Meteorological Winter… HUH? ~ WEATHER 101 with AL KAPRIELIAN

By: Al Kaprielian – Dec 2017


Welcome to December and the start of what is called the meteorological winter.

kaprielianDuring this month we will see the shortest days of the year as well as the longest nights of the year. The winter solstice will occur during this month.

The winter solstice is when the tilt of the earth in the northern hemisphere (here) is furthest away from the sun. This is what causes the changes in daylight hours.

After the winter solstice we will start to see the days begin to get longer because the earth will start tilting closer to the sun.

During the month of November we saw cooler temperatures compared to October. A series of cold fronts along with wind brought cooler temperatures in November.

The jet stream remained fairly progressive last month. This pattern caused air fronts and low pressure systems to move along and not stall out.

This progressive air flow pattern in the atmosphere was the result of no air masses, creating a block in the atmosphere. This caused a more zonal flow to the jet stream.

This zonal flow kept all the real cold, artic air up at the north pole. It also brought air off the Pacific Ocean which is not as cold as the air up at the north pole.

However, long range computer models do show a change in the weather pattern for mid-December. If these long range computer models are right, we will see more amplification to the jet stream.

This amplification will bring some of the cold, arctic air from Siberia into our region. This will result in much colder temperatures by Mid-December for our region.

With more amplification to the jet stream will also come the arrival of the Greenland HIGH PRESHA! System. The Greenland HIGH will cause more upper level ridging over Greenland. In contrast, we will see more troughing over our area.

This trough can lead to storm development due to more clashing of cold artic air with milder air over the Gulf coastal states. If storm development does occur, this doesn’t mean we will get a lot of storms. It will depend on the amount of phasing between the northern and southern branches of the jet stream.

If there is no phasing between the two jet streams, then this will mean we will see more of a cold and dry pattern. Time will tell how much phasing occurs between the two jet streams.

In the past we have seen some big snowstorms during the month of December, so have your snow shovels ready! Especially in the EVENING!

The one good thing about meteorological winter is that hurricane season is finally over. November 30th was the last day of hurricane season.

This hurricane season was an active one. We saw hurricane Harvey, and the major impact it had on Houston Texas.

Also, hurricanes Irma and Maria caused major deaths and property damage. We saw the widespread damage Maria did to Puerto Rico. We also saw Tropical Storm Jose produce rain and wind in our area with the greatest impact of rain & wind over Cape Cod & the Islands.

These hurricanes became very intense due to the very warm ocean waters which were in the mid-upper 80s. The hurricanes get all their energy from the very warm ocean waters. Ocean temperatures in the Atlantic basin between the U.S. East Coast and the African Coast were above normal.

Next month we will recap December’s weather and will see if the Greenland HIGH PRESHA! system did develop along with a more amplified jet stream. We will also take a look at what to expect in the month of January and recap the temperatures and precipitation for 2017. Until then, prepare for winter and when the first snowstorm occurs remember to keep the speed down when driving and also allow extra time for travel!!!


Al Kaprielian is the exclusive weatherman for The Valley Patriot and Paying Attention!