West Coast Storms and Hurricane #Rick #Mexico (Sunday 24 Oct 2021)

Only one tropical system of interest, Hurricane Rick (EP17) should hit the west coast of Mexico Monday (more below), but there are two big non-tropical storm systems impacting the US today. Here is the TAFB surface analysis this morning, showing Hurricane Rick off of Mexico, the tangled fronts and low pressure in the middle of the country, and the big Pacific storm system starting to stream moisture into California …

Click to embiggen

Two areas are of concern in the US – the first is in the middle of the country, where a complex system is likely to produce some strong thunderstorms today. But the big Pacific storm (just under the label in the upper left of this graphic) has been getting media attention with the usual breathless headlines like “Atmospheric river, high winds to wallop California and Pacific Northwest” and talk of “Bomb Cyclones.” The terms “Atmospheric River” and “Bomb Cyclone” both have specific meanings and really aren’t necessarily scary or destructive unless you say them in the right tone of voice.

The more accurate term for “Bomb Cyclone” is “Explosive Cyclogenesis.” There is in fact a technical definition, that a storm decreases in minimal surface pressure by at least (24 sin φ/ sin 60°) mb in 24 hours, where φ represents latitude in degrees. I never liked the term “bomb” as being overly dramatic, but it has been in used in meteorology for a long time. They do have the potential to cause a lot of damage – the one approaching the Pacific Northwest has winds of hurricane force and higher. In addition, a second phenomena called an atmospheric river (AR in NWS abbreviations) is setting up over California today. That stream of moisture will drop a lot of rain there, which has the potential to cause flash flooding and over a foot of snow at higher elevations since in combination with the approaching cold fronts (the saw-toothed lines in the upper left of the above map) there will be a big temperature drop because, well, WINTER IS COMING! This year there is another factor, the large burn scars from this year’s wild fires. That means the vegetation that normally helps slow down or hold back rain is gone, so the potential for epic mudslides is present. You can get accurate and relatively drama free (and totally advertising free since you already paid for it!) reporting on all this at the National Weather Service web site (link). The short range weather discussion is always a good place to check for the “big picture” …

Click to go to Short Range Weather Discussion.

For those in Mexico, here is the damage swath expected from Rick:

Click to embiggen

NHC’s Key Messages regarding Hurricane Rick caution that as is typical for landfalls in Mexico, inland flash flooding and mudslides in the mountains are always a risk with this storm in addition to the threat of storm surge and wind on the immediate shoreline.

2 thoughts on “West Coast Storms and Hurricane #Rick #Mexico (Sunday 24 Oct 2021)

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