Welcome to the last full day of summer

Autumn officially begins Tuesday evening at 8:05 PM.  The weather will be on a loop for the first half the week before we start to see a coastal storm bring impacts for the second half of the week.

We’re going to have a frontal boundary that will stall to our south with a few areas of low-pressure systems tracking along the boundary from an upper-level low over the Great Lakes. These little shortwaves will keep it unsettled across Pennsylvania, New Jersey and points south. We’re also going to have strong high pressure to our north over eastern and Atlantic Canada. All of this will keep us in a fall pattern with fall like temperatures.  However, we do have summer like heat in the Tennessee River Valley, that will keep southern moisture streaming northward. All of this is going to interact as the first big storm of the fall is developing. If that ULL over the Great Lakes and the coastal systems interact and work in tandem, a coastal storm is forecast to form and strengthen into a nor'easter along the mid-Atlantic coast this week.

 

Surface Chart, Radar and Satellite

 

 

 

Today

Today will be damp and dreary with on and off showers and areas of drizzle, however, skies will begin to clear as the day goes on. But the first big storm of the fall is starting to develop.

The week ahead

Nor’easter/hybrid

Tuesday into Thursday we will be dealing with a persistent northeast to easterly wind keeping things coolish. The onshore flow will aid in the coastal flooding that could develop as a strong coastal storm moves up the coast.

Looking at the 500mb pattern on the GFS from Tropical Tidbits. We can see the blocking pattern that will develop. This will lead to these shortwaves tracking east out of the Midwest stalling. Then a strong cold front will push offshore. All of these pieces will interact, and low pressure will develop and move up the Coast.

The key to all of this is the interaction between the system in the Midwest and the Coastal. If they interact just right, we’re going to see this develop into a strong nor'easter. This will bring about two scenarios. How these scenarios play out will have a lot to say about the risk of flooding rain, damaging winds, storm surge and beach erosion. Starting late Wednesday and Thursday, we’re going to be watching all this develop!

scenario #1 The storm will track closer to the Coast, where it will become cut off and meander offshore for a few days, then retrograde (drift west) closer to the Coast for Friday into the Weekend. If this is the case, high surf, strong winds of 60-70 mph, several inches of rain, coastal flooding and severe beach erosion, with offshore waves reaching 15 to 20 feet.

As I said above we’re going to have an onshore flow, that will last through multiple high tide cycles, this will add to the potential problems as water stacks up along the coast, this will be especially true for the bays and sounds of New Jersey, Delaware, and Long Island.

Scenario #2 will have the storm track farther east and away from the Coast. This scenario still brings a lot of wind to the Coast, but we end up with much less rain.

Scenario #1 would mean a lot of coastal flooding extending from the Carolinas up through the Middle Atlantic and Long Island during the work week, then this would push into New England for Friday and the Weekend.  It is unclear if much of this will make it into Maine, where the rain is very much needed.

There is a chance that this coastal/nor’easter ends up developing into a hybrid system (a combination of a cold core and warm core system). There is also a chance this becomes the next named system, if it does the next name, is Gonzalo.

  

The Atlantic

Tropical Storm Fay has max sustained winds of 50mph (down from last night's 70mph). Fay’s min central pressure is 1000mb. Fay is going to keep wandering out in the middle of the open northern Atlantic and she poses no threat to land. The window for her to develop into the first hurricane of the season is closed, she will continue to weaken and dissipate as the week moves forward.