Forecast Discussion:

The big storms formed, were far apart (on Tuesday), and dumped serious hail on a few locations. Longmont dodged a big one around 5pm Tuesday (Figure 1).

The atmosphere continues to dry out at most levels (low level moisture kept Tuesday storms alive).  The red and black colors are atmospheric columns are low on moisture content in Figure 2.  The GFS is forecasting little rain over the next 48 hours (Figure 3).  Both this model and the one used Tuesday morning on Channel 7 news had storms up in Nebraska send a gust front back to the Front Range today that initiated a big storm around Fort Collins.  That will be interesting to see if it occurs.


Figure 1: Radar image from iOS app RadarScope Pro posted on Twitter by Matt Makens
Figure 2: the water vapor satellite image from Tuesday night. Reds/Oranges are dry air, greys/whites are moist air regions.
Figure 3: The total accumulated precipitation between Tuesday PM and Thursday late PM from the GFS and

The longer range forecast:

The 10 day forecast has a chance of a storm Wednesday (our storm from above?) then very little but a few afternoon storms in afternoon by the weekend and beyond. Temperatures change very little and hover in the upper 80’s F throughout the forecast period (Figure 4).

As an interesting note, we have four tropical systems between Mexico and Hawaii (Figure 5). As Joe Bastardi from WeatherBell says, you get a “Ridge over Troubled Water.”  There has been a big ridge over the southwest for a long time, so this makes sense. What is even more interesting is that the eastern two-most storms (Llena and John) might merge in a few days.  I’ve seen tropical system dance around one another, but I’ve not seen two merge (Figure 6).

Figure 4: the next 10 days of the graphical forecast for Longmont, CO from
Figure 5: The hurricane lineup Tuesday in the western Pacific. From the National Hurricane Center.
Figure 6: Hurricane John impacted Tropical Storm Ileana on Tuesday, bringing rough surf conditions and heavy rain to the coast of Baja California. Forecast winds speeds. National Hurricane Center.
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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 – . 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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