Parts of the West could be in the beginning of a megadrought pattern
We’re about halfway through March and precipitation totals here in the Inland Empire are quite healthy. A series of storms has brought our seasonal total in Coeur d’Alene to just over 9 inches as of early Sunday, compared to the normal of slightly less than 7 inches of moisture. There’s little doubt that the drought here in the Inland Northwest is “over.”
It looks like we’ll get a bit of break from the rain toward the middle to the end of this week as the long-range computer models are indicating drier than normal weather, along with milder temperatures. However, more rain is likely next week and should continue off-and-on through the full moon lunar cycle March 23-30. There is a chance of rain on Easter Sunday as well. It’s also possible that we could see a few more flakes of snow during that time. By the way, our observer in Hayden did report about a half-inch of snow last Wednesday.
Since late last year, ocean temperatures were warming at record levels. We were all looking at one of the strongest El Nino events in history. The abnormal warming of that magnitude had many scientists predicting of flooding rains for California with drier than normal conditions in the Northwest.
During most strong El Nino events, moisture often streams in from Hawaii and slams into the West Coast as the Sub-Tropical Jet Stream moves northward. With lots of tropical moisture, California has historically reported seasonal rainfall totals at least twice their normal levels during a strong El Nino. But, this last El Nino was different. Much of the moisture originated from the cooler Polar Jet Stream in the late fall and winter season.
After the big December snowfalls in Coeur d’Alene and surrounding regions, El Nino’s influence finally took hold and did manage to warm our atmosphere and modify the Pacific storms. Much of the moisture since the first of the year fell as rain in the lower elevations of North Idaho, but did bring plenty of snowfall to the higher mountains.
There’s no question that this record-setting warm water phenomenon was one of the most unusual events. Instead of the flooding rains in California, most stations in the northern and central portions of the Golden State are averaging about 100 to 150 percent of normal. For example, thanks to last weekend’s rainfall, Sacramento is now about 110 percent of average since Oct. 1. Areas to the south and north are slightly higher. Water officials were counting on a lot more rain and snow to put a bigger dent into the historical drought.
Snowpacks this season in the Sierra Nevada Mountains are the best in about 5 years. The statewide Sierra Snow Water Equivalent is near 100 percent. That’s much better than last year when it was around 5 percent of average in early April of 2015. Reservoirs are looking better, but still below the historical averages.
The normal rainfall season extended southward to about Santa Barbara, but around the Los Angeles area, the drought is likely to extend into its 5th year. As of late last week, seasonal precipitation totals were about 50 percent of normal and even less than last year in some places in Southern California.
As I mentioned earlier, the warm El Nino may soon be replaced by a cooler La Nina sea-surface temperature event perhaps as early as late this year. The latest data is already showing El Nino weakening at rapid rate and we’re also seeing cooler than normal waters beginning to form near the South American coastline. A new La Nina at the end of this year would likely lead to heavier than normal snowfalls for North Idaho and drier conditions across central and southern California during the winter of 2016-17.
Although this period of drought has been rough for residents and farmers of California, historical evidence shows that “megadroughts,” some lasting for decades, have been reported in the Far West. Within the last 1,200 years, scientists say that two dry long spells in parts of California each lasted for nearly 200 years.
A study conducted last year by Science Advances suggests that climate change is expected to increase the severity of droughts from the central Great Plains westward to the Southwest during the second half of this century.
From the late 1970s to the mid 1990s, California was enjoying a period of generally wetter than normal weather. With a much bigger population and agriculture, the demand for water is higher than ever. Water tables are already much lower than in previous years and if a new cycle of a long period of dryness is moving in, then California may be in for some challenging times later this century.
Contact Randy Mann at randy@longrangeweather.com