Elsewhere in Weather News: July 14th, 2012

Japan Faced With Severe Flooding

Significant flash flooding struck Japan this week due to severe thunderstorms that remained nearly stationary for several hours over the southern island of Kyushu. The stationary boundary collided with warm, moist air from the Pacific igniting the thunderstorms and continuing for nearly 24 hours now, from Thursday afternoon to Friday night causing tremendous amounts of rain to fall over the same areas.

Surface map of Japan

Surface map of Japan with stationary boundary in red and flash flooding region talked about in green box. Effective 1pm Friday, CDT. (Source: Japan Meteorological Agency)

According to the Japan Meteorological Agency, a record of 500+mm (20 inches) fell in Aso and Kumamoto City in less than a 24 hour period overnight Thursday, causing severe mudslides in the area. In all, 15 people have died as a result of the flash floods and mudslides, with 11 still reported missing. Authorities have sent out search teams, where it is safe to do so, to find the missing or buried. As of Friday night, they have found eight survivors buried in the mudslides. The severe mudslides forced people to shovel their way out of houses and to wade through thigh-deep mud to make their way around. Thankfully 68,000 people had been evacuated from the area prior to the storm, avoiding additional casualties. Among the damage, about 22,000 households lost power, train services were shut down, many roads were inaccessible, and rice crops were severely damaged.


First responders searching for survivors where a mudslide destroyed homes. Taken in Minamiaso, Japan. (Source: Reuters)

Kumamoto City

Road covered in mud and cars left over by the flash floods in Kumamoto City. (Source: Jiji Press)

Unfortunately the stationary boundary is not going anywhere any time soon and is forecast to continue to spawn thunderstorms for the next three to five days as the warm, moist air continues to collide with it and the mountains. Another 100+mm is forecast for Saturday in the region once again, with even a slight chance of tornadoes added to the mix. Friday night, heavy rains warnings (including ground-loosening and inundation) and flood warnings were still in effect with an advisory (watch) for severe thunderstorms in the region.

Hot Weekend Ahead

Hot weather will continue through the Red River Valley this weekend, but unsettled weather will return at weekend’s end as an upper trough swings across the Prairies.

850mb Temperatures from the NAM for Friday Afternoon

850mb temperatures from the NAM for Friday afternoon. While temperatures have cooled since Wednesday, very warm air is still in place over Southern Manitoba.

We’ll see quite a nice day today with plenty of sunshine and a high near 31°C. Winds will light out of the west-northwest across most of the Red River Valley. We’ll see a warm night tonight with an overnight low of just 19°C.

For Saturday, we’ll see another sunny day with highs in the low 30’s across the Red River Valley. Some thunderstorms are possible over portions of southwest Manitoba, including Melita, Virden, Brandon, and the Pilot Mound areas. Some communities very close to the western escarpment of the RRV may also have a slight chance at seeing a thundershower.

Clouds will begin to roll in Sunday morning as a upper trough begins pushing into our region. It’s too early to tell who will get what for precipitation, other than it looks like there might be a slight chance of showers for the Southern Red River Valley on Sunday afternoon before the main system pushes through on Sunday night into Monday morning. Precipitation distribution is still questionable with this system, but amounts generally look light with less than 5mm for areas that see rain. We’ll narrow down the expected areas to see rain as we get a little bit closer to this system’s arrival. The cloud cover will limit our high temperatures to the mid-to-upper 20’s and the wind will be out of the southeast at 15 to 30km/h.

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Hottest Day of the Year to Give Way to Unsettled Weather

Winnipeg may see the warmest day of the year today as temperatures soar into the mid-30’s under the influence of an upper ridge and southwest wind. The upper ridge that has brought us our sunny weather will then be weakend by multiple upper disturbances tracking across the Prairies, bringing us a few days of more unsettled weather across Southern Manitoba.

850mb Temperatures for this afternoon.

850mb temperatures from the NAM for this afternoon.

A southwest wind, combined with significantly warmer temperatures under the upper ridge (around 22 or 23°C at 850mb) today will help Winnipeg’s temperature soar to a scorching 35°C if we can stick to sunny skies. Today will be the warmest day of the week, with temperatures returning to near 30°C for Thursday and Friday. Overnight lows will be mild with the temperature bottoming out at only around 19°C.

Several disturbances are set to track through the southern portion of the province beginning this afternoon/evening, which will bring us a risk of thunderstorms late this afternoon and this evening as well as tomorrow afternoon/evening. While some storm parameters will be significant given the heat, a distinct lack of wind shear will ensure that any storms that form will likely be relatively slow moving pulse-type storms. They may strengthen to severe levels, but they will likely be scattered and it will be quite hit and miss as to who sees them and who doesn’t. The main threat from the storms would be large hail and heavy rain. Strong winds area also a possibility. Extremely weak wind shear will likely preclude the development of tornadoes, but it’s important to remember that any thunderstorm has the potential to produce a tornado; some are just more likely than others.

Things clear up a bit for Friday (although a few hit and miss storms are possible through the Red River Valley) before another system pushes in for the weekend and we’ll see more significant chances for thunderstorms return.

Surprise! More Hot Weather

This week will be another hot one in Southern Manitoba and indeed all over Western Canada. The potential for thunderstorms during the week may temper the heat somewhat.

A large ridge of high pressure will reside over Western Canada this week

A large ridge of high pressure will reside over Western Canada this week

The weather forecast for this week will be rather tricky. What we do know for sure is that it will be hot all week, with high temperatures being near 30C every day. However, what is somewhat unclear is the risk of thunderstorms during the week. Let’s start with the easy part – the heat.

Temperatures will start out the week in the upper twenties or near thirty on Monday and Tuesday in Southern Manitoba. Humidity levels should remain low on these day making conditions hot, but not excessively so. By Wednesday high temperatures should be be in the low thirties with the humidity making it feel closer to 40. It currently appears that temperatures for late week will remain around the 30C mark, with humidity levels remaining elevated.

A shortwave will move toward the Eastern Prairies on Wednesday, potentially helping to trigger thunderstorms

A shortwave will move toward the Eastern Prairies on Wednesday, potentially helping to trigger thunderstorms

The presence of heat and humidity over the Prairies this week will cause the atmosphere to become unstable, creating the risk of thunderstorms on many days. Unfortunately, the thunderstorm forecast is not entirely certain. The issue is that a large region of high pressure, such as the one we’ll be under, does not typically promote widespread thunderstorm activity. In fact high pressure usually suppresses convective activity. It looks like this ridge will not be very good at suppressing thunderstorms, which complicates the forecast significantly.

At this point it looks most likely that Southern Manitoba will see thunderstorms mainly during the second half of this week, from Wednesday onward. During that time period the atmosphere will be most unstable and there will be some weather features moving through the region which may trigger storms. The jet stream has weakened significantly over the Prairies as of late, meaning that most storms will be non-severe in nature. Heavy rain will likely still be a concern though due to slow storm motion. Some severe storms will also be possible just simply due to the instability present in the atmosphere. Although stronger storms will certainly be less widespread than weaker ones. As the week progresses we’ll have to reassess the thunderstorm risk one day at a time.

While my forecast for this week might seem a bit equivocal, that will just be the nature of the weather in the short-term. Unfortunately thunderstorms are just simply unpredictable a frustrating but unavoidable aspect of mother nature.