A Bit of A Mixed Bag For The Long Weekend

Brad Leave a comment

Fairly nice weather is ahead for the long weekend with plenty of sunshine and hot temperatures. The only chance for rain will come on Saturday night as a low pressure system passes through the Interlake.

GFS Precipitation for Saturday Night

12 hour rainfall accumulations from the GFS for Saturday night, depicting the showers expected to develop over southern Manitoba.

Temperatures will climb to 30°C today across the Red River Valley as southerly winds build over the region and advect in slightly warmer air. We’ll see an overnight low of around 15°C with clear skies tonight. Tomorrow will likely be a few degrees cooler than today as cloud cover works it’s way into the area in the afternoon. We’ll see slightly stronger winds closer to 30km/h, develop by the afternoon as a low pressure system begins to push across Saskatchewan.

A strong low-level jet (LLJ) is forecast to develop on Saturday evening. Current consensus is that a 40kt LLJ will develop over central North Dakota and slowly push eastwards overnight. An area of showers and thundershowers look to develop on the nose of the LLJ, mainly through areas between the International Border northwards towards Riding Mountain Provincial Park eastwards across the Interlake. There is one great uncertainty with this system, though: Isaac. The storm previously known as Hurricane Isaac will be pushing northwards towards Iowa before shifting it’s track eastwards on Sunday. The moisture required for us to be able to see precipitation on Saturday night sits along a narrow boundary left behind across the Northern US. As it stands now, the LLJ that forms tomorrow evening is supposed to tap into that pool of moisture and transport it northwards into the RRV. Should the track of Isaac change significantly between now and then, the location of the moisture pool may change and move to an area that the LLJ wouldn’t be able to tap into. Should that happen, it’s unlikely we’d see much more than scattered showers over the RRV with little accumulation.

Things will clear out early Sunday morning and we’ll have some sunshine before a few clouds bubble up in the afternoon. We’ll have a cooler day with a high of 25°C.

Holiday Monday looks like a beautiful day with plenty of sunshine and a high once again near 25°C and breezy westerly winds gusting to 40-50km/h.

Red River Valley Set to Bake Today

Brad Leave a comment

Some of the hottest temperatures of the year will be seen today in the Red River Valley as extremely warm air is brought into the province by a low pressure system passing through the northern Interlake.

850mb temperatures from the GEM-REG

850mb temperatures from the GEM-REG for late this afternoon. Temperatures are expected to peak at just over 25°C at 850mb over the Red River Valley today.

Southerly winds have brought some of the warmest air yet this year over southern Manitoba. 850mb temperatures have climbed to 25°C today which, when combined with southerly winds at the surface, will help to push our daytime highs towards the mid-30’s. There is fairly good agreement among the models that winds will remain southerly in the Red River Valley through the day; this will eliminate any significant downslope effects and make temperature forecasting a little bit easier.

In general, daytime highs should range from 34-36°C through the RRV tomorrow, with the warmer temperatures closer to the American border. There is a slight chance that a few areas in the SW RRV could see highs push a degree or two higher than that (35-37°C), but such temperatures would be fairly localized. Winnipeg will have a chance of breaking it’s record high for today, which was set in 1972 when the temperature climbed to 36.1°C. It’s by no means a guarantee that we’ll break it, but we’ll certainly take a good run at it.

Dewpoints will climb to around the 18°C mark, however some areas may see dewpoints peak at 21-22°C before we start mixing air near the surface a little deeper into the atmosphere. This will result in humidex values between 39-45. It’s quite likely we’ll see a humidex advisory issued by the Winnipeg SPC later today.

Manitoba Health suggests Manitoba residents take precautions against heat-related illnesses whenever the humidex climbs above 37. Manitoba Health advises the following:

  • Stay aware and be prepared
    • Know daytime and night-time temperatures-both outdoors and indoors- by checking your local weather forecasts and the thermostat in your home.
    • Stay up to date on weather alerts so you know when to take extra-care.
    • If you have an air-conditioner, make sure it’s working properly before the hot weather starts.
  • Stay hydrated
    • Drink plenty of water (that’s the best liquid) before you feel thirsty.
    • Avoid alcoholic beverages, as they can increase the amount of water lost by the body.
  • Stay cool and keep out of the sun
    • Plan outdoor activities for cooler parts of the day, but remember to wear insect repellant since mosquitoes are out too.
    • If you are outdoors during the hottest part of the day, shade yourself from the sun with an umbrella or a wide-brimmed hat with lots of ventilation (to allow the sweat on your head to evaporate), wear loose-fitting, breathable, light-coloured clothing, and remember to wear sunscreen to limit ultra-violet (UV) ray exposure.
    • If there is no air-conditioning at home- go to a cool place such as an air-conditioned mall, public library, or community centre.
    • Take a cool bath or shower or go for a swim to cool off.
    • Avoid using your oven or other appliances that could heat your home more.
    • Limit physical activities during the hotter parts of the day or exercise in an air-conditioned place.
  • Take care of yourself and others
    • Check on family members, neighbours and friends – especially older adults and those with chronic conditions. Visiting is best because it is easier to identify signs of heat illness that could be missed over the phone.
    • Never leave people or pets in your care alone in closed vehicles or direct sunlight.

— Heat and Your Health; Manitoba Health

A cold front will sweep through this evening, bringing more seasonal air back to the province. There is very little chance of any precipitation with the passage of this front.

The rest of the week will bring closer-to-seasonal temperatures with daytime highs near 28°C. The normal daytime high for Winnipeg for this time of year is about 22°C. The normal overnight low is around 9°C. Our blast of hot weather will likely ensure that Winnipeg has it’s 14th consecutive month with above-normal temperatures. We’ll have our regular post on Friday, and then two posts on Saturday: the regularly scheduled Elsewhere in Weather News and a climate summary of August/update on 2012.

Another Blast of Heat

Brad Leave a comment

Some more hot weather is in store this week as we close out August. We might even see our hottest day of the summer!

Temperatures in the mid to upper thirties are forecast for parts of Southern Manitoba on Wednesday

The WRF/NAM model is predicting temperatures in the mid to upper thirties in the Red River Valley on Wednesday

Yet another ridge of high pressure will build over the Prairie provinces for this week, bringing more hot weather. Monday will be a nice day, with light winds and high temperatures in the mid to upper twenties in Southern Manitoba. Skies should remain mainly sunny as high pressure suppresses convective cloud cover. By Tuesday temperatures will climb up around the 30C mark, but humidity levels should remain low keeping conditions at least somewhat bearable. Wednesday could potentially be the warmest day so far this summer in many parts of Southern Manitoba. Current models give the following high temperature predictions (for Winnipeg):

  • NAM: 36C
  • ECMWF: 35C (estimated based on 850mb temps)
  • GFS: 32C
  • GEM: 30C

Based on recent model performances, the NAM should be the favoured solution at this point. Given that low humidity is expected on Wednesday, there certainly is the potential for temperatures to reach the mid and upper thirties in Southern Manitoba. The two main factors that will determine how hot it gets are:

  1. How much warm air manages to flow in at the low-levels on Wednesday
  2. Whether or not a moderate-strong low pressure system forms to our west, causing winds to stay southerly or south-easterly on Wednesday

If 850mb temperatures manage to sneak up into the mid twenties over Southern Manitoba on Wednesday and the wind veers to south-westerly or westerly, then expect high temperatures in the mid to upper thirties in most areas. However, if the wind stays more south-easterly on Wednesday with cooler 850mb temperatures, then highs will likely stay stuck around the 30-33C mark. Of course all the above points assume that we will see sunny skies on Wednesday. At this point there doesn’t appear to be anything which would indicate that we will see extensive cloud cover, but that is always a wildcard to consider.

A cold front is expected to pass through at some point on Wednesday night or Thursday, cooling temperatures back down into the twenties for Thursday and Friday.

Elsewhere in Weather News: August 25th, 2012

Matthieu Leave a comment

Isaac Threatens Southern States

This past week a tropical disturbance in the central Atlantic, east of the Caribbean, has strengthened into a tropical storm – Isaac. As of Friday night, Isaac had sustained winds of 112km/h, a central pressure of 990mb and was eyeing (no pun intended) Haiti. It is especially worrisome that Isaac, a strong tropical storm, is moving towards one of the most impoverished countries in the world, where nearly 400,000 people are still living in tents after the major earthquake back in 2010.

Isaac

Isaac on infrared satellite with centre of circulation identified by arrow. Purple, red represents very cold cloud tops. (Source: WSI)

Isaac will make landfall as a strong tropical storm as it crosses Haiti and then heads toward Cuba. It might have trouble sustaining its strength due to the mountainous terrain of the islands but as it emerges into the Gulf of Mexico, Isaac should organize itself quickly as it takes aim at the Gulf States such as Florida, Alabama, Mississippi and Louisiana. It is expected that Isaac will make landfall on American soil, somewhere on the western part of the Florida Panhandle on Tuesday afternoon. By that time Isaac will have intensified enough to be of hurricane strength, most likely category one. Residents of the Gulf States will have to monitor conditions closely to secure items outside and be ready to evacuate; storm surge along the coast and flooding because of the heavy rains is likely to occur. It will not be uncommon to see rainfall amounts of 100-200mm in the hardest hit areas in the Caribbean and US, however, the more rugged terrain of the islands on the Caribbean could have more devastating effects; landslides and flash flooding.

Isaac track

Isaac’s projected track. (Source: News 13)

In other news around the world, Taiwan has been hit with yet another storm – typhoon Tembin that had sustained winds of 155km/h but struck a less populated area of the country, leaving the large cities like Taipei with only minor flooding and wind damage.