Tropics…Here We Go!

July 1st, 2014 at 9:10 am by under Weather

Well the Atlantic Hurricane season has just revved up, and the timing couldn’t be better (heavy sarcasm).  Just in time for the 4th of July we have a tropical system that could potentially become a hurricane and affect part of our region.  At the moment the system is a tropical depression. It is off the coast of Florida about 90 miles southeast of Cape Canaveral.  The pressure was 1007 mb (millibars of pressure).  The depression was drifting west at 2mph, but then it stopped its motion.  It is expected to start heading north by later today.

Satellite/Radar

Satellite/Radar

It may brush land or move over land briefly, but then it is expected to move back over the water.  By tomorrow morning winds are expected to increase to 45mph.  Winds are forecast to reach 60mph by Thursday morning.  At that point it is forecast to be about 300-400 miles east of Savannah, GA.  Then the system will begin to move northeast as it interacts with the upper level winds.  At that point the National Hurricane Center (NHC) has it reaching hurricane strength.  This would be sometime between late Thursday night into early Friday morning.

Forecast Track

Forecast Track

The latest forecast and most of the models have it moving out of the region by either Friday afternoon or Friday evening.  This could allow for some of the fireworks and festivities to resume Friday evening.  Of course it may be tough to celebrate if there is wind damage near your city.  We’ll see.  Also, even though the system will push away, the winds on the back side may be too breezy for fireworks.  For now I’m optimistic about that part of the forecast.  By Saturday morning the system should be long gone.  Then we’ll have a nice weekend following.

Now let’s talk about some of the more complex issues with this tropical system.  At the same time that this will be near our latitude, a cold front will be heading in from the west/northwest.

Day 3 Fronts and Pressures

The forecast map is from the Weather Prediction Center.  It was made before the NHC forecast increased the intensity of the tropical system, but it shows the position of the front as well as Arthur Friday morning.  Along with the cold front a large trough will move-in in the upper levels. The upper level winds will increase and pick up from the southwest.  This should help to move the system quickly to the northeast.  Therefore it could be jetting to the northeast at about 20-25mph between Thursday night and Friday morning.  The models have been trending a bit more offshore.  The most likely path (center line below) from NHC has the storm just offshore from Hatteras at its closest point, but the possible path (yellow cone) does extend over parts of the coast.

Forecast Track

Forecast Track

Some of the models weaken the system a bit as it moves north over the next 36 hours.  There is some dry air just north of the system.  Also upper level winds may increase a bit in the short-term.  The European model has it staying the most organized through the entire forecast period.  The models do strengthen it as it starts its northeast motion, but upper level winds will strengthen at that point.  The forecast models were tightly clustered over the coast yesterday.  However, today there is a bit more of a spread, and they are generally farther east.

Forecast Models

Forecast Models

The European model and the GFS both take it fairly close to Hatteras.  The European is the strongest so far.  The GFS has the system more as a tropical storm near our region.  Despite increasing upper level winds, the storm looks to maintain strength as it moves farther out to sea.

So here’s my general thoughts on this system…  It is weak right now, but it is predicted to strengthen greatly within 2-3 days.  The water temperatures are warm down towards Florida and South Carolina, but they are a little cooler off our coasts.  Also, the wind shear is forecast to increase as the storm moves northward.  So while I don’t disagree with the strengthening, I am a little dubious about it becoming a hurricane.  It will be coming from the southwest.  Typically systems that come from that direction don’t create big impacts on our region.  Tropical storms Hanna and Cristobal (2008) come to mind.  They can however, bring a threat for tornadoes if they move right over us.  For reference…Isabel (2003) came from the southeast.  I don’t expect anything like Isabel from Arthur.  If the system were to move along the coast, then the Outer Banks could see damaging winds, heavy rain, and some tidal flooding.  However, I don’t think it would be that bad for Hampton Roads.  If it were to move more inland, then Hampton Roads could see some problems with heavy rain and strong winds, but the system would likely be weaker.  Therefore the tidal flooding probably wouldn’t be that bad along the Chesapeake Bay.  We are close to new moon, so we will have to monitor.   It’s interesting that the BAM-shallow takes the storm more west while the BAM-deep takes it much farther east.  With it’s current strength forecast, I could see the storm moving due north or even northwest for a bit, then taking a strong turn to the ENE by late Thursday night.  So folks along the southern Outer Banks should monitor the forecast carefully.  You may want to think about a possible evacuation if you live around Hatteras.  Keep in mind that it is still early, and the forecast is very apt to change.  Especially considering the interaction with the cold front.  Folks in Hampton Roads should just monitor for now.  I’ll have another update out around midday.

Meteorologist: Jeremy Wheeler

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