Weather

A super rarity: Twin hurricanes in the Gulf of Mexico?

The experts were calling for a strong finish to the 2020 hurricane season in the Atlantic basin, and it looks like things are about to get really interesting in the Gulf of Mexico.

It looks increasingly likely that there will be two organized tropical cyclones in the GOMEX simultaneously next week.

The first is Tropical Depression 14, which formed a few days ago and is currently getting its act together in the Caribbean. It may briefly reach hurricane strength before reaching the Yucatan Peninsula Saturday evening, and then is currently forecast to regain strength as it reemerges over the open waters of the Gulf of Mexico and takes aim at the Texas coast. The current forecast brings it ashore east of Houston late in the day on Tuesday as a weak, Category 1 hurricane.

The second is Tropical Depression 13. It actually formed first out of the two disturbances, and has been marching across the Atlantic high seas. It is likely to be a tropical storm by late Friday, as it deals an indirect blow to the northern Leeward Islands.

As Tropical Depression 14 is potentially making landfall near Houston, TD 13 could be preparing to make landfall somewhere along the Florida panhandle. Currently, it is forecast to make landfall as a weak, Category 1 hurricane. But if either of these storms is going to rapidly develop and become a stronger storm, it seems like TD 13 has the most potential.

The next few days will be interesting. TD 13 is traveling over some very warm waters that are ripe for development. However, there should be sufficient mid-level wind shear to inhibit that development somewhat. If and when that wind shear relaxes, then conditions will be better for this developing storm to become a hurricane. If it were to strengthen more than expected, or more quickly than expected, it could wind up dealing a direct blow to South Florida before it potentially gets into the Gulf of Mexico.

As of this evening, models showed a pretty wide range of possibilities with this storm. Some solutions actually sheared it apart completely, while others showed it becoming a major hurricane.

Having two hurricanes ongoing simultaneously in the Atlantic basin is somewhat unusual — though certainly not unheard of nor necessarily uncommon. But having two hurricanes at once in the Gulf of Mexico would be rare indeed. In fact, it appears that it’s never happened before.

The most interesting scenario with these two storms is the Fujiwhara Effect. That’s where two cyclones that are close together actually feed off one another and close the distance between themselves. It has happened only twice that meteorologists are aware of: In September 1933 and in June 1959. One important thing to note: If the Fujiwhara Effect were to happen, it would not cause the two storms to become one and form a monster hurricane; that’s the stuff of SciFi movies. In fact, just the opposite is likely: the Fujiwhara Effect would possibly cause one of the storms or even both of them to weaken.

Weather

Tracking our incredible snow drought…and whether it’ll soon end

It isn’t that snowflakes haven’t flown across the northern Cumberland Plateau this winter, and there have been winters when that was the case.

But what makes Winter 2019-2020 incredible isn’t the lack of snow this winter, but how it’s a continuing theme of recent winters. Simply put, we’re in a snow drought.

So far in 2019-2020, there has been zero snow recorded in Oneida by the National Weather Service. Now, keep in mind that snowfall can be spotty when it’s light, and this is measuring snow only at one location (the Oneida Water Treatment Plant at the intersection of Industrial Lane and West 3rd Avenue, to be specific). There was a light snow in November and two more in December — totaling as much as 2-3 inches in some locations. So the NWS’s numbers aren’t the be-all, end-all … but when it comes to the official record, they’re all that matter.

So, officially, we’ve had no snow in Oneida this year. And, officially, we had only a trace of snow in Oneida last year. We also had no snow in Winter 2016-2017, and only 2 inches of snow in Winter 2017-2018. To find the last winter it really snowed in Oneida, you have to go back to Winter 2015-2016, when we had 10 inches of snow in January. The winter before that, we almost went without measurable snowfall, until a drastic pattern change in mid February that resulted in 7 inches of snow the second half of that month.

What gives? There is more precipitation falling in the Cumberlands now than ever before. The 4 wettest years on record have occurred in the last 6 years, an astounding statistic. Yet only 2 of those 6 years have featured average or above-average snowfall. One key reason why is that we’ve been warmer while we’ve been wetter. But while there’s no denying that our winters today are milder than they once were, the differences aren’t extreme. January 2017 was the third-warmest on record in Oneida, February 2018 was the warmest on record, while February 2017 was the third-warmest on record and February 2019 was the fourth-warmest on record, and December 2015 was the warmest on record. Still, there has been ample cold air…but it has presented in different ways, and mother nature hasn’t threaded the needle for winter weather in this region very often the past several years.

Unfortunately for the snow-lovers, if you’re looking for that to change this winter, you may be disappointed. I posted a few days ago about a coming pattern change, and how it was going to be colder — but also that there were no signs yet of it being snowier. And, so far, that’s still the case.

The extreme warmth that we saw in the first half of January is certainly gone. If the month ended right now, it would be the warmest January on record in Oneida. But the second half is going to be much colder than the first half. But still not that cold. And, with the arrival of colder air, the active storm pattern is also slowing down.

A rare (for this winter) outbreak of arctic air is still headed our way for the first of next week. After we warm up Saturday (so it can rain!), much colder air is going to settle in by the end of the weekend. We will be stuck in the mid 30s on Sunday. On Monday, we likely won’t get out of the 20s, after a low in the teens. And it now looks like we will hit single digits on Tuesday morning before we finally rise (slightly) above freezing Tuesday afternoon.

That’s a pretty impressive cold shot. But it’s still just a transient cold shot. The warm-up will begin quickly, and we’ll be well into the 40s by Wednesday and maybe back into the 50s as soon as Thursday.

After that, the next storm system will impact our area around one week from now: January 24-25. This one could end as a little snow, as cold air comes crashing in on the back side of the departing system, but the level of cold air isn’t nearly as impressive as the cold blast we’re going to see in a couple of days, and the amount of snow we receive — if any — probably won’t be anything to write home about.

From there, it had once appeared that another round of cold air would settle across our region on the last couple of days of January, but that is now looking unlikely, as it looks like average to slightly above-average temperatures will be in store as January ends and February begins. So, for now, there’s only one very slight chance of snow showing up in the next two weeks, and no real threat of a significant winter storm.

I blogged a couple of weeks ago about the threat of going through winter without a pattern change that would lead to wintry weather of any sort. We’ve certainly seen a pattern change, but we’re still not hardly where we need to be if you’re wanting to see sustained cold and snow chances. The major teleconnections (the NAO, the AO and the PNA, which I won’t go into further detail on in this post because we’ve talked about them before) look like they’ll continue to trend slightly more favorable for winter weather in the eastern U.S., though they’re still leaving a lot to be desired. With the MJO continuing to show signs of progression as well, I wouldn’t totally write off February. The pattern needs to evolve some more, but if it does, it could be that this will be a repeat of 2015. Remember, that winter featured no snow, either … until the middle of February. But once Ol’ Man Winter showed up, he did so with a vengeance. We had an ice storm in western Scott County, more than a half-foot of snow spread out across several events, and record cold temperatures for the month of February. I’m not saying that’s going to happen, just that it isn’t outside the realm of possibility.

Even so, we’re now moving quickly out of the heart of winter. The days are getting longer, the sun angle is getting higher in the sky, and the average temperatures are on their way up. We can, and have, recorded serious snowfalls after the calendar has flipped to February and even March. But, from a climatological perspective, the chances of appreciable snowfall begin to decrease dramatically as we move through the month of February.

So, right now, we can say with near certainty that it probably isn’t going to snow (not a lot) in the next 2 weeks. By that time, we’ll be in early February. And if we get there and we can still say with certainty that it’s not going to snow in the 2 weeks after that, it’s going to be getting awfully close to time to stick a fork in this winter, and chalk it up alongside other recent winters as our snow drought continues. In the meantime, we wait and see if the pattern continues to evolve into one that is more favorable for winter weather as we head towards February.

Weather

A pattern change is in the works; what will it mean for cold and snow?

Last week, I wrote about how Winter 2019-2020 has been a dud so far, and how we’re going to be at risk of it ending without ever getting started if we don’t start to see signs of a pattern change emerge soon.

Well, as we enter the second half of January, a pattern change is emerging, though it isn’t yet clear what that’s going to mean for sustained cold, or snow chances. Both have been MIA so far this winter.

After very warm temperatures again on Wednesday, January 15, a cold front is going to move through the region and begin to usher in colder air, and it’s going to be much colder by this weekend, after a stronger cold front passes through on Saturday. The high on Sunday looks to be right around the freezing mark, and then it gets even colder. By the first of next week, we could see isolated locations in favored areas of the northern Cumberland Plateau flirt with single-digit temperatures for the first time this winter.

This is probably the most impressive shot of cold air that we’ve seen so far this year. There won’t be a threat of snow accompanying it, but it’s still going to feel a lot different than what we’ve been accustomed to in a January that’s running a whopping 10 degrees above normal so far.

(Regarding January, here are some interesting numbers through the first half of the month: We’re exactly 10.0 degrees above average [54.2 degrees], and we’ve received exactly twice the normal amount of rain [4.10 inches]. The pattern change means we should be somewhat drier the rest of the month, so we aren’t going to flirt with record rainfall. And with temperatures turning much cooler, we should also get back in line in that regard, as well. But if the month ended today, it would be the warmest January on record, beating out 1974.)

The cold wave that is going to settle in on Sunday isn’t going to be sustained, and we’ll be well into a warming trend by the middle of next week. But we aren’t going to return to temps in the 60s and 70s anytime soon.

As for what happens in the extended pattern, only time will tell. The teleconnections are pretty much neutral across the board. I wrote last week about the positive North Atlantic Oscillation (NAO), the positive Arctic Oscillation (AO) and the negative Pacific North American (PNA) ridge index, and how all of those lend themselves towards warmer-than-average conditions in our region. Now the NAO, AO and PNA are all trending towards neutral territory. The Madden-Julian Oscillation (MJO), which was also briefly touched on in the last post, is moving into more favorable regions but not the regions that correspond to the coldest weather for our region — at least not yet. All of that adds up to a weather pattern that doesn’t really have a driver. At face value, you could say there are equal chances for above-average or below-average temperatures as long as this pattern is in place, with no strong signs for either extreme warmth or extreme cold. In such a pattern, if I had to bet for one or the other, I’d bet for cold over warmth.

Right now, the next storm system looks like it’ll impact us around January 24-26. There have been some winter storm signals with this one; it’s primarily going to depend on the track of the storm, assuming it does develop. However, the cold air that’s going to be in place in advance of the storm will be rapidly eroding, and at first glance there doesn’t appear to be an impressive reinforcing shot of arctic air coming down the pipes, so don’t be surprised if this storm winds up too far north, or without enough cold air, to produce snow for our region.

The next shot of real cold air after the week upcoming looks like it’ll settle in around January 28-31. That may again be a transient shot of cold air without a turn to sustained cold in the Mid-South region.

So the bottom line is that conditions are becoming more favorable for winter weather that actually feels like winter. But if you’re looking for snow, there’s still nothing on the horizon worth talking about as we move rapidly through the heart of winter. Remember, our average daily high is 44 degrees on January 15, but it’s increasing slightly every day. By February 1, it’ll be 46 degrees. By February 10, it’ll be 48 degrees. And by February 18, it’ll be 50 degrees. So if you don’t want cold or snow, take heart. Winter may be finally showing up, but spring is right around the corner.

Weather

The diminishing winter of 2019-2020

Because I have a lot of friends who are weather fanatics, finding strange joy in the bitter cold and frozen precipitation that most of the civilized world finds miserable, I see plenty of gnashing of teeth and rending of garments on social media when winter isn’t going as hoped for … and winter 2019-2020 is obviously not going as hoped for. It might’ve seemed like it early, when teachers and students were enjoying a November snow day, before the last of the fall foliage had even turned loose, but things just never materialized from there.

In recent days I’ve seen a couple of well-meaning folks admonishing the complainers, reminding them that winter is only a couple of weeks old. In other words, don’t give up on it just yet.

It’s true that winter isn’t far along on the calendar. Officially, winter doesn’t begin until the winter solstice, which is December 21. But from a meteorological standpoint, winter begins on December 1, ends on February 28, and we’re in the climatological heart of winter. The sun is climbing higher in the sky each day, and the proof is in the setting sun each evening. Sunset today was at 5:38 p.m. Just a couple of weeks ago, as we were preparing to celebrate Christmas, the sun set at 5:25 p.m. As it climbs higher in the sky, our temperature increases and the window for snow — real snow; serious snow that lays around on the days and causes all the chaos that winter-lovers dream of — begins to close.

In Oneida, we reach the coldest part of the year on December 30. That’s when our average daily high temperature drops to 44 degrees. It stays there for a while, but rises to 45 degrees on January 18, and just keeps increasing after that. By January 31 it will be 46 degrees, and then the uphill climb to spring accelerates as the calendar flips to February. By just four days after Valentines Day, our average daily high in Oneida is 50 degrees. The higher sun angle does more than warm the atmosphere and lengthen the daylight hours. Its penetrating rays make it more difficult for snow to accumulate, and melt it more quickly, even behind thick cloud cover. February snowfalls have less staying power than January snowfalls.

That’s not to say that we can’t have significant snowstorms in February and even in March. Obviously we can, and history speaks for itself. February 1998 and March 1993, anyone? But in terms of probability, you wouldn’t want to bet the farm on accumulating late winter or early spring accumulating snows.

So we’re in the heart of winter, and so far Winter 2019-2020 has been a winter that wasn’t … again. There are a variety of reasons why, but it didn’t always look like this was going to be the case. Long-range forecasts in late summer and fall certainly pointed towards a cold and snowy winter. Even the Farmer’s Almanac projected misery. There was a pre-winter buildup of cold air in the arctics — which is our source of cold air in the northern hemisphere, like freon to an air conditioning unit. But conditions simply haven’t lined up for that cold air to spill into the southeastern U.S.

What’s gone wrong? Several things. But perhaps chief among them, the Pacific Ocean simply hasn’t cooperated. With a lack of ridging in the eastern Pacific to help steer the jet stream, modified Pacific air has flooded the continental U.S. The result has been an active storm pattern — hence, the reason it’s been so wet in Tennessee since the latter part of November — but an unfavorable storm track (in a nutshell, we only get snow in this part of the world if storms track to our south and place us in the cold sector; if the storm track is to our north, we’re in the warm sector and will see primarily rain) and lack of cold air has prevented snowstorms from forming. There has been a lack of atmospheric blocking in the northern Atlantic that can cause cold patterns to take hold in the eastern U.S., and the lack of ridging in the eastern Pacific has allowed the available cold air to pool in the western part of the country, leaving much of the eastern U.S. in a milder weather pattern.

It’s not quite that simple, of course, but that’s a broad overview of what has happened.

Back to the admonishers’ point, it is true that the season is young. Winter may have begun in meteorologists’ eyes back on December 1 — meaning we’re about halfway through already — but snowstorms are uncommon in Tennessee in December. Our time to shine, if you like wintry weather, is January and early February. From 1981 through 2010, the rolling 30-year period currently used by the National Weather Service, our average annual snowfall in Oneida was 7.1 inches (which, by the way, is much lower than the average annual snowfall when numbers from 1971 through 2000 were in use). Of that, only 1.3 inches, on average, has fallen by December 31, and 4.2 inches has fallen by January 31. By February 28, the average for the season jumps to 6.4 inches. So, the numbers aren’t difficult to break down: 1.3 inches of snowfall in December, 2.9 inches in January, 2.2 inches in February, and 0.7 inches in March.

However, there is something to keep in mind, and that is the ability of meteorologists and the computerized tools they rely on to project weather patterns beyond the next 3-7 days. The medium-range guidance models most often used by meteorologists, the American-made GFS and the European-made ECMWF, are 15-day operational models and both are quite adept at projecting patterns for up to two weeks at a time. Beyond 15 days, long-range forecasting begins to become more of a crapshoot.

Just before Christmas, when I pointed out in a Facebook post that the next two weeks looked somewhat mild and rainy, I said that if we got through that two-week period and there was no sign of the pattern breaking down, it might be time to start preparing to throw in the towel on Winter 2019-2020.

And here we are. Two weeks have elapsed. We could be reasonably sure there wouldn’t be major winter storms in the Cumberland Plateau region during the Christmas and New Year holiday period, and there wasn’t. Some light snow on January 4 that didn’t amount to anything more than a light dusting in some areas was the extent of our wintry precipitation. So what does the pattern look like now, going forward? In a nutshell: More of the same.

For the next two weeks, the mild and wet pattern looks to persist. The upcoming weekend looks like a virtual washout for our region, and we’ll be talking more about the possibility of severe weather than wintry weather (chances of severe weather are relatively low on Saturday, but strong thunderstorms are possible). After that, there are signals of additional storm systems around January 14-15 and January 20-22. Combined, these next three storms could produce upwards of half a foot of rainfall for the already-saturated region, but virtually no snow. Temperatures are likely to push into or near the 60s with each of the storm systems.

If — and I stress “if” — we get through this next two-week period and a pattern change still isn’t on the horizon, we will be entering the final week of January and looking forward towards the middle of February. And if we get to Valentines Day and a pattern flip to cold and snowy weather still isn’t looking likely, it is almost certainly going to be time to declare the entirety of Winter 2019-2020 a big, fat bust.

So that’s why I say that this winter is dwindling. Chances for it to be a memorable winter in terms of snow and extreme weather are diminishing. With that said, there’s a major caveat that deserves to be highlighted: it only takes one significant snow storm to make any winter memorable. The Winter of 1992-1993 was quite bland before the Blizzard of ’93 that March, and the Winter of 1997-1998 was ho-hum before the devastating dynamic cooling storm that exceeded even the 1993 blizzard in terms of the havoc it created.

There are more recent examples, too. The Winter of 2014-2015 had featured zero — as in 0.0 inches — snow until February 17, three days after Valentines Day. Then we got slammed with a major pattern change, temperatures that bottomed out at -11 (an all-time record for the month of February, and the coldest temps that Oneida had recorded since January 1984), and a total of 7 inches of snowfall in the final two weeks of February. The cold pattern continued into March 2015 with record-low temperatures before spring finally arrived by the middle of that month.

So it’s certainly not time to declare winter over, not by any stretch of the imagination. And there are some signs that a pattern change could be on the horizon. For now, though, those signs continue to be delayed and I wouldn’t put much stock in the idea of a pattern change until it’s actually showing up with a little more consistency on long-range models.

For now, the North Atlantic Oscillation — which has been predominately positive this winter — looks to stay in positive territory through the middle of the month, though it does show signs of dropping back towards neutral territory as we get into the latter stages of January. The NAO is a measure of storminess in the northern Atlantic Ocean, and a negative NAO state is typically desirable for sustained cold and snow chances in the Mid-South. The Arctic Oscillation has spiked to extreme positive territory, and will stay there for the next several days before perhaps trending towards neutral by the latter part of the month. For now, models keep the AO in positive territory, however. The AO is a measure of storminess in the arctics, and a negative AO is generally preferred for cold air to be unleashed into the Lower 48, while a positive AO is viewed as a hindrance for serious wintry weather. Finally, the Pacific North American ridge index is trending into negative territory and will become sharply negative in the days ahead, before beginning to trend back towards neutral in the latter part of the month. For now, models keep the PNA for the foreseeable future. The PNA is a measure of ridging in the eastern Pacific. A lack of ridging, which places the PNA in a negative state, doesn’t force colder air into the eastern U.S. and often leads to a pattern where the West is generally colder than normal and the East is generally warmer than normal. A positive PNA is generally preferred for cold and wintry weather in the Mid-South.

Taken together, a +NAO, +AO and -PNA isn’t a death knell for wintry weather in Tennessee, but it’s definitely not an ideal setup. On top of this, the Madden-Julian Oscillation — a measure of omnipresent and eastward-moving storminess in the tropics — looks to remain in unfavorable position for the time being. The current forecast has the MJO progressing through Phases 4-6 for the next couple of weeks. Generally speaking, Phases 7, 8, 1 and 2 are where cold weather outbreaks occur in the eastern U.S., while Phases 5 and 6 tend to be where warm-weather extremes occur. Not surprisingly, with the MJO stuck in Phases 4-6, the next couple of weeks look mild.

If, over the next couple of weeks, the MJO begins to show signs of progressing into Phases 7 and 8, and if there are signs of increased ridging along the Pacific Coast, and if there are signs of the AO flipping to negative, those will be pretty good indicators that a pattern change is brewing. And I’ll add that brand-new guidance for February 2020 from the long-range CFSV2 model is showing cold air flooding much of the eastern half of the country in February. Previous guidance from this model was showing cold air only in the New England region for February. However, the model doesn’t have a good track record thus far this winter. It did not lock on to the mild January pattern in the eastern U.S. until late in the game.

The bottom line: It’s far too early to stick a fork in Winter 2019-2020, but we’re further along in the game than it might appear at first sight. For now, a mild and wet pattern is in command and will continue its death grip on the Mid-South region for at least the next 10 days or so. After that, it may be time to re-evaluate the broader atmospheric setup … and if there are no serious signs of pattern change, the ol’ fat lady may be starting to warm up her vocal cords.