Happy Monday! It’s inevitable as a meteorologist or weather forecaster in the United States to hear the phrase, “must be nice to be wrong 50% of the time and keep your job,” at some point in their career.
It can be a challenge to pin down what exactly Mother Nature will throw at us on a day-to-day basis, but forecast skill has improved greatly in the last 50 to 100 years as we’ve learned more about how the atmosphere works.
Which brings us to the coronavirus, which in addition to changing how Americans live their lives, has impacted the tools that forecasters use every day to predict the weather. To understand why this is happening, we have to explain how weather forecast models work.
You’ve probably heard us talk about “the European model” or “the American model” at times when we’re discussing the scenarios involved with an upcoming storm. Weather forecast models can be described by the area they forecast for (resolution) and how far out into the future they predict.
You’ve likely heard of the ECMWF and GFS, but Your Local Weather Authority also uses the NAM, HRRR and other forecast models to predict our weather each day in southwest Virginia.
So how do these models work? They run multiple times per day, taking current weather data (temperatures, cloud cover, precipitation, etc.) and plugging them into atmospheric equations. The equations get resolved by the model and produce an output of forecast data. Each model assimilates the data differently and uses different equations, hence the slight variations in model output.
Some forecasters trust certain models more than others and some models predict certain events better. In addition to examining model data, meteorologists and weather forecasters use their past experience, radar trends (”nowcasting”) and other methods to come up with the daily forecast.
According to a recent study, the pandemic’s main impact on our ability to forecast has come in the form of fewer aircraft flying through the atmosphere taking weather observations. By the end of March, more than 20 commercial airlines had completely canceled all flights and twelve others canceled international flights. This resulted in a reduction of 50 to 75% of the weather observations taken by aircraft from March through May.
The study compared forecasts over that time frame to those from 2017 to 2019 and found a significant deterioration in accuracy when predicting temperature, relative humidity, wind speed and pressure. The researchers found that regions that are typically flight-dense, like North America, southeast China and Australia were more affected by the pandemic than other regions.
As the world reopens and flights resume, we can expect forecast skill to recover, but in the meantime, it’s something to consider the next time a blown temperature forecast leaves you feeling frustrated.
Switching gears to what we expect in our corner of the Commonwealth this week, the 90-degree heat will be around for a couple more days before temperatures take a dip. This will coincide with an increase in storm chances and the possibility of heavy rain locally. Here’s Chris Michaels’ forecast discussion.
You can always get specific forecast details for your zone, whether it’s the Roanoke Valley, Southside, the New River Valley, or elsewhere around southwest and central Virginia, anytime at WSLS.com/weather. Know your zone!
In case you missed it, we’re posting great weather content on WSLS.com. Here are a few links from the past week to check out:
-- Justin McKee