WEATHER 101 with AL KAPRIELIAN ~ Summer is Here

By: Al Kaprielian – June, 2016

VPpromo-KaprielianAfter some cool days in May we saw a return to true summertime heat on Saturday, May 28. Boston reached 92 degrees on that day, which tied the record of 92 degrees set back in 1931. Fitchburg reached 97 degrees on that day. Many areas reached into the 90’s on that day.

The exception being the south coast, Cape Cod & the Islands surrounded by the cooler ocean waters. The reason for the intense heat on May 28 was a strong high pressure system off the east coast known as the Bermuda high. This high extended to the east coast and up into New England. This pushed the jet stream to our north, putting our area on the hot side, or south side of the jet stream. The hot weather only lasted a day in eastern New England. The reason was a cold front that moved through from the east. Usually cold fronts move from west to east. However, sometimes cold fronts approach from the east and they are called backdoor cold fronts. Another high pressure system moved into the Canadian Maritimes which helped push this backdoor cold front westward early Sunday morning, May 29th.

What can we expect as we start the month of June? It appears as though an upper level trough and upper level low will bring a return to cooler and wet weather for the first week in June. It is too early to say how long this weather pattern will last.

On June 1, hurricane season begins in the northern hemisphere. Two storms already occurred before June 1. Towards the later part of May, Tropical Storm Bonnie moved into South Carolina and caused a lot of flooding.

Although we were not directly affected by Bonnie, we did get some tropical moisture (rain) from her. Hurricanes form over warm ocean waters where the temperatures of the ocean are 80 degrees or higher. The warm ocean waters give the hurricane heat (energy) they need to intensify. When a hurricane moves over land, it looses the heat from the warm ocean waters, and this causes the hurricane to weaken. Also, the friction from the land causes a hurricane to weaken. Hurricanes cause tremendous flooding and this can pose a danger for us. This is why people need to evacuate areas where the hurricane makes landfall.

Flooding from a hurricane can cause drowning if proper evacuations are not taken. Also, hurricanes can produce severe thunderstorms, which can cause tornadoes to form. Hurricanes form on the Inter Tropical Convergence Zone. This is where various winds meet (come together). When these trade winds meet, the air is forced to rise. As air rises, it cools due to expansion (spreading out of the air). As this air cools, it cools down to the dew point (amount of moisture in the air.) When this occurs it causes clouds to form. As this process continues, the clouds continue to grow (get bigger) and eventually they grow into Cumulonimbus clouds. These clouds produce rain & thunderstorms. Hurricane season runs from June 1 through November 30 in the northern Hemisphere. After November 30, the Inter Tropical Convergence Zone shifts back to the south of the Equator. After November 30, hurricane season moves to the southern Hemisphere.

Hurricanes move by the jet stream. They can move up the east coast and affect New England like hurricane Bob did back in 1991. If a hurricane moves toward our region, they tend to weaken, as they are moving over colder ocean waters. The center of a hurricane is called the eye. This is the part of a hurricane where the winds weaken and the sun can come out.

This does not mean the effects from the hurricane are over!!

Once the eye moves away, the rain and strong winds return as you get on the other side of the hurricane.

Surrounding the eye is the eye wall. Surrounding the eye wall is the spiral bands. Unlike a low pressure system which has fronts attached to it, a hurricane has no fronts. It is its own entity. We have found that if the center (eye) of a hurricane passes to your west, you are on the east side, which get stronger winds and not as much rain. If the center of the hurricane passes to your east, then you will experience more rainfall and not as strong winds.

Hurricanes are given names to warn the public of their great impact and for people to take action to evacuate. Hurricane names rotate from male to female. For example, Hurricane Katrina, which devastated New Orleans in 2005, will not be used again. The name Katrina will not be used again because of the severity it caused. The same with Hurricane Andrew, which impacted Florida. The peak of hurricane season is mid August to mid September. This is when the ocean waters are the warmest.

Next month, we will talk about July weather and what you can expect.