Elsewhere in Weather News: August 11th, 2012

Barrage of Typhoons Continue to Impact Asia

Haikui, the third typhoon to hit China this month, made landfall on Wednesday affecting over 100,000 people on China’s east coast. Rain, rain and more rain is what the region has experienced these past few weeks as typhoons Saola, Damray and Vincente (reported in previous EIWN posts) have all made landfall. On top of the severe rains brought on by these recent typhoons, Haikui has dumped an additional 200mm in areas where the grounds were already extremely saturated – inland flooding now adding another element of concern for residents.

Haikui track

Haikui’s track as it made landfall on China’s east coast. Forecasted track was as of Wednesday August 8th. (Source: TSR)

Thanks to China’s meteorological authorities who issued a red code warning (most severe) for the city of Shanghai well ahead of the typhoon hitting, many lives were saved as residents had time to vacate the premises. Authorities helped relocate over a million and a half people, mostly from the Shanghai region, before Haikui made landfall, further lessening the risk of casualties in the areas prone to flooding and landslides. Storm surge was also a concern for townships along China’s east coast.


Satellite picture of Haikui as it made landfall just south of Shanghai. (Source: Earthweek)

In all, about one million acres of cropland and over six million of China’s residents have been impacted by this major typhoon. Flood damage has been extensive, ranging from roads washed out and stranding tourists and local residents, to homes being washed away by the flash floods. Estimated damage costs from this most recent typhoon are pegged at around the 1.5 billion dollars.

Haikui damage

One of many washed out roads caused by flash flooding in the Zhejiang Province. (Source: Global Times)

Six casualties have been associated with typhoon Haiku to date, however the death toll from the barrage of typhoons since the beginning of July, combined with heavy rains affecting the region, has brought the toll to over 100 people.

An Unsettled Sunday, Otherwise Pleasant

Fairly pleasant weather will be on tap for next couple days until an upper trough swings through the area on Sunday, bringing a risk of showers or thunderstorms to the Red River Valley.

Pleasant Weather Ahead

Pleasant weather is on tap for Winnipeg.

Through the next couple days, mainly sunny skies and warm temperatures will be the dominant weather across the Red River Valley. High temperatures today and tomorrow will climb up to around 29°C, while sunny skies dominate today and we move into more of a mix of sun and cloud tomorrow.

On Sunday, an upper trough begins to work it’s way into Southern Manitoba. It’s very difficult to say what exactly is going to happen with this system as it moves through. It seems clear that there will be two main areas of precipitation:

  1. An area of rain that moves through the Interlake.
  2. An area of showers and/or thunderstorms that develops over North Dakota and slides southeastwards.

As for what happens over the Red River Valley; it’s tough to say. Guidance currently suggests that there’s a moderate chance of rain for us. Should we see precipitation, it’s likely that we’d see a batch of morning showers then a little bit of sunshine before some afternoon convection bubbles up over the Red River Valley. There would be a risk of non-severe thunderstorms if that scenario happens. This system seems to be quite sensitive, so we’ll be sure to post updates in the comments below. The daytime high on Sunday will end up being somewhere between 24°C to 27°C depending on how much sun or rain we see.

Sunny skies return to start next week before another system brings a chance of rain mid-week.

Normal Weather Continues; 5th Hottest July in the Books

“Normal” weather will continue over the next few days as a ridge of high pressure builds into the Eastern Prairies, bringing us plenty of sun and daytime highs in the mid-to-upper 20’s. Before that, though, we’ll see a slight chance of showers this afternoon. A trough of low pressure is forecast to push into Manitoba on Saturday, bringing with it a chance of rain.

GEM-GLB Forecast of Prominent Ridge

GEM-GLB surface winds valid on Thursday morning. A very large ridge is the dominant feature over the Eastern Prairies.

There is a very slight chance of a shower or two over the Red River Valley this afternoon as a trough of cold air digs southwards as it heads east out of the province; the best chances should remain to our east, through the Whiteshell and Berens River regions, but it certainly can’t be ruled out for us. Accumulations will be minimal and the showers will dissipate fairly early in the evening.

A strong ridge will continue building in across the Northern/Eastern Prairies, forecast to strengthen to a 1028mb high by tomorrow morning, with the ridge axis extending from the Red River Valley NE into Hudson Bay/James Bay. This feature will ensure fairly sunny skies over the next couple days, limiting clouds to just some shallow fair-weather cumulus, as well as induce a broad southerly flow over Manitoba. This would normally result in hot temperatures and high humidity, but in this case, it’s actually going to result in…well, more of the same. The reason for this is significant: instead of being a high pressure system created by an upper ridge, this will be a high pressure system created by a cold trough of air descending from the Arctic. The southerly flow that will develop over the province, instead of being a flow of warm, moist air from the Gulf of Mexico, will be a return flow of air out of the high. So while we’ll have sunny skies, our temperatures will only creep up little by little, and our dewpoints will only climb into the low-to-mid teens.

It’s also worth noting that as crops mature, we’ll be significantly less likely to see days with very high dewpoints (20°C+) for two reasons:

  1. When plants mature, the evapotranspiration (ET) rate dramatically diminishes. Corn, for example, will ET up to 0.33“ per day at peak growth rate. That value then diminishes to 0.23” at maturity[1]. Mature trees may ET up to 50 gallons of water each day during the growing season. Again, this value diminishes in late-summer when all the growth has become mature. Most plants follow similar patterns.
  2. The crushing drought through the Central US will diminish pretty much any advection of moisture that may occur. There’s a long way between us and the Gulf of Mexico, and the normal ET contributions from plants through the Central Plains is missing this year.

One of the side effects to this is that our severe thunderstorm season will likely come to a fairly rapid halt over the coming weeks as good setups become moisture-starved.

Evapotranspiration is the process by which plants take up moisture from the soil and expel it as vapour into the atmosphere through the stomata on their leaves.

For Saturday, it currently looks like a trough of low pressure will work it’s way across the province, bringing with it a chance for showers. The track is highly dependent on the positioning of an upper low over the northwestern Prairies, so it’s a little early to say where exactly precipitation will fall. Either way, it doesn’t look to be very powerful, and any areas that see precipitation look to receive small amounts.

The next chance for rain looks to be not until the middle of next week.

July 2012 Closes Out as 5th Hottest

July 2012 closed out as an extremely warm month. The average temperature[2] for the month was 22.3°C, 2.7°C above the normal 19.6°C[3]. This places July 2012 in 5th place for all-time hottest July:

Warmest Julys on Record
Year Average
1 1936 24.2°C
2 1935 22.4°C
3 1916 22.4°C
4 1914 22.4°C
5 2012 22.3°C

The warmest day we had was July 11th, which reached 34.5°C. Our coolest day was July 15th, where the mercury topped out at only 19.4°C. Our warmest overnight low was 20.5°C on the night of July 10th/11th. Our coldest overnight low was 7.9°C on the night of July 26th/27th. In total, the Winnipeg Airport recorded 14 days with temperatures above 30°C in July. The hottest day in July on record is 42.2°C set in 1936. The coldest night on record in July is 1.1°C set in 1972.

The biggest story was, perhaps, the sheer lack of rainfall last month. The airport recorded 23.5mm of rain, which is the 11th driest July on record:

Driest Julys on Record
Year Amount
1 2006 10.5mm
2 1875 13.5mm
3 1925 15.5mm
4 1894 16.0mm
5 1886 17.0mm
6 1960 17.0mm
7 1920 19.3mm
8 1910 20.3mm
9 1964 22.4mm
10 1979 23.1mm
11 2012 23.5mm

July 2012 was the 7th driest July in the last 100 years. Fortunately, the drought wasn’t as hard hitting as areas further south, as Winnipeg had several months preceding July with above-normal precipitation.

As we covered on Monday, August looks to be off to a dry start with daytime highs sitting near-normal to just above normal[4].

  1. http://corn.agronomy.wisc.edu/AA/A046.aspx  ↩
  2. The average temperature is a mean of all the daytime highs and overnight lows. It is not an integrated parameter, so take that as you will.  ↩
  3. Normal average temperature calculated for the years 1981–2010.  ↩
  4. Normal daytime highs for the beginning of August in Winnipeg are generally around 27°C.  ↩

More Normal Weather

This week will start with weather that is normal for this time of year – a rarity in what has been a summer of extremes.

Normal weather is expected throughtmid- August

The NAEFS ensemble shows normal weather persisting through mid-August

High temperatures on Monday will be very similar to Sunday, with mid twenties expected. Tuesday will once again feature high temperatures in the mid twenties, with a risk of thunderstorms in border regions ahead of an approaching low pressure system. Any storms that develop on Tuesday will most likely be non-severe, but if dewpoints end up higher than expected a few severe storms may be possible. The wind will shift to northerly on Wednesday, but temperatures will remain fairly unchanged with highs once again in the mid twenties expected.

Models show mid to upper twenties temperatures continuing into late week. Previously it looked like we might end up with a prolonged period of 30C temperatures starting this week, but models have backed off that idea. In general it looks like we’ll stick with slightly above-normal temperatures for much of this week and into the weekend, which means more mid to upper twenties for the forseeable future.