January 18, 2022

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Houston’s autumn weather taking a bit of a hiatus – Space City Weather

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Hobby Airport has started December with back to back 80 degree days, and there could be more to come. The last time we did back to back 80s in December was in 2019. We also accomplished the feat in 2016, 2015, 2013, and 2012, so it’s not super abnormal. Whatever the case, this is quite a departure from when I last wrote in this space a week ago and we had multiple European model ensemble members depicting 30s for lows in Houston this weekend. You can forget that. Let’s talk about what we can expect.

Today

Look for more fog this morning that should again lift by mid-morning in most spots. Dense Fog Advisories are posted around the region, but the fog is a bit spotty. It appears Brazoria County has some dense, as may parts of Montgomery County. The Beaumont/Port Arthur area is also seeing dense fog. Everyone else seems to be fine or seeing lighter fog. But you may run into some patches of dense fog as you maneuver around the area this morning.

Most areas are seeing restricted visibility this morning, but dense fog is a bit spotty, mainly south or east of Houston. (NOAA)

Once the fog lifts, we will be left with a mix of clouds and sun this afternoon, as highs again make a run for 80 degrees. One of the differences between yesterday and today is that we could see a couple sprinkles or showers as a weak disturbance passes by. It may be enough to wet the ground in a few spots, but that’s about all.

Weekend

Saturday will see any morning fog lift once again, leading to a partly to mostly sunny day. A few showers can’t be ruled out Saturday afternoon, but those would be the exception, not the rule. Look for highs in the upper-70s to around 80 degrees after a warm morning in the mid-60s.

Look for mostly the same on Sunday, except it may be more like partly to mostly cloudy. Again, a slight chance of showers will exist, but nothing you need to change plans for I don’t think. Another morning in the mid-60s or warmer will transition to an afternoon in the upper-70s to 80 degrees or so.

Monday

Here’s where some intrigue begins. A cold front should actually press through the region early in the day. We will probably start the day well into the 60s in most spots, and then when the front passes through we will see temps hold or drop a bit. So 80 degrees probably isn’t in the cards for Monday.

Instead, expect a period of morning showers and storms, then cooler, breezy weather in the afternoon. Temperatures should drop into the 50s on Monday night.

Forecast lows for Monday night and Tuesday morning show something more autumn-like, at least for a day, with 50s and a few scattered 40s around. (Weather Bell)

Tuesday and beyond

Offshore winds are going to flip around and become onshore winds quickly late Monday night and Tuesday, leading to a substantial increase in moisture. Beyond that, we could be entering a bit of an active period of weather with showers, storms, and even some strong storms in the area ahead of another cold front. This would be most likely later Tuesday or Wednesday. Cooler air would settle in late next week but probably again for only a couple days. By next Saturday, the GFS Ensemble mean already has an over 90% chance that temperature anomalies will be at least 10 degrees warmer than normal.

If we look at multiple GFS Ensemble members, 90 percent of them, or more, say that temperatures will rebound back to at least 10 degrees warmer than usual next Saturday. (Weather Bell)

This means that of the 30+ GFS ensemble members, almost all of them see much above normal temperatures again next weekend.

The Arctic Oscillation

I’m going to take you more under the hood about things right now. Meteorologists use numerous tools to make forecasts. One of those tools is called “teleconnections.” We don’t often talk about those here in an effort not to bore you, but I think it’s instructive today and can explain some of why December looks to be so much different than how autumn has been for the last month or so.

Teleconnections are ways of explaining that because one thing happened in one place, there’s more predictability that something else could happen in another place. In other words, if you have a certain pattern over Alaska, that can often teleconnect to a certain pattern downstream over the continental United States. There are numerous teleconnections we can use, but one of the most useful ones is called the “Arctic Oscillation,” or AO. You can read more about the AO here if you’d like. The simplest explanation? As the AO trends more positive, this indicates a stronger polar vortex, one that’s more likely to stay near the North Pole where it belongs. We typically lean milder in those scenarios with most cold remaining in the high latitudes. If the AO flips significantly negative it can mean the polar vortex has weakened and is more likely to allow chunks of cold to travel south toward the mid-latitudes where more people live. For example, just ahead of the massive February freeze last winter, the AO got as low as -5, which was one of the most negative values of this index recorded since 1950. That did not cause us to get super cold here in Texas, but you bet it helped explain why.

So, why am I telling you about this? Well, if you look at a forecast of the AO Index for the next 2 weeks, what stands out?

The Arctic Oscillation is forecast to remain sustained positive the next 2 weeks, which should help skew the odds toward warmer than normal weather here most of the time. (Weather Bell)

It’s raging positive (green line). We are frequently forecast to be at or above +2, with some ensemble members getting as strong as +4 to +5 at times. While this doesn’t guarantee that we’re going to stay warm deep into December, it sure skews the odds that way. No single teleconnection is a magic bullet in meteorology, but they serve as pieces to a larger, complex puzzle we try to solve each day. Today, this one stands out as one that will have an outsized influence on our December weather, so I thought it would be a good time to explain this to you. Hopefully it’s insightful! Enjoy the weekend.

Matt Lanza
2021-12-03 08:15:36

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