A beautiful morning in southern and central Maine continues with a great beach day ahead. If you are headed to the beach, a tropical storm named Bertha could be making for some bigger waves and a bit of an undertow the next couple of days. This is only the second named storm of the Atlantic season thus far. This is just about exactly where you would expect things to be in the Atlantic on the 5th of August.
There is a risk of showers later this afternoon, but most of us stay dry. A better risk comes tomorrow, but then it should remain rain free for the following 5 days. I'll be updating the forecast on Twitter @growingwisdom. Please follow me there.
The chart below from the National Hurricane Center shows the number of named storms increases by about 1 every 10 days this time of year and then increases to about 1 per week during the peak of the season in early September before decreasing again. Notice the number of storms continues to increase into November before the season officially comes to an end November 30th.
Hurricanes are one nature’s way of moving an excess of heat from the tropical regions. These types of storms form over water and must form without much if any upper level winds. They need light winds up high so the thunderstorms can gather and eventually rotate. If you have strong winds aloft, this tends to blow the building thunderstorms apart and not allow a hurricane to form.
I tell my students a hurricane is basically a collection of thunderstorms rotating around a central core. If you don’t have favorable conditions for development, the storms never really rotate around anything. This is overly simplistic, but gives you an idea of what’s going on in Bertha right now.
Strength of storms
Unless you are a tropical weather enthusiast or professional you likely have not heard of the ACE index. This index measures, accumulated cyclone energy and is compiled by the National Oceanic and Atmospheric Administration (NOAA) Each storm has an ACE value for the life of it and each hurricane season has an ACE value. There are also ACE values for each region of the world. In late July, according to Ryan Maue, the ACE value for globe is below average for the time of year, but the Atlantic ACE is above because Hurricane Arthur had a lot of energy.
The two charts below show ACE values over longer periods of time. For the past 10 years or so, ACE values have been falling. Although some researchers feel there might be more and stronger hurricanes in the future, others believe the opposite.
As far as Bertha, which is now over very warm waters in the Atlantic, the upper currents will keep this storm off the coast and it is forecast to remain a tropical storm, not a hurricane. The good news is it poses no threat to land. The storm will produce some waves along our shoreline. The map below shows a pocket of waves off the New England Coast later this week. You can see the movement of this wave pouch by clicking here.
Most prognosticators are continuing their forecasts of a below normal hurricane season the rest of the summer and fall. This doesn’t mean a big storm still couldn’t strike somewhere in the United States, including New England, but it does appear there won’t be as many storms as normal.
As we get deeper into August where we look for storms to form will change. The two maps below show where past storms have formed through the 10th and then the subsequent 10 days.
We really won’t be past the threat of a storm until well into fall when the waters off the coast finally cool and the upper pattern becomes less and less favorable to see tropical system here in New England. Of course, by then I’ll be looking for the first snowstorm.