North America Pattern Could Encourage Tropical Trouble Next Few Weeks

Written by on September 2, 2013 in Tropical, United States of America with 0 Comments

The heat has been pretty much the main story for the US over the past 10 days but as we progress through the next 10, I have a funny feeling the tropics are going to become the main story as the Atlantic begins to light up and we see systems all of a sudden develop and threaten the US coast.

There are two features we’re currently watching. One that’s approaching the Lesser Antilles and the other that’s not far off the Senegal coast heading west.

rb-l

Here’s the much more active wave train streaming off Africa.

rb-l

The GFS ensemble temperature means for the next 7 days. Note the cool over eastern Canada down through the Lakes and into the Ohio Valley.

M7D7

Ridging builds north into Canada and shifts east towards James Bay and Quebec mid to late September while heights lower underneath and down over the Gulf and western Atlantic. A setup that needs to be watched for not so much the system now approaching the Caribbean but more the stuff coming off Africa which should be over the western Atlantic by day 10-14. All this is coming together just as the MJO pushes phase 2.

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It was Joe Bastardi on many occasions over the years made mention of the fact that when there have been big hits on the US coast during September, you often have the strongest heights up over Canada, particularly eastern Canada and note the CFSv2 500mb heights week 2 into 3 in in particular! We’re heading for that setup and it’s just as the Atlantic is becoming more conducive. Stronger heights further north with a positive NAO/AO means less shear over the tropics and a more productive African wave train too.

Week 2 shows the heights rise up into Canada while they lower to the south creating an incubator over the warm waters of the western Atlantic and Gulf.

wk1_wk2_20130831_z500

Week three could be interesting with the greatest positive anomaly centred over James Bay. Anything heading west over the Atlantic should get naturally pulled towards the US.

wk3_wk4_20130831_z500
Here are the temperature anomalies from the CFSv2 and note the warmth shifts to Canada while the Lower 48 cools thanks to lowering heights. This acts like a magnet for the tropics!

Week 1-2

wk1_wk2_20130831_NAsfcT

Week 3-4

wk3_wk4_20130831_NAsfcT

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