When you see an exceptional weather model run or two on a day 7 or 8 forecast you expect it to go away. Every once in a while we see a bit of long range weather porn pop up on the computer models only to quickly disappear.
Sandy is a bit of a pain, however. She’s not behaving like most tropical storms or hurricanes do. The “spaghetti plot” of this afternoon’s GFS ensembles really tells the story with 2 distinct possible paths for Sandy.
This is one of the oddest spaghetti plot I’ve ever seen for a storm threatening the northeastern U.S.! While half of the GFS ensemble members curve the storm east (including the operational GFS in white which is in the out to sea track) the other half of the models take Sandy to just east of Cape Hatteras and sling shot it west into New England. That would be one of the most unusual paths ever documented for a New England tropical storm or hurricane!
The operation European model agrees with the left hook bringing Sandy ashore in southern New England as a hurricane from the southwest. Exceptionally unusual.
There is no doubt in my mind that the European model is overdoing the strength of this storm. It has a tendency to strengthen storms like this that are undergoing extratropical transition a bit too much. Needless to say a track like this is concerning.
So what should we make of it all? At this point we are still at least 36 or 48 hours from really getting a good handle on Sandy. The reason for all these funky looking computer model solutions is that the weather pattern is very amplified and all blocked up!
The Euro Ensemble mean shows a monstrous ridge over Newfoundland and Greenland which may act as a block for Sandy and prevent it from moving out to sea. The positive height anomalies near Newfoundland are nearly 4 standard deviations above normal! The large rex block that develops in the next 72 hours will transition to a large omega block which is pictured above (the height contours make on outline of the Greek letter omega). How this block evolves will determine whether Sandy can escape to the east like the GFS shows or get shoved up the coast like the Euro shows.
While we have seen truly anomalous New England hurricane tracks in the past – they are few and far between. Here’s a look at Esther from 1961. What the heck was Esther doing out there???
The category 4 hurricane approached New England from the south and then the storm did a loop south of Cape Cod. The storm made 2 landfalls in New England.
Other storms have done odd things. Most notably, the Great New England Hurricane of 1938 which was in the process of being absorbed by a large cut-off low that was diving south of the Great Lakes.
This hurricane tracked due north or maybe even a hair west of due north and then hooked left south of Montreal toward Toronto.
The fact that we need to look back to 1961 or 1938 to find hurricanes that impacted New England that took really unusual paths says something about just how hard it is to get a storm to get absorbed at just the right time by the jet stream and hook left into the region and not head out to sea or continue due north.
Even if Sandy takes a path that will indirectly or directly impact us it’s not clear how strong the storm will be. While there is a very outside chance of a direct hurricane hit the more likely scenario is a brush or a hit with a hybrid system that will act like a fall-nor’easter that is spinning around in the north Atlantic.
No need to panic! Let’s watch things and see how they shake out over the next day or two. My gut feeling is that the computer models will trend away from the extreme solutions (they almost always do) and we’re left with something in the middle.