WeatherWatcher: Weekend storms report, forecast uncertainties, next week's forecast

Sunday, October 16, 2016


Our big windstorm ended up not being so big after all. All it took was a light shift in the direction of the storm to kill the threat of nasty winds.

The reason the National Weather Service issues warnings is for safety, to prevent loss of life when a weather system moving in has the ability to create life threatening weather.

This is the National Weather Service's primary goal, for everyone to be aware of and survive life threatening weather. Keep that in mind when warnings are issued, even though the weather might not produce the results expected from those warnings.

It is still a very good idea to pay attention to the watches and warnings and plan accordingly. You don't want to get caught out in a bad storm unprepared.

Forecast models are getting better these days, however none at this time are complex enough and high enough in resolution to accurately depict the coastal mountains (Olympic Mountain range) and Cascade Mountains to compute how such a narrow system will interact with the different terrains. This causes great uncertainty for extreme wind events and snow events in the region, especially for our little corner in North King County.

Thursday afternoon's models all seemed to be in agreement of the path of this storm system, thus the extremely likely threat of damaging winds.

Forecast model runs Thursday at 1pm.
Below is an infrared satellite image at 6:45pm Saturday night, about 30 minutes after wind gusts had reached their peak in Shoreline and Lake Forest Park.

Red is the actual path the storm took.
Cyan is the path that was forecasted.

I've highlighted the actual storm path in red, with a circle representing the low pressure center as it was making landfall midway up Vancouver island. The storm's change in path drastically reduced its effect of damaging winds for the middle Puget Sound region.

When this path is taken, the Olympic mountain range shields us from the heaviest winds. Cyan arrow is the path that was forecasted and why the National Weather Service issued the high wind warning for what this storm could have done. As you can see, it took a very slight change in direction to go from damaging winds, to just a strong gale knocking off just little tree branches.

This uncertainty and slight wobble in a low pressure center off of the Washington State coast is what makes the big difference between a breeze, severe wind, snow, rain / snow mixed, or just rain showers.

As a result of the change in the storm path, winds only gusted to 40mph in Shoreline at the North City Elementary station, with Central Market's station recording a gust of 37mph. Other stations in the area were in the mid 30's to near 40mph. Places south of Seattle and North of Everett saw gusts in the 50mph range, so Shoreline and Lake Forest Park were some of the calmest spots in the entire region during this storm.

Rain: We received a lot of rain from the two storms Thursday through Saturday. Thursday brought in a whopping 1.41 inches, Friday came in at 0.93 inches, and Saturday with 0.62 inches, bringing the total rain fall in just 3 days to 2.96 inches! October has averaged about 4 inches of rain for the entire month over the last 8 years. We are well over that now just half way into the month.

Forecast: Monday - Wednesday we are looking at showery weather with breezy conditions at times, temperatures reaching the upper 50's and lows in the upper 40's. Wednesday night into Thursday morning we have a new storm moving in with steady rain likely into Friday morning. Friday through the weekend we go back to a mostly cloudy with showers pattern, temperatures remaining fairly flat in the upper 40's for lows, and upper 50's for highs. Very October-like weather and no major wind events on the horizon at this time.

For current weather conditions visit shorelineweather.com



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