A look into the wonky weather New England has been experiencing this winter season
2019-03-02 08:36:37.000 – Jay Broccolo, Summit Intern
Well, our shift does not have a crazy wind event or any kind of weather to write home about so I am going to discuss something that, I personally, think everyone should have some understanding of. This is a fairly intensive post so go grab a snack or a drink, strap in and put your thinking caps on! Also, this starts with a bit of text, but, I promise, there are pretty pictures further down.
If you have not noticed, it has been a bit of a strange 2018/2019 winter season, to say the least. The summit of Mount Washington has seen some extreme wind events and conversely, some extremely calm winds. Precipitation type and accumulations have also been quite wonky throughout New England this year as well. While Northern New England has not been too far out of the ordinary other than Caribou, Maine observing a whopping 147 inches of snow at the time of this blog post, southern New England (Mass, RI, and CT) has seen predominately rain with a severe lack of snowfall. Especially, coastal Southern New England, which normally sees the most intense snowfall rates and accumulations during Nor’easters. Currently, the snow accumulation total for said area is hovering around 2 to 8 inches, depending on where along the coast we want to pinpoint. For example, my hometown of Westerly, RI has seen 3 inches of snow and lots of rain with the month of November being the second highest precipitation amount on record. Here at the summit, precipitation amounts, at least for DJF, have been within the realm of the monthly averages, respectively, with average temperatures as well. So, what is the deal? Whats up with the weird weather this year? Lets discuss one of the factors that influences the weather around New England, the oceans.
Well, the oceans and geology heavily influence the atmosphere. As ocean temperatures rise, sea level rises. Much like if you were to take a gallon of 40-degree water, heat it to around 180 degrees, you will then notice that you now have a little more than a gallon. While these changes in sea level are minimal, on the scale of single to double digit centimeters, they cause noticeable effects in the atmosphere. Therefore, a change in the temperature and a resulting change in sea level all the way down and over in the Eastern Pacific and Gulf of Mexico, affects the weather patterns here in New England and elsewhere. Let us put that aside for the moment though and I will explain as clearly and concise as I can why this matters.
When there are warm temperatures surrounded by cooler temperatures, the atmosphere reacts because it wants everything to be equal (this goes back to my last post where I discussed “the balance” of everything). We know that temperatures at the equator are warmer than temperatures at the poles. We know that warm air rises and cold air sinks, and we know that there is varying amounts of moisture in the warm air masses and barely any in the cold ones. Therefore, warm and moist air generally likes to rise and move towards the poles and cold air from the poles likes to sink and move towards the equator. Where the two different air masses converge is where we observe low-pressure systems, or at the mid latitudes, extra-tropical cyclones. These cyclones are the atmospheres way of mixing the air masses and precipitation is the result a phase change from water vapor to rain or snow as the water vapor rises, cools, and condenses. I digress though, I’ll cover all of that in a later post. Let us get back to the warm waters and heat rising. The point is that, in the northern hemisphere, we have warm moist air moving from the south to north.
Okay, so, we have anomalous warm water and higher sea levels as a result. At the surface or interface where the water meets the air many things are occurring, but I’ll just mention a few. During the day, radiation from the sun evaporates some of the water and turns it to water vapor, air moving over the water picks up some moisture because of friction, and the water itself is warming the air through conduction as well, but this occurs mainly at night. Regardless, we now have a bunch of moisture in the air and its moving to the north. The added moisture to the atmosphere is a form of energy. Think of the water vapor as the storage of energy because it takes energy, in the form of heat, to cause liquid to change phases to vapor. The heat and moisture flux from the oceans provide one of the main energy sources for atmospheric motions so now, let us throw in one of these low-pressure systems.
When a low-pressure system like a Nor’easter is near the Gulf of Mexico, it sucks a lot of that moisture and heat into the system. Specifically, between the warm front and the cold front, and we call this the warm conveyor belt. This is what gives many storms the comma look when observed through radar. As the cyclone heads to our region, it carries all that heat and continues to absorb more and more moisture from the Gulf and once the reaches the Eastern Coastline, from the Atlantic as well, which brings me to my next point. Sea surface temperatures off the coast of New England have also been significantly higher, fueling and intensifying these systems with more moisture and heat. The last piece of the puzzle goes back to the storage of energy in the form of water vapor I was talking about earlier. As the water vapor rises in the atmosphere, it cools and condenses back to liquid form and depending on cold the air temperature is snow can form. When this phase change occurs, that heat stored in the water vapor is released into the air, which we call a latent heat flux. In order to change water vapor to water you have to pull enough heat out of the vapor for it to change back to water, similar to the boiling water. A good portion of the heat that we added to the water from the stove-top then is released into the air as the steam produced from the boiling water cools under the pot cover. All that heat warms the air preventing the formation of snow, at least, near the phase change. Further north in New Hampshire and Maine the air temperatures are much colder than they are in Southern New England so the latent heat released due to the phase change is not enough to warm the air temperatures above the freezing mark. Therefore, precipitation occurs as snow.
Finally, it’s time for all the pictures to bring this all together…
Below, we can see the average sea surface temperature anomalies over the past 4 weeks. Note that the SST’s are significantly warmer off the east coast of the US, the Gulf of Mexico, and southwest of Mexico (El Nino Southern Oscillation, or ENSO). https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf
Now lets take a look at whats currently going on with the ENSO.
The higher SST’s correlate to a slight rise in sea levels seen below. Note the significant rise in sea level around New England and less so in the Gulf of Mexico and southwest of Mexico in the Pacific.
And finally, below is an image of precipitable water in the atmosphere with some skillfully drawn red arrows indicating the warm conveyor belt (WCB).
To conclude this post, I want to finish by saying a couple things. Precipitation type doesn’t just depend on sea surface temperatures and the amount of heat released by latent heat. There are many factors that decide precip type. One of the biggest factors is the track of the storm. The further south the track is, the better chance for snow. The last thing I want to bring up is that as I mentioned before the oceans are one of the main energy sources for the atmosphere. When we talk about climate change we tend to discuss the atmosphere and state of the climate. However, the ocean’s have an incredible heat capacity and mass, which allow it to store up to 1000 times the energy that is found in the atmosphere for an equivalent rise in temperature. So when we look at the state of climate change we also need to look at the oceans. Now, just because the SST’s are warmer this year because of an El Nino cycle, doesn’t mean this is an indicator for climate change. If it occurs year over year, decade over decade, and so one, it does become an indicator. So I implore anyone to check it out, do your own research and see whats going on!
As always, I appreciate you all allowing me to ramble about my passion and reading it. My hope is that it gives you all an idea of another avenue to look at when wondering about the state of the weather and climate. It can be extremely overwhelming, for sure. That being said, this post only describes one aspect of the wonky weather we have been having.
Jay Broccolo, Summit Intern