Convective Outlook Valid for June 14th, 2019

Convective Discussion

A low pressure system over the southern Maritimes will continue to produce rain over western NF&Lab today. The inversion along  the frontal boundary will generate severe wind gusts to the lee of  the Cape Breton Highlands and the mountain range on the west coast of Newfoundland.

Further west, a surface cold front extending southward from a low over western Quebec will reach the lower St. Lawrence/Maine/New Brunswick later today. A 30 kt southwesterly low-level jet ahead of this feature is pushing enough moisture over northern NB to sustain some instability this afternoon once the low cloud/fog dissipates. This will take a few more hours since the lowest 5 000 feet is saturated (CAR sounding is showing this). However once the cloud cover breaks, instability will increase and a number of ingredients will be coming together to support the development of strong pulse Storms. The deep layer shears calculated from this mornings upper wind soundings are probably too strong to support long-lived bowing lines, however the presentation of the CAR hodograph suggests veering winds with heights, and if this pattern was maintained after convective initiation this afternoon formation of a tornado might not be out of the question. Having said this, as the air mass becomes depleted of the higher water content in the mid-levels - downdraft CAPE values between 400 to 600 J/kg will evolve, at that point the Storms could potentially produce damaging wind gusts in excess of 90 km/h. This appear to be the main threat for today.

Regional Impacts

New Brunswick: Over Northern regions this afternoon, strong pulse type thunderstorms capable of producing brief downpours, small hail and damaging winds. Storm motion will be eastward at 50+ km/h. Hourly rainfall rates of 15-25mm/h are also likely during brief downpours.

Isolated thunderstorms from central Maine may propagate over the mid and lower Saint John River Valley this evening.

Elsewhere across the rest of the Atlantic provinces, no thunderstorms are expected.

Jean-Marc

Convective Outlook Valid for Thursday June 13th, 2019

Convective Discussion

A large low pressure system currently over the Great Lakes will move eastward today and tonight. A strong southwesterly jet will spread a very moist air mass with embedded thundershowers over the Maritimes tonight. The area of rain will spread northward to reach Western Labrador on Friday. Over the rest of Newfoundland and Labrador tranquil conditions are expected.

A cold front will approach Northern New Brunswick Friday giving a risk of afternoon thunderstorms.

Regional Impacts

Nova Scotia: Hourly rainfall rates of 15mm/h producing enhanced runoff over western region. Rainfall amounts of 20 to 40mm with the highest amounts along the South Shore.

New Brunswick: Hourly rainfall rates of 20mm/h or more producing enhanced runoff over the Fundy Region. Rainfall amounts of 20 to 40mm with the highest amounts over Grand Manan Island.

Jean-Marc Couturier

Convective Outlook Valid for June 11, 2019

 

 

Convective Discussion: There is a deep dry ridge over the Maritimes and Labrador moving east today. Behind it there is a deep trough extending from east of Hudson Bay south to New England, with an embedded weak low south of Long Island, New York. The only areas with a chance of convection are western Nova Scotia and New Brunswick, and it should be non-severe, except for the possibility of training.

 

The weak low will move just south of Nova Scotia this evening, giving some extra moisture.  There will also be midlevel destabilisation, partially due to cooling  aloft in the wake of the 500 mb thermal ridge currently over western Nova Scotia and New Brunswick moving out ahead of the 850-700mb thermal ridge just west of the Maritimes.. The moisture will mainly help Nova Scotia and southern New Brunswick get enough energy for possible thundershowers this afternoon into this evening.. For west to northwest New Brunswick, moisture will be less, but the deep upper trough, a weak left entrance region from an associated jet approaching the northwest of the province, and some PVA and indications of lift from 700 mb upwards, again gives a possibility of thundershowers.

 

 

Regional Impacts:

 

Newfoundland and Labrador: No significant convective weather expected.

 

Prince Edward Island: No significant convective weather expected.

 

New Brunswick: A chance of thundershowers this afternoon into this evening over western parts of the province. If they happen, expects local heavy rain, and gusty winds.

 

Nova Scotia: A chance of thundershowers this afternoon over parts of the southwestern mainland.. If they happen, expects local heavy rain, with a lesser risk of  gusty winds.

 

Marine Areas: Non-severe thundershowers this afternoon into this evening over southwestern Maritimes waters.

 

Doug Mercer

Lead Meteorologist

Atlantic Storm Prediction Centre

Meteorological Service of Canada

45 Alderney Drive, Dartmouth

Nova Scotia, B2Y 2N6

Doug.mercer@canada.ca

Office: (902) 426-9200

 

Premier Météorologue
Centre de prévision des intempéries de la région de l'atlantique

Service météorologique du Canada

45 promenade Alderney, Dartmouth

Nouvelle-Écosse, B2Y 2N6

Doug.mercer@canada.ca

Bureau: (902) 426-9200

Cell: (902) 403-7951

 

Convective Outlook for Atlantic Canada Valid for June 10th, 2019

 

Convective Discussion

 

Another quiet day across the region as we remain on the cold side of a large ridge of high pressure. The atmosphere is stable through a significant layer and with the very limited low level moisture no deep convection is expected.

 

Regional Impacts

 

None expected

 

 

Mel Lemmon

 

 

 

Convective Outlook Valid for June 9th, 2019

Convective Discussion:

Upper low at 500mb will continue to move eastward to the Grand Banks later today. The St John’s west sounding is indicating some mid-level instability which is producing weak shower activity over eastern portions of the island. In the cold pool, the weakening available energy is extending to 500mb where temperatures are around -25 to -30. Given these conditions,  there is a slight risk of an isolated CB/ACB east of the island during the next few hours.  

An upper ridge over western Quebec will continue to build over the rest of the Atlantic provinces maintaining fair weather conditions through Monday.  

Regional Impacts:

Newfoundland and  Labrador: No thunderstorms expected.

Prince Edward Island: No thunderstorms expected.

Nova Scotia: No thunderstorms expected.

New Brunswick: No thunderstorms expected.

Jean-Marc