible in this location on the Longmont Observer. ***
This article will provide a brief discussion concerning the ‘why’ behind the weather with a focus on severe weather, unusual weather, and snow (especially trying to predict snow depth and its human impact in Longmont).
Bio:
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 – www.strategies.org) . 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.
