The Year in Weather


As 2015 comes to a close this week, we do as we do each year and spend some time taking a look back at what has been another incredible year of weather across Colorado and the United States.

Nationally, there were many amazing weather stories over the last year: the persistent drought in the west, the tremendous drought reversal in Texas, flooding rains in Oklahoma, another below-average severe weather and quiet-ish Atlantic hurricane season, the South Carolina floods, record-setting snowfall in Boston, and of course many more.

For Colorado, 2015 also marked a year of good-ridence for the persistent drought we've seen over recent years. As we end 2015, Colorado remains drought-free, with just 11.85% of the state experiencing abnormally dry conditions, down from 30% of the state experiencing moderate drought at this time last year. This is the first time in 15 years that Colorado will end a year with 0% of the state experiencing moderate drought or worse.

We begin some 11 months ago in  Boston, MA, the city that stole winter in 2015. The 2014-15 snowfall season was the snowiest on record for the city recording 110.6" of snow, nearly all of that coming between January 4th and March 3rd, 2015. This broke the old record set in 1995-96 when 107.6" fell on the city, and the 3rd place record of 96.3" in 1993-94. While the western U.S. cooked, Boston was it's own little winter weather anomaly, with temperatures remaining below 40 degrees for a month and half straight according to Boston meteorologist Eric Fisher.

img: The Boston Globe

Meanwhile in the west it wasn't epic snowfall but  Drought that was the overwhelmingly dominate weather story this year. For California, the year started bad for drought, got worse, and is ending bad (though better than this summer), while across the Southern Plains and portions of the intermountain west there were regions which saw great recovery.

Early in the year Weather5280 tracked record rainfall across portions of Texas, Oklahoma and Colorado. For Texas, we plotted CoCoRaHS monthly precipitation reports for the last five years, showing how rapidly the drought conditions were broken with record rainfall this spring, after the height of severe drought in 2011/2012. Look how May, 2015 lights up after year after year of minimal monthly precipitation totals:

For the western states, drought relief did not come so readily. Only in recent weeks have we see the spigot turned on, with huge mountain snows and valley rains finishing off the year in the Pacific northwest, California, and the intermountain west. Nevertheless, exceptional drought conditions persist as the year comes to a close.

Below is an animated GIF where you can track the weekly Drought Monitor reports over the last year. You'll see the Texas drought wiped away (though short-term "S" does return for mid-Summer), and a persistent Exceptional Drought for California and west Nevada.

As of December 28, 2015 the outlook in the west was improving, with several weeks of heavy snow and rain trying desperately to make a dent in many years of below normal precipitation and snowpack. Take a look at the latest SNOTEL numbers across the west as of December 28th, with basins across Washington, Oregon, California and Nevada nearly all producing very healthy numbers of >130% of normal, compared with 2014 (left) where SWE numbers were just 30 - 50% of normal in many cases. A huge reversal for so many western water basins.

Texas and Colorado weren't the only places to experience flooding rains in 2015. South Carolina suffered catastrophic flooding during the first days of October, 2015, with upwards of 25 inches recorded of a 2 - 3 day stretch for some locations in the state. The Capital Weather Gang did an excellent breakdown of the meteorology behind the 1,000 year rainfall event, and it is certainly worth a read. Below is a look at the estimated rainfall totals for this event:

img: Capital Weather Gang

South Carolina's flooding was due in part to Hurricane Joaquin, one of many Atlantic storms that made landfall threats in modeling, but never in fact did make a U.S. landfall. Joaquin would go on to become the strongest Atlantic hurricane of the 2015, racking up the most ACE of any Atlantic cyclone as it become a major hurricane over the Bahamas and eventually track northeast parallel – but distant to – the U.S. coastline and out to sea. In 2015 there were 11 named Atlantic storms. Four of those were hurricanes (2 major), which is 1 short of the average 12 named storms, and 2.5 short of the 6.5 average hurricanes.

Severe Weather. There are several big headlines from 2015 when it comes to severe weather across the United States. Tragically, while it looked a few weeks ago as though 2015 could end with the fewest fatalities from tornadoes in at least 141 years, this won't come to fruition with multiple deadly tornado outbreaks in the last week. Through December 1st, 10 deaths were blamed on tornadoes, hedging out the previous least-deadly year, 1910. With tornadoes across the southeast before Christmas, and a deadly tornado in Texas on Saturday, that number has risen to more than 25 people. In fact, after nearly recording the least deadly year on record, December 2015 has become the deadliest December for tornadoes in over 60 years.

2015 will end below average in number of tornadoes recorded across the United States as well, with the preliminary count of 1,242 falling shy of the 2005 - 14 average of 1,374. While below average, preliminary numbers from 2015 pass up each of the last three years, all of which were well below normal.

RelatedTop U.S. tornado videos of 2015 via U.S. Tornadoes

Below is a map of all Severe Thunderstorm Warnings (yellow), Tornado Warnings (red), and preliminary tornado reports to date for 2015. The map can be panned and zoomed for exploration, also clicking on a tornado will pull the state, county, and remarks for each report.

While the spring was relatively quiet when it came to tornadic activity, there were some incredible tornadoes that swept across the countryside. In Colorado, two tornadoes come to mind, with Simla, Colorado possibly being one of, or *the* most photogenic tornado of the year.

For Colorado, 2015 marked a year of much anticipated drought recovery for the state. We end the year with none of the state classified as experiencing drought conditions, with just 11.85% of the state experiencing "abnormally dry" conditions. This will be the first time since December 2000 that this will be true, as each of the last 14 years have ended with at least some portion of the state experiencing drought conditions.

Thus, somewhat unsurprisingly, the lead story out of 2015 for Colorado was the tremendous rainfall – especially over northeast Colorado – this past spring which helped eradicate the persistent drought. Even with a failed monsoon, much of the state will end the year well above normal in the precipitation department. Officially, Denver will end December with 18.31" of precipitation for the year (normal = 14.2"), while many locations across northeast Colorado are nearing 30" on the year.

Denver's year was a warm and wet one. The city recorded record snowfall in February, recording 22.4" of snow, breaking the old record of 22.1" set in 1912. Otherwise the back half of the 2014/15 snowfall season was rather reliably uneventful. March, Denver's snowiest month, ended at #17 on the list of least snowiest Marches for the city. While we tried to make up for it in April, temperatures were running simply too warm, and most systems ended up as rain at lower elevations, despite their promising looks.

A wet April gave way to an even wetter May, with many locations across northeast Colorado (outside of Denver International Airport) receiving record rainfall. Portions of the eastern Plains recorded upwards of 10" for the month, while DIA settled for a respectable, but not top 10, 3.74".

As for Temperatures, the city saw one remarkable cold period, coinciding with the heavy snowfall in February. Outside of that temperatures were mostly normal and warmer than normal over the last year. A few months ago, Susie Lu created a cool visualization of New York's historical temperature data vs. 2015, which Elijah Meeks then made interactive. I've borrowed on both of these visualizations and created one for Denver. The medium dark blue lines indicate average temperatures, the light blue all time records. The burnt red and violet red lines are temperatures recorded this year in Denver – many fall within normal, a handful colder than normal, and many many above normal temperatures over the last 12 months. You can drag the gray bars at the top of the chart to explore segments:

For Colorado the 2015 - 16 snowfall season has started out as somewhat of a mixed bag. September and October were horrible snowfall months for the state but we have since seen those numbers rebound. Thanks to a favorable flow for much of the second half of December the mountains are now reporting above-average snowpack statewide as we head into the new year. El Niños generally aren't too favorable for Colorado during the heart of the winter, so we'll see how things look in another few weeks as our pattern quiets down for a period. With any luck at all, the break will be brief and we'll be looking back at wet, snowy winter and spring 2016 at this time next year.

Thank You
As another year comes to a close, we want to extend a heartfelt thank you to all of our readers new and old who have joined us over the last year. Each year Weather5280 continues to grow, and that's thanks to each and one of you who reads the site, subscribes to our various feeds, and interact with us on a daily basis. We look forward to sharing another year of weather with you in 2016!

What did we miss? Tell us your weather memories from 2015 in the comments below.

Thank you to Ian Livingston for the use of the header image taken June 1, 2015 in South Dakota.