In Brief:

The moisture flow has improved and afternoon storm chances are getting better. We won’t see extreme heat for a while, but the air will get noticeably more sticky feeling. A short wave and associated weak front will move through the state Thursday leading to our best chance of measurable rainfall and thunderstorms out of the next week to 10 days.

Forecast Discussion:

The water vapor satellite image shows a dramatic improvement of moisture flow over Colorado from the tropics (see the discussion for Monday for the progression in images – Figure 1). This is because the upper-level high center has shifted almost to the Texas panhandle (Figure 2). I drew the troughs and ridges and height centers on Figure 2 back on Figure 1 so you can see the reflection of air flow patterns in the moisture image.

For today (Wednesday)- we’ll see more cloud cover and a bit better chance of a storm than we saw Tuesday (Figure 3).

The Longer Range Forecast:

A trough will cut into the ridge and pass over Colorado Thursday (Figure 4) and will bring a wind shift, surface convergence and an enhanced chance of storms and wider-spread rainfall (Figure 3). Beyond that we hover in the upper 80’s F and lower 90’s F with daily thunderstorm chances.

Figure 1: the water vapor satellite image (browns/reds are dry air, whites and light grey is moist air, purple/blue is ice and high cloud tops). From the the Weather Channel from Tuesday.
Figure 2: The 500mb forecast upper air analysis for Wednesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 3: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 4: The 500mb forecast upper air analysis for Thursday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
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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.

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