Tuesday, October 20, 2020

More moisture lurking 'round the corner

by Randy Mann
| October 12, 2020 1:06 AM

The Inland Northwest finally received some much-needed rain over the weekend. For the 3-month period beginning on July 8 through Oct. 8, only .62 inches of rain fell in Coeur d’Alene. According to Cliff’s records, that’s the driest in the area’s history during the same time period. The previous record was way back in 1918 as .83 inches of moisture was reported.

We should see some additional showers early this week, but the strong ridge of high pressure is expected to rebuild and give us dry weather with mild temperatures.

Late October and early November should bring another threat of moisture with the possibility of snow in the mountains. Our wet weather pattern is taking a little longer to develop, but the extended wait for substantial rains does increase the likelihood of bigger moisture totals in November and December.

The big weather news over the past week was another hurricane hitting the U.S. coastline. On Friday, Hurricane Delta slammed into the southwestern coastline of Louisiana as a Category 2 hurricane. Winds were as high as 100 mph when the massive storm made landfall.

Hurricane Delta was the 25th named storm of the very active 2020 Atlantic hurricane season. The record is 28 named storms back in 2005, the season that included Hurricane Katrina. Although Delta’s name was used in 2005, that storm formed on Nov. 15, more than a month later than the weekend system when comparing the two years.

According to an article by CNN, Delta went from a tropical depression to a Category 4 hurricane in approximately 30 hours. That is the fastest increase of sustained winds by any storm this year. For a storm to achieve “rapid intensification,” top winds have to increase by 35 mph in 24 hours.

Earlier this year, Hurricane Laura had winds reaching 150 mph. However, Delta was the strongest storm that has used the Greek alphabet in history. The system was the 10th named storm to make landfall in the U.S., which is a record. The old record was nine landfalls in 1916.

There are only 21 names for tropical storms and hurricanes on the list each year. They are recycled every six years, but when a hurricane causes widespread death and damage, the name is retired.

The average number of named storms, based on a 30-year average, is 12 for each season. During October, there are typically two named systems, with one in November. Based on the current patterns and trends, Cliff and I believe that we’ll end up around 30 named storms before the season comes to a close.

The most intense tropical cyclone or hurricane, in terms of barometric pressure, was Typhoon Tip on Oct. 12, 1979. The central pressure dropped to 25.69 inches.

In the Atlantic Ocean, Hurricane Wilma was the strongest with a barometric pressure of 26.05 inches. By the way, the normal sea-level pressure is 29.92 inches.

Strong mid-latitude storms have dropped pressure to just under 29 inches. Lower air pressure against the body can allow tissues to expand and lead to pressure on joints, causing pain.

Hurricanes are measured by their wind speed based on the Saffir-Simpson Hurricane Wind Scale. It was developed in the 1970s and ranges from a Category 1, a minimum of 74 mph sustained winds, to a Category 5, the highest with sustained winds of at least 157. A Category 5 storm is likely to produce near total destruction.

In the U.S., only three Category 5 hurricanes ever made landfall. These included Hurricane Andrew in 1992, Hurricane Camille in 1969 and the Labor Day hurricane in 1935.

There have been discussions of creating a Category 6, but scientists believe there would not likely be much difference in the destruction of a Category 5 and what could potentially be labeled as a Category 6 hurricane.

According to the National Hurricane Center, the most intense hurricane in terms of wind speed was Hurricane Patricia on Oct. 23, 2015. For one minute, the maximum sustained winds hit a whopping 215 mph. The storm was off the coast of Mexico in the eastern Pacific Ocean.

The tropical storm and hurricane season in the Atlantic and Caribbean waters begins on June 1 and continues until Nov. 30. However, storms have formed outside of that range.

The earliest Atlantic hurricane to form happened on Jan. 4, 1938. Hurricane names were not issued at that time. The latest formation in the Atlantic was on Dec. 31, 1954, with Hurricane Alice. Both were Category 1 systems.

In 1932, the Cuba Hurricane reached Category 5 status on Nov. 5, the latest for the most intense Category 5 hurricane in history. With our active season, it’s quite possible that we could see tropical storm formation in December.