Thursday, April 25, 2024

CDA summer fourth driest since 1895

by Randy Mann
| August 31, 2020 1:06 AM

August 2020 was warmer and much drier than average across North Idaho and much of the Far West. Cliff’s records say that our summer season has been the fourth driest since 1895. From the period of July 8 through Aug. 30, it was the second driest in history as we’ve received only .09 inches of rain during that time. The last time it was this dry at this time of year was in 1913, when only a trace of rain was recorded in August.

Since 2015, our summer seasons in Coeur d’Alene have been below normal. During the three-month climatological summer of June, July and August, our average rainfall is 4.08 inches. The driest period was three years ago in 2017, when we had 32 percent of our normal precipitation. July and August 2017 were extremely dry as only .10 inches of rain fell.

By examining the trend over the last six years, when Coeur d’Alene and other locations across the Inland Northwest experienced a dry summer, especially in July and August, our September rainfall also tended to be below normal. Normal precipitation in September is 1.48 inches. Since 2015, every September finished below the 1.48-inch average in Coeur d’Alene. However, September of 2016 and 2017 were very close to normal as 1.44 inches fell in both years.

The driest September since 2016 happened in 2018 as only .37 inches was measured, which was 25 percent of normal. By the way, September 2012 did not see any measurable precipitation, the driest September in recorded history. Despite the lack of rainfall in September, 2012 ended up the wettest year in history in Coeur d’Alene as a whopping 43.27 inches of rain and melted snow was recorded. Talk about extremes. The normal precipitation in Coeur d’Alene is 26.77 inches.

For the meteorological summer season of June through August, depending on how much rain we receive today, Coeur d’Alene will end up between 80 and 85 percent of normal thanks to a wetter than normal June. If we take out June’s 2.64 inches, the total rainfall for July and August will be around .70 inches, or close to 35 percent of normal.

Last year, only .71 inches of rain fell in July and August, very similar to this year. Precipitation in September 2019 was drier than average with .63 inches. And, we can’t forget about the early snows as Cliff measured 1.1 inches of snow on the last two days of the month.

So, how is it shaping up for September 2020? Well, the long-range computer models are continuing to show a strong high pressure system locked in over the western U.S. It doesn’t look like we’ll see much moisture between now and the middle of next month. Based on climatology, especially over the last six years, September’s precipitation for Coeur d’Alene may end up below normal once again as most of our moisture should come toward the middle to the end of the month.

Then, thanks to the cooling of sea-surface temperatures in the waters of the south-central Pacific Ocean, the skies should open up once again as moisture totals are expected to swing in the other direction to above-normal levels this fall season. And, we’re still in this pattern of dry summers and wet winters, so the upcoming winter season looks good for snow, especially in the higher mountains. Some forecasters are predicting a rough winter season for the Northern Hemisphere, but we’ll just have to wait and see.

Speaking of sea-surface temperatures, ocean waters are continuing to cool down. Australian forecasters who closely watch the formation of the warmer El Nino and cooler La Nina events are now saying there is a 75 percent chance of a new La Nina forming or being declared during the fall season. Right now, this new La Nina is expected to be only a light to moderate event.

Our pattern of cooler waters along the Equator and warmer sea-surface temperatures in the Atlantic, Caribbean and the Gulf of Mexico have made our tropical storm and hurricane season far more active than normal. Hurricane Laura made landfall early Thursday along the Gulf Coast near the Texas and Louisiana border. The storm rapidly intensified from a Category 1 to a very strong Category 4 hurricane in about 24 hours. Sustained winds when the massive storm made landfall were 150 mph before weakening as it moved onshore. To reach a Category 5 status, the sustained winds must be greater than 156 mph. Property damage from Laura could be as high as $30 billion.

We’re now coming up to the climatological peak of the season, which is around Sept. 10, and there are two more disturbances brewing in the Atlantic Ocean as of late last week. The normal number of named storms for an entire season that ends on Nov. 30 is close to 12 based on a 30-year average. So far, we’re already seen 12 named storms and Cliff and I are forecasting at least 20 named systems before the season comes to an end.

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