Chicago Area Heat Advisories Issued For Sunday; Southern California Braces For Heavy Rains

A Heat Advisory is in effect Sunday 1 PM-8PM for the orange highlighted counties in the graphic below.  Heat Index values are expected to reach 100-107 degrees in the advisory area.  A breezy off the lake will bring some relief from the heat so that’s why Lake, Central & Northern Cook County aren’t in the advisory.  At least we’ll know where to find relief:


“Hilary” is on its way to becoming the first tropical storm to reach California in the 84 years since 1939—and, as UCLA climate researcher and California weather/climate guru Dr. Daniel Swain points out on his WeatherWest blog:

“The only other known tropical cyclone to actually make coastal landfall in California was the 1858 San Diego Hurricane. There have been other tropical cyclone remnant events (as recently as Kay last year in 2022, and memorably for some folks Kathleen in 1976) that have brought major summer storm and flood-related impacts over the decades, but in terms of actual tropical cyclone landfalls, Hilary would be only the third in California since the mid 1800s and the first in the era of SoCal’s massive population growth.”

As of its 3 pm MDT National Hurricane Center advisory—Hurricane Hilary is N/NW-bound at 17 mph from a position 710 miles south/southeast of San Diego and 816 miles south/southeast of Los Angeles. Check out the latest NATIONAL HURRICANE CENTER advisory here

Hilary has moved from the abnormally warm waters it was over when its sustained winds exploded to CAT 4-level (i.e.145 mph) Friday down to its current 110mph. THE DECREASE IN WINDS is occurring because the storm has moved over ocean waters much cooler than the 78.8°F known to flood such systems with the latest heat energy needed to maintain or increase strength.

The weather satellite folks at CIMSS (the Cooperative Institute for Meteorological Satellite Studies) at the University of Wisconsin-Madison generate a constellation of analytical products used by tropical forecasters across the planet—including a UNIQUE ANIMATED STORM CENTER MICROWAVE product which combines microwave data from a series of five low orbiting weather satellites to gauge precip intensity near the “eye” or center of the storm. It turns out precip intensity scanned by these sensors and blended is a great indicator or “proxy” of storm intensity. It’s clear from this animation that Hilary is in a weakening phase. Watch the latest animation here.

A WORD OF CAUTION: While “Hilary” is in a weakening state, don’t let that fool you. This storm will arrive in California and sweep northward as a formidable weather producer with waves of torrential rainfall and strong wind gusts in the hardest hit locations. Terrain will contribute to “lifting” the copious atmospheric moisture

“Hilary” is to bring into the region MAXIMIZING PRECIP IN UPSLOPE and in the drenching convective cells the storm will bring into the REGION. THERE ARE FEW STORMS CAPABLE OF HEAVIER RAINFALL THAN TROPICAL CYCLONES (i.e. tropical storms and hurricanes) like Hilary.

INTERESTING NOTE: Dr. Ryan Maue, whose analyses of the precip weather systems produce are always fascinating, estimate 12-trillion gallons of water are to fall in the areas of California, Arizona and Nevada on which this storm’s rains will fall.


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