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HELLO LESLIE

Hey folks,

I'm back from vacation and things are getting interesting, with Leslie looking more and more like a threat for Newfoundland early next week. 

As of now, (Tuesday afternoon) Leslie is a Tropical Storm with sustained winds of around 65 km/h. Leslie is currently sitting about 850 km South, Southeast of Bermuda and moving very slowly to the North, at ONLY 7 km/h!

LeslieSept4.gif

Someone on Twitter asked yesterday, why is Leslie moving so slowly? Well a quick look at the upper level winds shows Leslie is into an area with slow moving "steering winds" aloft. She'll continue at a snail's pace, South of an area of High pressure over the next few days.

UpperLevelSept4.GIF

During the next few days, Leslie's intensity isn't expected to change too much with the Storm moving so slowly through an area with moderate wind shear. That wind shear will help to blow the tops off of developing thunderstorms within Leslie and will likely help to keep Leslie's strength relatively unchanged through Wednesday.

By Thursday and into Friday, Leslie will get some assistance from the upper level winds, with the wind shear expected to decrease, which should allow Leslie to gain some strength, perhaps to Category 1 Hurricane status. However with her slow pace expected to continue, she could have a tough time strengthening more than that. Tropical Storms & Hurricanes need very warm (26.5° or more) ocean temps for "fuel". However these big storms churn up a lot of 'cooler' ocean water from below the surface. This isn't a big issue with a regular quick moving Hurricane, however with Leslie just crawling along, her own stirred up cooler ocean temps could be a factor.

CURRENT OCEAN TEMPERATURES

atlm_marine.gif

When Leslie finally starts to excel Northward near Bermuda late Friday and into this weekend, it will be moving through Ocean temps near 29° or 30°. With favourable upper level winds also expected, this will be prime development time for Leslie. If the Storm isn't a Hurricane by Friday, it's expected to reach that strength by this weekend. Some models are predicting a Category 2 storm by Sunday.


IntensitySept412.png

As Leslie moves North, a big upper level trough currently moving into the Pacific Northwest, will dig its way into the Great Lakes and Eastern U.S. this weekend. This upper level trough will actually help to pull Leslie Northward, towards Atlantic Canada. The timing and strength of this trough moving Eastward, will be one of the main factors for whether we see Leslie here in NL, or not.

0Z GFS 500MB Heights, Vorticity & Winds

500mbGFS.png

Many forecast models are indeed bringing Leslie into NL waters as a Tropical Storm or Hurricane near next Monday the 10th or Tuesday the 11th. In fact, some long range models including the GFS & ECMWF Euro models (2 of the best hurricane forecast models) are currently forecasting a track right over the Island.

Spaghetti-Sept4.gif

Until we see how a slow moving Leslie makes out over the next few days and what exactly this upper level trough moving into Eastern North America will look like, we'll likely continue to see a lot of different model ideas about how strong Leslie will be and where she'll track.

The best thing to do right now is stay tuned. I'll have the latest on Here & Now tonight and the Live Blog will be updated a lot over the next few days. So make sure to check back at cbc.ca/ryansnoddon

As always, I'll keep you posted!

Ryan 


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