Saturday, November 15, 2014

Thanksgiving Potentially Significant Storm System

Model guidance is now hinting at this Thanksgiving storm system to impact the Central and East US.

PSU
Beginning with the ECMWF model, with this forecast going out to 10 days, we see a deep trough pushing into the Southern Plains, neutrally-tilted, as the isobars pushing due south show. Note how pressure tendencies have rotated to the southeast corner of the vort max, likely telling us that this trough will start its maturing phase into a negatively-tilted trough in the next few days, if this model forecast were to go out further. A better description of tilted troughs is below from theweatherprediction.com .

The Weather Prediction
Given the freezing line / 540 thickness line in the top-right image being pulled all the way to the Southern Plains on that ECMWF graphic, as well as the expected negative tilt to this trough, the going ECMWF forecast would likey deliver severe weather to the Southeast, as well as some snow to those in the Great Lakes and southern Midwest, with exact areas to be determined.

Tropical Tidbits
Moving ahead to the GFS-Parallel forecast for the same November 24th timeframe as that ECMWF graphic, we see a very similar forecast. Once again, a strong trough is located in the Southern Plains, as shown by the deep negative height anomalies centered over Texas. If you guessed this trough was neutrally-tilted, you are correct! The height contours seem to be 'pushing' due south, which means it's neither positive or negatively-tilted. Unfortunately, I don't have access to the jet stream forecast for this timeframe from the GFS-Parallel model, which means we cannot tell if this trough is preparing to tilt negatively or not.

We don't have much to work with right now, since the storm's still about 10 days away, so here's a few graphics of precipitation forecasts from the GFS and GFS-Parallel model with this storm.

Tropical Tidbits

Tropical Tidbits
Andrew 

12 comments:

Anonymous said...

Doesn't tell us anything !! Rain or snow for the Midwest !!!

Andrew said...

There's no way to tell right now. Perhaps if you looked at the two maps immediately above this comment, you could see what model guidance is showing...

steve said...

hello andrew--so far, the forecast for the toronto area for that time frame is rain for 3 days and highs of 4-6 degrees celcius. The last time we had that type of forecast, we had 6 inches of freezing rain---what are your thoughts on that? Also we never did get the personalized forecasts for the toronto area.

John Hamric said...

Well said.

Anonymous said...

Well said.

Anonymous said...

If philly gets rain again I wont be happy

BearCub said...

This is looking like very snowy year for Binghamton, NY, with all the storms missing us, or taking a path that warms the area to rain, after freezes with flurries.

Anonymous said...

How is the November weather setting up the upcoming winter? What is the LRC pattern?

Anonymous said...

Andrew, I'm in Chicago. When should I put my snow tires on?

Anonymous said...

This new guidance also shows an adjustment north of earlier guidances which coincides what I've been seeing for a couple days in longer range forecasts. That's too bad for those in Chicago who wanted a snowy Thanksgiving!,,,,Looks more now like a windy wind driven rain now....:(

Anonymous said...

You're "surprised" by the two storms? This has been a thing for like two days now.

Andrew said...

Steve: Not every storm is the same, this one's likely to be different. As for the personalized forecasts, those are still delayed for some time.

Anonymous at 9:28: This should feed into this winter's recurring patterns.

Anonymous at 9:46: That's a decision that's up to your discretion, since I'm not exactly a car buff, per se. ;)

Anonymous at 10:04: Far too early to bang the gavel on that. It's certainly plausible, but too early to confirm.

Anonymous at 11:41: Forgive me for not realizing everyone catches on to weather events at the same time...