Weather Hazards and Hazard Climatology Extreme Events in New Mexico What extreme weather events have you experienced? What can you tell us about them?

What do we mean “Extreme Events?” Extreme Heat El Niño events Winter Weather Large Fires Monsoon Rains and Flooding Drought The Last Drop

Extreme Heat Summer heat levels have already become worse. 3.6 degrees doesn’t seem like much, but as shown on the next slide can lead to large changes in heat index. Also reflective of on average higher temperatures, which means persistent dry soil and atmosphere. http://statesatrisk.org/uploads/general/2015SummerTempTrends_Southwest_sm.jpg

Warmest days are usually in July as Monsoon season begins to set in.

Those most as risk include people without access to air conditioning, the chronically ill, elderly, very young, socially isolated and disabled. The number of extreme heat events is only going to increase with climate change. Heat index- A measure of the apparent temperature the human body experiences due to high humidity and lack of cooling by evaporation. Bottom left – NWS heat index chart, top right – projected increases in extremely hot seasons per decade to 2039 (note becomes close to one a year as opposed to one every 2-3 years). In other words, extreme heat will become the seasonal norm, instead of just a frequent occurrence.

El Niño (and La Niña) Events We’ve already discussed ENSO events a lot, but this section is to drive home how much of an effect they have on New Mexico. During La Niña events (2011, left) precipitation levels are much lower than normal, in cases reaching almost to zero. During El Niño events, as on the right (2010), portions of the state actually receive almost double the usual precipitation. These events happen every 2 to 7 years, making them important to track because of how frequently they occur (LNs often follow ENs). https://www.climate.gov/news-features/event-tracker/influence-el-niño-and-la-niña-southwest-rainfall

Recent Events These comparisons use the MEI, or multivariate Niño Index, which is a compilation of information from atmospheric and oceanic evidence of ENSO events. On the right is the EN event of this past year as compared to the seven strongest EN events since 1950. Note that five of these events have occurred in the past 30 years, and three of those in the past 20. In other words, strong EN events appear to be more common. On the left is a similar comparison using the 2010-12 LN. Note that LNs tend to last longer than ENs, sometimes 3+ years as opposed to 1-2 for ENs. The 2010-12 LN was quite strong, but the strongest was 1954-56, and all but one other (1988) occurred before 1980. In other words, LN events seem to mostly have become weaker over the past 30 years. We are quite likely to enter another LN event soon, and are exiting out of the 2015-2015 EN event. http://www.esrl.noaa.gov/psd/enso/mei/

Winter Weather Winter storms are often named now – Goliath was part of an unusually strong set of storm cells that moved across the US during the winter of 2015. Outside of snowfall well above normal in the SW US, also produced downstream river flooding in lower Mississippi Basin, tornadoes, and other weather-related disasters. https://weather.com/forecast/national/news/winter-storm-goliath-forecast-snow-blizzard

Winter weather can cause disruption to travel and damage to infrastructure due to snow or ice and wind. Changing precipitation patterns will bring new challenges (more rain, less snow). Winds also cause a tremendous decrease in perceived temperature, called wind chill, that speeds up frostbite. As mentioned earlier, changes in precipitation are predicted with increased air temperatures. Less snow means less snow pack, resulting in reduced river and stream flow in the spring. More winter precipitation will be sleet and rain, rather than snow. However, those snowstorms that do form could become more intense. Winter precipitation varies heavily, with some areas (especially lower and to south) receiving less than 10” per year, while others (especially mountain areas to North) have received 300”. Windchill can be an incredibly dangerous problem in much the same way as the heat index, but in this case speeding up frostbite on exposed skin. In most extreme cases, just a five mph increase can halve time to frostbite. Sub zero temperatures are rare outside of the mountains, but do occur. Note that windchill doesn’t become much of a factor until close to or below zero degrees.

Large Fires Wildfires can lead to devastating loss of life and property, but are part of the natural ecosystem of large parts of the southwest. Improper forest management combined with increasing air temperatures and prolonged drought have made large fires a more frequent occurrence. More on this later, but wildfires are a natural occurrence that is exacerbated by human activity. Poor forest management combined with increased air temperatures set the stage for large amounts of deadwood to catch fire. https://www.env.nm.gov/swqb/Wildfire/images/Photo1-LittleBear2012.jpg

Monsoon Rains Monsoon flooding is related to seasonal rainfall and soil conditions. Summer heat over the land creates a low pressure front that pulls in atmospheric moisture from the ocean. Dry soils are less able to retain the resulting rainfall, causing floods. Warmer summers will mean stronger (though less frequent) monsoon events. http://www.weather.gov/abq/?n=prepawaremonsoondust Monsoon rains bring dramatic storm events during the summer, as shown by the graph. Basically late summer is the rainiest part of the year because of the tremendous temperature difference between the ocean and land. As the moist air is drawn over the southwest from the Gulf of Mexico, it eventually reaches New Mexico, where it meats drier air and mountains, causing precipitation to suddenly occur. Monsoon rains will become more intense due to both climate change and shifts in different climate oscillations. Rainfall highly variable across state. Zack Guido, CLIMAS, The University of Arizona

Flash floods follow monsoon rains, so as this graph shows most flash floods happen in July-September, the same months with higher than average precipitation (monsoon season). http://www.weather.gov/abq/svrwxclimo

Drought A normal and recurrent feature of climate, which consists of a deficiency in precipitation over an extended period of time. Droughts in New Mexico can be severe, lasting for years and covering large expanses of the state. In the early 2000s large portions of the state were under the designation D3-D4, which means extreme to exceptional drought conditions. Drought Monitor map is from November 2004, winter precipitation levels are usually less than summer (no monsoon, mountains to west block most of the moisture coming off of the Pacific) so large amounts of the state end up in drought conditions. In addition, the early 2000s featured a linking up of PDO and AMO (discussed more later) which made the drought more severe. Drought is also highly variable across the state (see map).

Precip trends for New Mexico over the past 120 years Precip trends for New Mexico over the past 120 years. As we will discuss later, drought is more complex of a phenomenon than just precip levels, but they are often a good indicator of drought periods (i.e., less moisture in the system = more likely to be in a drought, aka a meteorological drought).

The Last Drop What happens when droughts become more prolonged and severe? When water reservoirs run dry?