Hurricane/Hybrid Sandy Timing and Impacts

If you have been watching The Weather Channel for coverage of Hurricane Sandy, you may have noticed the two different computer models they keep showing.  These two models, the EURO and GFS, are just two of many solutions meteorologists use to forecast the weather.  However the EURO and GFS are two medium range global models and over time have proven to be the best.  The EURO is run by the European Centre for Medium-Range Forecast (ECMWF) and is usually the most reliable model.  The GFS is an American model run by the National Center for Environmental Prediction (NCEP).  Weather models solve the known equations that govern atmospheric physics.  It is for that reason meteorologists study years of calculus and physics in school.  Thank god we developed computer models to solve these equations.

The models use data collected by upper air measures (balloon launches, satellite data, observed data) to input into these equations to start the process.  These measurements are usually taken twice a day, at 8 NAM/PM during Daylight Savings time and at 7 AM/PM when it ends.  They run on Coordinated Universal Time (UTC) which begins at 00z at midnight on the Prime Meridian (0 degrees longitude, border West/East Hemisphere) .  This is done so all balloon launches are done at the same time.  In a rare move the government ordered balloon measurements 4 times a day until Sandy passes.  This is an impressive step by the government and shows they are taking the storm very serious.  

Now on to the weather.

I've zeroed in a New Jersey impact.  I am going to support a northern NJ landfall although that doesn't change the forecast for New England all that much.  I apologize in advance for the length of this post; I promise that when the weather is normal I will be much more brief.

Bottom Right is Sandy, Blue arrow pointing to cold front, yellow highlight is energy that will combine with Sandy

Here is the National Hurricane Center forecast track and cone of uncertainty.  This is useful to determine who exactly gets the highest winds, but it really does not matter.  I am slightly closer to the GFS model as I have a hard time believing a storm of this size can make a left hook into the Delmarva as the EURO depicts.

Red X's my track

I've set the line for severe New England impacts at 40 degrees North latitude.  If it comes in above we see a storm unlike any in recent times.  For my parents generation it almost seems like the Hurricane version of the Blizzard of 1978.  Sandy is rather ugly looking this morning but her wind field is huge.

X's are energy on Satellite, Lots of moisture for Sandy to work with

And the latest wind field, which is only going to expand

Not only will this field expand, it will intensify 

The predicted rainfall, which for Southern New England is almost an afterthought with the winds we are going to experience.

Valid Sunday 8 am-Monday 8 am

Anything that falls in this period are from the extreme outer feeder bands of the Hurricane (note I will be calling this a Hurricane even though it is going to be a hybrid Nor'Easter/Hurricane).  The real rain from the storm's core will roll in Monday Morning between 8 and 11 am.

Valid Monday 8 am-Tuesday 8 am

Typically the highest winds are on the northeast side of a system while the heaviest rains are on the west.  If anyone remembers Hurricane Irene last year knocked power out to a lot of MA/RI/CT residents, but caused severe flooding in NJ, NY, and VT.  These rainfall forecasts are provided by the Hydrometeorological Prediction Center (HPC).  Of course while all this is going on along the Mid Atlantic coast and New England, a snowstorm will be raging on the backside.  I will not focus on the snow, but will mention it because there has been only a handful of storms like this in the modern era.

GFS six hour snowfall accumulations.  I think DC sees some flakes

If you are a fan of the weather and would like to read more about similar storms throughout history I recommend looking up on Hurricane Hazel, Great Hurricane of 1938 , Gale of 1878, and October 1804 Snow Hurricane.

Coastal Flooding

A long duration of onshore winds will force significant storm surge into the the beaches of Long Island, Northern New Jersey and Southern New England.  Even Northern New England will see moderate water rises.  Waves offshore are forecast to on the order of 40 feet.  Throw in a high tide and coastal residents have a disaster on their hands.  There is a Weather Channel program called "It Could Happen Tomorrow" on New York City being hit from the Southeast by a major Hurricane.  This system might be as close as it gets to that scenario.  

Click to enlarge.  Red circle shows where worst coastal flooding will be.  Everywhere sees awful beach erosion

There is a full moon so tides will already be 20% higher.  Even worse is that the October full moon (Harvest Moon) has the strongest effect on tides.  Coastal communities must seriously consider evacuations.  If you live on Cape Cod and want to leave do so ASAP.

Finally the wind speeds. Residents along the coast will have to deal with dangerous winds and major surge.  Further inland the wind speeds are the major issue.  When compared to Hurricane Irene last year, she does not compare to Sandy.  I lost power for 5 days during Irene.  Our trees have been weakened by Irene and the October Snowstorm last year.  Further this will produce winds of Tropical Storm force for 24-36 hours.  Hurricane force gusts (or sustained in some areas) will be felt for roughly 12 hours.  We didn't see a single Hurricane force gust in MA during Irene.  Block Island gusted to 79.  I think Block Island or Blue Hill gust well over 100.  I set the over/under at 115 mph.  Here is my support for this forecast

GFS 900 mb winds Sunday morning 2 am, maps from Dr. Ryan Maue and Weatherbell

By 2 am winds are beginning to pick up along the east coast.  This is about 5000 feet up in the atmosphere.  All it will take is a some convection (showers, thunderstorms) to bring these to the surface.

Sunday 8 PM.  Tropical Storm force gusts begin

The EURO model at the same time, but at 850 mb instead of 900 mb.

Very similar set up.  Look at the size of this storm.

On Monday morning the winds are approaching 60 MPH

Slowly moving, so water just piling up offshore, waves building

And then Monday evening, the brunt of the storm

GFS Monday 8 PM.  

This is a devastating blow Monday afternoon and evening.  Wind gusts would be over 100 mph for most of southern New England (areas in grayish color), especially coastal regions. Sustained winds would likely be near 65-70 mph.  Further inland 50-60 mph with gusts to 80.

EURO Monday 8 pm

The EURO has the heaviest winds over NYC, NJ, LI.  Awful scenario for these regions.  Yet we still see gusts to 85-90 mph in this scenario.  Again this is stronger than Irene by a longshot.  Also will affect many more people.

Finally GFS Tuesday at 2 am.

Still Hurricane force gusts for SNE

Look at the US/Canadian border.  This would rival Hazel in those areas.  I do not think Sandy will weaken quickly once inland like most tropical cyclones.  She is not going to be a pure tropical cyclone, she will be supported by the jet and infused with Pacific stream energy.  This is why I have been a bit "dire" or perhaps over the top in covering Sandy.  I'd rather hype this storm and have it be a dud than allow people to be under prepared.

Tuesday will still be windy as its unknown how exactly Sandy reacts once over land.  Some model guidance suggest a loop over NY state and then back out to sea.  We can fine tune that later today or tomorrow.  Folks I expect power to be out for a significant period of time. The stores will be mobbed today but get what you need.  Take loose furniture inside, tie down anything you do not want to blow away.  If you sleep in a bedroom in which a large tree could fall on, move to a safer place in the house.  I think thats all.  Any questions leave a comment here, on facebook, or tweet me @zgreenwx.  Thank you for your time.