Brian Lehrer: Brian Lehrer on WNYC and we're doing a 10-minute explainer series for the end of the show during the membership drive through Thursday. For today's explainer we're going to talk about weather forecasting. Whether you check the weather app, turn on the morning news, or tuned into WNYC before you step outside. Weather forecast obviously supply that information or do their best to supply it, but what does it actually take to predict the near-term future of weather? Joining me now to shed some light on weather forecasting is Sally Ann Mosey. You can see her on NY1 and other tri-state media outlets. Thanks for coming on Sally and welcome to WNYC.

Sally Ann: Oh, I'm glad to be here Brian. Thanks for having me.

Brian Lehrer: One of the reasons that we thought of this is because after Hurricane Ida we realized we were talking so much more about climate than about weather on this show because this is an issue-oriented show. We were looking at the underpinnings of why storms like that are happening more frequently in our area but made us realize that we sometimes take daily forecasts for granted. Let's start on forecasting the really big storm hurricane or another really big storm when you really have people's attention. What goes into predicting how hard a hurricane will hit?

Sally Ann: There are several factors, Brian, and I guess I should start with saying we don't wait for that big storm to come before we follow what's happening in the atmosphere. There are trends and as meteorologists, we all say the trend is your friend and it is. It helps you predict which computer models are actually performing the way they should. There are several computer models that are out there. For me, my go-tools are the GFS which is your Global Forecast Model, the European, the NAM, the National North American Model. These are the ones that I go to daily and you look at them in and you compare the different levels of the atmosphere and what the temperatures come in for them so you could get an idea of what precipitation may be coming down.

There's a lot to it and the computer models can perform differently, that's what makes it such a challenging job. While it is a science, it's not an exact science and that's where it gets more difficult to predict, but when the area that you're predicting for and that you're forecasting for, you become a better forecaster. The longer that you've been in an area the better you are at predicting how the mountains may affect it, when a system comes over to the Poconos and things like that.

In the case of a hurricane, I mean Superstorm Sandy was a perfect example. The computer models were actually showing us coming our way from off the water and quite frankly, I had been a forecaster for years at that point, you almost didn't believe it. It was hard to fathom so computer models are the go tools for the big ones for sure but you just can't wait until that day or days before we follow it day in and day out.

Brian Lehrer: It's interesting about there being different computer models and I guess that applies to micro weather forecasting as well. For example, I went upstate this past weekend leaf-peeping and was trying to decide on Saturday when am I

going to go out. In the area that I was, there was rain in the forecast and I have two different weather apps on my phone. One of them said it's going to start raining within the hour and the other one said it's going to start raining in about two hours. Why does that happen?

Sally Ann: First of all can I just say I think it's great that folks use apps, I certainly use them myself. I am the mother of four and we had a big soccer game on Saturday [unintelligible 00:04:06] soccer my son's playing for him. I, like you, was paying attention to everything I could to find out how much weather gear I should bring quite frankly. I came ready for the worst. It worked out that where we were in Queens because it was against St. John's. It ended up being in a spot that did not get as much precipitation as a lot of the computer models were suggesting areas just to the north and west we're going to get. There are other more detailed mezzo scales as we call them meteorology models to look at to predict thunderstorms within a small radius several miles wide. Yes, you do have to know your apps Brian let me encourage you to use the NY1 app that really takes care of the five boroughs wonderfully.

Brian Lehrer: When the apps these days get so specific to your neighborhood. I can get a forecast for Inwood or I can get a forecast for Washington Heights, the next neighborhood down in Upper Manhattan. How do they get that precise?

Sally Ann: That is a computer modeling quite frankly and it really is like I said to you it's a science, but it's an inexact science. What we're really gauging our perspectives on are where that stream of moisture in the upper level of the atmosphere will land. Sometimes I know it's happened for myself, the soccer fields are not that far from our home, a few miles away. It could be pouring there and the game has called off and I'm at home going, why did they call for the game?

That is the most difficult part about forecasting is trying to get it within a few miles and really quite frankly you can't. You do your best and that is why sometimes people when they hear something like, oh, there's a 30% chance of rain and somebody would say, oh, but it didn't rain in my area, their forecast was wrong. In 70% of the area, it did. It was more widespread so we give percentages based on what the chances are where you will be.

Brian Lehrer: You work for a few different news stations I see. I see you on NY1, I guess you're on some other places too. Can you explain if different news directors asked for different weather coverage from somebody like you?

Sally Ann: That's funny that you say that. Yes, without a doubt. What comes to mind is not my New York example, but I was working in Pennsylvania and in the Philadelphia station in that market. One of the news directors who had held from New York at one point was now working in Philadelphia and he actually, if you would say there was a chance of let's say two to six inches of snow, he would tell his producers this is what you need to tease. There could be half a foot of snow, where? Now that was the extreme part of it. The same news director also like the idea and subscribe to a service that provided weather cast 365 days out. What? Really was crazy.

He did that as a way to get the viewers, he felt would be interested as they're planning their weddings and they're planning their future endeavors to be able to at least access through that station a way of having an idea of what the weather might be on that particular date. Needless to say we as meteorologists, the team of meteorologists there really didn't love that idea or embrace it, but he was the news director. We used it for a short time before the people viewer speak, at the end of the day that news director wasn't there long.

Brian Lehrer: Do the curve on how accurate the seven-day forecast tends to be, let's say three days out compared to four days out compared to a full seven days out?

Sally Ann: Brian, it's funny because I've been doing this for over 25 years and the progress made in the computer modeling has improved significantly. In other words, it's improved by about a day a decade so the five-day forecast today is about as accurate as a three-day forecast was back in the 90s. It has improved, there's no doubt about that, but certainly the closer you get to the data the more accurate it's going to be.

Brian Lehrer: We've got like 15 seconds left. Last question, when you say there's a 50% chance of rain, why don't you just say we don't know?

Sally Ann: We do know that a front is crossing and that's our way of saying that listen, moisture should be coming and it's not exactly we don't know- [rosstalk]

Brian Lehrer: 50% of the time in the past under these conditions it would have rained. Sally Ann Mosey, you can see around NY1 and other tri-state media outlets as a meteorologist. Thank you so much, this was fun.

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