Elsewhere in Weather News: May 12th, 2012

China Gets Battered by Torrential Rains

On the afternoon of Thursday May 10th, the north-west part of China (province of Gansu) saw severe thunderstorms roll through its higher elevations and bring with them dangerous hail and downpours that wreaked havoc across the region. With heavy rains being the most threatening hazard in this part of the country because of the mountains and easily-triggered mudslides, around 3,000 residents were evacuated for precautionary measures in the areas most prone to flooding.

Residents evacuating

After heavy rains fell many residents had to be evacuated or rescued as roads were blocked off. (Source: Shanghai Daily)

As the large hail and heavy rain fell, the Minxian County in the province of Gansu was hit the hardest when 70mm of rain fell in about an hour. Mudslides and large hail impacted the county significantly as they destroyed 7,000 acres of farm fields, closed roads leading in and out of the county including a large interstate, and damaged more than 30,000 houses. The mudslides also sent 40 people to hospital, killed 37 others, and the toll may rise as over 20 other residents are still missing. In total, 17 of the 18 townships in the region were affected – this comprises of one fifth of the county’s entire population. China’s flood control headquarters issued more warnings in the same regions on Friday in an effort to raise awareness about the dangers of flash floods and the need to prepare for another possible bout of heavy rains again this weekend. The Red Cross chipped in by donating quilts and coats to the now homeless, and Chinese government pledged $320,000 to fix damaged schools, hospitals and water treatment plants.

Torrential rains

Roads become small creeks as torrential rains fall in the province of Gansu, China. (Source: China.org.cn)

About 3,000 first response workers, still battling with Mother Nature’s wrath, worked fervently around the clock on Friday evening, one day after the storms struck, to find those still missing.

A Warmer, But Stormier, Week Ahead

After a spell of cool, uneventful weather, things are set to become a little more interesting this week. We’ll see temperatures close to 20°C many days, but it won’t be all sunshine as we’ll have to contend with a more active storm track that will bring multiple storm systems through our region. How rainy will it be, and when can we expect thunderstorms? Read on to find out…

850mb Temperatures for Monday Night

850mb temperatures on Monday night, valid at 09Z May 1st, depicting the sharp warm front aloft present over Southern Manitoba.

We’ll see a beautiful day today with highs right around 20°C for the RRV and a fair amount of sunshine with some clouds developing in the afternoon due to some lingering instability from yesterday’s system. A low pressure system tracking it’s way into Saskatchewan through the day will be lifting warm air northwards over Southern Manitoba, and by evening, a fairly strong warm front will exist aloft, running W-E through Southern Manitoba, with a cold front draped southwards from SW Manitoba to Wyoming. A 30-40kt LLJ will help thunderstorms trigger near the triple point in North Dakota, where additional lift will aid the jet as it overrides the surface warm front.

The triple point is the location where the warm front and cold front of a system intersect, signalling the location of the surface low or the associated occlusion. Triple points are an important feature in forecasting thunderstorms as they often are areas with enhanced lift and wind shear.

The first storms will likely fire in North Dakota and begin to lift into Southern Manitoba travelling NE with the upper flow, with more developing as they do so. Once more mature, the storms will tap into the convergence present aloft in a trough extending eastwards from the low heading into Saskatchwan and continue their way across Southern Manitoba. By morning, a line of thunderstorms present over Southern Manitoba will merge into a line of rain and showers extending all the way from SE Saskatchewan all the way back to the Rocky Mountains.

Thunderstorm Outlook for Monday Night

Thunderstorm outlook for Monday night (April 30/May 1).

The storms are not expected to be severe, however any regions that may see multiple thunderstorms training over the area could see in excess of 20mm of rain and cool temperatures aloft raise the possiblity of marginally severe hail (which, in Canada, is about the size of a nickel). Current indications are that the greatest risk for hail would be over the south-central RRV and back into the western RRV, from the US Border to near Carmen. Other than that slight risk, no severe weather is expected from the night’s storms.

Things will continue to lift northwards on Tuesday, however we may see some afternoon showers through the RRV as a secondary system tracks through the Dakotas. Temperatures will be warm, though, with daytime highs once again near 20°C despite the cloudy skies.

Wednesday and Thursday look nice, with more sunshine and highs continuing near 20°C with overnight lows in the mid to high single digits. A powerful system is forecast to track into the region on Friday bringing with it showers and thunderstorms. It’s far to early to say with any certainty where it will end up, but we’ll keep a close eye on it through the week and provide updates.

Elsewhere in Weather News

Suspected Tornado in UK Causes Damage

Britain’s dreadful spring continues to be plagued by extreme weather as flooding, very high winds and even a suspected tornado hit the Rugby area on Wednesday, April 25. Investigations are still underway, however, most evidence does point to a tornado. A path of destruction about a mile long through the neighbourhood could be seen – sheds tossed, a roof blown off – evidence that this was a tornado and not straight-line winds. More damage was reported where telephone lines had been snapped or torn down and roof tiles scattered across yards and roads. No injuries or deaths were reported but residents were in shock as only 30 tornadoes are reported yearly across the UK.
A separate incident occurred in Essex County where severe damage was caused to a barn and house, killing the 20 chickens inside. The farmer, who was outside at the time, got picked up off the ground and threw by what he described as a tornado swirling around him. Thankfully, he survived the ordeal.

Large Tree Down

Large tree down in Rugby as a result of the suspected tornado. (Source: Diane Slater)

Roof blown off house

Roof blown off a house in Rugby by suspected tornado. (Source: Sky News)

Destroyed Barn

Barn completely destroyed in Essex. (Source: Huntley/HVC)

Soggy April in UK

Britain’s odd weather doesn’t end there however. This past month, Britain has experienced very wet conditions, a big contrast from the extremely dry conditions experienced the past two winters. As restrictions are in place for water use because of the drought, UK is experiencing one of its wettest Aprils officially recorded. The main reason that they are still experiencing drought as this very soggy month moves on are for a couple reasons:

  • Spring/summer rainfall doesn’t refill aquifers (underground reservoirs of water).
  • Vegetation soaks up a significant amount of the rain that falls.
  • Downpours don’t reach very deep underground due to the hard soil on the surface, causing water to have trouble penetrating the ground and even worse, creating lots of runoff that leads to flooding.
    As of April 25th, the southern half of UK has placed 9th in all-time rainfall for the month of April since records began in 1910. With this being only 40mm off the record, they have a shot surpassing the old record before the end of the month as a strong system came ashore Saturday and is forecast to persist until at least May 1st.

UK Sat Image

On Sunday a very large area of low pressure could be seen off UK’s coast, bringing soggy conditions to most of the region. On Monday the low is expected to move slightly west, bringing another round of rain to the UK, perhaps dumping enough rain to reach the wettest April ever recorded. (Source: SAT24)

Elsewhere in Weather News is provided by Matt

Powerful Thunderstorm Rips Through Winnipeg; What’s Next?

Winnipeg Lightning
Photo by Phil Hossack, The Winnipeg Free Press

A powerful thunderstorm developed rapidly along an advancing cold front last night, pounding the city with heavy rain, strong winds and hail. Things looked like they would pass north of the city until the front reached about 30-40km west of Winnipeg, where rapid southward development of the existing storm line occurred. This storm, a rarity this summer, comes after a month and a half of hot, dry weather where thunderstorms constantly split as they approached the city and passed north of our south of the area. For storm lovers, we couldn’t have asked for more from a late-evening thunderstorm: great structure in the clouds, much-needed rain, some hail, and one of the most impressive light shows I’ve seen in a long, long time. Read on to see pictures and video of this storm in action!

I was able to capture this video from the west-end of town around 9:45 last night, shortly after it had stopped raining. I haven’t seen as much lightning in a single storm as the one last night in a long, long time:

Intense Lightning in Winnipeg (August 18, 2011) from buffaloseven on Vimeo

User submitted photo
Photo submitted by @hubertguiggsy on Twitter

Twitter user @hubertquiggsy sent me this picture of the storm. It’s a beautiful shot that shows the gust front crossing the city (this picture is facing North) with ample amounts of scud being sucked up into the storm.

Lightning + Mammatus
This picture is one of a few great ones at http://www.steinbachweather.ca from the storm as it moved through his area, such as the one above. I highly recommend you visit the site and take a look.

The Weather Network always has plenty of submissions, and last night’s storm was no different; here are some of the highlights:

Clouds; submitted by Arienna Paul

This shot (Clouds) shows the impressive structure the leading edge of this storm had, with a well-defined lowering and gust front, complete with beautiful striations running along the main lowering.

Wow!; submitted by Christina Unger

Seen from a different angle, Wow! shows us how ominous this storm looked as it approached. Scud getting sucked up into the storm as it advanced on the city, with nothing but ominous behind the gust front. Again, striations can be seen running along the gust front on the upper half of the lowering.

funnel cloud
funnel cloud; submit by Wendy Buleziuk

This shot, taken near East St. Paul, shows another beautiful shelf cloud. The photo is titled “funnel cloud” and I chose not to change that, but it’s important to note that there is no funnel cloud in this picture. The elongated strands of clouds pointing towards the lower left of the picture, protruding from the shelf cloud itself, is known as ‘scud’. This is very low level cloud that is generated by strong lift right ahead of the gust front. These clouds are indicative of a powerful thunderstorm, but do not have a direct connection to the development of funnel clouds or tornadoes.

Thunder Storm Winnipg
Thunder Storm Winnipg (sic); submitted by Greg Pecold

Another beautiful shot of the gust front as it advanced into town.

What’s next for Winnipeg? Cooler weather for today and tomorrow with a mix of sun and clouds. It looks like there’s a chance of showers tomorrow afternoon/evening as a weak disturbance slides through the interlake in the northwest flow, although it looks likely that the showers will stay north of Winnipeg. Sunday may be a little more unsettled as another system moves by and starts to push the cold air out of the province. We’ll see temperatures rebound to close to 30°C Sunday afternoon as the system brings warmer air into the province, and then for the first half of next week we’ll be under the influence of a building upper ridge, which will bring sunshine and temperatures near 30°C for Monday, Tuesday and Wednesday.

Showers and Thunderstorms, U2, Then More Rain

While the temperatures may not be completely summer-like, today will be a day that indicates a clear shift towards summer weather.  An incoming disturbance will produce widespread convection today with showers and thundershowers covering much of Southern Manitoba.  Pleasant weather should make an appearance for tomorrow’s U2 concert, but Winnipeg will quickly return to rainy weather on Monday as a system that will bring significant challenges to those with housing near the lake moves into the province.

A substantial stacked low pressure system currently positioned just east of Regina is set to move across Southern Manitoba today.  A few factors will combine to produce what could be a fairly interesting afternoon today.  

First, a southerly wind, combined with yesterday’s rain has pushed dewpoints to nearly 10°C throughout the Red River Valley with a relatively deep layer of evidenced by the stratus cloud that has managed to form overnight despite winds of 15-20km/h.  This moisture will provide the fuel needed for thundershowers. 

Secondly, rather cool mid-level temperatures will be in place.  As the low pushes in, temperatures in the mid-levels should drop to -7 to -8°C, which when combined with daytime heating will produce ample instability to get convection initiating.  It is also indicative of fairly low freezing level, which will help in the generation of small hail.

And last but by far not least, the fact that this upper disturbance is stacked on top of a surface low means that there will be significant rotation through the mid and upper levels which will help storms develop rotation.

When these things combine, it’s considered a pretty classic case for cold core funnels.  These funnel clouds do not develop in the classic sense; instead of developing in the rapidly rotating updraft of supercell thunderstorms, they develop through the descent of cold air through a storm that has developed rotation due to significant mid-to-high level spin.  Think of it as a funnel cloud that develops because of how air is coming out of the cloud rather than how air is being ingested into the cloud.

These funnel clouds do have the potential to touch down and become tornadoes.  If they do, they are often extremely short lived (< 1-2 minutes) and are much weaker than the tornadoes that form from supercell thunderstorms.  Any of the storms that could produce a cold core funnel cloud are also extremely likely to be capable of producing hail.

I think that most areas across Southern Manitoba could see hail today, although the threat is biggest in the Red River Valley and east.  Winnipeg and areas south should most likely see pea-sized hail should it develop.  Further east in the Whiteshell and Sprague regions, the potential exists for marginally severe hail (about dime to quarter-sized).

The biggest hindrance to the development of all this is the lack of focus for convection.  With no strong front or trough, convection may simply blow up all over the place instead of in any organized fashion, which will leave all the storms fighting each other for resources.  If this happens, it’s likely that it would quickly blossom into a big area of showers with only the odd lightning strike.

My bet for the Red River Valley is this: low stratus this morning will burn off quickly with the morning sun.  By mid-morning, most areas should be seeing a mix of sun and cloud.  Daytime heating, combined with a weak cap, will initiate the convection earlier than typical, resulting in showers spreading into the Red River Valley around 12-1PM or shortly thereafter.  Any showers that develop in the RRV are just as likely to become thundershowers, and I think there will be numerous funnel clouds today.

As for Sunday and the big U2 concert, it should be quite a pleasant day.  We’ll see a sunny morning give way to a mix of sun and clouds in the afternoon with a daytime highs around 15-17°C.  It will cool off quick in the evening, so make sure to bring a sweater if you’re headed to the concert.

12hr. QPF valid 06Z May 31 from the 06Z May 28 GFS

After that, it looks like a significant low pressure system will track through Southern Manitoba, bringing nothing but headaches and grief for residents on the lakes.  Current indications are for a widespread area receiving 20-40mm of rain with winds potentially as high as 50 gusting to 70 km/h.  This system will do no good for the flood-striken areas near the lakes, and I would suggest that residents in the area should begin to make preparations already as with the strong winds out of the north-east, significant water damming will likely occur on the western to southern beaches.