Tag: Rain

Unsettled Weather Brings Seasonal Cool-Down

Brad Leave a comment

After a pleasant, summer-like start to the week, the weather is set to turn more unsettled as a disturbance rolls through Southern Manitoba tonight. Fortunately, the agitated weather will only bring temperatures back towards seasonal values before we see the heat move back in through the weekend, setting Winnipeg & the Red River Valley up for a hot start to next week.

Today will be a fairly pleasant day in the Red River Valley. There’s a slight chance of some shower activity early this morning as a trough passes through the region, but afterwards we’ll see the cloud begin to clear out through the remainder of the morning leading to just a few clouds this afternoon through the region. Daytime highs will climb to around 21°C–but with significantly less humidity than yesterday–with winds initially out of the northwest at 20–30km/h tapering off through the morning.

The more significant weather will roll into the province this evening as a low pressure system lifts northeastwards out of North Dakota and pushes across southern Manitoba. An area of showers, likely with thunderstorms embedded, will develop across southern Saskatchewan and northeastern Montana and spread eastwards through the night, pushing into southwestern Manitoba early in the evening and then spreading into the Red River Valley and Interlake through the remainder of the night. As is typical with systems that involve convection through the night-time hours, model solutions are a little scatter-shot as to what the outcome will be. Overall, it appears that the bulk of the precipitation will pass to the north of Winnipeg, however some models are coming up with solutions that bring significantly more precipitation into the region.

NAM Forecast Simulated RADAR Reflectivity valid 12Z Thursday September 17, 2015
This simulated RADAR image from the NAM forecast valid on Thursday morning shows a band of heavy, convectively-driven rain over Winnipeg & the Red River Valley.

The NAM-based solutions all tend to produce fairly strong, convectively-driven rainfall over the Red River Valley late tonight into Thursday morning. With PWAT[1] values near 35mm, the rainfall could be quite intense, however strong winds aloft should be moving anything that develops along at a fairly decent clip, meaning overall rainfall accumulations shouldn’t be excessive with around 10–20mm in any heavier precipitation that develops. Outside of thunderstorms/heavy rain cells, the more general rainfall amounts from this system should be around 2–5mm or so in regions south of the Trans-Canada Highway, and closer to the 5–10mm range for areas northwards.

NAM Forecast Sounding for Thursday Morning
This forecast sounding for Winnipeg from the NAM for Thursday morning indicates heavy rain or thunderstorms may be possible.

Temperatures will dip to around 14°C tonight. Thursday will see a high near 15°C with winds increasing out of the northwest to 40 gusting 60km/h in the afternoon. A chance for showers will persist through the remainder of Thursday under mainly cloudy skies.

Friday will bring calmer weather to the region with mainly sunny skies and a high near 19°C. Winds shouldn’t be too bad at around 15–20km/h.

Warmer Weather Returns on the Weekend

Our cool-down to seasonal temperatures will be short-lived, however, as warmer weather is set to build back into Manitoba through the weekend. The upper-level trough that will bring us our unsettled weather will push off to the east and a zonal flow is forecast to quickly develop across the Prairies, pushing in warmer air aloft that will begin to bump our temperatures back upwards. Saturday looks to have a high around 20°C, while Sunday will see the mercury climb towards the mid–20’s.

GPDS Forecast 850mb Temperatures valid 12Z Monday September 21, 2015
This forecast of 850mb temperatures from the GDPS shows temperatures pushing into the upper teens on Monday morning.

The GPDS is forecasting 850mb temperatures pushing into the upper teens through Monday, which would equate to temperatures in the upper 20’s as long as we see the sunshine. Afterwards, it looks like we may see a couple more disturbances roll through in the remainder of the week, bringing temperatures back towards seasonal.

While we will have occasional cool-downs, long-range forecasts continue to forecast above-normal temperatures through the remainder of September.

  1. Precipitable Water  ↩

Seasonal Weather Ahead, Rain Possible At Week’s End

Brad Leave a comment

Benign weather will continue over the Red River Valley for the next few days as a weak ridge of high pressure remains entrenched over the region until Friday. Heading into the weekend, however, it looks like rain may be possible as a low pressure system moves into the region through the day.

There isn’t a whole lot to say regarding the coming days, so I’ll keep this post fairly brief! The weather for today and tomorrow will be largely dictated by a weak ridge of high pressure over the region that’s more a result of larger low pressure systems to our west and east than being particularly potent in and of itself.

Today will see temperatures climb to around 23°C with breezy winds building out of the north to 30–40km/h thanks to a low pressure system passing to our east. The day will start overcast with some mid- to high-level cloud that will gradually clear out through the day. Winds will taper off this evening as low temperatures head to around 9°C.

Thursday will be mainly sunny day with light winds and a high near 25°C. Expect a low near 13°C on Thursday night.

GDPS 12hr. QPF valid through Friday Night
The GDPS is showing a low pressure system moving through Southern Manitboa on Friday night capable of bringing some rain to the Red River Valley.

Friday will see increasing cloudiness, particularly in the afternoon as a low pressure system begins working into the region. Temperatures will climb to around 25°C. Friday night will likely bring some rain, although specifics are still quite fuzzy. Temperatures will dip back down to around 13°C again.

Mixed Weekend

This weekend looks mixed at this point, with slightly cooler, cloudier weather on Saturday with a chance of showers and sunnier conditions on Sunday. There’s quite a bit of uncertainty with Friday night/Saturday’s low pressure system, so it’s a bit early to make much in the way of concrete forecasts. High temperatures will likely be in the low 20’s with a chance of warmer weather returning for the beginning of next week.

Typhoon Nangka Wreaks Havoc on One of Japan’s Main Islands

Matthieu Leave a comment

This past week a typhoon made landfall on one of Japan’s islands, the island of Shikoku and with it brought winds the equivalent of a category one hurricane gusting up to 185km/h.

[map type=”terrain” autofit=”1″ disable_scrollwheel=”1″] [pin]Island of Shikoku[/pin] [pin]Kamikitayama, Japan[/pin] [/map]

 

Nangka initially formed in the middle of the Western Pacific Ocean about over a week ago and slowly strengthened as it approached Japan; it traveled over 5000km to make landfall. Over open waters it peaked at the equivalent of a category four hurricane, with sustained winds of over 200km/h and gained super typhoon status. Slightly cooler ocean waters (of 26°C to 27°C) towards Japan weakened the typhoon somewhat before it made landfall, but with that said, the typhoon’s impacts were still fairly significant. In expectation of the typhoon 550,000 residents were either issued a mandatory evacuation notice or voluntary evacuation notice, in the most prone-to, low-lying areas near the coast.

Beautiful satellite image of Nangka earlier this week while it was still over open waters. (Source: NWS OPC)
Beautiful satellite image of Nangka earlier this week while it was still over open waters. (Source: NWS OPC)

In total, two people perished from the typhoon and about three dozen people sustained injuries – thankfully it wasn’t worse due to good planning by authorities to get the people most at risk out. Numerous rail runs and flights were cancelled, affecting about 200,000 people’s daily activities. Some flooding did occur as the typhoon brought a plume of tropical moisture to the region with it, which led to rainfalls in excess of 700mm in the hardest hit areas in 48 hours (740mm reported in Kamikitayama). Just over 100 houses were reported to have been completely flooded out

Since Nangka has made landfall it has progressed to its dissipating stage, and possibly extratropical transition by the end of the weekend. However, it will still bring with it the threat of heavy rainfall in the northern Japanese islands and mountainous areas even though it continues to weaken. On average there are 16 typhoons in the Western Pacific in a year, and this year’s count is currently at seven. Most storms form in the Western Pacific between May and November (because shear is weaker) but there are occasional storms that form in the other months of the year.

Unsettled Weather Continues To Week’s End

Brad Leave a comment

The unsettled weather that’s been in place for the last few days will continue through the end of the week as the general instability remains in place as more weather systems push through the region.

Today will be a fairly pleasant day that’s quite similar to yesterday other than a couple degrees warmer. Temperatures should climb to around 28°C this afternoon with more clouds popping up and developing into an afternoon/evening chance of some scattered thunderstorms. Thunderstorm activity should be fairly limited as the main story will be the low pressure system that will move into Southern Manitoba overnight and will set the stage for Thursday’s weather. Expect temperatures to dip to just 19°C as increasing cloud and the humidity continue to keep temperatures warm.

Thursday Brings Heavy Rain Potential

Tomorrow may actually end up being quite a wet day as multiple models are showing a low pressure system moving through tapping into the ample moisture in the region to produce a fairly large, and intense, area of rain.

NAM Precipitable Water Forecast for 15Z Thursday July 16, 2015
NAM Precipitable Water Forecast for 15Z Thursday July 16, 2015

The NAM (shown above) is forecasting precipitable water values as high as 1.8 to 1.9” (in the 45–50mm range) which is very high for our region. Precipitable water correlates strongly to potential rainfall amounts of storm systems[1], so it’s not unrealistic to say that rainfall totals of 1.5” to 2” (~ 35 – 50mm) are not out of the question albeit on the high end. If heavy convection were to set up, then even higher amounts would be possible. We’ll keep an eye on things and see how the storm progresses this evening; if the outlook changes much, we’ll provide an update at the bottom of this post.

So, the general forecast for Thursday would see the rain moving in overnight on Wednesday night and see the rain persisting at least until mid-day, but possibly into the late afternoon or early evening. Rainfall totals may end up being variable, but in general will likely be 20–40mm with the potential of seeing double that if system becomes vigorous enough. The high temperature will be in the 21 to 23°C range with an overnight low around 16°C. Winds will be fairly light much of the day.

Friday

The thunderstorm risk returns Friday, although it will be a fairly mild risk with just some isolated to scattered non-severe storms possible. The daytime high will sit near 26 or 27°C with light winds out of the southwest. The humidity continues to remain fairly high with dew points in the high teens. Skies will clear out Friday night as we head to a low near 15°C.

  1. Thunderstorm rainfall totals can greatly exceed PWAT values due to the convergence of the inflow wind that can “accumulate” PWAT from areas around the storm.  ↩