How accurate are those long-range forecasts?


From golf tournaments and baseball playoffs to running marathons and throwing weddings, this is a time of year that forecast accuracy can be paramount. Generally, the weather is perfect this time of year which is why so many activities get scheduled, but those pesky raindrops can really get in the way!

So when you look at those forecasts, especially the 10-day, just how reliable are they? According to the National Oceanic and Atmospheric Administration (NOAA), pretty darn accurate. From its website: A seven-day forecast can accurately predict the weather about 80 percent of the time and a five-day forecast can accurately predict the weather approximately 90% of the time. However, a 10-day—or longer—forecast is only right about half the time. HALF THE TIME? That’s actually impressive for 10 days out. When I first started as a weatherman in 1982, we predicted tonight, tomorrow, tomorrow night and the following day -- we were lucky to get tomorrow’s forecast right. This accuracy rate is amazing:

from NOAA

To be considered accurate, NOAA allows a temperature spread of +/- 3° (some of you may remember when I had the two-degree guarantee. Who knew I could have gone three?!). As for precipitation, that has to be within two inches which is pretty generous. I suppose we could debate NOAA’s accuracy stats all day long. After all, microclimates have their own forecasting hiccups. To be sure, satellites and computer modeling have brought a wealth of information and data to the whole prediction challenge but the good news is that these accuracy rates can only get even better.

With that in mind, FRIDAY is a big day. I’ve been invited to play in the SabreCats Golf Tournament raising money for their Youth Rugby Program and then there is that baseball game. While the forecast calls for an 80% chance of rain, our microcast model from IBM doesn’t wash out the whole day:

Another line of showers on the way
Showers moving through
Rain out of here in the afternoon

If this model proves accurate, then Friday’s morning rain will be gone in time for Astros FanFest and the game itself! Saturday should be just perfect with Halloween anything but scary. Here’s our whole 10-day forecast:

You can count on it!

According to NOAA, we’ll be 90% right through Sunday, 80% right through Tuesday and half right late next week! You can pretty much count on it!


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About the Authors:

KPRC 2's chief meteorologist with four decades of experience forecasting Houston's weather.

Amanda Cochran is an Edward R. Murrow award-winning journalist. She specializes in Texas features, consumer and business news and local crime coverage.