Alright so here’s the situation in the CB weather center: It’s gonna fucking snow. How much? No one knows.
Why doesn’t anyone know?
Forecasters (this is everyone from the local TV people to hardcore meteorologists in our STORM Twitter list) have been noting the disagreements between computer models. Most of the estimates you’ve been seeing are some combination or an average of all these models. As I mentioned in the Roundup, the models differ on when the storm takes shape and intensifies– if it’s earlier and farther to the West, off the coast of North Carolina, then Philly gets the higher amounts… if it’s later, and off the coast of New Jersey when it fully forms, then we get more of the back end of it and less snow.
Why are the models so far apart?
Most meteorologists agree that the EURO is more accurate, and all along that’s been forecasting the higher snow amounts. All models, however, have trended downward over the last 18 hours or so. But that doesn’t mean we still won’t get hit hard. Some experts still predict the higher end of the totals.
Who predicts that?
DiMartino has all along been sticking with the higher amounts for our area, noting that the storm has taken shape relatively earlier and farther to the west than predicted by most models, which means the higher forecast for our area. He writes: “The surface low is CLEARLY further west than the majority of models had suggested.”
The guy from EPAWAWeather.com says that the storm has taken a “negative tilt” (basically the upper atmosphere tilting the storm back toward the west) earlier than expected, which means the system will remain closer to the coast and produce higher accumulation in our area. He writes on Facebook:
The latest analysis at the surface shows the low pressure is stronger and more WSW than the model guidance at 12z (this late morning/early afternoon) suggested. This matches up with our observations of the trough taking a “negative tilt” earlier. This means the trough axis is from SE to NW, this allows air to diverge over the low pressure system aloft. Which then allows air to rise faster and speed up the development of the low. The next thing we will be watching for is when this trough closes off and allows the low to slow down and stay closer to the coast. That should occur later this evening. Current forecast stands as called, no reason to change it right now.
But what about the models– aren’t they reliable?
Yes. And they may be right. But they’re only computer models, and they don’t take into account expertise and observation (it’s like the SABR-scout battle in baseball). DiMartino and EPAWAWeather.com are basically saying that the models aren’t yet accounting for the atmospheric conditions that will force the low to form earlier and remain closer to the coast. The latter has even gone after Adam Joseph over this… just hours after apologizing to Joseph and Cecily Tynan because his followers were harassing them:
In other words: What’s actually happening isn’t reflected in the models yet. But the most recent NAM is skewing higher:
So who’s predicting less?
Fuck if I know. The people who have been saying “more, more, more” have stuck to their guns all along. The models, which are typically calling for less, haven’t been as consistent in their projections. Philadelphia is right on the line and a shift of just a couple hundred miles could drastically impact snow amounts.
Still gonna be a big storm?
Uh, yeah. Meteorologist Ryan Maue has a massive weather erection right now– perhaps he calls it a storm surge: