Tuesday, October 8, 2019

Rukavina's Winter Outlook 2019-2020

Cooler temperatures have finally started to bring a whirl of fall feeling to the air and reminds us that the cold season is just around the corner. Like winters past, there can be a wide range of weather conditions that can either make snow lovers rejoice or send people running for the Florida sunshine. Each winter is completely different and subtle changes in the global weather pattern can have varying impacts on our region.
To gain better insight forecasting into the season ahead, looking to similar weather patterns of the past can suggest likelihoods of temperature and precipitation trends. Meteorologists look at monthly data from Dec - Jan - Feb to determine a winter season average and define that period of time as Meteorological Winter. An average winter in the Paducah and surrounding area shows an average temperature of 37 degrees (January being the coldest), average precipitation total of 12.18" and average snowfall of 9.0".
Much of late Spring and Summer were influenced by a weak El Nino weather pattern. The Climate Prediction Center has officially concluded that the El Nino episode has ended and the Pacific Region is no longer on El Nino watch. Conditions (temperature anomalies) in the Eastern Pacific have returned to neutral and this transition has a  55-60% chance of staying that way headed into Spring 2020.

The National Weather Service in Paducah has historical data that covers eight of the past El Nino transitioning to neutral episodes in the past 75 years. This includes the Winter Seasons of 1952-19531958-1959, 1991-1992, 1992-1993, 1994-1995, 2002-2003, 2004-2005 and 2006-2007. I have extracted those winter periods and their corresponding temperature/precipitation records. The results are shown on the two maps above. In a large majority of these episodes, temperatures averaged above normal. Precipitation was less convincing of any trend and resulted in being fairly close to average.
Click to enlarge

TEMPERATURES: In two cases, 1951-1952 & 1991-1992, both winter seasons reached top 10 warmest of record for the Paducah area. In many of the winter cases, the preceding November also registered warmer than average. Alternatively, the following February averaged colder than average. It can be concluded that while the entire winter experience is milder than most, the end of winter is likely to become a little more harsh. The winter cases analyzed are shown in the graph to the left. Blue bars represent the recorded temperatures and the pink line represents the difference from the climate average shown in dark blue.
PRECIPITATION: There is no real identifiable trend when it comes to precipitation for the winter seasons in this case. There are equal chances for a wet/dry average when a weak El Nino episode transitions to neutral moving into the winter season. There were a few trends that were notable when looking closer at individual monthly data. In a majority of the past winter cases, January was the wettest of the Dec-Jan-Feb time period. When emerging into the Spring season, every past case  except one, showed a drier than average March and start to Spring.

SNOWFALL: Snow chances each winter are always of most interest. It's a uniquely polarizing weather type....people either love or hate it! Three of the past winter cases set records as top 10 snowiest winters. 1992-1993, 2002-2003 and 2004-2005 had some big time snow events. While most cases registered below average snowfall for the season, only 1991-1992 measured a trace of snow, and also corresponded with the warmest season in this case. Overall, snow chances are most likely to remain close to average with an increased chance for bigger, single events.

The National Oceanic and Atmospheric Administration will be releasing it's Winter Weather Outlook by mid-October. I will post their outlook for comparison when it is released. Here is a look at what is summarized in the information I provided above. Here's hoping Winter will turn out just how you like it!

Friday, May 10, 2019

Battling a longer allergy season

The National Phenology Network is showing the early arrival of leaves on trees in the Ohio Valley, the Midwest, and Western United States this year. This trend has become more of a norm over the past past 50 years.
Climate Central published data this week showing the same trend since 1970 with notable attention to the West where states are seeing as many as 17 more frost-free days, extending the growing season. Here in the Local 6 area, the growth is not as notable but still averaging between 4-9 days additional to the growing season. Why does this matter? Aside from having an influence on which plants are suitable for planting zones, it has a much higher societal impact by extending the allergy season. 

"As the climate warms from the increase of greenhouse gases into the atmosphere, the last spring freeze is trending earlier and the first fall freeze is coming later. This means the growing season is getting longer, and so is the pollen season— whether it is from tree pollens in the spring, grass pollens in the summer, or ragweed in the fall. A study sampling 10 locations from Texas to Saskatoon, Canada indicated that pollen seasons lengthened between two to four weeks from 1995 to 2009, with the largest increases in the northernmost areas.
In addition, increasing atmospheric carbon dioxide enhances photosynthesis in plants, meaning that they produce more pollen. Lab studies have confirmed this, with timothy grass producing twice as much pollen for a doubling of carbon dioxide, and ragweed producing twice as much pollen even before a doubling of carbon dioxide is reached. And the lab studies are supported from the field. One study in Baltimore, where carbon dioxide concentrations were 30 percent higher than outside the city, found that ragweed grew faster and produced more pollen in the city.
Pollen allergies are not just a nuisance. Asthma symptoms can be triggered by exposure to pollen, with the number of emergency room visits increasing on days with high pollen. An analysis of emergency room visits in New York City during 1999 showed peaks in the number of visits correlated with high spring pollen counts, and is consistent with other work connecting allergy-induced asthma to increasing in hospital visits." -Climate Central