Announced in our special weather program at 8 PM on Monday, April 22, "Project Weather: Spring," I'll now be offering an exclusive, nightly TEN DAY forecast on New England's Only News at 9 PM, Monday through Friday nights in our NECN Weather broadcasts. I'm excited to offer this forecast for the first time in New England weather, including the Boston television viewing area, and I hope the new extended forecast will help everyone at home to better plan ahead.
Some of you have undoutbedly seen my 8 to 14 day forecast on Monday night's News at 9 on NECN - that "Week Two" forecast has featured the overall weather pattern for the long-range, and has been a regular Monday night feature for nearly a year. This new venture into nightly ten day forecasting has grown from that Week Two forecast, and the overwhelming strong, positive response garnered from offering that extended prediction. Of course, we're all aware that a ten day forecast should be viewed as guidance, not gospel - there will be changes needed, just like there always have been to forecasts.
Just how accurate can you expect the ten day forecast to be? If you watch NECN often, or read my online posts, you know that one of the big things I look at regularly is "predictability" - that is, how much agreement on a particular forecast solution is there? Sometimes, we see excellent predictability from far in advance - I've made plenty of forecasts from two weeks out that have verified. Then again, sometimes we see very low predictability on a given day or weather event, and this can sometimes remain very low, even as we near the day, which is why there are days in New England weather that may be as much as ten or, very rarely, even fifteen degrees off our forecast for the next day! The key to finding the right length of forecast period is to examine average error of the forecast, rather than the exceptionally good or bad forecasts.
Back in the 1970s, a three day forecast saw a 6 to 6.5 degree error. Today, the error at Day 3 is closer to 3.5 degrees. The five day forecast has seen a similar improvement, with Day 5 verifying at about a 7 to 8 degree error when it began in the 1970s, and now closer to 4.5 to 5 degree error. Seven day forecasts are more recent, and therefore haven't seen such a substantial improvement, but since the 1990s have gone from a 6.5 degree error to a 5.5 degree error. In the summer months, our NECN Weather Team has verified closer to 4.5 degrees as an average error at Day 7.
So...what do we expect for Day 10? I expect an error of approximately 6.5 to 7 degrees is a reasonable estimate, though I hope reality will be even better. Regardless, that's the equivalent of what the three day forecast, five day forecast, and seven day forecast all saw when they first debuted - in other words, the time has come to make this advancement. It seems reasonable that if we can give you the forecast temperature to within 6 or 7 degrees, on average, at ten days out, this is guidance (not gospel!) that you can use to help plan. Deep summer heat or a cool down en route? Should we put in the air conditioner? Make an order for heating oil? These are the types of questions I believe you should have guidance to answer from ten days out.
I know I speak not only for myself, but for our NECN Weather Team, when I express our excitement to lead the way in New England weather forecasting - pioneering in the television industry for our area, but also doing so responsibly and after an in-depth evaluation to ensure we'll continue bringing you the same, high-quality forecasts you've become accustomed to from our team.
All My Best,