Good afternoon. Its time to analyze the 12 Z GFS and 12 Z ECM.. I am going to use the ensemble mean for the GFS and the precipitation maps for the ECM.
Looking at the 12 Z GFS operational run you notice it has one major problem. Its trying to run the primary low into the great lakes despite the blocking and despite the confluence from high pressure over the Lakes and the Northeast. However...as it continues to show from last night..if you look at hour 156 you will see an "X" off the south carolina coast. The GFS makes the error of putting too much emphasis on the primary when it should be transferring over to that "X" off the Carolina coast and developing the secondary. It finally develops this secondary but not until hours 168..
Looking at the ensemble means it appears that this is going to drop down from the plains as a clipper and then move on a East Northeast basis and go off the coast around Southern NJ or the Delmarva and then move northeast from there.
Looking at the ECM at 144 hours you can see that there is one area of moisture in the GOM. You can also see this looking at the 12 hr precipitation map ending at hour 156. . At 168 hours the low is sitting around Southern LI (approximately)..The mistake the ECM is making is the same mistake that the GFS is making in having the primary to far north.
The keys to this system are actually quite simple. The first primary piece of the puzzle is the teleconnections. The NAO is forecasted to be quite negative (posted last night) the PNA is rising and is expected to be slightly positive (posted last night)..This is key #1.
Key #2..is where does the secondary develop? Again the answer to this is relatively simple provided the teleconnections are correct. So what to look for in future model runs?
Look for the S/W dropping from the plains to dig further to the south and to the east. Meanwhile look for the S/W in the GOM to lift NE and converge and develop into a low pressure system somewhere between VA and the Delmarva and then to track to the Northeast from there.
The teleconnections in place argue for more amplification and the trough digging deeper. Be back for the 00z model suite!
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