Monday, August 30, 2021

Summer Is Ending with Hazards Aplenty

Tomorrow (Tuesday) is the last day of meteorological summer.  September is almost here!  Celebrate with Earth, Wind, and Fire.

On the other hand, there's not much to celebrate this morning as summer is ending with hazards aplenty.


The children's song goes "What does Idaho, she hoes her Maryland," but yesterday, Ida raked Louisiana, coming ashore after rapidly intensifying into a ferocious category 4 hurricane.  

Ida at Landfall.  Source: NCAR/RAL.

The track and intensity forecasts for Ida were quite good, as pointed out by Sam Lillo below.  

Still, it is a devastating event and one with compound hazards from wind, storm surge, precipitation-related flooding, and COVID-19.  The phrase "it's over" doesn't really apply today in southeast Louisiana.

Caldor Fire

Fires continue to rage in California, with the Caldor Fire now an immediate threat for the Tahoe basin and ski areas.  

The latest mapping at FireMappers shows the fire perimeter has pushed past Sierra-at-Tahoe ski area with hot spots at Echo Summit.  Kirkwood is also in the cross hairs further south.  

Source: #Firemappers

Photos from the ski resort below from @ABCliz.

I'll call the forecast "not good" with an upper-level trough moving across the Pacific Northwest producing   dry, southwesterly flow in the Tahoe area through Thursday morning.  Below is the GFS time-height section for south Lake Tahoe showing very low relative humidity and SW winds at low levels of 20-30 knots through Thursday morning.  

Western Air Quality

Air quality in northern Utah has been intermittently poor this summer, although it's nothing compared to the smoke-filled communities in northern California.  The latest from PurpleAir shows hazardous air quality conditions at some locations near fires. 

Source: PurpleAir

Really, the air quality near the fires should be called "haute category," "hors catégorie" a French phrase meaning "beyond category" that is used to classify the most extreme climbs in road cycling.  The threshold for hazardous air quality is 250 μg/m3. Purple air sensors suggest values well over 300 μg/m3 and in some areas over even 700 μg/m3 near South Lake Tahoe.

Source: PurpleAir

For comparison, concentrations reported by Purple Air in the Salt Lake Valley at 9 AM this morning are generally in the 35-55 μg/m3 range, about 1/10th that in South Lake Tahoe.

Salt Lake City Summer Temperatures

We conclude with a quick look at the race for hottest summer in the history of Salt Lake City.  With two days to go, this summer has an average temperature of 81.0˚F, just barely ahead of 2017 for hottest on record.  

Source: xmacis

Based on last night's minimum and forecasts for this afternoon and tomorrow, we may hang on to the record, but it's going to be close.  


  1. Jim, I believe the phrase is “hors catégorie.” In French, “hors” means beyond, while “haute” mean high or tall.

    1. You're absolutely right. I even took French in high school and watch far too much cycling. Blame it on spell check ha ha