simpsonsbuff

Great stuff, Will. This jibes with other posts I saw on this board... Everybody cracks jokes at the long range NAM (with some good reason), but it occasionally sees something nothing else sees...

Here is my detailed recount of the March 4-6, 2001debacle.

There's a lot of "stories" behind it. First off, almost all guidance was going for a monster Mid-Atlantic HECS about 96-108 hours out. Back then the time range beyond 96h meant very little...but models actually did have it further out than that. Only a few model went further. The UKMET, ECMWF and the MRF (the extension of the AVN which is now the GFS all in one package) all called for it. By the time we got to 84 hours out, all models showed it still...basically 2-4 feet for DC-NYC with Boston getting fringed....except the old ETA-x....the old ETA went to 60 hours, but the "ETA-x" was the ETA to 84h which eventually became the NAM (run under the ETA) to 84 hours but is now run under the WRF and not the ETA anymore...ETA has been retired from operational use, only used in the SREF now. That run of the ETA-x had the storm much further north and crushing New England while limiting the snow in the Mid-Atlantic. I believe this was Friday at 12z. Nobody took it seriously as it was the ETA extended beyond its already 60h limit.

The next run at 00z Friday night, the ETA-x showed it again, but the other models held serve....the ECMWF didn't run at 00z back then...only at 12z, so its solution was non-existent. It was the best model back then too like recent years. We were now at 72h out or closer. The 12z runs came out on Saturday morning and they shifted north, limiting the snow for DC (probably from 2-3 feet to about 1-2 feet), but from Wilmington DE northward it was still monstrous except the UKMET shifted slightly north of that, to Philly and northward.

A little side note. The AVN had performed absolutely brilliantly in the other big east coast storm on December 30, 2000 and also on the December 3, 2000 North Carolina/Virginia bust. The ETA hadbeen way too bullish and far west in both events while the AVN schooled it. So a lot of attention and credence was being given the AVN. That was a big factor in the forecast IMHO.

After those Saturday morning runs at 12z (while the ETA showed a huge hit north again at 48-60h now in the operational run)...the forecast was still for a monster M.A. hit. The 12z ECMWF wouldn't come out until around 8pm that evening. It used to come around at that time back then. As 8pm rolled around, the ECMWF all of the sudden jumped way north and agreed with the ETA solution. But most forecasters disregarded it as it had been pretty steadfast before (maybe a burp run?) and the AVN was holding really steady and it had done so well on East Coast storms that winter. By Saturday night, the GGEM started to go north, the AVN held serve once again (having been the model of choice all winter), the ETA went north again taking Philly and nearly NYC out of the huge snow and hammering New England/Boston with a storm like Feb 1978. UKMET I don't recall what happened, but I know the forecast stuck close to the AVN.

Again there was no 00z ECMWF run back then. Only 12z.

By 12z Sunday morning just 24h before the event, the AVN once again gave a monster hit to the mid-atlantic except it shifted a bit north...it was mostly Philly northward. The ETA gave New England a huge HECS again, the GGEM finally went well north...and so did the UKMET. The ECMWF would have to wait until 8pm as usual. Most forecaster were trusting the AVN because it had served them well that winter after the obscene ETA busts and the AVN had nailed two major east coast storms.

When 8pm came in, the writing was on the wall if there was any doubt left. It was way north and took Philly and possibly even NYC out fo the big snows, though NYC was still on the line.

The forecasts started being revived when the 00z AVN came in late that Sunday night and it finally jumped north, but still not far enough....it still gave big snows to Philly (but not historic totals) and historic totals to NYC. I think this is when most operational forecasters knew something was terribly wrong. You have to remember it was so hard to trust any model that winter and the AVN was the best until that point.

That was the first storm that I recall Dave Tolleris (whether you like him or not) came up with the old "EE rule"...when the ETA and ECMWF (both start with "E") agree, you don't go against them. I was lurking on ne.weather back then. When the EC came north to agree with the ETA back on Saturday, he said the M.A. was cooked and got a lot of crap for it on the boards as you can imagine.

That's just my personal recollection of all of that storm. I don't claim for all of it to be 100% accurate, but I usually remember things very vividly, so I think at least most of it is right. There was a lot of controversy and talk amongst the weather people both on ne.weather and the NWS back then. It ended up being a huge interior New England and NY State HECS. Even the models at the last second kind of busted at Boston...only getting 10" while they were forecasted for double that...but the suburbs got all the snow.

Very incredible storm both from a forecasting standpoint and also as a student observer back then when I first learning a lot of the intricacies of forecasting and models.