Wednesday December 2nd… Dear Diary. The main purpose of this ongoing blog will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉
Main Topic: Dire Notes From The West Pointing To A Deepening Climate Crisis
Dear Diary. To start out this December, I’m still continuing to see some disturbing information coming from around the world, with perhaps the most eyepopping messages from the U.S. West. California desperately needs rain, and now that we are in their traditional rainy season, not much is on the horizon. Lack of precipitation is not a problem in Alaska, but a rapidly warming climate has affected rainfall and snowfall there. For today’s main subject I am offering some rather shocking messages from both California and Alaska.
Rich Thoman and Brian Brettschneider, our Alaskan climatologists, have let us know that the southern part of Alaska has already experienced some eye opening weather during this early boreal winter:
Evidently the jet stream is being forced further north by western climatologist Mark Swain’s “ridiculous resilient ridge” to produce a pineapple express type hose of moisture into Alaska, along with very warm temperatures for this time of the year.
That ridge is keep California and much of the West dry. During my career I can’t recall 500 millibar heights being persistently as high as they gave been from 2019 into 2020 across California. Here are some of Dr. Swain’s notes:
Alas, dry conditions and offshore winds are working hand in hand to produce very high fire danger once more:
Looking at just one location, San Francisco, we see some startling statistics. Here is a quoted note I received from weather historian Chris Burt last evening:
“Let’s look at the data from San Francisco Downtown. POR since late 1849.
With a 170 year POR, SF Downtown (four different locations) has one of the longest-continuous-daily precipitation records in the U.S.
As of Dec. 2 San Francisco has picked up 0.54” since the season began on July 1.
There are only six other seasons that began drier than this since 1850.
If no rain falls by Saturday, this season will rank as the 3rd driest start on record.
If no rain by Friday, Dec. 11 then the 2nd driest.
Even if SF picks up another .26” by Dec. 22 the year would still be the driest start in at least 170 years.
The concern, of course, is that the GFS for one, has NO measurable rainfall in the forecast for SF through Dec. 17. That likely will change going forward. However, it is 99% certain that no rain will fall in SF prior to next Saturday (Dec. 5) at least. So by then it will be the 3rd driest start out of 170.”
Of course, this fire weather is dangerous for our health:
Here is the middle part of Dr. Swain’s latest blog. I would invite you to click the link and read this thorough article in its entirety to see just how dire the situation is in California:
Short to medium range outlook: high confidence in a very dry period ahead
I’m afraid that the next 2-3 weeks look very dry across nearly all of CA. In fact: SoCal may see no precip at all over this period, while even far NorCal may see only 20-30% of average. Now that we’re approaching December, each passing dry week becomes progressively more consequential–as climatological average precipitation increases steadily throughout California from November into December. This potentially prolonged upcoming dry spell will add to already substantial rainfall deficits accumulated both during the autumn and over the calendar year more broadly.
It’s actually somewhat striking just how high confidence in a prolonged dry spell is across all the major model ensembles. Some individual ensemble members from the ECMWF and GFS are completely dry through mid-December for all of California. While I don’t think that’s especially likely, it is not out of the question and the odds of an unusually dry period are very high.
Assuming this evolution comes to pass, I think it’s fair to say we’ll be entering “resilient ridge” territory. I’m not quite willing to dig out the “ridiculous” modifier again just yet–but it’s not out of the question that’ll happen later this winter given the seasonal outlook. Interestingly, it appears that the storm track over most of the North Pacific will be quite active over this period–it’s just that the cyclonic activity south of Alaska will be in exactly the right position to produce episodes of successive ridge-building along the West Coast for the foreseeable future–keeping California (and much of the West, really) dry for some time to come).
Long-range: still looks pretty dry
I don’t really have much good news to pass along for the month of December. Right now, both traditional dynamical ensemble predictions and experimental statistical outlooks point to high odds of a substantially drier-than-average month across California–especially the southern 3/4 of the state. Given the already moderately strong La Nina event ongoing in the tropical Pacific, and predictions of further strengthening into “strong” territory, I don’t really see any reason to doubt these outlooks. That said: “drier than average” does not equate to a total shut-out in the precipitation department. There should eventually be more rain and snow across California this winter. But when all is said and done, the odds that the seasonal total will be below average looks pretty high–and increases with each passing dry week.
I’ll be adding more more notes from the West the next few days. Look for them in my daily news section.
More November climatology:
Here is more climate and weather daily news from Tuesday:
(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)
Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:
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Guy Walton “The Climate Guy”