Click the link to read the article on the Summit Daily website (Shelby Reardon). Here’s an excerpt:

March 1, 2024

This is where Colorado’s resorts’ snow totals stand so far, according to resorts’ websites and unofficial tallies from OpenSnow.com:

• Steamboat Springs, 294 inches
• Winter Park, 257 inches
• Wolf Creek, 238 inches
• Powderhorn Mountain Resort, 220 inches
• Vail Mountain, 215 inches
• Copper Mountain, 215 inches
• Aspen Highlands, 214 inches*
• Crested Butte, 213 inches
• Snowmass, 211 inches*
• Breckenridge, 208 inches
• Beaver Creek, 203 inches
• Monarch Mountain, 202 inches
• Silverton Mountain, 190 inches
• Telluride, 185 inches
• Aspen Mountain, 179 inches*
• Arapahoe Basin, 177 inches*
• Loveland Ski Area, 177 inches
• Keystone Resort, 169 inches
• Purgatory, 167 inches
• Ski Cooper, 165 inches
• Eldora, 150 inches
• Buttermilk, 118 inches*
• Sunlight Mountain Resort, 98.5 inches

Unofficial number from OpenSnow.com are marked with an asterisk.

Click the link to read the post on the Colorado Climate Center blog (Peter Goble):

March 1, 2024

Hello, and welcome to meteorological spring (March-May). The month of February just ended, and frankly, this winter felt different. The northern Front Range of Colorado has just been through a bizarre meteorological winter. For Fort Collins, this was the second warmest and second least snowy meteorological winter since the beginning of the 21st century, and certainly warmer and less snowy than the historical past. At the same time, precipitation (the combined accumulation of rain and melted liquid from snow/ice) has been well above average this winter. The official Fort Collins Weather Station winter precipitation total of 2.42” is the 8th wettest winter on record, and ranks only behind 2007 and 2016 in the last 30 years. Boulder also recorded its 8th wettest winter in over 100 years while remaining only 0.6” above the 1991-2020 average snowfall mark. Our neighbors at the University of Northern Colorado in Greeley recorded their 3rd warmest winter, but with 151% of normal precipitation. On top of this, winter 2024 has also been speckled with rain only events, freezing drizzle, and a very heavy, spring-like rain snow mix. Is this a sign of things to come? Will rainy, drizzly, sloppy winters replace the fine, snowy powder of our past? Let’s dig into the numbers and the literature to find out.

Winter Rain Only Events

Rainfall events during the winter months on the northern Front Range of Colorado are perhaps more common than some realize. Since 1951 there have been 80 rainfall events with no measurable snow for Fort Collins, and 95 for Boulder. That is an average of 1.0-1.5 rain only events/meteorological winter. Fort Collins and Greeley had three such events this year (Boulder only one). There is no statistically significant trend in winter rain events over this time. If somebody says “it never rains in northern Colorado during winter” be skeptical.

One reason we may be inclined to believe winter rain is rare in Colorado is these events generally aren’t memorable. Precipitation accumulations are almost always small. 80-90% of rain-only winter events tally less than one tenth of an inch of precipitation. Fort Collins, Greeley, and Boulder have never seen a rain event greater than half an inch during winter. The largest rain only value occurred in Boulder on January 18th, 1974 (0.43”).

Freezing Rain/Drizzle

We also experienced a freezing drizzle event this winter on February 16th, 2024. This is not the only winter freezing drizzle events in recent years: Northern Colorado also saw freezing drizzle on January 24th, 2017, January 19th, 2022, and March 7th, 2014 (though this last date falls just outside the scope of “meteorological winter”). Anecdotally, it feels as though these events are becoming more frequent. A couple notes on freezing rain and freezing drizzle: 1. While freezing drizzle is obviously possible for northern Colorado, true freezing rain is nearly impossible. 2. Freezing drizzle is not well archived historically. One possible source of freezing drizzle records is the Automated Surface Observing System (ASOS), a network of weather stations designed to aid aviation endeavors. Some ASOS stations do mark the occurrence of freezing drizzle, but not all, and existing records are spotty. All this to say, it is unclear whether or not freezing drizzle is becoming more likely for northern Colorado.

February 3rd, 2024 (A Spring Storm in the Middle of Winter)

February 3rd was a special day on the northern Front Range of Colorado. The official Fort Collins weather station received 1.66” of precipitation between 7:00 PM on the 2nd, and 7:00 PM on the 3rd (7:00 is the official weather station daily observation time). Boulder and Greeley received 1.74” and 0.74” of precipitation respectively. This was a top ten wettest storm for Greeley and a record setter for Boulder. In Fort Collins, 1.66” of precipitation is not only a record amount of moisture for any day in February (135 years of record), it single-handedly made February 2024 the wettest February Fort Collins has ever experienced. Furthermore, Greeley’s all-time wettest February storm also occurred in 2024 just one week later, but as heavy snowfall.

Northern Colorado locals have seen these types of rain/snow events before, but they are more of a calling card of spring. Typically, in February, the air is too cold and dry to support such accumulations. The weather pattern on this day was unique in a couple key ways allowing this event to happen. For one, the storm tapped into a corridor of tropical moisture extending all the way from the central tropical Pacific Ocean to the western United States, greatly increasing the potential for high moisture totals. These events are often called “atmospheric river events,” and are more common in coastal settings like California, Oregon, and Washington. Secondly, we experienced a split polar jet stream pattern with Colorado lying in the middle of the two currents. The southern flank of the split polar jet brought the atmospheric river to our doorstep while a high pressure airmass in the middle of the two flanks deflected the moist air back against the eastern side of the Rocky Mountains, and blocked cold arctic air from sweeping this storm out over the plains (figure 1). Both factors were important for producing such spring-like storm conditions.

Winter Precipitation and Climate Change

Our office teamed up with Jeff Lukas of Lukas Consulting to synthesize what the academic literature says about how Colorado’s climate may change over the remainder of the 21st century. This resource can be accessed here. If you have not had a chance to scan this document, I highly recommend it. We can use this document to get a glimpse into the future of winter precipitation, snowfall, and winter storms for Colorado.

Colorado has warmed, and continues to warm, significantly in all seasons due to increasing greenhouse gas concentrations in the atmosphere. Atmospheric physics tell us that warmer air can hold more water vapor, meaning there is potential for higher precipitation measurements from each individual storm under a warmer climate. We do see evidence that meteorological winters are getting wetter. Since 1950 we have seen a 3% increase in statewide wintertime precipitation. This trend is actually higher for the northern Front Range +14%, but somewhat offset by marginal decreases in western Colorado. Most climate models do suggest further increases in wintertime precipitation are likely. One experiment from our report shows an average of 6% more winter precipitation across Colorado by mid-Century with nearly 90% of the 36 global climate models used agreeing on the sign of the trend. Further increases are possible by the end of this century, and under high carbon emissions scenarios.

Accurately assessing trends in snowfall is more complicated. Snow measurement protocols have changed over time, muddying the waters of snowfall trend analysis. We do know average high elevation snowpack has decreased over time in Colorado, but 3”+ snowstorms on the Front Range have not. Annual maximum snowfall event totals have not fallen yet either (Figure 2). We also know that extreme cold outbreaks, which often follow winter snowstorms, are likely to continue decreasing in frequency and intensity, but will not disappear.

Winter storms are complex, and can be measured in a number of ways. For instance, just in recent years, we have seen the northern Front Range covered with 20-30” of snow (March 2021), a new lowest central pressure record from a winter storm (March 2019), and one of the most intense cold fronts in decades (December 2022). We have high confidence that winter will continue to get warmer on average across Colorado over the coming years and decades, but snow, extreme cold, and wildly varying conditions will not be out of the offing anytime soon.

Based on the evidence we have about climate change in Colorado, it is reasonable to hypothesize that our warming trend made this event more likely. Even so, climate models do not suggest that events like February 3rd, 2024 will become commonplace by the end of the century, even under high emissions scenarios.

Click the link to read the article on the NOAA website (Amy Butler and Laura Ciasto):

February 29, 2024

We’ve talked about how the reversal of the west-to-east winds during a major sudden stratospheric warming sets up a feedback between large atmospheric waves and the winds, and how this results in the stratospheric wind changes being communicated down into the troposphere. But what does this mean for weather patterns down here after the polar vortex is disrupted?

By taking the average of the surface temperature and atmospheric thickness for the 30 days after all the major sudden stratospheric warmings in the observational record, we can average out day-to-day variations in the weather and see more clearly what weather patterns related to major warmings look like.

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From a stratospheric hot mess to a tropospheric cold brew

Sudden stratospheric warmings (and sometimes just the phrase “polar vortex”) are often associated with cold and snowy weather; and indeed, anomalous cold is evident over some regions like northern Europe and Asia and the eastern United States after these events. How does a warming of the stratosphere cause widespread cold at the surface?

During major warmings, the atmospheric thickness increases over the pole, which shows up on these maps as a positive anomaly in tropospheric geopotential height over the Arctic, particularly Greenland. This increase in atmospheric thickness in the troposphere is linked to the build-up of air over the pole during the sudden warming: it can act like a rock dropped in a bucket, pushing down on the troposphere such that the cold Arctic air “sloshes” out into lower latitudes. An alternative way to think about it is that the increased atmospheric thickness over the Arctic induces changes in tropospheric winds that push cold air from the Arctic farther south in some regions and pull warm air from the south into the Arctic in other regions.

But… it’s not cold everywhere

Not all regions need to bring out snow shovels and gloves when a polar vortex breakdown is on the menu. The map shows that there are also large areas with generally warmer than normal surface temperatures after major warmings. These regions include eastern Canada and much of subtropical Africa and Asia. This is one reason why, even though we might care most about what happens where we live, we shouldn’t equate polar vortex disruptions with cold air outbreaks.

Weather effects are strongly regional

Another reason to not automatically assume that a major stratospheric warming means colder weather is that the magnitude of cold varies widely from place to place, with the strongest cold appearing over northern Europe and Asia, and more moderate to weak cold appearing over central Europe and the eastern United States. These regional differences arise because the changes in atmospheric thickness, and thus the effects on the tropospheric jet stream, are centered over the North Atlantic [footnote 1], and so the strongest associated temperature changes occur just upstream or downstream of this region.

An atmospheric gamble

It’s important to remember that the maps of “typical” surface impacts are not a forecast and do not represent the expected day-by-day weather when one of these events occurs. These maps show an average over many major warmings, each occurring in different years and with different global climate conditions (such as different phases of ENSO). These maps don’t give a sense of where the weather may vary substantially from one event to another.

Furthermore, they’re also an average over the 30-day period after one of these events, which means that from day to day or week to week after a major warming event, the weather could look vastly different in any given location than from what is shown here. What this type of map does is provide a sense of where changes in temperatures and pressures are most likely to occur in the month after a major warming, allowing us to assess the probabilistic risk of certain extremes. In other words, a major warming “loads the dice” for certain conditions, but by no means guarantees them.

Another way we can get a hint about which areas are most likely to follow the average pattern is to look at how much variability there is at a given location from event to event. That’s what the maps below show.

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Current polar vortex conditions: did it or didn’t it? 

So did we see the second sudden stratospheric warming of the year? Well… it’s complicated. The stratospheric polar vortex did indeed rapidly weaken and warm as predicted, so physically-speaking, a sudden warming occurred around February 19, 2024.

However, whether it will be classified as a major or minor event is still unclear. This is because the way a major sudden warming is commonly defined [footnote 2] requires the daily-mean west-to-east winds, averaged around the 60N latitude circle and at the altitude corresponding to an atmospheric pressure of 10 mb, to fall below 0 m/s. In this case, the winds came very very close to that threshold (within +/- 1 m/s), so that some reanalysis data products [footnote 3] likely will show the winds falling below 0 m/s and others will not. This disagreement between data products has happened in the past and is one of the caveats of using a threshold-based definition of these events; there is some sensitivity to which events get “counted” as major warmings, even though a rapid weakening and warming of the polar vortex was observed.

Nonetheless, perhaps because the weakening of the vortex wasn’t substantial enough to significantly reverse the stratospheric winds (if at all), the winds have re-strengthened quickly. The continued west-to-east winds will allow further onslaught of the polar vortex by atmospheric wave activity. [Remember from our earlier post that only when the polar vortex is whipping along from west-to-east can waves from below penetrate and disrupt it.] Current forecasts show potential for a more substantial reversal of the stratospheric polar vortex than we’ve seen so far this entire winter taking place early next week. However, we are also heading into spring, which is when the stratospheric polar winds typically transition to an east-to-west summertime state. So it remains to be seen whether this upcoming reversal will essentially kill the polar vortex for the remainder of the season (the “final warming”), or whether the vortex will return to west-to-east flow in April for a brief period [footnote 4]. 

Footnotes

1. Why the North Atlantic jet stream appears more strongly affected than the Pacific region after major warmings is still not well understood.
2. The most common definition is based on Charlton and Polvani (2007), but many other definitions exist. Which events are classified as “major” is sensitive to the definition used.
3. Reanalysis products take multiple observational sources like satellite and balloon measurements and assimilate them into a model to create a product that is both temporally and spatially complete at each grid space of the model, and is constrained by observations. Because different data centers use different models and data assimilation techniques, and may assimilate different satellite and balloon records, reanalysis products can exhibit differences from one another. Note that because it can take some time for this data to be released, we often have to wait several weeks to determine if the major warming occurred in each dataset.
4. There are more technicalities to the major stratospheric warming definition that have implications for the final count of events this winter. In particular, because events must be separated by 20 consecutive days of west-to-east stratospheric winds, this upcoming wind reversal will not be counted separately from the February 19th event, if it occurred. Additionally, if it is a final warming, it will not be counted as a major warming which only includes “mid-winter” events. Ultimately, these details are all somewhat arbitrary and only matter for statistical purposes!

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor website.

Click the link to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

Several weather systems moved across the contiguous U.S. (CONUS) during this U.S. Drought Monitor (USDM) week (February 21-27). Their fronts and surface lows spread rain and snow across parts of the West at the beginning and end of the week, and over the Tennessee to Ohio Valleys and Appalachians at mid-week. These systems were associated with an upper-level circulation pattern that consisted of low-pressure troughs just off the west coast and east coast, with a high-pressure ridge over the central part of the country. The ridge brought above-normal temperatures to much of the CONUS, from the Rocky Mountains to Appalachian Mountains, with weekly temperatures averaging 15-20 degrees F above normal from Texas to the northern Plains and Upper Mississippi Valley. Temperatures averaged near to cooler than normal in parts of the interior West to Pacific Coast and along the Eastern Seaboard. The ridge also inhibited precipitation from the Rockies to Mississippi Valley. The precipitation in the West was mainly over mountain ranges but was not enough to improve drought conditions. The precipitation in the Midwest was enough to prevent further drought expansion or intensification where it was wetter than normal for the week. In other areas, drought or abnormal dryness expanded or intensified in parts of the Plains and Midwest, and a few parts of the Pacific Northwest, Gulf of Mexico coast, and Mid-Atlantic coast…

High Plains

There were a few areas of half an inch to locally 2 inches of precipitation in the High Plains region this week – in North Dakota and parts of Colorado and Wyoming. But the rest of the region had little to no precipitation. Daily high temperatures reached into the 80s F some days in Kansas and up to the 50s and 60s in the Dakotas. Weekly temperatures averaged 10 to 20 degrees above normal across most of the region, increasing evapotranspiration (ET). Since this is February and vegetation is still dormant, the above-normal ET had little effect on vegetation, but soil temperatures were well above freezing in southern parts of the region and the high ET helped to dry soils. D0 expanded in the Dakotas, and D1 crept into northwest North Dakota, to reflect the 1- to 2-month dryness and unusually warm temperatures, and D0 expanded in eastern Kansas where recent precipitation has been low and soils were drying. In Wyoming, very low mountain SWE (snow water content) and dry 1- to 4-month SPI values prompted the expansion of D0-D2…

West

Two to locally 5 inches of precipitation fell in the Oregon and Washington Cascade and Coastal mountains this week, with half an inch to locally 2 inches in the northern and central Rockies and southern California, and 0.5 to 1.5 inches in the Sierra Nevada and parts of coastal California. Outside of these areas, precipitation was generally less than a fourth of an inch, with rainshadow areas and the Southwest (Four Corners States) mostly dry. The precipitation was above normal for the week in some areas, particularly parts of the Cascades, Rockies, and southern California. But amounts were not enough to bring month-to-date totals to near normal values, with these areas still well below normal for the month. And snowpack improved little, with just a few inches of new snow added to most Cascade and Coastal mountain SNOTEL sites. Mountain snowpack and SWE values were still well below normal to near-record low in Washington, Oregon, Idaho, and Montana. In California, as of February 27, mountain SWE was 94% of normal in the northern Sierra Nevada Mountains, 78% of normal in the Central Sierra, and 76% of normal in the southern Sierra. In Washington, D0-D1 was expanded in the northern Cascades and D1 added to the Olympic Mountains to reflect the low snowpack and subnormal precipitation. Low SWE and 1- to 4-month SPEI values resulted in expansion of D0-D3 in parts of Montana…

South

Northern parts of Tennessee received 0.5-1.5 inches of precipitation this week, but most of the South region was dry with no precipitation occurring. Much warmer-than-normal temperatures accompanied the dryness, with daytime maximum temperatures in excess of 90 degrees F recorded in Texas. Dallas/Fort Worth reached 94 on February 26, which was a daily record and 31 degrees above normal. The hot temperatures increased evapotranspiration which drew moisture out of the soils. The recent dry weather, accompanied by low relative humidity and windy conditions, contributed to an outbreak of wildfires across parts of the region. D0 expanded in southwest Texas where air temperatures were hot, soils were hot and dry, and the last 3 months were drier than normal. Dry 1- to 3-month SPI values prompted expansion of D0 in eastern Oklahoma and adjacent parts of northeast Texas and western Arkansas. Dead fields in Sebastian County, Arkansas, were reported via the CMOR (Condition Monitoring Observer Reports) reporting system. D0 expanded in southern Mississippi, adjacent parts of Louisiana, and southeast Texas where SPI was dry, streamflow was low, and some soil moisture indicators showed dryness, and D0 expanded in southeast Tennessee where 1- to 2-month SPEI (Standardized Precipitation Evapotranspiration Index) showed dry conditions. A reassessment of data resulted in the deletion of the relic D0 along the southeast Louisiana coast…

Looking Ahead

In the two days since the Tuesday valid time of this USDM, Pacific moisture continued to move across the Coastal and Cascade ranges in the Pacific Northwest, with precipitation falling in areas east of the Mississippi River and in parts of the southern Plains. For February 29-March 5, a ridge over the eastern CONUS will bring warmer-than-normal temperatures to much of the country east of the Rockies while a trough contributes to cooler-than-normal temperatures in the West. Forecast models predict a wet period for much of the West, in the Upper Rio Grande Valley, and from the Lower Mississippi Valley to the East Coast, as low-pressure systems and fronts bring locally heavy precipitation. The Coastal, Cascade, and Sierra Nevada mountain ranges could see 5 to 10 inches of precipitation, or locally more, while the central to northern Rockies could receive 2 to 4 inches of precipitation. Parts of southern New Mexico and western Texas could receive up to an inch of rain. An inch or more of precipitation is predicted from southern Louisiana to southern New England. Outside of these wet areas, up to half an inch of moisture could fall in the lower elevations of the West, across the northern and southern Plains, and Midwest to Northeast. Areas that could miss out on the precipitation stretch from southern California to the central Plains, where little to no precipitation is expected, and the southern Plains and Mid-Mississippi Valley to eastern Great Lakes, where less than a fourth of an inch may fall.

For much of the next 2 weeks, the atmospheric circulation is expected to continue an upper-level trough over the western CONUS and a ridge over the eastern two-thirds of the country, with Pacific weather systems migrating through the trough/ridge pattern. The Climate Prediction Center’s (CPC) 6-10 Day Outlook (valid March 4-8) and 8-14 Day Outlook (valid March 6-12) favor a fairly stable pattern of warmer-than-normal temperatures from the Plains to East Coast and cooler-than-normal temperatures over the West and Alaska. The outlook is for above-normal precipitation over eastern and southern Alaska and much of the CONUS, especially east of the Mississippi River, with odds favoring near to below-normal precipitation over the northern Rockies to northern Plains and over the west coast of Alaska.

From email from the Colorado Water Trust (Barrett Donavan):

Here are the details:

• Write a maximum 300-word story about a river (or rivers) in Colorado.
• Stories should inspire your fellow Coloradans to love and care about Colorado’s rivers.
• Submissions may be poetry or prose and silly, serious, or sweet. You can do a fairytale, a real river story, or anything in between. It can be as short as you like, but no more than 300 words. Title not included in word count. The field is wide open! Have fun! The more creative the better!
• Illustrations and/or photos are welcome but not required.
• You may submit more than one entry and all ages of writers are encouraged.
• Entries should be emailed by Friday April 19th at 11:59 PM MT to Barrett Donovan at bdonovan@coloradowatertrust.org.

We have four great judges who will choose the top five stories. First, second, and third place winners will receive an awesome prize, and all top five submissions will be shared on our website, in our newsletter, and on our social media accounts.

The Judges:

• Anne Castle: Senior Fellow, Getches-Wilkinson Center, University of Colorado; US Commissioner, Upper Colorado River Commission; Water Trust Board of Directors
• Luke Runyon: Journalist; Co-director of The Water Desk at the University of Colorado’s Center for Environmental Journalism
• Radha Marcum: Poet and writer with a focus on the intersection of the environment, culture, and personal history
• Amelia Marsh: Editor in Chief, University of Denver Water Law Review

Judging Criteria:

• River Inspiration: Your story must inspire readers to love and care for their Colorado rivers.
• Quality of Story: Entries must tell a story, including a main character of some kind and a true story arc even if it’s tiny. Entries must not be merely descriptions or mood pieces.
• Quality of Writing: If you’re going to rhyme, give us your best. Overall writing quality and use of language are also important.
• Originality and Creativity: These two elements are often what sets one story above another. You will want yours to stand out from the crowd!

Click the link to access the article on the Science Advances website (Karen E. King, Edward R. Cook, Kevin J. Anchukaitis, Benjamin I. Cook, Jason E. Smerdon, Richard Seager, Grant L. Harley, and Benjamin Spei). Here’s the abstract:

Across western North America (WNA), 20th-21st century anthropogenic warming has increased the prevalence and severity of concurrent drought and heat events, also termed hot droughts. However, the lack of independent spatial reconstructions of both soil moisture and temperature limits the potential to identify these events in the past and to place them in a long-term context. We develop the Western North American Temperature Atlas (WNATA), a data-independent 0.5° gridded reconstruction of summer maximum temperatures back to the 16th century. Our evaluation of the WNATA with existing hydroclimate reconstructions reveals an increasing association between maximum temperature and drought severity in recent decades, relative to the past five centuries. The synthesis of these paleo-reconstructions indicates that the amplification of the modern WNA megadrought by increased temperatures and the frequency and spatial extent of compound hot and dry conditions in the 21st century are likely unprecedented since at least the 16th century.

Click the link to read the article on the NOAA website:

Highlights

• Temperatures were above average over much of the globe, but the eastern United States, most of Europe and a few other areas were cooler than average. 
• There is a 22% chance that 2024 will be the warmest year in NOAA’s 175-year record and a 79% chance that El Niño will transition to neutral conditions by mid-year.
• Northern Hemisphere snow cover was near average, but Antarctic sea ice extent was fifth lowest on record for January. 
• Global precipitation was nearly record-high in January, following on the heels of a record-wet December. 

Temperature

The January global surface temperature was 2.29°F (1.27°C) above the 20th-century average of 54.0°F (12.2°C), making it the warmest January on record. This was 0.07°F (0.04°C) above the previous record from January 2016. According to NCEI’s Global Annual Temperature Outlook, there is a 22% chance that 2024 will rank as the warmest year on record and a 99% chance that it will rank in the top five.

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January saw a record-high monthly global ocean surface temperature for the 10th consecutive month. El Niño conditions that emerged in June 2023 continued into January, but according to NOAA’s Climate Prediction Center it is likely that El Niño will transition to ENSO-neutral by April–June 2024 (79% chance), with increasing odds of La Niña developing in June–August 2024 (55% chance).

Temperatures were above average throughout the Arctic, most of northeastern North America, central Russia, southern and western Asia, Africa, South America, eastern and southeastern Asia and Australia. Much of northwestern North America, the central and southern United States, northern and eastern Europe, northeastern Asia and Antarctica experienced near-to- cooler-than-average temperatures during January. Sea surface temperatures were above average across much of the northern, western and equatorial Pacific Ocean, as well as parts of the western Indian Oceans. 

Precipitation

• The El Niño rainfall anomaly pattern over the central and western Pacific Ocean and Maritime Continent has weakened.
• Further afield the patterns over the Indian Ocean, Africa and the southern U.S. are more clearly El Niño-like.
• Overall the pattern correlation between this January’s rainfall anomaly pattern and the El Niño composite plummeted from a high of +0.59 last month to only +0.19.
• Global total precipitation for this January is nearly a record high following December’s record high for that month of the year.

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The current El Niño continues through January, but the departures from average on the global map show a mixed pattern, with some rainfall excess/deficit features typical of El Niño situations and others differing from the expected pattern. In the central and eastern Pacific along the Intertropical Convergence Zone, there is still a narrow, strong positive anomaly as typical of El Niño, with a rainfall deficit just to the north and south. But just to the west the wide positive feature expected at ~180° longitude at the Equator is weak this month, despite the Niño 3.4 Index being +1.9, easily within strong El Niño range. [The “Niño 3.4 Index” tracks sea surface temperatures in the central-eastern tropical Pacific Ocean: the key ENSO monitoring region].

The match between this January and the El Niño composite becomes even more fraught over the Maritime Continent to the west where generally very dry conditions are typical of El Niño, but rainfall is in excess over Borneo and Malaysia, although deficit features exist over some surrounding areas, especially between Sumatra and Australia. Australia itself is typically very dry during El Niños, but for this January it is mostly wetter than normal across the continent, and there was even flooding first in Victoria and then heavy rains in northern and northeastern parts of the country later in the month.

Northern South America is mostly dry, as is typical of El Niño, but the rest of the pattern does not match well. The spatial correlation of January’s anomaly pattern with the El Niño composite has plummeted to +0.19 from a high of +0.59 in December, seemingly indicating a weakening of El Niño at core tropical locations. It will be interesting to see if that type of change continues next month, or if this is a temporary change. Models are predicting an end to the El Niño over the next few months. [Read more about what we can expect from the El Niño-Southern Oscillation this spring in Climate.gov’s latest ENSO Blog post.]

For a deeper dive on January 2024 climate, including circulation patterns, major events, and separate statistics and rankings for Earth’s land and ocean areas, see the full January 2024 monthly report from NOAA NCEI.

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor website.

Click the link to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

An atmospheric river of Pacific storm systems slammed parts of the West Coast with heavy precipitation during this U.S. Drought Monitor (USDM) week (February 14-20). The weather systems dried out as they crossed the western mountains, then produced anemic precipitation amounts east of the Rockies. Parts of the Midwest and Northeast received limited precipitation amounts from passing cold fronts, and heavier rain fell along the Texas coast and across Florida from another frontal system, but much of the country east of the Rockies, as well as the southwestern U.S., received little to no precipitation. The weather systems distorted the upper-level circulation over the contiguous U.S. (CONUS), which otherwise consisted of a high-pressure ridge over western North America and a low-pressure trough over the east. The end result of this distortion was a temperature anomaly pattern that consisted of warmer-than-normal weekly temperatures in the Upper Midwest and parts of the interior West, and below-normal temperatures in the Pacific Northwest, Rockies, and southern tier states, with near-normal temperatures elsewhere. An upper-level ridge over the Caribbean brought generally dry and warmer-than-normal weather to Puerto Rico and the U.S. Virgin Islands, while ridges also kept Alaska mostly drier and warmer than normal and Hawaii drier than normal this week. Drought or abnormal dryness expanded or intensified this week in parts of the Pacific Northwest, northern Rockies, northern Plains, Upper Midwest, Middle Mississippi Valley, Rio Grande Valley, eastern North Carolina, and much of Hawaii. Drought or abnormal dryness contracted or reduced in intensity in parts of the Four Corners states and Lower Mississippi Valley…

High Plains

Half an inch to locally 2 inches of precipitation fell this week over the Colorado mountains into adjacent Wyoming, and over western Wyoming. A band of precipitation extended across South Dakota, with locally up to half an inch falling. Otherwise, the High Plains region received little to no precipitation. D0 was expanded in the Dakotas, and D1 expanded in North Dakota, where the last 3 months have been dry and the lack of snow cover has exposed bare ground. D0 and D1 were adjusted in north central and southwest Colorado where recent precipitation resulted in local improvements and continued dryness caused local expansion. D2 was introduced in north central and northeastern Wyoming…

West

Five inches or more of precipitation fell along the California coast, across much of northern California, and in southwestern coastal Oregon, with 2 inches or more inland to the Sierra Nevada, Oregon Cascade mountain range, and over southwestern coastal Washington. Half an inch to an inch of precipitation fell across southern parts of the Pacific Northwest inland to the Rockies and a few areas to the north, with up to 2 inches falling from the Great Salt Lake area to Yellowstone National Park. Another area of 1 to 2 inches of precipitation occurred over the Colorado Rockies into adjacent Wyoming. Parts of California have received over 10 inches of precipitation during February and the Sierra Nevada range has received 1 to 3 feet of new snow since the end of January. But even with a wet February, much of the Sierra Nevada still has a below-normal snowpack. As of February 16, the northern Sierra snow water content (SWE) was 83% of normal, the central Sierra SWE was 74% of normal, and the southern Sierra SWE was 72% of normal. So, the D0 along the California-Nevada border was left unchanged.

While this week was dry across New Mexico, precipitation from the last 2 weeks to 3 months prompted the elimination of the D4 in southwestern New Mexico and the northwest D2, and contraction of the D3 in north central and D2 in southwestern parts of the state.

In northern parts of the West, precipitation for the water year to date (October 1, 2023-February 18, 2024) has been largely below normal and the winter snowpack is significantly below normal. Parts of the northern Rockies have record low SWE values, according to SNOTEL data. D0 expanded in parts of Idaho, Oregon, and Washington; spots of severe drought (D2) were added in north central and northeast Wyoming; and D2 was expanded and new D3 added in parts of Montana, especially the western and southern mountains, where the last 3 to 4 months have been dry and SWE values are record low…

South

Half an inch or more of precipitation fell across parts of the Texas coast, and there were a few areas of up to half an inch of precipitation in Arkansas and Tennessee, but otherwise the South region received no precipitation this week. D0 and D1 were expanded in west Texas along the Rio Grande Valley to reflect dry conditions over the last 7 days to 3 months, low streams, drying soils, and stressed vegetation indicated by satellite. D0 was contracted in South Texas and D1 contracted slightly in central Texas (Bell County). No change was made in Oklahoma, where reservoir levels remain historically low. A reassessment of conditions resulted in the removal of the D3 (extreme drought) and trimming of D2 in northwest Mississippi, trimming of D0-D1 in Arkansas, Louisiana, and Mississippi, and trimming of D0 in Tennessee. Precipitation is near to above normal in these areas for the last 1 to 4 months, streamflow is near to above normal, and surface soil moisture has been recharged. In Louisiana, stock ponds mostly refilled. The remaining D0-D2 is sufficient to reflect the longer-term dryness which shows up most severely at the 6- to 12-month time scales…

Looking Ahead

In the two days since the Tuesday valid time of this USDM, Pacific moisture continued to move across parts of the West, with little precipitation falling east of the Rockies. For February 22-27, one weather system will move across the eastern CONUS, while another moves into the West by the end of the period. The first is forecast to drop 0.5 to 1.5 inches of precipitation across the Tennessee Valley and southern Appalachians northward to the southern Great Lakes and central Appalachians, with half of an inch or less over the Northeast and even less over the Southeast. The second is expected to bring an inch or more of precipitation to the central and northern Rockies, coastal ranges of the Pacific Northwest, and Sierra Nevada, with up to 3 or 4 inches in the Washington Cascades. Other areas of the West are forecast to receive less than half an inch of precipitation, with little to no precipitation over the Southwest and to the lee of the Cascades in Washington. For the Great Plains to Mississippi Valley, little to no precipitation is predicted. Temperatures are expected to be warmer than normal, with the warmest anomalies across the Plains and Mississippi Valley due to upper-level ridging.

For much of the next 2 weeks, the atmospheric circulation is expected to consist of an upper-level trough over the western CONUS and a ridge over the eastern two-thirds of the country, with Pacific weather systems migrating through the trough/ridge pattern. The Climate Prediction Center’s (CPC) 6-10 Day Outlook (valid February 27-March 2) and 8-14 Day Outlook (valid February 29-March 6) favor a fairly stable pattern of warmer-than-normal temperatures from the Plains to East Coast and cooler-than-normal temperatures over the West and Alaska. The outlook is for above-normal precipitation over much of the CONUS, especially along the West Coast and Great Lakes, with odds favoring near to below-normal precipitation across the Plains and over most of Alaska.