Saturday, September 12th 2020, 8:45 pm - As the Atlantic hurricane season hits its peak this month, the basin continues to churn out storms and disturbances that are keeping forecasters busy.
Several forecasters predicted an above-average Atlantic hurricane season, and have been proven right, with multiple named storms being their earliest of their letter on record.
With September being the peak month of the hurricane season, the Atlantic is full of activity – from tropical storms Paulette and Rene to disturbances near the Gulf of Mexico and West Africa coast that show signs of development in the next five days.
CURRENT ATLANTIC STORMS
The tropical activity continues with three named storms, Paulette, Rene and Sally. Paulette is expected to become a hurricane by Sunday as it continues to head towards Bermuda.
As of Saturday evening, the National Hurricane Center says Paulette is currently 670 km southeast of Bermuda, packing maximum sustained winds near 110 km/h, with higher gusts. Paulette is forecast to strenghten into a hurricane on Saturday.
"Paulette is moving toward the northwest near 15 m.p.h.(24 km/h). A west-northwest or northwest motion is expected through Sunday night. A turn toward the north with a decrease in forward speed is forecast on Monday, followed by a northeastward motion Monday night and Tuesday. On the forecast track, the center of Paulette will move near or over Bermuda Monday morning," the NHC says.
A hurricane watch and a tropicial storm warning are in effect for Bermuda, with forecasters warning of rainfall amounts of 50-100 mm, with isolated totals of 150 mm possible.
Rene, meanwhile, continues to weaken. Currently it is 1,935 km east-northeast of the northern Leeward Islands. Its maximum sustained winds are holding steady near 55 km/h, with higher gusts. Little change in strength is forecast during the weekend, but some weakening is predicted to occur early next week.
"Rene is moving toward the northwest near 14 m.p.h.(22 km/h). A slower northwestward motion is expected by Sunday, and a slow westward motion is forecast by Sunday night. On Monday and Tuesday, the system is forecast to turn west-southwestward," the NHC says.
Tropical Storm Sally sits 70 km southeast of Naples, Fla. and is moving westward near 13 km/h. Sally is set to move a west-northwestward or northwestward through Monday.
The NHC says, "On Monday night and Tuesday, a decrease in forward speed and a turn toward the north are forecast. On the forecast track, the center of Sally will move over the southeastern and eastern Gulf of Mexico tonight and Sunday, move over the north-central Gulf of Mexico Sunday night and Monday, and approach the north-central Gulf Coast within the hurricane watch area late Monday and Tuesday."
A Hurricane Watch is in effect from Grand Isle Louisiana to the Alabama/Florida border, Lake Pontchartrain and Lake Maurepas (including metropolitan New Orleans).
Rainfall amounts of 50-100 mm, with isolated totals of up to 150 mm, are expected across west-central and southern Florida, including the Florida Keys, through Sunday.
OTHER ATLANTIC DISTURBANCES
Elsewhere in the Atlantic, there are three disturbances the NHC forecasters are keeping a close eye on for development in the next five days.
Tropical Depression 20 is 3,265 km east of the Northern Leeward Islands. Its maximum sustained winds speeds are 55 km/h, with even higher gusts. The NHC says, "Slow strengthening is expected over the next day or so, and the depression is forecast to become a tropical storm by Sunday night. A faster rate of strengthening is possible early next week."
On the eastern side of the Atlantic, a broad area of low pressure is located several hundred kilometres southwest of the Cabo Verde Islands, producing a large area of disorganized showers and thunderstorms. Development of this system is forecast and a tropical depression is expected to form within the next two days, while the system moves across the eastern and central tropical Atlantic. The chances of development over the next five days is 90 per cent.
As well, many models have this particular disturbance intensifying into a major hurricane, taking a westward track toward the Caribbean.
The third disturbance that has forecasters' attention is another area of disturbed weather, associated with a tropical wave, near the Cabo Verde Islands. A tropical depression could form over the far eastern tropical Atlantic early next week while the system moves slowly westward. The chances of development over the next five days is 60 per cent.
WHY DOES ACTIVITY PICK UP IN SEPTEMBER?
We typically see more frequent tropical systems, with greater lifespans and greater intensity, in September due to a few factors.
By this time of year, we have encountered peak summer heating, and the oceans are typically warmer than early months in the season. Warmer waters fuel tropical systems, allowing excessive rising motion over the water, resulting in strong thunderstorms that can become organized into tropical systems.
Another factor that comes into play is that we typically have less wind shear in the pattern this time of year. The Jet Stream is weaker in the summer months and wind shear fades through June and July, becoming almost non-existent in August and September. This is not a good thing, as wind shear can help weaken tropical systems.
When forecasters warn of an "above average" season, they are talking purely in terms of expected named storms, and none of these predictions typically make any claims to the expected severity of the storms. Indeed, so far the 2020 season has only produced one major hurricane -- that is, Category 3 or higher -- in the form of Hurricane Laura, which reached Category 4 prior to impacting the U.S. Gulf Coast with extreme winds and major storm surge last month.