As March transitions to April, meteorologists throughout the country begin to turn their attention from winter weather to severe weather. Although severe weather can strike at any time (tornadoes have occurred throughout every month of the year), the peak of severe weather risk in the United States occurs during spring and summer.
Warm air, humidity, and strong frontal systems are the fuel for severe storms, and all three of these ingredients begin to meet during spring – that most welcome transition from winter’s bitter cold to summer’s sweltering heat.
As southerly spring breezes push warm, humid air from the Gulf of Mexico northward and deeper into the heart of the North American continent, it inevitably clashes with cold, dry air pushed southward by powerful low pressure systems that swing across the country, refusing to give up winter’s ghost. Where the warm, humid air meets the cold, dry air, explosively powerful thunderstorms often form.
Although we should ideally be prepared for severe weather at any time of the year, the onset of “storm season” offers an annual opportunity to refresh our emergency plans, supplies, and knowledge about severe weather.
When severe weather threatens, the National Weather Service alerts the public by issuing a severe weather watch or a severe weather warning. Severe thunderstorm, tornado, and flash flood watches and warnings are common during the spring and summer months.
Watches are generally issued first, cover a large area, and indicate that conditions are ripe for the development of a particular type of severe weather. A watch does not indicate that severe weather is immanent at your location, just that such weather is likely to occur somewhere within the region for which the watch has been issued (the “watch box”). When a severe weather watch is issued for your location, be alert for rapidly changing weather conditions and prepare for the possibility of severe weather.
If a severe weather warning is issued for your location, start carrying out your emergency plan. A warning means that severe weather is bearing down. Tune in to your NOAA weather radio and local meteorologist to monitor the progress of the storm or weather event. Seek appropriate shelter and follow the recommendations issued with the severe weather warning.
Although emergency plans and supplies depend largely on the specific type of weather that you’re preparing for, there are a few essentials necessary for all types of severe weather. These include:
Additional information about compiling a complete disaster supply kit can be found at FEMA’s Ready.gov .
When severe weather strikes, you should be prepared for several hours to possibly days without electricity as well as possible disruptions in the supply of drinking water. During that time, you’ll want to be able to receive weather and news updates as well as see where you’re going (hence the radio and flashlights). Preparing for hurricanes is even more involved, and we’ll cover that in a later post.
Some basic information about preparing for and responding to severe weather is provided below. For comprehensive information about preparing for severe weather, please visit FEMA’s severe weather readiness website.
Basic Preparations and Plans for Different Types of Severe Weather:
Note: Blue Skies Meteorological Services presents on the topics of severe weather preparedness and the meteorology of severe local storms. We are also available to assist in the development of emergency plans tailored to the specific needs of your business as well as the weather and climatology of your region.
Well, El Niño is looking more and more likely during summer and fall of 2014!
As we mentioned back in February, both traditional El Niño Southern Oscillation (ENSO) indicators as well as a new statistical forecasting technique that utilizes Pacific air temperatures are suggesting possible El Niño conditions by later this year.
During the first week of March, the Climate Prediction Center issued an El Niño Watch, suggesting a moderate (50%) likelihood that warmer than average sea surface temperatures (SSTs) will develop in the eastern equatorial Pacific Ocean by the summer or fall of this year. ENSO is arguably the most important driver of interannual climate variability across the globe, strongly affecting both temperature and precipitation patterns. Here in the US, El Niño is most strongly felt during winter, when it typically brings mild weather to the northern states, wetter weather to the southeastern states, and drier weather to the upper Midwest. For a more in-depth discussion of the causes and impacts of El Niño, please check out NOAA’s Pacific Marine Environmental Laboratory and the Climate Prediction Center.
Because of its large impact on weather, El Niño also has a large impact on national and global economies. From agriculture to fishing, from energy production and demand to home construction, from natural disaster costs to tourism — ENSO directly affects up to 10% of the US economy. Intense El Niño events cost the US economy tens of billions of dollars. Some of that cost is unavoidable, but much of it is not. For that reason, early and accurate forecasts of ENSO conditions are critical.
And there is good news on the forecast front! We mentioned in February that, due to budget cuts, NOAA’s network of buoys dedicated to monitoring equatorial ocean temperatures (and therefore detecting the early signs of El Niño or its opposite condition, La Niña) had degraded to operating at a mere 40% effectiveness.
The Tropical Atmospheric Ocean Array (TAO) is about to get some much-needed TLC, according to Bloomberg News and the National Weather Service (NWS). Thanks to some budget relief in 2014, NWS is set to start repairing 70 TAO buoys, bringing the operational capacity of the TAO array up to 80%. This doubling of the current capacity will provide significantly more detail about ocean conditions, which in turn can increase lead-time for El Niño forecasts by several months, thereby allowing weather-sensitive industry to prepare early and thoroughly.
After several relatively quiet years in the equatorial Pacific Ocean, El Niño may be on its way back.
A new research study published in the Proceedings of the National Academy of Sciences (PNAS, February 2014) utilized a novel, long-range statistical approach to El Niño forecasting and found a 75% likelihood that El Niño conditions will begin to present by the end of 2014.
El Niño is the warm phase of a larger ocean-atmosphere cycle called the El Niño Southern Oscillation (ENSO). During an El Niño event, the waters of the eastern equatorial Pacific off the coast of Central and South America become anomalously warm. During the opposite phase of the cycle, La Niña, those same waters become anomalously cold (see figure at right, credit: NASA).
This fluctuation in water temperature may seem like a relatively localized phenomenon, but because the ocean and atmosphere are coupled (interconnected) and circulate the entire globe, an increase in water temperatures off the coast of Peru is not only devastating to the local fishing industry, but is also the most important driver of natural interannual climate variability across the entire planet.
Globally, El Niño conditions result in a major shift in atmospheric circulations and, consequently, weather patterns (see figure below right, credit: NOAA), as well as an increase in globally averaged temperatures.
In the northern hemisphere, El Niño conditions typically result in
Conventional El Niño forecasting techniques rely on dynamical and statistical climate models that analyze observations of sea surface temperatures (SSTs) and wind patterns. Although this forecast method can be quite accurate when making predictions a few months out, its skill is rather limited at longer-range forecasting. Accurate long-range forecasting is critical, however, to preparing for and mitigating the economic effects of El Niño events. For example, in the agricultural sector, farmers need to be able to plan which crops to plant based on expected weather conditions (e.g. hotter than normal, wetter than normal, drier than normal, etc) to reduce the likelihood of crop failure.
The study published by Ludescher, et al. this month claims to have developed a forecasting technique that can accurately predict ENSO fluctuations up to a year in advance by relying solely on statistical correlations between air temperatures across the Pacific region and upcoming changes to equatorial Pacific SSTs (i.e. upcoming El Niño or La Niña events). Although the study’s authors tout its long-range predictive ability, it cannot currently predict the magnitude (severity) of those upcoming events.
The study’s authors say that their technique accurately predicted the absence of El Niño during 2012 and 2013, but because the forecasting methodology is so new, it has yet to be tested in a prediction of non-neutral ENSO conditions. Many atmospheric scientists not involved with the study remain skeptical of the skill of the new technique for that reason as well as for the fact that the study does not propose an explanation as to why the statistical correlation should work. In other words, the study does not advance scientists’ understanding of the physical mechanisms that drive the ENSO cycle.
If the new statistical forecasting technique proves successful, though, it may alleviate a problem that has been plaguing conventional ENSO forecasters for the last couple of years and that may now be negatively affecting the skill of seasonal climate (e.g. ENSO) forecasts.
The National Oceanic and Atmospheric Administration (NOAA) maintains a network of moored buoys in the tropical Pacific Ocean to monitor real-time ocean temperatures for input into the climate models used to forecast El Niño and La Niña. Since budget cuts in 2012 forced NOAA to reduce its maintenance schedule of the buoys, however, over half of them have failed. With less detail about ocean temperatures in this critical location being provided by the thinning buoy network, forecast models may suffer a loss of accuracy.
Only time will tell. The dynamical and statistical climate models used to provide conventional ENSO forecasts are also beginning to predict an increased likelihood of El Niño conditions beginning in late 2014. It’s still too early for significant confidence, but those readers who are involved in weather-sensitive industries should monitor the situation closely and consider planning early for possible El Niño conditions beginning in late fall 2014.
We at Blue Skies Meteorological Services were fortunate to escape (by a margin of about 50 miles) the late-January winter storm that crippled much of the southeastern US last week. That storm, which brought one to three inches of snow to areas that rarely receive even a trace of frozen precipitation, clearly demonstrated the danger and damage that can occur when weather does not agree with climate norms.
A common, if somewhat over-simplified, explanation of the difference between weather and climate is:
Climate is what you expect;
Weather is what you get.
The day-long traffic gridlock in Atlanta, GA, on Jan 28th epitomizes the hazards of getting climatologically unexpected weather (and of failing to incorporate updated forecast information into emergency management decisions, but that’s outside the scope of this article). The magnitude of the weather event itself is relatively unimportant (as several colleagues from the Upper Midwest have noted, “Two inches of snow is just a normal Monday commute back home”). What matters in terms of societal impacts is the deviation of the event from normal, expected values. And the reason for this is simple – we prepare for what we expect.
As a student at Purdue University, receiving a couple inches of snow was an almost weekly winter occurrence. Snow in northern Indiana is a climate norm, so everyone is generally well prepared for it. Life proceeds without interruption thanks to stockpiles of salt/sand, fleets of snowplows, and battalions of snow plow drivers.
It’s a different story in the South, though, where 50 degrees is deemed parka weather, and where ice is typically found in tidy cubes in your sweet tea, not in impenetrable sheets coating your car windshield. Frozen precip is an anomaly, and as such, residents and municipalities don’t maintain the infrastructure nor have the experience to deal with it as “business as usual”.
However, what is lacking in infrastructure can be addressed through effective planning. By understanding the range of extreme weather events and their climatological recurrence intervals, businesses and municipalities can develop and implement emergency plans that mitigate the damage and disruption that inevitably accompanies extreme weather events.
Two inches of snowfall will always be a big deal in Atlanta (and normal January weather in the Midwest), just like temperatures above 100 degrees will always be a big deal in Maine (and a standard late July afternoon in Oklahoma). When planning for and understanding the impacts of extreme weather in any location, we must remember that it’s not the absolute magnitude of the event that matters – it’s the deviation from the norm. It’s the difference between what you expect and what you actually get.
Note: Blue Skies Meteorological Services provides climate analyses, including of extreme weather recurrence intervals, in support of business and municipal emergency planning and hazard mitigation.
Welcome to Blue Skies or Gray, the official blog of Blue Skies Meteorological Services!
After our website redesign at the beginning of 2014, Blue Skies Meteorological Services is excited about the opportunity to communicate with current and potential clients via our new blog. We’ll be focusing on weather and climate-related news, with a special emphasis on legal, environmental, and business implications and concerns. Please check back often for the latest updates, and navigate through our archives using the toolbars to your right.