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Thursday, November 30, 2017

5 Musings as November comes to an end

The month of November is wrapping up and we now head into the season in which people start asking (more) about important things (like snow). It's also the end of a couple of other seasons though. Here's more on that, as well as a look ahead to this weekend's beautiful weather, a major weather pattern shift on the horizon, and why a satellite that produces amazing imagery went dark today.

1. November 30 marks the end of what we in the business refer to as "meteorological fall." We all know that REAL (astronomical) winter doesn't start for a few weeks yet. But weather folks have to be different. So for us, winter starts tomorrow. That's mainly because when computing climate statistics and so forth it's much easier to break the seasons by in 3-month groupings at the start/end of a month. September-November was fall, and it ended warm. Check out these numbers: 63, 68, 66, 67, 68, 67, 68. Those are the high temperatures for the past week. Who says we don't get fall? For the meteorological season, our unofficial average temperature was 65.1°, or roughly 1 degree above the long-term average. Precipitation totaled 7.46", which is a bit over 5" below average, with only 1.81" of that falling in November. That results in conditions like this:
The U.S. Drought Monitor, zoomed into the Lower Mississippi Valley, shows "abnormally dry" conditions creeping into the metro from the south.
2. November 30 also marks the official end of the Atlantic hurricane season (and all the people say "Amen!"). There's no way else to slice it, it's been a brutal year. From Harvey in Texas, to Irma in Florida and the southeast, to Maria in Puerto Rico, this will be one for the record books. I don't necessarily believe in "we were due," but it had been 12 years since the last U.S. landfall of a major hurricane (if you don't count "non-tropical" Sandy). Here's a summation of the numbers:
17 named storms, ten hurricanes, six majors, and two category 5's. And a bunch of other records broken. Good riddance! (If you want to hear what The Weather Channel's Jim Cantore had to say about the season, check out the Carolina Weather Group episode that aired just last night, with yours truly on the panel!)

Preliminary storm tracks for the 2017 Atlantic hurricane season. Click for larger view. (NHC)
3. So when will this warm weather end? Not for several more days! With a fairly tranquil weather pattern nationwide for the next few days, no major fronts are expected through the weekend. We'll see mild weather with highs in the 60s continuing into early next week as high pressure aloft dominates.
The GFS model for the jetstream level of the atmosphere, valid Monday morning, shows a ridge of high pressure over our region (the large "hill" in the eastern U.S.). However, the first signs of a significant pattern shift can be seen in the western U.S. where a large trough (the "dip" in the jet stream) can be found. (PivotalWx)
Precipitation forecast through Sunday evening. The beginning of the next system to affect our area shows up in the Northwest U.S. (NOAA)
As for weekend activities, the forecast is grand! Here's a planner for Saturday, which features the St. Jude Memphis Marathon, a Tiger football watch party at the Liberty Bowl, and Christmas parades among other things. You can find the official MWN Forecast here or in our app.



4. What brings the warm weather to an end and how cold does it get? If you looks above again at the jetstream forecast for Monday morning, you'll see a huge dip over the western U.S. As that shifts east, it "dips" even further south, allowing cold air from Canada to spill south into the eastern U.S. Early signs are that this pattern - dominated by an eastern U.S. trough and western U.S. ridge - could last right into the middle of December. There will be ebbs and flows of course, but much colder air will be found in the eastern U.S., including the Mid-South, in this pattern.

As the pattern shifts, watch for the potential for some heavy rain and thunderstorms near a front that moves through sometime between next Monday night and Tuesday night. A relief from the dry weather, but also the end of fall most likely. Below is what this morning's GFS (American) model ensemble said about temperatures for the next 2 weeks. Note that these are not exactly right, but give you a good idea of the trend.

The GFS model is run multiple times with slightly different parameters to create an "ensemble" of potential solutions. Above is the average high and low temperatures for the next 2 weeks from this ensemble. (WxBell) 

5. Finally, November 30 also brought to an end (if everything goes well) the "preliminary, non-operational" phase of GOES-16, our new awesome-sauce meteorological satellite that was launched just about one year ago. It's been in testing phase for much of this year and has provided dramatic and beautiful imagery from 22,500 miles up. For the next 3 weeks, its propulsion systems are pushing it a bit further east from its test location, where it will become fully operational in mid-December as GOES-East. This day will be nearly as monumental in the meteorological community as the day it was launched and the day it sent back its first images. For more on GOES-16 (formerly GOES-R) see this blog post.

By this time next year, its sister satellite (GOES-S/17) will likely be operational over the west coast as GOES-West. A new chapter in satellite meteorology is being written! Below was the parting image, in natural color, from GOES-16 this morning at 7:32am CST.


Erik Proseus
MWN Meteorologist

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