A new La Niña may be around the corner

Sunday’s high temperature of 105 degrees in Coeur d’Alene was, and will likely be, the hottest reading of this summer season. Since July 5, readings have been at or above 90 degrees with an average daytime high of 95 degrees at Cliff’s station. Sunday’s reading marked the third day of the season with highs at or above 100 degrees.

From July 1 through 21, the average high temperature in Coeur d’Alene for this month is 92 degrees. In the torrid July of 2021, the average high temperature was 92 degrees. However, readings are expected to cool down into the 80s later this week, so we may come under 2021’s reading, but not by much.

In California, the heat has been practically unbearable, especially for those living in the Central Valley. As of last Saturday, there were 16 days with highs at or above 100 degrees in downtown Sacramento. My relatives who live in some of the outlying areas are telling me that readings were near 110 degrees for six days in a row. More hot weather is expected in that area through at least the end of the month.

Cliff and I believe that this summer heat was likely the most intense of the summer. We do see 90-degree days in August, but the upcoming warm to hot spells are not expected to be as hot. Later in August and September, we should also have an increased chance of above-normal moisture across the Inland Northwest.

The Equatorial Pacific Ocean is now in a “neutral” condition, or as we often refer to as a “La Nada,” the in-between warmer El Niño and cooler La Niña. Ocean temperatures near the West Coast of South America, one of the indicators for the trend of sea-surface temperatures, have recently turned cooler than normal. In fact, the cooler waters have expanded across the Equatorial regions.

 In addition to the examination of sea-surface temperatures, to determine El Niño and the cooler La Niña events, are the differences in air pressure between Darwin and Tahiti. This measurement of pressure is referred to as the Southern Oscillation Index. During El Niño conditions, the average air pressure in Darwin is higher than in Tahiti, which indicates a positive value. However, a strong negative reading would have a La Niña. Currently, the latest value is slightly negative.

 Many of the long-range computer models and sea-surface temperature forecasters are predicting that we are not expected to remain in this current La Nada pattern for very long. Most of the international climate models are indicating the return of the cooler La Niña by the fall season. In fact, the Climate Prediction Center is forecasting a 70% chance of a new La Niña to emerge during the August through October period, which is a little later than expected.

We’re already beginning to see some indications of another La Niña with some cooling along the Equatorial regions. According to the Climate Prediction Center, this forecast is supported by “the continuation of below-average subsurface ocean temperatures.” If a new La Niña manages to form later this year, it would be the fourth one within the last five years. According to historical records, there have never been three La Niña events, followed by an El Niño, and then the formation of another La Niña in a short period of time.

If ocean temperatures continue to cool over the next 4-6 months, the chances will be higher for heavier snowfalls across the northern U.S., with drier conditions returning to the southern portions of the country, especially the southern Great Plains. This would likely mean we would see snowfalls this winter season greater than the 69.8 average in Coeur d’Alene.

With a recent faded El Niño and ocean waters in the Atlantic and Caribbean waters still well above normal, the upcoming tropical storm and hurricane season may be another big one. We’ve already had at least three named storms, one a Category 5 hurricane. In fact, Hurricane Beryl was the earliest Category 5 storm to form so early in the season in the Atlantic Basin.

With the tropical storm and hurricane season heading toward its most active period in August and September, it’s very possible that we could rival, or even surpass, last year’s total of 20 named storms. With ocean temperatures still much above average in the Atlantic Ocean, we could see a total of named storms in the low to mid-20s if sea-surface temperatures cool down as quickly as many are projecting.

Despite an El Niño year, which often leads to less activity, the 2023 tropical storm and hurricane season was the fourth most active on record with 20 named storms. There were seven hurricanes, including three major ones that contributed to damage of 4.19 billion dollars in the U.S.

For tropical storms and hurricanes to form in the Atlantic and Caribbean waters, as well as the Gulf of Mexico, ocean temperatures need to be at least 80 degrees Fahrenheit. Last year, ocean water readings were at record levels and sea-surface temperatures this season continue to be well above average in the Atlantic Ocean, especially in the region of tropical storm formation.

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Contact Randy Mann at randy@longrangeweather.com.