Unsettled Weather to Continue

Brad Leave a comment

This week will continue to be unsettled weather-wise. It appears that we will see the chance for rain virtually every day for the next several days.

A trough of low pressure over the Prairies

A trough of low pressure over the Prairies (the jet stream is in blue)

A trough of low pressure sitting over the Prairie provinces will be responsible for our unsettled weather over the coming days. This trough is created due to the fact that the jet stream will be to our south, allowing cooler air from the north to spill down into lower latitudes. As weather systems track along the jet stream they will create chances for rain in Southern Manitoba. It appears that rain is a possibility on every day from Monday through Thursday. At this time it looks as though rainfall amounts on Monday and Tuesday will be fairly light, if it rains in your location at all, but the precipitation forecast for later in the week is less clear.

Due to the cloudy and potentially wet conditions expected on Monday and Tuesday, temperatures won’t be very warm. Highs on Monday will generally be in the high teens over Southern Manitoba, except for border regions and parts of south-eastern Manitoba where temperatures should be closer to twenty degrees. Tuesday is likewise expected to remain cool, with highs in the mid to upper teens expected. Temperatures on Wednesday will be governed by when and if it rains, but it doesn’t look like it will be warmer than twenty for midweek (if it indeed gets that warm at all).

Too much uncertainty exists in the forecast at this point to talk about the weather much beyond Wednesday. However, at this time it doesn’t appear that we will be going back into a prolonged spell of nice weather in the short-term.

Elsewhere in Weather News: June 16th, 2012

Matthieu Leave a comment

Large Waterspout Makes Landfall in Venice

A large waterspout made landfall on the islands of Venice on Tuesday, June 12th. The tornado caused considerable damage on the islands but missed the picturesque city centre of Venice altogether. As the waterspout made landfall on Venice’s lagoon, it traveled towards the island of Saint’Erasmo and Certosa where there were numerous reports of trees being shredded and uprooted, roofs being torn off and the city’s well-known gondolas being thrashed around. Two significant structures that were reported as being damaged include a soccer stadium and a naval academy where a tree fell, trapping 15 students inside the building. Winds were estimated to be howling at a rate of about 145km/h inside the twister at the time it made landfall, classifying it as an EF-1 tornado under the Enhanced Fujita Scale. One man was injured and the damages are estimated to be near a couple of millions of dollars.

Venice waterspout

Picture of the waterspout/tornado as it makes landfall. (Source: Cristian Cavallarin)

Damage path

Damage on one of Venice’s islands. (Source: EPA)

Waterspouts in the region are usually associated with small spin-ups and pulse storms over a large body of water, which typically dissipate when making landfall. However, this waterspout in particular had not dissipated as it moved over the islands due to its unusual strength and cone-like shape – signifying strong rotation present. According to a satellite picture taken at the time, it appears a shortwave provided the necessary ingredients to spawn the tornado and lengthen the duration of the storms.

Satellite picture

Satellite picture on the morning of June 12th, 2012. Approximate location of Venice, Italy represented by the green dot on the map. (Source: EarthSky/CIMSS)

Even though tornadoes are not as common in Europe as they are in North America, Italy has seen its fair share of deadly tornadoes this past century. A couple of notable tornadoes are:

-The Montello tornado in 1930 – possibly the strongest tornado ever to touch down in Europe, it brought gusts of over 500km/h and completely levelled brick buildings.
-The Venice tornado outbreak of 1970 – which included a notable tornado that went through Venice causing deaths and destruction throughout the city.

View of the tornado from downtown Venice. (Source: The Telegraph)

Storms were reported to have cleared out of Venice’s region near the end of this week. The weekend forecast in that area calls for light showers on Saturday and all-out sun on Sunday.

A couple other notable events that have happened in other parts of the world since last weekend include: a hurricane spinning up in the Eastern Pacific heading towards Mexico’s western coast; and significant flooding in Pensacola, Florida where over 540mm (more than a year’s worth of precipitation in Winnipeg, Manitoba) fell in 24 hours!

Stormier Weather Set To Return

Brad Leave a comment

Southern Manitoba will be under an increasing risk of thunderstorms as the week progresses. Heat and humidity will slowly build back into the region as a deep upper trough begins to build over the Rocky Mountains before tracking eastwards across the Prairies later in the week.

GEM-REG 6-hour Precipitation for Thursday Afternoon

6-hour accumulated precipitation through Wednesday afternoon from the GEM-REG model.

We’ll see warmer temperatures today as warmer air pushes in behind a warm front that passed through overnight. Daytime highs should be near the 25°C mark through most of the RRV. By this afternoon a weak frontal wave will be positioned near the international border with a trough extending NW to a low pressure system tracking into Western Manitoba. Showers and thunderstorms will develop over SW Manitoba early this afternoon and slowly develop northeastwards into the Red River Valley. It will mainly be regions through the northern Red River Valley that face the risk for showers or thunderstorms (Portage la Prairie, Winnipeg, Selkirk; as seen in the image above). The showers and thunderstorms will lift northwards into the Interlake overnight while overnight lows drop to the mid-teens over most of Southern Manitoba.

12 hour accumulated precipitation through Thursday

12 hour accumulated precipitation through Thursday from the GFS model.

Opinions differ for Thursday, however it’s generally expected that a north-south band of showers with a chance of an embedded thunderstorm will develop over the Red River Valley or the Whiteshell in the afternoon. This line will slowly move eastwards and intensify into a band of thunderstorms. Again, there’s still quite a bit of uncertainty to where this line will develop, and the potential exists for fairly large (close to 1”) rainfall accumulations. We’ll be keeping close track of this system’s development.

Friday looks to be a fairly nice day with comfortable humdity and daytime highs in the mid-20’s. A large MCS is forecast to develop on Friday night in North Dakota, bringing the chance for a stormy and rainy Saturday. We’ll take a closer look at that system later this week.

What a Difference a Week Can Make

Brad Leave a comment

The difference between the weather experienced last week and that which is coming for early this week will be quite extraordinary. Temperatures on Monday look to be nearly 20 degrees cooler than values experienced last week.

850mb temperatures (about 5000ft above the ground) are forecast to sink to near or below zero degrees on Monday

850mb temperatures (about 5000ft above the ground) are forecast to sink to near or below zero degrees on Monday

High temperatures on Monday are not expected to stray far from the 10C mark in Southern Manitoba. Eastern most sections in the south may manage to hit the mid teens, but the rest of Southern Manitoba shouldn’t be much warmer than 10 degrees. This comes as quite a contrast to the 30 degree temperatures of last week. The above graphic shows the extent of the cold air, with freezing temperatures just 5000 or so feet above the ground. We will most likely see some shower activity develop across Southern Manitoba on Monday, but amounts should be relatively light in most areas. Thankfully Tuesday and Wednesday will be warmer, with highs moving sharply higher. Tuesday should be near or above twenty degrees (depending on which model you believe), while Wednesday is expected to be in the low to mid twenties. There may be some convective rain and/or thunderstorms on Wednesday as humidity levels increase ahead of an approaching low pressure system.

The Preliminary outlook for later this week is for more warm to hot weather. Highs back in the middle or upper twenties will be possible on Thursday and Friday according to the latest modelling. However, my confidence level in the late week forecast is lower than normal since there is some uncertainty as to how quickly a series of fronts will pass through the province late in the week. Given my lack of confidence in the Thursday-Friday forecast I won’t say much about the weekend. You can read more about longer range predictions in the next paragraph.

The long-range forecast calls for above-normal temperatures in Southern Manitoba for the second half of June

The long-range forecast calls for above-normal temperatures in Southern Manitoba for the second half of June

The NAEFS forecast seen above shows the long-range temperature forecast for the June 18-25 period. It appears that we will stick with above-normal weather for most of the second half of June. Also note that we are on the edge of the warmest air, meaning that approaching systems coming out of the colder air to our west (a trough) could potentially trigger strong thunderstorms as they interact with the warmer air to the east. This type of trough-meets-ridge pattern is to blame for the severe thunderstorms on Saturday night.

AWM Chases!

The A Weather Moment team took to the highways of Southern Manitoba on Saturday for our first chase of the year. Hot and humid surface weather combined with an approaching low pressure system and a strong jet stream aloft made conditions ripe for severe supercells thunderstorms which could potentially produce tornadoes.

A thunderstorm east of Altona on June 9, 2012

A thunderstorm east of Altona on June 9, 2012

The AWM team decided to drive toward Holland, MB to start the day. After arriving in Holland it was decided that Pilot Mound would be an appropriate new target given the new weather information available. Upon arriving in Pilot Mound and watching the latest weather conditions evolve we felt our location was ideal. At that point it was time to wait…and wait..and wait. After watching numerous towering cumulus clouds fail to breach the cap we decided to abandon Pilot Mound and follow some storms to our east which were approaching the Red River Valley. As we began to get a good visual of the storms around the Altona region it was clear that there was little chance of a tornado. Cloud bases were high and there were no significant lowerings to be found – the storms were elevated – not surface-based tornado producers. Nevertheless we stopped for awhile near Altona to take a closer look at the storms, a look which revealed nothing of significance. Having taken a few anvil and sunset photographs it was time to head back toward Winnipeg, just missing the infamous hailstorm (which put down tennis ball sized hail) that hit the city around sunset.

Overall it was a good chase. It was not a complete bust since there were storms, but it was definitely a bust in the fact that tornadoes were really nowhere to be found (I’ve kept the door open here for you to decide whether or not this is a tornado: http://tornadohunter.ca/tornado-hunter-blog/2012/6/10/the-longest-chase-day-ever-but-we-got-a-tornado.html). It is only early June and the severe weather season is just beginning, the next chase will be here before we know it.

The AWM team (Brad, Scott and Matt) would like to thank the 311 unique visitors who made 624 visits to this website yesterday, a new record number of visits for this website. Thank-you.