October "Bomb"

[Stormposter]

A very interesting weather pattern shaping up for the middle part of the week. Looks like the making of the first 'bomb' of the season is in the works. Right now the culprit is just just a little shortwave trough over North Dakota. But the feature will be moving out over the Gulf of Maine early Tuesday, and then will interact with a strong baroclinic zone (area of huge temperature contrasts). That will send the low into a period of explosive deepening. The Canadian Global model suggests it will deepen by 39 mb in 24 hours. The American GFS is not quite that extreme, but still shows an impressive 34 mb pressure drop in the same time period. The models are in remarkable agreement on the track of this system as well. :o

Of course the important question is, what kind of weather will this bring?

For the Maritimes, nothing too out-of-the-ordinary is likely, as the low will only be getting wound up as it passes south of NS during the day Tuesday. However a cold rain will likely affect all of NS with raw northeasterly winds. Southern NB will be on the northern edge of the precip envelop, but it just might be cold enough for some snow in certain areas. PEI will be on the northern edge of that precip too, but I suspect the onshore winds will keep it as a cold rain there. However, can't rule out the possibility of some wet snow mixing in over inland NS Tuesday night on the backside of this low just before the precip ends.

Now, for Newfoundland, things get really interesting. Right now the centre of the low is progged to cross the Avalon, with a very tight pressure gradient over the central part of the island. UMOS is currently indicating 92 km/h sustained northwesterly winds for Twillingate! In addition, both the Global and GFS models are showing a bullseye of over 50 mm of precipitation to the left of the track, in the cold air (500-1000mb thicknesses near 534 decametres). It seems a bit early in the season to be talking significant snows, but if this plays out as progged, chances seem good for a major wet snow event for interior sections of the Island. Precip would likely start out as rain, but as the low intensifies and the air cools, a change to snow seems highly probable, and the big question would be how much will accumulate. Will discuss that more when the system gets a little closer.

Here is a depiction of the system as shown by the Global, valid at 9:30pm Wednesday night. The precip chart is a 24-hr total, ending at that time.

(Posted Image)

[Eastcoaster]

Very interesting system indeed, looks like a true Newfoundland gale.

[kbg1]

hi all

also something in the works for friday/saturday.
marine warnings to 45 knots from the east.
looks potent on the nam.
seems pretty far out for these warning yet.

regards,jeff

[cfogarty]

Nice preview discussion Rodney ... the latest 48HR GEM REG shows a hell-of-a-gradient over the eastern part of the Island:

http://www.weatheroffice.gc.ca/data/model_...st/3295_100.gif

Chris

[Relliott]

Thanks for the the info Rodney :)

[Eastcoaster]

This storm will be fueled by a strong baroclinic zone, so it wont be a Tropical Hurricane in no way. Although im sure the winds will gust past 120 km/h based on everything ive seen.

[New Chelsea Weather]

I will have to start storing patio furniture tomorrow before the big blow!

Attached Image (Click thumbnail to expand)

[Stormposter]

00z UMOS guidance showing some incredible winds:

Sustained 93 km/h for St. John's, and 158 km/h for Bonavista. Sustained! :o I've never seen the guidance forecast anything like that before.

Disclaimer: I'm just reporting raw numbers. I haven't assessed this model run at all yet. But it looks rather scary. :unsure:

Stay tuned.

[Stormposter]

UPDATE: Model guidance is showing a swath of 65 kt winds at 40 m above the surface just off the Bonavista Peninsula in the northwesterlies behind this thing on Wednesday night. If that works out, it ought to translate to some 100 gusting 140 km/h winds along the exposed parts of the coast. Not sure how the UMOS is coming up with 153 km/h sustained, but it seems a tad extreme.

GEM shows a mix of snow/rain over areas west of Clarenville and south of Gander most of the day on Wednesday. I think it may be underestimating the snow - the model has a tendency to be a bit too warm in the low levels with these early season events. In any case, there should be fairly widespread snow on the back side of this storm on Wednesday night, with the immediate coastline being the main exception.

[New Chelsea Weather]

Seas building to 5 to 7 meters Wednesday evening. Surfers in New Melbourne is sure going to like that.

Attached Image (Click thumbnail to expand)