Tag: Trough

Elsewhere in Weather News: March 22nd, 2014

Matthieu Leave a comment

Below Normal February Temperatures for most of Continental US; Will Return

What seems to be the winter that won’t give up in Southern Manitoba has not only been persistent in the Canadian Prairies, but also a good chunk of the United States. The central and eastern half of the US has been fairly consistent in staying below normal in February thanks to a persistent trough on the east coast and ridge over the west coast. Consequently, a northwest flow in the upper levels of the atmosphere has established itself over the Northern US Plains and Midwest and, as a result, Arctic highs were continuously helped down into the region. Interestingly enough, central North America has been one of the only regions in the world to experience below normal temperatures in February.

Temperature anomalies across the globe for February, notice the below average in Central/Eastern US, contrasted by the much above normal just to the east, over the ocean. This is caused by persistent troughing on the East Coast. (Source: NOAA)
Temperature anomalies across the globe for February, notice the below average in Central/Eastern US, contrasted by the much above normal just to the east, over the ocean. This is caused by persistent troughing on the East Coast. (Source: NOAA)

The pattern, which has not shifted around much this winter, has caused extremes to occur not only temperature-wise but also precipitation wise. The problem is that with the ridge staying put over the area systems have trouble making their way into the region and instead diverted further north. California continues to experience severe to exceptional drought – the highest level of drought, as per the US Drought Monitor. Consequences might not be immediate but could spell trouble once the wildfire season rolls around, and when water reserves literally start to run dry in the state. Currently, about 60% of the state is considered to have an above average risk for wildfires due to the drought, according to NICC.

Sunday night into early next week yet another blast of Arctic air is expected to infiltrate across a good chunk of the United States. In addition to this cold blast, models are showing a potent Nor’easter Tuesday-Wednesday next week blasting through the Northeast US and Atlantic Canada which could drop significant amounts of snow. However, there is a glimmer of hope for the central United States as most models are in agreement that temperatures late next week into next weekend will be either bounce back to normal or slightly above normal.

500mb northwest flow returns to the region this week, shown by the NAM here, on Tuesday morning. (Source: Twisterdata)
Northwest flow returns to the region this week, shown by the NAM here, on Tuesday morning. (Source: Twisterdata)

Elsewhere in Weather News: February 1st, 2014

Matthieu Leave a comment

Southeast US Paralyzed by Storm

On Tuesday a large trough was in place over the eastern half of the US. The longwave trough extended all the way down to the southeastern states and brought adverse weather conditions along with it. This trough did not produce the typical severe weather the southeast would see around this time of the year; thunderstorms and flooding rain, but produced an event featuring snow, ice pellets and freezing rain.

Arctic air flooded in behind the cold front all the way down from Texas to the Gulf of Mexico to Florida, providing good environment for freezing precipitation right behind the front. Freezing rain fell as far south as Pensacola in the Florida panhandle where over 200km of interstate had to be shut down because it was deemed to be too dangerous for travel. The last time Pensacola saw snow was 2010 – it melted the same day it fell. In comparison, Atlanta saw a trace of snow in 2008. This time around the city received 6cm, which snarled traffic on the commute back home. Officials decided to not cancel schools and students were stranded in schools and buses overnight until the next morning. Commuters were in the same situation, being stranded on roads overnight as many commuters are not accustomed to winter weather leading to many accidents. The sub-freezing temperatures across the Deep South also wreaked havoc, bursting water pipes above ground.

Wednesday morning surface temperatures. Freezing temperatures can be seen reaching all the way down into Mexico and the Deep South. (Source: Twisterdata)
Wednesday morning surface temperatures. Freezing temperatures can be seen reaching all the way down into Mexico and the Deep South. (Source: Twisterdata)

Medium range models continue to show cold air entrenched across the Canadian Prairies and most of the United States, even infiltrating into the Deep South again next week. A persistent ridge off the West Coast, partially associated with the well above normal temperatures in the North Pacific, can be blamed for the persistent troughing and Arctic air over Canada and US the past few weeks. Longer range models do show the ridge eventually breaking down in a week but this remains to be seen as it’s still a long ways out.

Elsewhere in Weather News: June 29th, 2013

Matthieu Leave a comment

Australia Faces Flooding Problems

This spring has been disastrous flood-wise across the globe; hundreds of billions of dollars of damage to crops and infrastructure from a few significant floods such as the Chinese floods, European floods and closer to home; Albertan floods as talked about in last week’s EIWN. Extreme flooding continues this week, most notably in Australia’s New South Wales state.

In the past few days coastal areas of New South Wales have received copious amounts of rain. Consequently, flood evacuations have had to be issued for a few towns just outside of Sydney (Richmond Lowlands, Pitt Town, Gronos Point). The Warragamba Dam, located to the west of Sydney, was overwhelmed by the 150mm of rain that fell in a 24 hour period starting Wednesday, prompting for the flood evacuations. Many roads and a few key bridges in the area had to be shut down because of the overland flooding. In addition, a few search and rescue missions have had to be executed because of people trapped in floodwaters. Thankfully no casualties have been reported as of yet related to this flooding.

Rainfall June 29

Rainfall map for the past 7 days as of Friday. Circled in red the area experiencing flooding, localized areas of 200mm+. (Source: Australia’s BoM)

It appears as though a lingering trough of low pressure is to blame for all the rain on the eastern coast of Australia on Wednesday. Sydney and surrounding areas get on average about 130mm of rain for the whole month of June. Compared to this past week where in some areas 200mm (or more) have already fallen, these areas have already doubled their average rainfall for June, significant flooding is not surprising. This weekend appears to bring more rain to the coast of New South Wales, though not another significant rainfall event.

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.