Model Ensembles Prefer East Coast Landfall

Above, you see the GFS Ensembles on top and the ECMWF Ensembles on bottom, forecasting MSLP values in the Atlantic. They are both valid for 7 days from now.

The ECMWF Ensembles combine to believe that a strong system will make landfall in the Mid-Atlantic, with heavy winds and rain following along. I do not doubt the presence of some snow in the Ohio Valley from this system as well if the ensembles give enough cold air to the west of the original landfall.

The GFS Ensembles are even stronger and also hit the Northeast with Sandy at a strength in the 980's, indicating that the system looks to be pretty strong. It should be noted that for both sets of ensembles, some members are stronger than this, and some members are weaker than the forecasts above. This is a mean (average) of all of the ensembles within the GFS' base or the ECMWF's base.

I show you these forecasts because the models themselves may as well be as good as a life raft in the desert- sometimes it's practical (for shelter), sometimes it's not (there are no oceans in the desert). I think it's time to take a few steps back and see what the ensembles have to offer, because they are the best bet at this long range forecasting of a tropical cyclone.

Andrew

Sandy Likely To Threaten Mid Atlantic

The following is my own personal thoughts on Sandy and is provided as an advice article. I am not responsible for whatever actions you take in response to this article, and do not endorse or reject doing any activity directly in response to the following information.

**THERE IS NO HYPE IN THIS ARTICLE**

I now believe Tropical Storm Sandy has real potential to affect the East Coast, whether it be from a tropical viewpoint or on the snowy side. This is indeed a pretty bold statement, so let's decipher why I think this could get serious.

The first thing we must examine is teleconnections. Above is a multi-model display of the 0z models and ensembles' predictions of the North Atlantic Oscillation. The North Atlantic Oscillation, or NAO, has two phases: positive and negative. In the negative phase, a colder and stormier pattern is encouraged over the East US as the jet stream dips south. In the positive phase, warm conditions can be found in the East.

Models are forecasting the NAO to stay well in negative territory, possibly well into November, but that's another story. The key piece is that the NAO will be extremely negative from now until October 27. Because teleconnections observations and their effects are delayed (the atmosphere doesn't work that fast), we want a good 3 day lag of negative NAO values before the storm strikes to show that the NAO would support such a possibility of an East Coast threat. Looking at the NAO forecasts, there is a good consensus on such a negative period through Halloween, which will enable the jet stream to dip in a negative NAO pattern. This provides a base for a theory on an East Coast threat.

The second item, potentially of much more importance, is something called the Fujiwhara Effect. The Fujiwhara Effect is named after Sakuhei Fujiwhara, and deals with interactions between two cyclones in close proximity. When I say 'cyclones', I mean a disturbance, tropical or non-tropical. The Fujiwhara Effect states that, when two cyclones are in close proximity, they will begin to orbit each other in a cyclonic flow (counterclockwise). To build off of this theory, let's look at the latest ECMWF forecast below.

This is the ECMWF forecast for hour 96, showing 850mb vorticity, 500mb heights, and MSLP readings. These three combine to give a fairly accurate depiction of where disturbances and high pressure systems are located. 96 hours (4 days) away from now, we see a very strong Sandy sneaking by Florida. However, notice the reds and oranges in the Ohio Valley and Northeast. That is a disturbance. We can now apply the Fujiwhara effect.

As the storm moves north (likely influenced by both the strong cyclone to the northeast and the advancing disturbance to the west), it has two options, which is the key player that is confusing the models. Here is a breakdown of each option.

Option 1: The storm moves north and is coaxed east by the strong disturbance located to the northeast in the image above. The storm keeps moving northeast and does not affect the US mainland.

Option 2: The storm moves north, but is more influenced by the disturbance in the Ohio Valley. The Fujiwhara Effect comes into play, and Sandy cycles to the west to orbit with the incoming disturbance over the Ohio Valley. This cycling persuades Sandy to move towards the US and make landfall.

If we look at the 12z ensembles forecasts for Sandy, we can see that they are showing both potential options happening. However, one can see that the edge is given to Option 2, where Sandy makes landfall on the Mid Atlantic/Northeast. Such a situation could be dangerous- similar to how Nor'easters 'bomb out' (rapidly strengthen) in the wintertime as they go up the East Coast, Sandy could very well do the same, bringing a tropical hurricane to an extratropical (not a hurricane) monster that would likely bring rain, snow, and a severe weather threat to much of the East US.

The ECMWF Ensembles (very reliable in my eyes) go as far as to say Sandy will merge with the Ohio Valley disturbance mentioned above and make landfall. Such a merge is called 'phasing', meaning two storms coming together into one. Again, the storms would be attracted to each other and Sandy would be persuaded to move west and retrograde (storms moving west in the North Hemisphere) into the US.

I honestly don't want to even discuss snowfall amounts, but here's some 'eye candy' for you winter weather lovers. This is off the 0z ECMWF and is 240 hour (10 day) snowfall total. This is from AccuWeather Pro and should be referenced as such if you are going to use this image. (Know that the data is not from Accuweather (snowfall forecast), the layout of the image is (color scheme, outline of image, etc.))

In summary: I believe that the East Coast has a threat on their hands. How great this threat actually is has yet to be determined. However, I advise all East Coast residents to keep a close eye on this system. If I lived in the Mid Atlantic, I might want to just keep an eye out at the moment, maybe make sure you have necessary supplies in the event of any evacuation at any time, not just for this event.

Andrew

Tropical Storm Sandy Forms; Models Out To Lunch

Tropical Storm Sandy has formed in the Caribbean, and is shown at the latest satellite image as a big mess of showers and thunderstorms. If we take a closer look, however, we can see that these showers and storms are actually moving in a cycling fashion, which would indicate the presence of a center of circulation.

I do not feel comfortable going over the models today, as each model has taken massive steps away from yesterday's runs, telling me that this is just a bad situation for the models to be involved in. However, as the recon aircraft investigated Sandy today, it did gather crucial data that will be fed into the 0z model suite tonight. Whatever forecasts come out of the models should be taken against previous forecasts, as data from inside Sandy is a crucial tool.

If you really want to see the models, none of which I endorse at the moment, they are below.

ECMWF, Hour 240

CMC, Hour 144

ECMWF ENSEMBLES, Hour 168

GFDL Hour 126

NOGAPS hour 132

Andrew