Heavy Rain and Moderate Winds Will Mark Ernesto's Passage South of Newfoundland Monday

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While tracking Hurricane Ernesto for the past few days, there was some uncertainty between models when it came to the path that the storm would take either through or around Newfoundland. Thankfully, it became clearer, as the storm continued its approach, that it would pass south of the Avalon Peninsula, greatly limiting the impacts to land.

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Ernesto restrengthened to a Category 1 Hurricane on Sunday and it will maintain that intensity as it makes its final push into Canadian waters later Monday morning. Precipitation from its outer bands will spread across most of Newfoundland as light to moderate rain starting in the mid-morning along the South Coast and moving northward across the province into the afternoon. Total rainfall amounts will be 5-20mm from this early rainfall.

By the time the storm travels to south of the Avalon Monday evening, it will have weakened to a tropical storm with wind gusts at its centre of 110km/h. The intensity of the winds will decrease further away from the centre and the strongest winds on land are expected in the Southeast Avalon, topping out at 70-90km/h. Across the rest of the Avalon and through the Burin Peninsula, wind gusts will be in the 50-70km/h range during the evening and into the overnight hours.

This is also the time frame in which Ernesto will bring the most precipitation to Southeast Newfoundland. The rain could be very heavy at times during this 6 hour window and up to 50mm could easily fall across most of the Avalon Peninsula and up to 30mm for the Burin Peninsula, with higher amounts locally. The rain and large waves from the storm could result in some coastal flooding, particularly along southwest-facing shorelines so be sure to exercise caution in these areas. By Tuesday, the storm will be well east of the island and the large waves will start to subside, marking another hurricane in the books for Newfoundland.

Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 18th at 9Pm

Rainy Start to the Week Across the Maritimes as Hurricane Ernesto Passes Offshore

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While tracking Hurricane Ernesto for the past few days, it was been clear that the storm would stay well offshore of Nova Scotia. This has been good news because it means that there would be very little impact from the storm across the Maritimes. The greatest threat will be moderate to heavy surf, along with riptides, that have already begun to arrive along the Atlantic Coast of Nova Scotia this evening which will continue through the day Monday and into early Tuesday. Despite the storm staying over open water, the Maritimes can expect a wet start to the week.

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A band of thunderstorms will make its way northward from Ernesto and cross in Nova Scotia shortly after midnight tonight along the length of the province, but more concentrated to the eastern mainland and Cape Breton. This will be followed by a secondary band in the mid-morning, once again focused more along the eastern half of the province. These storms will bring localized downpours and could bring up to 30mm by the lunch hour. The threat of isolated onshore storms will continue throughout the afternoon and into overnight which could push into Southern New Brunswick and across PEI with some light rain.

Meanwhile, a secondary tropical air mass will bring rain to Northern New Brunswick beginning Monday afternoon, lasting until late in the day Tuesday. This rain will be quite heavy at times, especially in the Edmundston area, and could lead to up to 50mm falling. These two rounds of precipitation make for a very interesting looking rainfall map!

Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 18th at 9Pm

Hurricane Ernesto's Track Through Atlantic Canada Becoming Clearer; Could Maintain Category 1 Strength Deep into Canadian Waters

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Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 17th at 9Am

Hurricane Ernesto made landfall on Bermuda early this morning as a Category 1 Hurricane. The storm luckily weakened from a Category 2 in the few hours before landfall, but it still packed a punch with 135km/h winds. Now the storm will continue to churn northeastward into Atlantic Canada for the beginning of next week.

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The Canadian Hurricane Centre is now issuing their own forecast track and there has been very little change in their prediction with their 9am update compared to the maps from the past two days. They maintain that the centre of Ernesto will stay well offshore of Nova Scotia and pass south of the Avalon Peninsula. Major weather models have made a shift since yesterday morning and now there is agreement that the centre of the storm will stay off the coast of Newfoundland. This is certainly good news because this will keep the strongest winds from hitting land, but it will still be an impactful storm.

Now that we’re starting to see a clearer picture of Hurricane Ernesto’s path through Atlantic Canada, we can more accurately forecast the impacts of the storm, especially for the Maritimes. Pounding surf will hit the Atlantic Coast of Nova Scotia beginning late Sunday and continuing through Monday. Rip currents will also be a concern in these coastal areas. Light rain from the storm will spread across Nova Scotia and even into PEI and Southern New Brunswick, with rainfall totals at this point expected to be in the 5-30mm range across the region for Monday. Exact amounts and locations will become clearer by this time tomorrow. Since the storm will be passing so far offshore, winds will not be a concern in the Maritimes.

Newfoundland, particularly the Burin and Avalon Peninsulas, will get hit harder than the Maritimes since Ernesto will be passing much closer. Southwest-facing coastlines can expect to begin seeing the ocean swell from the storm beginning late Sunday with large waves and hazardous surf starting late Monday and continuing into Tuesday. These waves and the storm surge will likely result in coastal flooding along these southwest-facing shores. Since Ernesto is expected to pass close to the Avalon late Monday, the winds won’t be as strong on land as they will be closer to the centre of the storm. Nonetheless, wind gusts of up to 100km/h can be expected along the southern shores of the Avalon, especially from Saint Vincent’s to Cape Race, and weakening further inland. Rainfall will be heavy for a brief period of time late in the day Monday for Eastern Newfoundland, including into Bonavista. Light rain will spread across the rest of the Island ahead of the storm Monday afternoon. It is still a bit too early to predict exact totals, but at this point the Avalon could see 30-50mm of rain in a 6 hour period.

Model Forecast Tracks for Hurricane Ernesto, Courtesy of Tomer Burg.

While the track of Ernesto through Atlantic Canada has become clearer, the intensity at which it will travel through the region appears to have also become clearer. The Canadian Hurricane Centre predicts that Ernesto will maintain hurricane strength up to its final approach of Newfoundland, with winds of 120km/h, which is just above the threshold for a storm to be considered a hurricane. Then, just as it passes south of the Avalon, it will transition to a post-tropical storm.

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Previous forecasts from the CHC/NHC showed that Ernesto would weaken somewhere between being offshore of Nova Scotia and around the Avalon, with no indication of where this transition may take place. This has now become clearer now that the storm has passed over Bermuda. Ernesto will experience a decrease in shear, giving the storm a chance to recover from ingesting so much dry air and it will undergo a short period of restrengthening tomorrow before hitting the point in which sea surface temperatures drop below 26°C and it begins to lose fuel. The image below shows that wind speeds at the storm’s centre will increase between Hour 24 and Hour 48, indicating this window of restrengthening. As a result of this strengthening in the storm, it will then take a bit longer to weaken to a post-tropical storm and it will maintain its status as Category 1 Hurricane deeper into Canadian waters. We will continue to monitor the storm and we will have our own rain and wind forecasts coming later tomorrow.

Forecast Track and Intensity of Hurricane Ernesto with Sea Surface Temperatures, courtesy of Tomer Burg.

Hurricane Ernesto Still on Track to Impact Atlantic Canada; Could Pass Through Newfoundland

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Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 16th at 6Am

Ernesto is continuing to barrel towards Bermuda, now as a Category 2 Hurricane, with wind speeds up to 160km/h. The centre of the storm is expected to pass near or over the island on Saturday while maintaining its strength at a Category 2.

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The Canadian Hurricane Centre and the National Hurricane Center have made very little change to their track forecast for Ernesto in the 6am update as it travels northeastward towards Atlantic Canada beyond Bermuda. There is still a large degree of uncertainty since we are still a few days out and this is reflected in the size of the cone on the forecast map.

Individual weather models, on the other hand, have begun to show a western shift. There still are a few models that are more in line with the NHC forecast that keeps Ernesto passing offshore of the Avalon. However, just as many are now suggesting that the storm could pass over the Peninsula instead and one outlier still has it tracking through Central Newfoundland. We may see a change in the official forecasts from the CHC and NHC that reflects this western shift in the models.

There is definitely more agreement in the path of Ernesto as it passes offshore of Nova Scotia on Monday. The amount of rain it brings to the Maritimes will be entirely dependent on just how far offshore it stays. Nova Scotia will most likely see rain, but if the storm passes closer to the province, we could see rain move into New Brunswick and PEI as well. Given its offshore track, strong winds likely won’t be much of an issue, but pounding surf is expected to begin for the Atlantic Coast of Nova Scotia ahead of the storm on Sunday and continuing until after its passing on Tuesday.

The exact impacts to Eastern Newfoundland will be entirely dependent on the path that Ernesto takes either around or through the province. The strongest winds will be found around the centre of the storm and at that point in the storm’s life, gusts are projected to be around 110km/h so hopefully it will stay offshore. Rainfall across the province will also vary, with higher amounts expected closer to the middle of the storm. These impacts will become clearer once there is more consensus in the track. The hazardous surf will hit south-facing shores of Newfoundland beginning late Sunday and large waves should impact the Avalon and Burin Peninsulas throughout the day Monday. The large waves, combined with storm surge. could result in coastal flooding so be sure to exercise caution in these areas.

Model Forecast Tracks for Hurricane Ernesto, Courtesy of Tomer Burg.

Ernesto strengthened into a Category 2 late yesterday and further strengthening stalled overnight, despite being in warm water, likely due to continued ingestion of dry air. It is expected to continue to strength through today, but that could be limited by an increase in wind shear, which works against hurricanes. At this point, Ernesto will top out at a Category 2.

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Hurricane Ernesto will begin to lose strength after it hits Bermuda and pushes northward into cooler waters and experiences increased shear. It will enter Canadian waters as a weak Category 1 Hurricane and it should rapidly weaken into a post-tropical storm as it approaches Newfoundland mostly due the much cooler sea surface temperatures, but also even more wind shear. Hurricanes need water temperatures of at least 26°C to survive and Ernesto will lose that as it tracks into Atlantic Canada. Nonetheless, winds at the centre of the storm are still expected to be in the 110-150km/h range as it moves through the region.

Forecast Track and Intensity of Hurricane Ernesto with Sea Surface Temperatures, courtesy of Tomer Burg.

Hurricane Ernesto Likely to Impact Atlantic Canada; Uncertainty Looms on Exact Track

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Forecast track for hurricane Ernesto from the Canadian Hurricane Centre - August 15th at 12pm

Hurricane Ernesto is currently a Category 1 Hurricane and is still moving northeastward towards Bermuda. While it is fairly certain that the island nation will take a direct hit from the storm, its track as it continues northward into Canadian waters is much more uncertain.

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In the 12pm update from the Canadian Hurricane Centre, in conjunction with the National Hurricane Center in the US, Ernesto is still expected to have some sort of impact to the Maritimes and Newfoundland, despite the uncertainty in the exact track.

Guidances from different individual weather models, as shown below, indicate potential paths that the centre of the storm may take over the next few days. In some cases, the storm may stay well offshore and only sideswipe Newfoundland with heavy rain and wind while missing the Maritimes completely. On the other hand, one model has the storm tracking straight though Central Newfoundland, which would not only greatly impact the island, but this track would also bring rain and wind further west into the Maritimes.

However, we are starting to see some agreement between some of these models that would see Ernesto stay well offshore of Nova Scotia, with only a bit of rain hitting the province, before passing just south of the Avalon Peninsula, bringing strong winds and heavy rain to Eastern Newfoundland and strong surge to coastal areas across Atlantic Canada. The swells are expected to arrive in the Maritimes beginning Saturday, with more dangerous surf starting Sunday, ahead of the storms arrival to the region early Monday.

Model Forecast Tracks for Hurricane Ernesto, Courtesy of Tomer Burg.

So what are we looking at strength wise? Ernesto is currently a Category 1 in 29°C waters. This sea surface temperature will certainly help the storm strengthen, however, dry air is being pulled into the centre of the storm which is limiting its organization. The warm waters and dry air, combined with some moderate vertical shear (which needs to be low in order for a hurricane to survive and strengthen), means that Ernesto will strengthen to a strong Category 2 Hurricane.

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As the storm continues to travel north-northeastward beyond Bermuda, it will encounter cooler waters and shear will increase, which will work to weaken it back down to a Category 1. As it moves into Canadian waters, the sea surface temperatures fall below 26°C. This is the magic number for hurricane development and growth so at this point, it will weaken even further. Ernesto expected to travel through the region starting as a low-end Category 1 and weakening to a post-tropical storm, with winds in the centre of the storm in the range of 110-150km/h.

Forecast Track and Intensity of Hurricane Ernesto with Sea Surface Temperatures, courtesy of Tomer Burg.

Debby to Bring Flooding Threat to Parts of Southern Ontario on Friday With Up to 50-100mm of Rain Possible

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After making landfall in Florida earlier this week, what was Tropical Storm Debby has brought significant rainfall along the US East Coast. Now a post-tropical system, Southern Ontario is on track to feel the effects of the remnants of Debby over the next few days.

Significant rainfall is in the forecast with a particular focus on Eastern Ontario, which could see up to 100mm by the end of the week. This is not what many across Southern Ontario will want to hear, considering this year's unusually wet summer.

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There is still some uncertainty about the exact track of the system, as it won’t arrive until Friday. A more eastern track would shift the heavier rain across the border into the Northeastern US and Quebec.

On the other hand, if the system tracks further to the west, we could be talking about more widespread significant rainfall totals, potentially extending into Central Ontario and the Golden Horseshoe. Hence, it’s important to note that the forecast may change as we get closer to the arrival of the system.

MODEL IMAGE FROM WEATHERBELL

At this point, we are expecting to see some isolated pop-up showers and non-severe thunderstorms develop throughout the day on Thursday across Southern Ontario. This is in advance of the system on Friday, which is when we expect the bulk of the rainfall to occur.

Due to the localized nature of these storms, the rainfall totals will be extremely variable, ranging from a few millimetres to up to 15-20mm in the heaviest pockets by the end of Thursday.

MODEL IMAGE FROM WEATHERBELL

One thing we are closely monitoring is the potential for a persistent band of precipitation with embedded thunderstorms to develop late Thursday and carry into Friday. Current data suggests it will set up somewhere around Woodstock/Kitchener, stretching across Lake Simcoe and into Central Ontario.

This line could produce locally significant rainfall totals overnight and Friday morning as it essentially locks in place as the remnants of Debby approach from the southeast. Keep in mind that this line could shift and will be extremely localized, so not everyone will see the heavy rain. Local rainfall totals could approach 25-50mm by Friday morning, perhaps even higher if a particular area sees multiple rounds of thunderstorms.

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The precipitation associated with the system is expected to spread across Eastern Ontario by Friday morning, which is when we expect to see the bulk of the forecasted rainfall. This will only heighten the flooding threat since it will all happen within the span of a few hours.

In addition to the rain, we are also likely to see some embedded thunderstorm activity within the bands of precipitation throughout the morning and afternoon on Friday.

These storms should stay mostly non-severe, but we’ve seen in the past that these tropical systems have a tendency to present a tornado threat, especially along the western side of the system, which is where Southern Ontario will be positioned.

This is certainly not a guarantee for tornadoes, but we will be closely watching this aspect of the system and will issue a more detailed forecast if it becomes more likely.

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MODEL IMAGE FROM WEATHERBELL

Rain is expected to taper off in the west through Central Ontario into the Golden Horseshoe by early afternoon on Friday. For Eastern Ontario, heavy rain is expected to continue throughout the afternoon and early evening hours on Friday.

We should begin to see some clearing in the west by dinner time, with the rain finally coming to an end around midnight for the Ottawa Valley and those along the St. Lawrence.

As we’ve mentioned, the highest impact of this system is expected in Eastern Ontario, which will be closest to the track of the system. Rainfall totals are likely to generally range from 50-100mm, but some localized pockets could even exceed the 100mm mark based on some of the latest model data.

It is important to keep in mind that thunderstorm activity will play a big role in the rainfall totals, so the actual totals could vary significantly between locations. That’s why we have a large range of 50mm - it’s hard to nail down the exact totals due to the localized nature of thunderstorms.

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The forecasted rainfall totals drop off quite fast once you head further west. We are projecting between 25 to 50mm of rain for the Golden Horseshoe and parts of Central Ontario around Lake Simcoe.

At this point, we are expecting 15-30mm of rain for the Greater Toronto Area (GTA) along the Lake Ontario shoreline into the Niagara region. That could change if that line of rain overnight Thursday shifts into the GTA, as the latest models suggest should develop just to the northwest.

Less than 20mm of rain is expected for Southwestern Ontario, with even lower totals for Deep Southwestern Ontario, which may see barely a drop of rain from this system.