Rain, Wind & Even Snow Arrive As Josephine Passes South
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You see that right there? That is Subtropical Storm Josephine. It’s packing winds of 100 km/h, with gusts as high as 120 km/h, and as of late this morning it was east of Cape Cod and about 700 km south-southwest of Halifax. Josephine is already playing a role in the weather in Nova Scotia, where rain is falling, some of it rather heavy. Meanwhile in Newfoundland, that rain is just starting to arrive in the south and will become more widespread overnight. There’s also the potential for some snow tomorrow, and high winds for much of southern Newfoundland tomorrow afternoon and evening.
Where Josephine is headed
The forecast track for Josephine’s centre over the next few days, through Sunday morning, keeps the storm very far south of Newfoundland and pretty far southeast of the Maritime provinces, with wind speeds around the system remaining fairly high. But that doesn’t mean the impacts won’t be felt on a wider scale. We can already see cloud from this storm stretching from New Brunswick almost all the way down to Bermuda, so it’s a very large system, and that’s certainly a sign of a subtropical system rather than a tropical one.
As Josephine works its way south of Newfoundland, it’s going to pull in some cooler air. That will expand the precipitation field and turn it into more of a post-tropical storm, or mid-latitude cyclone, rather than a subtropical or tropical system.
Tropical, subtropical or post-tropical?
So what’s the difference between these three types of lows? It’s really about the temperature structure.
- Tropical storms are warm throughout the whole column of the atmosphere, and they rely on the heat of the ocean to drive them.
- Subtropical storms are a bit of both: the warm ocean, plus cold air aloft (a cold upper low) that helps destabilize the atmosphere and get that lift going.
- Mid-latitude lows, like a nor’easter or a post-tropical storm, are basically cold air wrapping in and around the centre of the cyclone.
With a hurricane, the strongest winds are very close to the eye; that’s the eyewall you hear about. With subtropical storms and post-tropical storms, the wind field is bigger but not as intense. We can still get hurricane-force winds, though, like we’re going to see with Josephine as it passes south of Newfoundland and out over the Grand Banks.
Fronts don’t exist with tropical or subtropical storms, but they do play a role in mid-latitude lows, and there will eventually be a cold front with this one. And as these storms leave the tropical realm, they expand significantly in size, their precipitation spreads out, and in some cases a storm that was once tropical or subtropical can even produce frozen precipitation. It looks like we’re going to see that tomorrow.
Why? Looking at the temperature map, it’s quite cold over Quebec, Labrador and Newfoundland, and Josephine is beginning to pull that cold air in. It’s still pretty warm over the northeastern United States, and around Josephine’s centre we’re still seeing those brighter oranges, which tell us it’s still a warm-core system. There isn’t a lot of cold air wrapping around it just yet. But watch what happens as we go through time: the warmth around the centre disappears as the cold air gets pulled in. That’s Josephine going from a subtropical system to a post-tropical system, or mid-latitude low. It’s always neat to see the nitty-gritty meteorology, but it also makes for a difficult forecast, because when this happens, we can get high winds, copious amounts of rain and sometimes even snow. That’s what we’re going to see this go-around.
Wind Warning for Friday 💨
A Wind Warning is already in effect for southern parts of Newfoundland, from Burgeo–Ramea to the southeastern Avalon Peninsula. Tomorrow we’ll see winds gusting between 80 and 110 km/h, mainly in the afternoon and evening.
The winds pick up tonight, but tomorrow is when they really ramp up, especially after lunchtime. By 5 or 6 PM, we’re looking at gusts of 80 km/h in St. John’s, 93 in St. Bride’s and 86 in Trepassey, and those wind speeds stay elevated until about midnight before they begin to slacken off by Saturday morning.
If we’re going to see gusts between 90 and 110 km/h, it’ll be in the Burgeo and Harbour Breton areas, on the Burin Peninsula and on the southern Avalon. Forecast peak gusts elsewhere: St. John’s 83 km/h, Ferryland 99, Clarenville 74, Bonavista 72, and just under 70 for Twillingate. So, breezy, yes, but truly windy in a relatively small area.
Snow over higher terrain ❄️
We’re also going to see the potential for a little bit of snow, mainly at higher elevations. Earlier it looked like the Burin Peninsula might see some snow, but the latest computer model guidance shows the most likely spot is the Bay d’Espoir / Connaigre region, mainly inland over higher terrain. Right along the coast, temperatures of 3 to 5 degrees will be too warm for snow. If we do see a few centimetres, it’ll be inland over the high ground, like the southern part of the Bay d’Espoir Highway, not on or near the coast.
Places like Harbour Breton, St. Alban’s and Conne River will likely just see rain or rain mixed with wet snowflakes. Computer guidance today has kept the track a little farther south, pulling the precipitation a little farther south with it, so we’ll keep an eye on that.
How it plays out
Rain is falling across Nova Scotia right now and continues overnight, and it makes its presence known over southern and eastern Newfoundland by tomorrow morning. As we’re getting up and the kiddies are heading off to the bus stop, it’s going to be pretty miserable out there for much of southern, southeastern and eastern Newfoundland. Once you’re west of Clarenville, though, it may not be too bad.
By midday tomorrow, that first batch of rain moves east. We may see rain or ice pellets at times over the Burin and Avalon peninsulas, and maybe a few wet flakes here and there, but it looks like the bulk of the snow may be limited to the Cape Breton Highlands and parts of Nova Scotia, and it may actually fall offshore and stay to the southwest of Newfoundland. We’ll see how that transpires, but either way, if we see snow, it’ll be during the day tomorrow.
Tomorrow night and Saturday morning, we dry out for at least a little while. But as what’s left of Josephine stalls and swirls, we may get another round of rain on the Avalon Saturday afternoon, especially on the southeast Avalon and the Southern Shore. The ECT50 takes place Saturday morning, so fingers crossed we stay dry for that, depending on how the rain moves in later in the day. I’ll have a forecast for that for you tomorrow.
How much rain? 🌧️
The highest amounts look like they’ll be on the southeast Avalon, with 30 to 40 mm of rain. There’s about 14 mm in the forecast for the St. John’s area, close to 20 mm for Placentia and Argentia, and lesser amounts as you go north and west of there. So this is not going to be a prolific rainmaker by any stretch of the imagination.
Feeling like November 🥶
The wind is going to make it feel pretty darn cold tomorrow. By midday, the wind chill will be −3.5 in St. John’s, −3 in Marystown and −2 in Grand Falls-Windsor. As the afternoon goes on, it’ll feel close to −5 in Millertown, −3 in Corner Brook and −4 in St. Anthony by 8 PM. It’s not even November yet, but it’s going to feel a lot like it.
Overnight lows are 2 to 4 across Newfoundland, and tomorrow’s highs are 3 to 5, even in the areas that may see some snow. Again, it’s inland over higher terrain where we might see it.
Saturday looks breezy, drizzly and cold, and is by no means going to be a peach of a day across most of the province. But the 7-day forecast shows significant improvement by Sunday, with temperatures back into the mid-teens by Monday, before cooling off again for Tuesday, Wednesday and Thursday.
Labrador
It’s clear and cold in Labrador tonight, down to −7 in Wabush. Tomorrow brings highs of 2 to 5 under sunny skies in the Big Land.
In southern Labrador, temperatures are between about 9 and 12 degrees through Monday, a little cooler Tuesday, Wednesday and Thursday. In the north, there’s some snow going to rain on Sunday. In the west, it’s up to 9 or 10 degrees for the weekend, but look at Tuesday: a high of only −1. It’s looking very cold, but there’s no major snow in the forecast for the time being. The Goose Bay area sees highs in the mid-teens for a beautiful weekend (not so beautiful if you’re wanting cold weather), before cooling down Tuesday and Wednesday.
Have a great evening, folks, and I’ll see you bright and early tomorrow morning!
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Thanks, Eddie.
Welcome!