We are watching a few systems for Thanksgiving. One is early in the week that could extend towards the holiday, the other is later in the weekend. This blog will address the potential nor'easter for early in the week. The good news is pattern will support a high chance for this storm missing and going out to sea. Finally giving us a break from the stormy pattern. However, the European model still wants to bring in some rain and winds along with the CMC. We will break it down as the pattern is very confusing.
First a s/w in the southern plains is going to move east and enhance a stationary front offshore the eastern US. This enhancement will lead to the development of a sfc low/preexisting vorticity for the main trough to pick the system up and create a stronger area of lower pressure.
This focus area is along the Gulf Stream where a trough will move across and allow for an organized sfc low pressure system to develop.
The trough splits into two with the main trough progressing eastward quickly. But when the trough begins to split will be a crucial part to the forecast and the answer is not that far away. The European model begins the split earlier and allows the southern part of the trough to move slowly east as it becomes cut off from the main flow. This allows the Gulf Stream convection to continue to pump up heights to the east favoring a negative tilt and a closer to the coast low.
The GFS says the trough remains intact for longer and becomes more progressive and does not allow as favorable environment for the Gulf Stream convection to pump up heights, resulting in a more easterly track.
Old European run below shows faster split and some coastal problems for Thanksgiving: Note that the European has a bias in this situation of holding too much energy back so it is not surprising it is the faster to split this energy.
Northern stream gets out of the way quicker and the heights build resulting in a negative tilt an a track closer to the coast! Similar results showed up on the 12z CMC from Tuesday (new CMC continues to agree):
The GFS shows a more progressive trough with a later split. This allows the northern stream to take its time from moving out preventing height rises and keeps the precip and low offshore. The new European is starting to come over to the GFS. To an extent the CMC also, which kept the trough intact longer but splits it just in time to keep a similar situation.
New Euro: (Correcting the bias)
New European and CMC still cause problems for the East Coast in the form of onshore flow and rain, but it is much better than the previous runs and the trend east is showing up. The GFS shows no storm with the low pressure system passing east far enough to not cause any problems.
- Trough splitting earlier supports a westward trend and the models that show a coastal low.
-Trough splitting later supoprts an eastward trend and the models that show a out to sea low.
-European has a bias that may be allowing the coastal solution to show up. So watch this to continue to trend east.
Mike, I'm curious on the timing of this first storm. My husband is planning to run the Philly Half Marathon which is scheduled early Sunday morning. It's not starting that early, is it? Just wondering how we might need to plan for that morning. Thanks!