All posts by Jim Woodmencey

Defining the Wind

One of my all-time favorite weather books is Defining the Wind, by Scott Huler. It is the story of Sir Francis Beaufort (1774-1857), an admiral in the British Navy, former head of the British Hydrographic Office and the first person to quantify the wind.

Beaufort had great observational weather skills. After years of sailing the world’s oceans, Sir Francis put together a scale by which one could communicate how strong the wind was blowing, based on the condition of the sea. The Beaufort Scale was first introduced in 1805, with a 13-point scale to denote the strength of the wind, ranging from calm to hurricane force.

The scale was originally used to let sailing ships know how much sail to carry. As sails switched to steam, the scale was modified. Today’s more modern version also includes visual clues for land-lubbers and assigns the relative wind speeds associated with those visual observations.

My Observations

I recently spent a week in the desert of Southern Utah, watching the wind blow the tumbleweeds around. With no computer, no cell or Internet service, totally off-the-grid, I had to simply observe the weather and gauge the wind, without any access to weather information or instruments. I thought of Beaufort.

Out there in the middle of the desert, I could observe the scarce trees sway, the sand getting transported, and of course, dodge those annoying tumbleweeds. I could translate my observations to a specific wind speed, without a fancy anemometer, thanks to Beaufort’s work from a couple hundred years ago.

I still refer to the Beaufort Scale from time to time when I am out in the backcountry or observing winds around the valley, with a pdf copy of the scale on my iPhone as a reference.

Beaufort’s Scale

Beaufort, along with every other sailor, used knots (nautical miles per hour) as their measure of speed. Although wind speeds were added to the scale after Beaufort’s death, I thought it would make a good history lesson to understand how speed was calculated back then and where the unit of knots came from.

Measuring the speed at which a ship was moving involved a length of rope with knots tied at uniform intervals, 47 feet 3 inches apart, to be exact. The rope was tossed over the back of the ship, with a piece of wood tied to the end of it. The rope was allowed to feed out through a sailors hands, measured with an hourglass or sand timer for 30-seconds.The number of knots that fed out in that time were counted to determine the ship’s speed.

Beaufort’s original scale related the observed conditions of the sea to an approximate strength of the wind, from zero being calm to 12 being a Category-1 hurricane. In 1946 the International Meteorological Committee extended the scale to 17 points, to cover winds speeds up to Category-5 force, of 157 mph or higher.

Click for a printable copy of the Beaufort Scale >>

Speed versus Force

Compare a rating of 5 on the Beaufort Scale, a “Fresh Breeze”, which forms moderate waves with many whitecaps, in the ocean. On inland lakes, crested wavelets form and small trees begin to sway. That relates to a speed of 17 to 21 knots or 19 to 24 mph.

If you double that speed, make it 34 to 40 knots (39 to 46 mph), you would have what is described as a “Gale”, an 8 on Beaufort’s scale. Moderately high waves on the ocean, twigs breaking off trees on land. Walking into that wind would become difficult.

As wind speed increases, the strength does also, and it does it exponentially. Effectively, if you double the wind speed, you quadruple the force of the wind. Newton’s Second Law of Motion explains why:

Force is equal to mass times acceleration (F = ma). Acceleration is velocity squared. Velocity is speed. Thus, a doubling of the wind speed results in an exponential increase in the force of the wind.

To keep the physics simple, a 40 mph wind is not twice as strong as a 20 mph wind, it is actually four times stronger.

The Wyoming Wind Sock is how we gauge the wind out here!

Feel the Force

We can sense that force every time we experience strong winds on the lake, up in the mountains, or out in the desert. The beauty is, with Beaufort’s scale we can assign a speed to what we observe, on water or on land.

Try using Beaufort’s Scale to estimate the wind speed when you are out and about this summer. ¬†As the author of Defining the Wind put it, “The human body is the greatest perceptive instrument ever designed.”

My time in the desert with the tumbleweeds allowed me to reflect on the wind in its most basic form. It’s kind of refreshing to exercise your observational skills and not always rely on technology to tell us everything.

(Note: This post originally appeared in the Jackson Hole News & Guide, June 3rd, 2020 issue, but unfortunately without the Beaufort Scale or other photos.

Post by meteorologist Jim Woodmencey

Going from Hot to Cold

This past week has been warmer than normal over much of the Western United States, warm at least for late May and early June. In Jackson Hole we just had a string of days topping 80 degrees, 82-degrees for a high temp in town on May 29, 30 & 3, 2020. Looks like we’ll be back to around that same temp at the end of this week. Then, it gets abnormally cold for early June.

None of that was record high territory, but it sure feels warm for this time of year. Back in 2003 Jackson had a high of 90-degrees on May 29th and in 1988 there was a a couple of days in the first week of June that tagged 89-degrees.

This weekend and into early next week is looking much cooler and also it looks like we’ll get some precipitation¬† this weekend, something that was lacking most of May.

Cold Low-Pressure Coming

A very cold Low-pressure system that is sitting in the Gulf of Alaska is going to slow-roll its way across the Pacific Northwest at the end of this week. A stronger southerly flow aloft ahead of that Low will bring the warm temps up from the Desert Southwest on Friday. Then the cooling begins Saturday through Monday.

We could see a drop in temperatures of almost 40-degrees, based on daytime highs. That means by Monday, June 8th, the high temps in Jackson might not get out of the 40’s! The number to beat on that date is a high of only 43-degrees, which occurred here in 1950, for a record cold maximum temp.

Mountains also go Warm to Cold

Mountain temperatures have been very warm this past week, as well. Highs at the top of the Tram at Jackson Hole Mountain Resort were tagging 60-degrees this past weekend, with overnight lows temps in the 40’s up there. The freezing level during the day were was above the summit of the Grand Teton (14,000-ft. +).

CLICK image below to play video of computer model forecast.

Weather pattern and temperature forecast for @10,000-ft. on Friday, June 5th at 3PM. (Note: 59F at top of tram).

This has led to a pretty good melt-down of the snowpack and subsequent run-off into the creeks and rivers. That will all screech to a halt after this weekend. Looks like by Monday the temperatures will not get above freezing at 10,000-ft.

Hope you didn’t get too used to the warm, because it is about the swing in the other direction.

Weather pattern and temperature forecast for @10,000-ft. on Monday, June 8th at 3PM. (Note: 24F at top of tram)

Keep up with the latest forecast info for Jackson Hole and the Teton Mountains as the weather this weekend goes through these changes: Click for JH Forecast

Post by meteorologist Jim Woodmencey

Another SNOWY Winter in Jackson Hole

You have probably heard the old saying that Jackson Hole gets nine months of winter and three months of bad skiing (substitute: boarding or sledding here). Some years, that is very true, as winter weather can start in September and last until June.

Last month on this Blog, I reviewed the “meteorological winter” season, which includes the months of December, January and February. In this post, I will add the month of March to the mix, to tally up how much snowfall there was during the traditional ski season ( December 1st to April 1st) .

Snowy March Piles it On

A big storm mid-month dropped a record daily snowfall amount in town, with 12 inches in 24-hours on March 14th. Jackson Hole Mountain Resort also broke a record for that same date in March, with 23 inches of snow in 24-hours.

Snowfall in town for the month of March tallied up 24 inches, more than double March’s average snowfall of 11 inches. By the way, that was only 2.5 inches shy of the record snowfall in March of 26.5 inches set back in 1985.

Mountain snowfall in March was also above the norm for March, with 86 inches of snow recorded at the Rendezvous Bowl weather station at the Jackson Hole Mountain Resort (Elevation 9,580-feet). Almost 20 inches more than the average snowfall for March of 67 inches.

Plentiful Valley Snowfall

Adding up snowfall numbers from December 1st, 2019 through March 31st, 2020 for the Town of Jackson Climate Station: 89 inches of snowfall was recorded during that four-month period. That is 28 inches more than the historic average snowfall for December through March, which is 61 inches.

If you add October & November 2019’s snowfall amounts to that total (15 inches), then our six-months of “winter season” snowfall total goes up to 104 inches. That’s well above the historic average for those six months in town, of 71.5 inches.

Abundant Mountain Snow

The total snowfall for the traditional “ski season”, December 1st to April 1st, at the Rendezvous Bowl weather station at Jackson Hole Mountain Resort was 417 inches this winter.

That is over 100 inches more snow than the long-term average for that four-month period, at that location. Average snowfall for December through March, at the Rendezvous Bowl site is 308 inches.

January took the biggest prize this winter with a record-breaking 169 inches of snowfall for the month at Rendezvous Bowl. That was the snowiest January ever recorded at this weather station.

The grand total for snowfall measured this “winter season”, from October 1st, 2019 to April 1st, 2020, at Rendezvous Bowl, was 510 inches. That is 119 inches (almost 10 feet) more snow than the long-term average seasonal snowfall up there, which is 391 inches.

That exceeded last winter’s total snowfall of 496 inches but fell short of the total from the winter of 2016-17, of 560 inches.

As a matter of fact, this winter was one of only five winters on record that have exceeded the 500-inch mark at JHMR. Three out of those five have occurred in the last 10 years.

Upward Trend in Winter Snowfall

See graph below: 45 Year Snowfall Records at Rendezvous Bowl, Oct. 1st to April 1st.

 

I don’t want to jinx it, but it would seem that we are a roll with above average snowfall winters here in Jackson Hole. (See Graph).

Post by meteorologist Jim Woodmencey

Some of this content originally appeared in the Mountain Weather column of the Jackson Hole News & Guide