Wet, Cool Weather Ahead for Much of the West Coast

 Generally, April is a month of rapid drying over much of California....but not this year.

A pattern that brings a series of low-pressure systems to California will be the rule for much of the month.

Let me illustrate by showing you a series of upper-level (500 hPa pressure, about 18,000 ft) maps.  Blue colors indicate much lower than normal heights/pressures.

Thursday evening, a strong low center will be parked off California, bringing a moisture flow into central and southern California

Saturday will bring a stronger low to Northern California.

This pattern will not go away.....a week later (Sunday, April 19) another strong low will be offshore the CA/OR border.

This series of troughs/low-pressure systems will bring bountiful precipitation to the West Coast.

Over the next ten days, substantial precipitation is expected over California and southern Oregon (see below), locations where the snowfall has been below normal.    This precipitation will top off reservoirs and ensure good river flow this month.

The predicted total snowfall for the same period is substantial, with large amounts in the Sierra Nevada.

One should note that the substantial precipitation this winter has filled California reservoirs, many approaching full (see below).  Right now, CA reservoirs are about 120% of normal. 

As noted earlier, the snowpack is substantially below normal (see below), savaged by the recent warm/dry period.  Thankfully, California has a massive water storage capacity.

The above-normal water storage in reservoirs will buffer the low snowpack, while rain this month will moisten soils going into the dry season.  This is important considering the drying effects of the recent warm/dry weather over California.

Major Global Cooling of the Past Two Years and the Big U.S. Heatwave Last Month. Climate Change?

One of the most effective and accurate ways to monitor the slow warming of our planet from increasing greenhouse gases is to use satellites that measure the radiation emitted by our atmosphere.  

One of the leading groups in using this technology is at the University of Alabama, Huntsville, led by Drs. Roy Spencer and John Christy.  

Below is their plot of lower atmosphere temperatures based on satellite data since 1979.

You will notice a slow rise in temperature over the past 50 years, by about 1°C.  This is probably mainly due to increasing CO2 and other greenhouse gases in the atmosphere.

You will also notice a lot of ups and downs on shorter time scales, which are mainly due to natural variability.  Of particular note is the big spike in warming in 2023, followed by rapid COOLING during the past few years.

The media and climate activists made a lot of false claims that the sudden warming in 2023 was due to human-emitted greenhouse gases, but have been very silent about the recent cooling.

Clearly, the cooling is not consistent with their "messaging" about global warming.

The truth was that the huge 2022 Hunga Tonga volcanic eruption ejected massive amounts of water vapor (a VERY potent greenhouse gas) into the stratosphere, which led to the spike in warming.  

The rapid warming had nothing to do with human emissions, with the global temperatures naturally declining as the excessive water vapor was slowly removed from the system.

Recently, the media and advocacy groups have been going bonkers about the recent March heatwave over the U.S., claiming with great certainty that it is the result of human-caused global warming.

These claims are easily disproved:  the heat wave was highly localized and some nearby areas were much colder than normal.

I can demonstrate this by showing you the temperature differences from normal (climatology) over the entire planet for March using the satellite observations noted above.  Red, orange, and yellow indicate warmer than normal temperatures, and blue indicates colder-than-normal temperatures (see below).

You can see the large area of warmer than normal temperatures centered over the western U.S.  No doubt about it.  But temperatures even MORE extreme on the COLD side to the north, from Alaska through northern Canada. 

Global warming advocates are often talking about the Arctic warming due to climate change, with sad stories about dying polar bears.   But in this case, a broad swath fo the Arctic was much colder than normal.

In the tropics temperatures were near normal. 

It is easy to determine the real cause of the temperature anomalies:  a highly perturbed upper-level flow pattern (see 500 hPa pressure level, about 18,000 ft, below).     Red indicates ridging or enhanced high pressure aloft, blue indicates troughing (ehanced low pressure).

The flow pattern was highly perturbed over North America.  Research is very clear that global warming does not contribute to such a pattern. 

 

Let me end with the Golden Rule of Climate Change.

The more extreme the anomaly from climatology (the average climate), the LESS likely it is that human-forced global warming is the cause.  This was true of the warming in 2023 and is true for last month's warm event over the western U.S.

Human-caused global warming is real, but it is slow and modest in magnitude, and global in scope.