Wasatch Weather Weenies

It sure can get exciting around here when monsoon (and tropical storm remnants) can interact with a mid-latitude trough.  This morning in the Salt Lake Valley has been incredible with round after round of heavy rain and thunder.  These are not those high-based "virga storms" that we sometimes get around here, but the real deal with pretty good downpours and loud, crashing thunder.  Love it. We discussed the ingredients for today's rain in the post from a couple of days ago entitled An Unusual Moisture Pathway .  Those ingredients included the remnants of tropical storm Iselle and a front that was expected to develop over central Nevada.  Indeed these ingredients came together ahead of a deepening trough along the Pacific Northwest coast.  The front is especially apparent at 700 mb (lower left panel below) where there is temperature contrast and wind shift between southern Utah and northern Nevada and Utah.  The large-scale wind pattern is one that mete...

I'll just put these here for some high stoke, low probability snow possibilities.  There are some ensemble members producing snow in northern Utah late next week and weekend.     OK, truth be told it's three ensemble members out of 82.   I told you it was a low probability possibility.

The remnants of Tropical Storm Iselle are taking an unusual pathway into the western US interior and will be visiting northern Utah this weekend.   Yesterday morning (1200 UTC 26 August), Iselle's remnants were to the west of the Baja Peninsula.  The color contours below are precipitable water in millimeters with warmer colors indicating higher values.  Precipitable water is a measure of the total water vapor in the atmosphere expressed as the depth of water if all of that water vapor were to condense and fall out.  Iselle's remnants were associated with a maximum in precipitable water above 65 mm.   Iselle's remnants moved northwestward yesterday and last night.  As this happened, they began to interact with the southwest flow ahead of an upper-level trough off the Pacific Coast, resulting in a plume of high precipitable water movign northeastward toward California.  That plume spreads eastward and ultimately serves as the locus for precipit...

The last few days have brought regular afternoon and evening thunderstorms to the Salt Lake Valley.  It's worth taking a closer look at the drivers for the storms and who has gotten the rain.   On average, the 500-mb heights in August are characterized by  a ridge that is centered roughly over west Texas and a trough over or just to the west of the Pacific coast.  This pattern yields mean easterly flow at 500-mb over central Mexico which turns clockwise (cyclonically in meteorology speak) near Baja California before moving into Utah.   Source: climatereanalyzer.org The pattern above is characteristic of the so-called North American Monsoon.  This monsoonal pattern has been amplified the past several days.  As an example, below are the 500-mb height anomalies (departures from average) for today.  Positive height anomalies over the western US and Mexico are strongest over west Texas and the Mexican border area to the west, right where the ...

Forecasts from the ECMWF Artificial Intelligence/Integrated Forecast System (AIFS) are now available on weather.utah.edu.  Look for ECMWF AIFS in the left-hand nav bar.  An example forecast is below.  Based on the data available, most of our favored four-panel variables are available, but due to limitations in the data provided, there is no forecast of outgoing longwave radiation (used for a forecast infrared satellite image) in the upper-right panel and the precipitation is six hourly, which is a longer accumulation period than many of our products.   As illustrated in the link at the top of this post, AIFS forecast skill at 500 mb is roughly the equivalent of the ECMWF IFS (called HRES on weather.utah.edu) through about day four. At longer lead times, it exhibits somewhat better skill.  The AIFS forecasts after 9 days are about as good as the IFS at 8.5 days, so they are basically giving you an extra half day of skill at longer lead times.  That's ...

Classes start at the University of Utah this coming Monday, August 24.  Campus is getting busier and energy levels are rising.  The start of a new school year is coming! I was on sabbatical last academic year and although I did teach for a full semester at the University of Innsbruck, it feels like higher ed has changed dramatically since the last time I taught at the U in spring 2025.  One reason for this is the rapid advancement of AI, including weather forecasting models and generative AI assistants like ChatGPT. My approach to teaching has been one that has brought new tech into the classroom.  The weather analysis and forecasting classes I teach today use tools and techniques that did not exist when I started as a professor and in some cases even a couple of years ago.   As we go into the new semester, I've been thinking a lot about how to utilize AI in the classroom but also how to ensure that students are using AI tools responsibly.  The lowest-...

Following up on the post from August 8th ( The Death of Summer Skiing ), as reported over the weekend by weathertoski , the last operating ski area in the Alps, Passo Stelvio in Italy, closed on Saturday, August 15th.  There are no summer skiing options left in the Alps.   They suggest this may be the first time there's no (lift served) summer skiing operations in the Alps.  It's likely that applies to the Northern Hemisphere.  Mt. Gassan (Japan) appears to have closed in early July.  Timberline on Mt. Hood appears to have closed on July 19.   I believe late operating resorts in Norway are also closed.   2026.  The year that summer skiing died.