Assessing the Rate of Warming Across Parts of the United States of America (credit: Climate Central)12/14/2017  DISCUSSION: As the global meteorological community continues to discuss issues pertaining to planetary warming trends, it is important to keep in mind that some places are statistically being more impacted than others over the course of time. As shown in the graphic above (courtesy of the Climate Central research group), a good portion of the North-Central and Northeastern United States have been more notably impacted by the effects of gradual planetary warming issues. Even more specifically, some cities (including but not limited to) Burlington, Vermont and Mankato, Minnesota have experienced average temperature increases of just over 6°F per decade. Thus, towns and cities situated across the northern tier of the United States have undoubtedly encountered more dramatic temperature increases over the course of the last 30 to 40 years and counting.
The best explanation for this northern-biased temperature increase is due to the fact that this part of the United States has such a dramatic average temperature change between Spring/Summer-time and Fall/Winter-time that there is a greater signal for average temperature change over the course of time further north. On the contrary, the further south that one goes, there was less of a notable average temperature change per decade likely due in part to the fact that season-to-season temperature variability does not vary quite as much. Thus, over the past 30 to 40 + years, there was less of a longer-term average temperature change. The only other part of the country which this was also the case across portions of the Inter-Mountain Western United States; though the signal was closer to neutral longer-term temperature variability. In all likelihood, this was due to natural inter-decadal variability coupled with gradual planetary warming influences and you can also see how parts of the Rocky Mountains are also within this region of near-neutral long-term temperature variability. To learn more about other insights concerning this particular story, click on the following link. To learn more about other global climate stories, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz
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 DISCUSSION: In light of an increasingly more tumultuous situation defined by gradually increasing global temperature trends, this also has had definite impacts on other factors as well. One such factor is the degree of coverage of North American snowfall which has varied somewhat over the course of the past 30 to 40 years. There is no question that North American snowfall coverage has experienced a definitive gradual decreasing trend over the past few decades. However, there is much more to this issue than "meets the eye."
In looking at recent historical North American snowfall coverage, a key component of this issue is the degree to which certain regions during the Fall to Winter transition period do or do not have snowfall cover by a given time. The reason for this issue is that by not having snowfall on the ground for a given first snowfall event, the ground is more susceptible to absorbing ultraviolet and infrared radiation from the Sun which will keep the upper-most layers of soil relatively warm. Thus, even when the first substantial snowfall event does occur in the given region of choice, a warmer upper-most layer of soil would inhibit a good portion of snowfall earlier on in the first major event from sticking which would limit net snowfall potential. Thus, anticipating longer-term snowfall trends is not as simple as one may think. To learn more about this particular issue, click on the following link. To learn more about other climate stories and topics from around the world, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz How Might La Nina Influence the 2017-2018 Winter (credit: NWS NOAA Climate Prediction Center)12/7/2017  DISCUSSION: As we get further into the 2017-2018 Winter season, there is no question that there are a lot of important questions which still remain. One big question is as to whether or not there will be prolonged periods of particularly colder weather across the northern tier of the United States. This is a critical question which bears much concern due to the fact that more frequent Arctic air outbreaks can often times lead to there being a greater propensity for more memorable winter storms. That is chiefly due to the fact that when colder air is more prevalent throughout a given winter, there is consequently a greater prevalence of geographic regions characterized by stronger baroclinicity (i.e., a more rapid change in temperature over some given horizontal distance). Thus, with stronger baroclinicity in place, this facilitates a more favorable atmospheric environment for any low-pressure systems which develop with these "baroclinic zones." Attached above is a typical storm track and temperature/moisture trend map for both the warm and cold phase of ENSO courtesy of the NOAA NWS Climate Prediction Center.
Moreover, when such low-pressure systems are suppressed further south (e.g., often in the vicinity of the Gulf Coast region), this allows those low-pressure systems to pick up plenty of warm, moist "tropical" air which frequently sets the stage for a classic coastal winter storm or more often referred to as a "Nor'easter." Thus, monitoring larger-scale climate patterns such as the Arctic Oscillation which is effectively a proxy by which the semi-permanent statistically-identified "Arctic low-pressure system" is measured with respect to its average strength (i.e., based upon its shorter- and longer-term minimum central pressure). When this semi-permanent "Arctic low" is weaker in strength, this more often than not allows for colder air to make its way towards the mid-latitude regions of the world. A perfect example of this situation is precisely what is happening at the present time across the North-Central and the Northeastern regions of the United States where a lobe of the core of the Arctic air from the southern edge of the Arctic Circle has descended down into the northern tier of the United States. Depending upon how long this and other cold air outbreaks persist along with how active the more southern storm-track remains, this will largely dictate how active the Winter season is. To learn more about other global climate stories/topics, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz |
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