Hurricanes and Meteorological Summer ~ WEATHER 101 WITH AL KAPRIELAN

By: Al Kaprielian – June, 2017

kaprielianWelcome to June the start of meteorological summer and the beginning of hurricane season.
The month of May saw three consecutive days where the temperature reached 90 degrees or higher. This resulted in a heat wave that was the result of the Bermuda high pressure system strengthening and forcing the jet stream north of New England.

Warm to hot air circulated around the western side of the Bermuda high pressure system and moved into our area. New record high temperatures occurred during this three day hot stretch which really gave us that summer time feel with families going to the beach and enjoying the outdoors.

However, this heat was short lived and did not last more than three days. A cold front moved through and brought cooler air from Canada. May averaged out with cooler than normal temperatures and above normal rainfall. That’s because the jet stream moved back down to our south as the result of blocking in the atmosphere. An omega block formed in Canada.

What’s an omega block? An omega block forms when the jet stream winds take on the Greek symbol Omega. When this occurs, weather systems at the surface slow down and can even stall. This can cause a weather pattern to remain unchanged for several days or even a few weeks. Our part of the region is north of the jet stream in regards to the Omega block. This puts our region on the cool side of the jet stream.

This Omega block has also caused the Bermuda high pressure system to be suppressed well to the south. This has caused the summer heat and humidity to remain well south of our area. Our weather will remain the same, cooler than normal with possible wet weather at times until this break in the atmosphere breaks down.

A bias of the computer models is that they can want to break this block down too quickly. Eventually the block will weaken and break down but timing of this is difficult.

It is not abnormal to get an omega block. However, in years past, these blocks used to occur more in March and April and not so much in May or June. By June the jet stream used to move from west to east and be located north of the U.S. and Canadian border. This gave us many hot & humid days in June. It is difficult to say why we are seeing this block late into the month of June. We have to remain patient for this block to break down. Once it does, summer weather will return along with the Bermuda High.

As noted above, June starts the hurricane season in the northern Hemisphere. Hurricanes from on the Inter Tropical Convergence Zone. This is where all the trade winds meet or converge. Hurricanes form over ocean waters where the temperatures are 80 degrees or higher.

Hurricanes move by the flow of the Jet Stream. Hurricanes can move up the east coast and strike New England, however, they can tend to weaken as they encounter colder ocean waters at higher latitudes and longitudes. Unlike low pressure systems which are attached by fronts, a hurricane is its own entity. It is not attached to other fronts.

Areas to the east side of the hurricane get the strongest winds and lower rain totals. Areas to the west of the track of the hurricane get heavier rain totals and not as strong winds. Areas that are hit by a hurricane have to contend with flooding and also power outages due to the strong winds. The center of the hurricane is called the eye. This is where the winds go calm and the sky can briefly clear.

Once the eye passes the rain and wind begin all over again.

Hurricanes weaken when they track over land because they lose their energy from the warm ocean waters. Also, the friction of the land lowers the wind speed. When the winds reach 74 miles per hour or higher, the tropical storm becomes a hurricane.

Hurricanes are given names to make us aware that they are dangerous storms. When a large hurricane like Katrina or Andrew occurred, their names are now retired and will not be used again with future hurricanes. Time will tell how this year’s hurricane season will be.
Next month we will recap June’s weather and talk about what we can expect in July.