HOW DO WE ** KNOW ** THIS ?
Understanding why hurricane LARRY …which is going to become a category 4 hurricane …is no threat to the East Coast may seem like a bold statement to some. But it is the difference between meteorology and MODELOLOGY….. although in this case… the various weather models are in excellent agreement. Of course one could make the argument …”well you know things could change “…but not really. Not in this case. Let’s take a look and see what’s going on
As we all know IDA was a mighty powerful hurricane that transformed itself into a regular large East Coast LOW with a fairly strong well-organized area of Low pressure. The grounds were already saturated in the Northeast US because of the previous tropical cyclones known as FRED and HENRI. It was this widespread supersaturated grounds in the northeast US that hat made the extremely heavy rains from IDA so devastating. It must also be remembered that IDA became absorbed with the big trough that formed on the East Coast which allowed Ida to develop extra-tropical characteristics very quickly. In other words, it became a coastal storm.
Image #1 ne is the Thursday evening operational GFS model. Note that there are three maps here. The map in the upper left map is valid 9/4. The BIG RED L refers to the anticipated forecast position of LARRY. There is a long wave Trough in the Eastern Atlantic Ocean and another trough (which I designate Trough #2) which contains the remains of IDA that has left the East Coast, and is now moved out into the western Atlantic Ocean. And behind that, is another significant Trough in the upper Plains which I designate Trough #3. In between the first trough and Trough #2 is a fairly strong Ridge in the middle of the Atlantic Ocean.
The map in the upper right corner which is valid 9/8//21 shows that Trough #2 which contained the remains of IDA is now long gone. Trough #3 is rapidly amplifying and pushing into the Great Lakes headed for the East Coast. The interaction with this major trough and the strong Ridge in the central Atlantic ocean forces LARRY to turn to the northwest. The bottom image valid September 9 shows that Trough#3 in the Great Lakes is amplified and pushed has reached as south as Georgia. This major Trough is too strong for the hurricane and forces LARRY to turn sharply to the north staying well off the coast and headed out to sea.
Indeed looking at the GFS surface weather maps we see a strong surface cold front pushing into the East Coast from the Great Lakes on September 8 and reaching the East Coast on September 9th. You may see or read or hear some people tell you that the cold front is going to turn LARRY to the north that is actually not accurate. It is the deep and powerful trough in the jet stream which is going to turn Larry out to see not the cold front.
Next we have the European model from Thursday evening and here we can see the same sort of thing. The image in the upper-left is the 500Mb European model projection valid for Sunday and we can see what appears to be a powerful hurricane in the ideal position to threaten the East Coast. The RED L refers to LARRY. But again notice that Trough #2 is quite deep and contains the remains of IDA and it has moved off the East coast into the northwest Atlantic Ocean. This trough is going to turn LARRY to the Northwest just like it does on the GFS. The map in the upper right which is valid Tuesday, September 8… shows Larry tracking NW and Trough #3 rapidly developing and intensifying as it moves into the Midwest. The bottom image shows a track and solution very similar to the operational GFS. A deep powerful trough for early September along the East coast which has turned hurricane LARRY shortly to the north and out to sea.
This next image is the same thing but here we looking at the North America projection and we can clearly see the Deep trough #3 turning Larry out to sea.
And finally… this is what it looks like on the European surface images for the western Atlantic Ocean on the East Coast. It looks very similar to the operational GFS. The problem here is that as long as Trough #3 is this deep and it is located on the East coast …. and it most assuredly will…. there is no mechanism or pathway for Larry to approach the east coast in any capacity whatsoever.
Larry is a fish storm and nothing on God’s Earth is going to change that.