Click the link to read the article on the NOAA website (Sukyoung Lee, Kris Karnauskas, Ulla Heede, AND Michelle L’Heureus):

“How will climate change influence ENSO?” is one of the most common questions that we get on the ENSO Blog. While it makes sense folks want to know about the future changes in El Niño and La Niña—are they becoming more/less frequent? stronger? weaker? (1)—there is an even more basic question for future climate change that scientists are pondering:

How will trends in sea surface temperatures change across the equatorial Pacific Ocean? 

It is very likely that the equatorial Pacific Ocean is going to warm up somewhere, but where exactly the strongest warming occurs is an important question. In particular, scientists want to know more about the geographic pattern of trends (2). By modifying the heating in the tropics, these changes will then have knock-on influences across the globe because, as we like to say, what happens in the Pacific does not stay in the Pacific!

The trend pattern is critical to understanding how the average or background atmospheric circulation of the tropical Pacific will change. Remember: the background state of the atmosphere in the tropical Pacific—the Walker Circulation—is fueled by the difference in sea surface temperature between the west and the east.

If temperatures warm faster in the western Pacific than in the eastern Pacific, the background tropical circulation could become more La Niña-like (3). But if the trend pattern changes as global temperatures continue to rise, meaning the east starts warming faster than the west in the future, the whole circulation across the tropical Pacific could become more El Niño-like. So actual ENSO events would be occurring against a different background climate than they do today. Yeah, it’s complicated.

How the sea surface temperature trend pattern will change has profound, world-wide implications for impacts such as regional changes in rainfall, where drought occurs, numbers of tropical cyclones, the rate of global mean warming, ocean biogeochemistry, etc. If you are trying to make decisions based on projections of the future, you need to know the answer. And, at this moment, there is some significant (perhaps even growing) debate that surrounds it.

Some scientists believe the recently observed trends suggest the models may be not reproducing some key mechanisms that are critical to provide accurate projections for the tropical Pacific Ocean. There are some long-standing biases in how models simulate the tropical Pacific that we have covered before on this blog, which could be playing some role.

To help us better understand this question, we have assembled a panel of three experts: Professor Sukyoung Lee at the Pennsylvania State University, Professor Kris Karnauskasat the University of Colorado- Boulder (who has previously written on the ENSO blog), Dr. Ulla Heede who is now a CIRES postdoctoral visiting fellow, following her PhD with Alexey Fedorov at Yale University. Keep in mind that this is not a complete representation of all possible perspectives on the matter, and there are some angles not represented by this group (4).

Questions and Answers

(A) So, what are the trends in sea surface temperature (and other variables) across the tropical Pacific Ocean? Why can’t you just measure past trends and assume they will continue? What’s the problem here?

UH: Since at least 1980, the tropical Pacific warming pattern has become more La Niña-like in the observations. This means that SSTs are warming faster in the western tropical Pacific Ocean than the eastern Pacific, and that surface winds are blowing stronger from east-to-west along the equatorial Pacific Ocean (5). This is opposite to the El Niño-like trend many climate models are projecting into the future because of greenhouse gases. Right now, there is a vigorous debate in the climate community whether the La Niña-like trend we are observing now is being driven by greenhouse gases or has natural causes. Because natural variations in the ocean circulation are slow, it is difficult to estimate the signal of global warming in a short observational record.

KK: It might sound simple, but quantifying those trends in the past observed record is more challenging than you might think! This is because the tropical Pacific is home to ENSO, which can either hide the long-term trends with its large variability, or make trends appear that are just temporary and could change later on.

UH: There is another reason why we cannot simply assume the recently observed La Niña-like trend will continue in the future. Mainly, we don’t know with enough certainty what the trend was before we had satellites monitoring the vast expanse of the tropical Pacific Ocean.

KK: Ulla is right, we have a tougher time reliably estimating the trends prior to the satellite era (late 1970s), and this problem gets even worse prior to the 1950s. Back then the instrumental data (mostly from ships) have gaps and changes in measurement protocols. Think of it like this: ideally, we would like to estimate the trend using as long of a record as possible (going back to the 1800s) but this is hampered by gaps in space and time. With 40 years of satellite data, we can be more confident that we’re accurately measuring the whole tropics, but with that shorter record, it is harder to distinguish trends from just a random pileup of ENSO events.

(B) Why is it so important we know the pattern of tropical Pacific trends? Who cares?

UH: I’d like to rephrase this question another way: What are the climate impacts associated with the tropical Pacific climate change? (6) The short answer is: a lot! This is because the tropical Pacific plays a key role in distributing energy and moisture to the rest of the planet, so any change in the tropical Pacific will be felt in other parts of the world. Let’s look at an example: in the last several decades we have observed drought conditions in many parts of the southwestern United States. This is likely partially related to the stronger tropical Pacific winds (more La Niña-like trends) we have recently observed. So, if the trends in the tropical Pacific changes, we might also see a change in these drought conditions.

SL: During La Niña, the atmospheric circulation over the middle latitudes is unusually wavier in the east-west direction (7). Surface temperatures can also be more variable as this blog recently pointed out. This increased waviness can mean the Arctic tends to be unusually warm and a large area of the North American and Eurasian continents tend to be unusually cold (8). Conversely, during El Niño, the atmospheric circulation is less wavy and the mid-latitude continents tend to be unusually warm and the Arctic tends to be colder than average.

Because climate change might have similar effects, we really need to know how the tropical Pacific sea surface temperature pattern and latent heating [the heating of the atmosphere that occurs when water vapor condenses into rain or clouds] will change. If it becomes more La Niña-like, the likelihood of undesirable conditions such as an even drier southwest U.S., as Ulla mentioned, or an amplified cold continents/warm Arctic pattern, would increase (8). Because most of the population resides in the mid-latitude continents, this clearly has implications for energy and water usage planning.

(C) Why is this happening? Why are future projections more El Niño-like while observations are more La Niña-like? What would even cause more El Niño- vs. more La Niña-like changes?

KK: Perhaps we should not be that surprised that future projections and past observations do not always give the same answer. Future projections are from imperfect computer models, and past observations are from imperfect attempts to measure the vast ocean. The causes of these possible changes have been hotly debated for decades, and it was like “love at first sight” when I was introduced to it as a postdoc!

SL: One explanation is “internal variability,” which essentially suggests that natural causes explain the recent La Niña-like trend. However, recent work by Dr. Richard Seager (here and here), among others, suggests models are either deficient at correctly estimating this internal variability or the response to greenhouse gases may not be right. Either outcome raises some doubts on the future projections of the tropical Pacific made by the current generation of climate models. Thus, it is important to understand the mechanisms that could drive El Niño-like vs. La Niña-like trends.

KK: One mechanism that could lead to more La Niña-like change is that cold water upwelling in the eastern Pacific may keep warming at bay — the idea here is that the coldest waters at depth in the ocean are slower to feel the effects of climate change and provide a break on local rates of warming (see figure above). Another mechanism that could lead to more El Niño-like change is that radiative effects of global warming [the upward transfer of heat away from the surface] would cause the tropical atmosphere to become more stable, slow down the Walker circulation, weaken the upwelling in the eastern Pacific, and lead to more warming there (see figure below).

SL: A final possible mechanism may result in a La Niña-like future. The air over the western Pacific Ocean could become moister, promoting even stronger convection (showers and thunderstorms), and therefore strengthening the Walker circulation. At the same time, in the periphery of the Indo-Pacific warm pool, contraction of the cirrus cloud cover could cause more surface cooling by allowing more infrared radiation to escape to space, again helping to create a more La Niña-like sea surface temperature pattern (see figure below).

(D) Can we reconcile the seemingly different trends in the models versus the observations? Could they both be “right?”

 UH: It is entirely possible that the La Niña-like trends in the Pacific we are observing now are transient (short-term) and will reverse at some point in the next 100 years and start to look more like the modeled projections, with the eastern Pacific Ocean warming faster than the rest of the tropical oceans (9). Even if it is just transient, we need to understand these trends better: is it a response to global warming? (I tend to think so!), natural variability, or some mix of the two? However, this is difficult to diagnose using the models because the historical model simulations (run using observed historical forcings) and the observations still do not agree very well.

KK: It is fair to say both might be “right” in the very general sense that both sets of mechanisms are real and part of the fundamental physics controlling the climate system, but I don’t think we can say that both are right in terms of their relative importance. If the models and observations agreed on what *has* happened since the beginning of the Industrial Revolution, then that would be one thing, but they don’t. As for the future, it is possible that a mixture of physical processes can evolve, and some of Ulla’s work has really been groundbreaking in thinking along those lines. However, I suspect that as time goes on, we will learn that the models are still not representing some of the key ocean processes very well (10), such as the currents and upwelling, and their relation to changes in the wind—especially in places like the eastern equatorial Pacific Ocean where the thermocline is very shallow.

(E) How and when will scientists figure out where we are headed? What more could be done to help resolve this important question?

KK: Progress on the observational side might be slow. I don’t know how much more we can improve our ability to describe historical trends back to the 1800s. Even as different groups of scientists throw new statistical techniques to fill in the gaps, etc., the observational uncertainties aren’t being reduced very much. That said, we now have 40+ years of satellite data. When I started grad school, that was only 22 years. We probably have a few more decades to go, but we are getting closer to an acceptably long satellite record that can distinguish between ENSO, decadal variability, and long-term trends that are arising from human activities.

On the modeling side, heroic efforts are being done at modeling centers around the world to improve the representation of the physical processes. Perhaps gains will come from moving toward higher spatial resolution of the models as computers get cheaper and faster, which I suspect is critical for resolving upwelling, the shear between currents flowing in different directions, and the way that the friction from wind makes its way down into the ocean to influence the currents and mixing. I’m hopeful, and I’m glad I still have a few decades left to work on this fun and important problem!

SL: I agree with Kris that as the length of observational records increases, the impact of the internal variability on the trend diminishes, and therefore increasing the likelihood that the La Niña-like trends we’ve seen represents nature’s response to greenhouse gases. However, it is difficult to lengthen our historical record and infill where there are few measurements, so improving the accuracy of climate models is critical. Kris points out that we need to better resolve the ocean, but I think we also need to focus on how well tropical convection and rainfall is captured, which occur on scales that are unresolved by current model grid spacing. The current generation of parameterizationsstill warms the upper troposphere too aggressively and therefore weakens the simulated Walker circulation, leading to a more El Niño-like state.

For good reason, improving the parameterization is one of the most prominent research activities in climate science. At the same time, I believe that continued efforts should be made to develop new theories and to improve existing theories of fundamental mechanisms. In the meantime, for users who need to make decisions, it is important to recognize that there may be two different “storylines” for the tropical Pacific in the future, which they need to take into account.

Lead Editor: Michelle L’Heureux (NOAA CPC)

Footnotes:

(1) Tom has done a masterful job going over these questions. Check out his most recent post going over the latest IPCC findings related to ENSO and climate change. I also really like his older post using a dimmer switch metaphor.

(2) I’m avoiding using the term “zonal gradient” up top because it involves two fairly jargon-y terms that I think confuse most non-scientific readers. But, for those who are familiar, I’m talking about trends in the zonal gradient across the tropical Pacific Ocean. In other words, we’re interested in the relative rate of trends in tropical sea surface temperature, sea level pressure, rainfall, etc. in the zonal, or east-west, direction—i.e. comparing impacts between the eastern Pacific versus the western Pacific.

(3) Now some readers might ask “Wait, isn’t ENSO already tied to the pattern of sea surface temperatures across the tropical Pacific Ocean? El Niño is associated with ocean temperatures warming up (more than average) in the central and eastern equatorial Pacific and La Niña is linked to cooler ocean temperatures there. So how is this question about trend patterns any different from asking how ENSO itself will change?” Good question smart readers! 

Changes in El Niño and La Niña are most strongly tied to seasonal (3-month) average anomalies in the climate system, and this seasonal variability has its own mechanismsthat result in the growth and decay of events over the span of a year or couple years. In contrast, what we are talking about here is the slower, smaller background changes in the tropical Pacific that occur over multiple decades or even centuries. Even though the timescales and mechanisms are separate and distinct from the seasonal ENSO cycle, folks often use the phrases “El Niño-like change/trends” or “La Niña-like change/trends” to describe these longer, gradual trends.

Although potentially confusing, these terms provide a handy shortcut because El Niño-like change means that these trends will look more El Niño-like over the tropical Pacific (relatively warmer in the central/east Pacific and cooler in the western Pacific) or La Niña-like (relatively cooler in the central/east Pacific and warmer in the western Pacific).

(4) I think Sukyoung Lee’s review paper (which available through open access) is a nice place to start reading about different ideas and approaches (disclosure: two ENSO bloggers are co-authors). There are also more papers that have been released since that review paper was assembled that are also worth checking out:

Hartmann, D. L. (2022). The Antarctic ozone hole and the pattern effect on climate sensitivity. Proceedings of the National Academy of Sciences, 119(35), e2207889119. https://doi.org/10.1073/pnas.2207889119

Wills, R. C. J., Dong, Y., Proistosecu, C., Armour, K. C., & Battisti, D. S. (2022). Systematic climate model biases in the large-scale patterns of recent sea-surface temperature and sea-level pressure change. Geophysical Research Letters, 49, e2022GL100011. https://doi.org/10.1029/2022GL100011

Dong, Y., Pauling, A. G., Sadai, S., & Armour, K. C. (2022). Antarctic ice-sheet meltwater reduces transient warming and climate sensitivity through the sea-surface temperature pattern effect. Geophysical Research Letters, 49, e2022GL101249. https://doi.org/10.1029/2022GL101249

(5) For example, one recent study has shown that the ocean surface near the Galapagos Islands in the far eastern equatorial Pacific cooled down by about a half degree Celsius over the past 40 years.

(6) It is often useful to make a distinction between climate change and climate impacts. Climate change refers to the ‘big picture’ of how earth’s climate is changing in response to more greenhouse gasses in the atmosphere. This includes questions like how much the surface of the planet is warming, how the jet stream is changing, how fast the ice sheets are melting, and – you guessed it – how the tropical Pacific is changing. Climate impacts are the consequences of climate change that impacts humans locally. For example, climate impacts could be increased droughts, more frequent forest fires, flooding of coastal cities, stronger hurricanes making landfall. 

(7) The reason why La Niña events bring about wavier conditions is because the latent heat released during cloud formation in the tropics is mostly confined to the western part of the tropical Pacific. The latent heating generates so-called Rossby waves which are responsible for the aforementioned waviness (see Figure 6 in Lee et al., 2022). If the latent heating is uniform in the east-west direction, the heating cannot generate Rossby waves. Therefore, the more east-west confinement of the latent heating, the more the waviness, which has profound impacts on temperature and precipitation locally around the globe. The pattern of the future tropical Pacific is not necessarily the same as either El Niño or La Niña.

(8) For more details see: 

Lee, S. (2012). Testing of the Tropically Excited Arctic Warming Mechanism (TEAM) with Traditional El Niño and La Niña, Journal of Climate, 25(12), 4015-4022.

Clark, J. P., & Lee, S. (2019). The role of the Tropically Excited Arctic Warming Mechanism on the warm Arctic cold continent surface air temperature trend pattern. Geophysical Research Letters, 46, 8490– 8499. https://doi.org/10.1029/2019GL082714 

(9) Here are some papers that delve on the issue of future Pacific warming:

Heede, Ulla, and Alexey Fedorov. 2021. ‘Eastern Equatorial Pacific Warming Delayed by Aerosols and Thermostat Response to CO2’.

Heede, Ulla K., Alexey V. Fedorov, and Natalie J. Burls. 2020. ‘Timescales and Mechanisms for the Tropical Pacific Response to Global Warming: A Tug of War between the Ocean Thermostat and Weaker Walker’. Journal of Climate, April. https://doi.org/10.1175/JCLI-D-19-0690.1.

Wu, Mingna, Tianjun Zhou, Chao Li, Hongmei Li, Xiaolong Chen, Bo Wu, Wenxia Zhang, and Lixia Zhang. 2021. ‘A Very Likely Weakening of Pacific Walker Circulation in Constrained Near-Future Projections’. Nature Communications12 (1): 6502. https://doi.org/10.1038/s41467-021-26693-y.

Ying, Jun, Matthew Collins, Wenju Cai, Axel Timmermann, Ping Huang, Dake Chen, and Karl Stein. 2022. ‘Emergence of Climate Change in the Tropical Pacific’. Nature Climate Change, March, 1–9. https://doi.org/10.1038/s41558-022-01301-z.

(10) Karnauskas, K. B., J. Jakoboski, T. M. S. Johnston, W. B. Owens, D. L. Rudnick, and R. E. Todd, 2020: The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations. J. Geophys. Res.–Oceans, 125(11), e2020JC016609, doi: 10.1029/2020JC016609.

This paper analyzed a ton of climate models, from the ones that were state-of-the-art a dozen years ago (CMIP3 / IPCC AR4) to the most recent generation of CMIP6 models that fed into the 6^thIPCC Assessment Report. While the currents along the equatorial Pacific have improved over time, there is still a ways to go, and this has implications for how SST changes.

Coats, S., and K. B. Karnauskas, 2018: A role for the Equatorial Undercurrent in the ocean dynamical thermostat. J. Climate, 31, 6245–6261, doi: 10.1175/JCLI-D-17-0513.1.

This paper analyzed a recent generation of global climate models (CMIP5 / IPCC AR5) and found, among other things, that the relationship between the wind stress and the underwater currents does not match observations in the eastern equatorial Pacific, which has implications for how SST changes in that climatically important region.

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

The vast majority of the country was drier than normal for the week with only areas of the southern Plains, South, and Southeast seeing precipitation that was well above normal. Dry conditions were prominent over the central and northern Plains, Midwest, Northeast and Southwest. Most of the country experienced cooler-than-normal temperatures with the greatest departure from normal over the central Rocky Mountains. Warmer-than-normal conditions were observed over the northern Rocky Mountains and in the Southeast with departures of 5-10 degrees above normal. A reassessment of conditions took place for many locations in the West to analyze the current drought intensity levels compared to the suite of indices and indicators used each week. Some adjustments were made based on this analysis and not directly related to anything that took place during the last week…

High Plains

Most of the region was dry for the week with just some light precipitation over eastern Wyoming and surrounding areas. Temperatures were cooler than normal from eastern Colorado through western Kansas and into Nebraska as well as the eastern areas of the Dakotas where temperatures were up to 5 degrees below normal. Temperatures were near normal to slightly above normal through the central to western Dakotas, eastern Wyoming and eastern Kansas. Minimal changes were made this week as only areas of southeast Wyoming improved with a reduction of severe and exceptional drought. Some improvements to severe drought were brought into western North Dakota based on reassessing the data going back a couple of years…

West

Most of the region had a dry week with below-normal precipitation. The exceptions were in California and Nevada with the Sierras picking up above-normal precipitation. Some coastal areas of California were at to slightly above normal from the central to northern portions of the coast. Areas of northwest Washington as well as south-central Washington into northeast Oregon also recorded above-normal precipitation. Temperatures were cooler than normal over much of the region with departures of 10-15 degrees below normal over Nevada, Utah and southern Idaho. Warmer-than-normal temperatures were observed over much of Montana with departures of 5-10 degrees above normal. With a quieter week in the West, a reassessment of drought intensity levels was made over portions of the region where data and indicators were analyzed going back to the last 3-5 years. In areas where there was not a consensus of support for the current drought intensity levels, improvements were made to better reflect where the data were pointing. For the reassessment, severe and extreme drought levels were reduced in Montana and Utah while moderate drought was improved over portions of California and Nevada. Acknowledging that some of these areas are still being impacted by long-term drought issues, the new depiction is better supported by the data. Some of these areas had minimal data support for the new drought intensity levels and this process may need to continue. Improvements were made in western Wyoming based on the short-term while degradation took place in portions of western and northern Oregon as the short-term has been especially dry…

South

Cooler-than-normal temperatures dominated the region from south Texas into Arkansas and Louisiana. Departures in south Texas were 8-10 degrees below normal. Portions of central Oklahoma as well as the panhandle regions of Oklahoma and Texas were normal to above normal and departures were only 2-4 degrees above normal. The same areas that were the warmest were also the driest as west Texas into the panhandles of Oklahoma and Texas did not receive any precipitation. The coastal areas of south Texas and into southern Louisiana were also drier than normal. Central Texas into northern Louisiana and southern Arkansas recorded the most precipitation with up to 200% of normal observed. In the Big Bend area of Texas, well above-normal precipitation was also recorded. In eastern Texas where the most precipitation took place, some improvements to abnormally dry conditions were made. With the continued warm and dry conditions over the Oklahoma panhandle, there was an expansion of extreme and exceptional drought this week with dryness going back 18-24 months. Short-term dryness over portions of west Texas allowed for the reintroduction of abnormally dry conditions. The coastal areas of southern Louisiana are being monitored for degradation…

Looking Ahead

Over the next 5-7 days, an active pattern is expected to develop over the Midwest and into the Southeast, with the greatest precipitation anticipated over Arkansas and southern Missouri as well as throughout the Southeast into the Mid-Atlantic. Temperatures are expected to be above normal over much of the northern Plains into the Midwest and Northeast, with departures of up to 10 degrees above normal. Cooler-than-normal temperatures are anticipated over the West with departures of 8-10 degrees below normal over Utah, Nevada and western Wyoming.

The 6–10 day outlooks show that temperatures are expected to be above normal over the eastern half of the country with the greatest probabilities of above-normal temperatures over the Northeast. Temperatures are anticipated to be cooler than normal over much of the West and Alaska. Much of the country is showing a high probability of above-normal precipitation, with the best chances of above-normal precipitation anticipated to be over the upper Midwest and Great Lakes region. There are above-normal chances of below-normal precipitation over northern Alaska and the Big Bend region of Texas…

Just for grins here’s a gallery of early February US Drought Monitor maps for the past few years.

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

Key Points:

• The average temperature of the contiguous U.S. in January 2023 was 35.2°F, which is 5.1°F above average, ranking as the sixth warmest January on record. New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New Jersey and Maine each had its warmest January on record.
• January precipitation for the contiguous U.S. was 2.85 inches, 0.54 inch above average, ranking in the wettest third of the historical record. 
• A series of nine Atmospheric River events from December 26 to January 17 caused significant flooding, power outages and mudslides in California that resulted in at least 21 deaths, 1,400 rescues and 700 landslides.
• For the first time since 2017 and only the third time since 1950, over 100 tornadoes were confirmed by the National Weather Service during the month of January. 
• According to the January 31 U.S. Drought Monitor report, about 42.7% of the contiguous United States was in drought. Severe to exceptional drought was widespread from the Great Basin to the Pacific Coast and across much of the Great Plains to Mississippi Valley, with moderate to severe drought in parts of the Great Lakes and Southeast and moderate drought in parts of the Northeast and Hawaii.

Other Highlights: Temperature

Generally, temperatures were above average across much of the contiguous U.S. east of the Rockies with near- to below-average temperatures from the central Rockies to the West Coast. New York, Pennsylvania and Indiana each ranked second warmest, with 17 additional states experiencing a top-10 warmest January on record. 

The Alaska statewide January temperature was 10.9°F, 8.7°F above the long-term average. This is the 13th-warmest January in the 99-year period of record for the state. Temperatures were above average across most of the state, while parts of western Alaska and the Aleutians experienced near- to below-average temperatures for the month.

Precipitation 

Precipitation was above average from California to the Great Lakes, from the southern Mississippi Valley to New England and in parts of the Southeast. Precipitation was below average from the Pacific Northwest to the northern Plains and in the Florida Peninsula and parts of the southern Plains and Mid-Atlantic. On the dry side, North Dakotaexperienced their 13th driest January in the 129-year record. Conversely, an abundance of precipitation received during the month resulted in Nebraska ranking third wettest on record. Massachusetts ranked fourth and Rhode Island ranked seventh wettest on record, with four additional states experiencing a top-10 wettest January on record.

Monthly precipitation averaged across the state of Alaska was 3.06 inches, 0.33 inch above average, ranking in the middle third of the 99-year record. Conditions were wetter than average across the North Slope, West Coast, southeast Interior and in parts of the Panhandle. Much of the Gulf of Alaska and northeast Interior experienced near-average conditions while much of central Interior Alaska and the western Aleutian Islands experienced below-average precipitation for the month. 

Other Notable Events

A series of nine atmospheric river events from late December into mid-January dumped a record amount of rain and mountain snow across parts of the western U.S., hitting California particularly hard and causing significant damage to the region including power outages. In California:

• The perpetual deluge resulted in at least 21 deaths and prompted more than 1,400 rescues throughout the state.
• California’s Geological Survey mapped more than 700 reported landslides due to rainfall.
• The San Francisco Bay area experienced its wettest three-week period in 161 years.

January had several notable weather systems that brought severe thunderstorms and an unusually high number of tornadoes to portions of the United States. Over 100 tornadoes have been confirmed by the National Weather Service.  This is the third time since 1950 that January had more than 100 tornadoes during the month.

• On January 2-4, a tornado outbreak occurred across portions of the southern Plains, Southeast and Illinois. A total of 61 tornadoes were confirmed by the National Weather Service. The tornadoes and severe thunderstorms with hail caused significant damage to the region. Nine of these confirmed tornadoes occurred in Illinois on January 3 – the highest number of tornadoes in January for the state since 1989.
• On January 12, severe thunderstorms and tornadoes swept through parts of the Midwest and Southeast. The National Weather Service confirmed 69 tornadoes during this outbreak including two EF-3 tornadoes.
• On January 16, two tornadoes were confirmed by the National Weather Service in Iowa – the state’s first January tornadoes since 1967.

Drought

According to the January 31 U.S. Drought Monitor report, about 42.7% of the contiguous U.S. was in drought, down about 3.6% from the beginning of January. Drought conditions expanded or intensified across portions of the southern Plains, the Florida Peninsula and parts of the Rockies, Pacific Northwest, Midwest and Hawaii. Drought contracted or was eliminated across large parts of the West and Midwest, and portions of the Plains, Great Lakes, Southeast, Northeast and Puerto Rico.

Monthly Outlook

According to the January 31 One-Month Outlook from the Climate Prediction Center, areas from the southern Plains and Great Lakes to the East Coast and Alaska Peninsula favor above-normal monthly mean temperatures in February, with the greatest odds in southern Florida. The best chances for below-normal temperatures are forecasted from the central Rockies to the West Coast. Much of the eastern U.S. and portions of the Northwest and northern Plains as well as southwestern Alaska are favored to see above-normal monthly total precipitation. Below-normal precipitation is most likely to occur across the southern Southwest, south Texas and much of Florida. Drought is likely to persist across much of the West, Plains and portions of the Southeast Coast. Some improvement and/or drought removal is likely to occur across portions of northern California, Oregon, eastern Oklahoma, southeast Kansas,, Michigan and Hawaii. Drought development is likely across parts of Texas and in the Florida Peninsula.

According to the One-Month Outlook issued on February 1 from the National Interagency Fire Center, portions of Texas, Georgia and Florida have above normal significant wildland fire potential during February.

This monthly summary from NOAA National Centers for Environmental Information is part of the suite of climate services NOAA provides to government, business, academia and the public to support informed decision-making. For more detailed climate information, check out our comprehensive January 2023 U.S. Climate Report scheduled for release on February 13, 2023.

Click the link to read the release on the NRCS website (Brian Domonkos):

A consistent series of storms throughout the month of January brought substantial snow accumulation to most mountainous regions of Colorado helping to boost the seasonal snowpack. All major basins received well above normal precipitation in January ranging from 137 percent of normal in the Arkansas and South Platte River basins to a high of 231 percent of normal in the combined San Miguel-Dolores-Animas-San Juan River basins. NRCS Hydrologist Karl Wetlaufer comments that “The precipitation over the last five weeks that has greatly improved the snowpack across most of the state is welcomed news from a water supply standpoint. This is particularly true in western Colorado river basins which have had several years of below normal streamflow volumes resulting from snowmelt runoff.” Currently the Arkansas is the only basin in the state holding a below normal snowpack at 79 percent of normal. The snowpack in other major basins ranges from 101 percent of normal in the Rio Grande River basin to 148 percent in the combined Yampa-White-Little Snake River basin.

Following the trend of January precipitation, the most significant increases in streamflow forecasts over the past month were seen in river basins of western Colorado, as well as the North Platte and Rio Grande River basins. The combined Yampa-White-Little Snake River basin, which had the highest forecasts last month, also had the largest increase in streamflow forecasts with February 1st forecasts for 164 percent of normal April-July flows. Streamflow forecasts in the South Platte and Arkansas basin observed the least change since January 1st. Wetlaufer continued further “In addition to above normal snowpack, we had a particularly wet summer which helped improve soil moisture conditions significantly going into winter. This should help a higher percentage of spring snowmelt make it to stream channels as opposed to being absorbed by dry soils, as it has in recent years.”

Current reservoir storage across the state reflects streamflow runoff trends over the last several years, and in some cases also impacted by reservoir management needs in the broader region. The Gunnison and combined basins of southwestern Colorado continue to have the lowest reservoir storages relative to normal in the state due to extended drought conditions and management priorities. While no major basin in the state is currently holding very much above normal reservoir storage, all others are holding much closer to or slightly above normal volumes. “If current trends in snowpack and streamflow forecasts continue, abundant runoff could even the playing field across the major basins of Colorado with respect to reservoir storage.” concluded Wetlaufer.

Colorado’s Snowpack and Reservoir Storage as of February 1st, 2023

* *For more detailed information about February mountain snowpack refer to the February 1st, 2022 Colorado Water Supply Outlook Report. For the most up to date information about Colorado snowpack and water supply related information, refer to the Colorado Snow Survey website.

Click the link to read the report on the NRCS website. Here’s an excerpt:

Click on a thumbnail graphic to view a gallery of 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

Winter storms brought heavy rain and snow much of the eastern U.S. and from the Pacific Northwest to the central Rockies this week with above-normal precipitation observed from the southern Plains to the Southeast and along the East Coast. Precipitation led to abnormal dryness and drought improvements in the central Plains, Midwest, Southeast and Northeast. Conversely, conditions worsened over dryer areas including Idaho/Montana, southern Texas and the Florida Panhandle. In the eastern United States, temperatures have been above-normal resulting in rain falling over many areas instead of snow. Many cities including New York, Baltimore, Philadelphia and Washington D.C. remain snowless for the season. New York City recently set a new latest first measurable snowfall previously set on Jan 29, 1973. In California, a series of atmospheric rivers brought significant amounts of rain which gave reservoirs a much-needed boost, but California lacks infrastructure to make use of such a massive rainfall. Despite the deluge, the winter storms may not have eased the state’s drought. In Hawaii, a strong low pressure system aloft combined with a low pressure trough at the surface to produce conditions favorable for heavy rainfall and flash flooding over portions of the main islands…

High Plains

A half an inch or more of precipitation fell across parts of Colorado and Wyoming, mainly in the higher elevations, resulting in improvements to moderate to severe (D1-D3) drought and abnormal dryness (D0) in eastern Wyoming and improvements to abnormal dryness western Colorado. Much of the High Plains remains in a holding pattern as areas that received abundant snowfall over the Water Year are slow to make improvements due to the long-term nature of drought in the region…

West

Precipitation was below-normal across the region, especially along the West Coast. Due to weeks of heavy precipitation, from a series of atmospheric rivers, halted most degradations or improvements this week despite the deluge, placing much of the region on a holding pattern. The rain did give reservoirs a much-needed boost, but California’s infrastructure is not set up to make use of such a massive rainfall. Because of California’s system of dams and levees, which try to control surface water flow, underground aquifers are not always able to recharge their overpumped supplies during heavy rain events. When rivers are restricted, less water comes into contact with soil surfaces and less water is therefore able to seep down into aquifers. In the drier areas of the West, moderate (D1) drought expanded into parts of northern Idaho and northwestern Montana due to continued degrading conditions that can be observed in soil moisture, streamflow, and precipitation deficits (up to five inches) for this area. In Utah, much of the state has above normal snowpack but no improvements were made this week based on the current issues with groundwater and depleted reservoirs…

South

A half an inch or more of precipitation fell across much of the South with the heaviest amounts falling across the eastern part of the region. Two inches of more of rainfall fell across parts of eastern Texas, Arkansas, Louisiana and Mississippi, which resulted in moderate to exceptional (D1-D4) drought and abnormal dryness (D0) improvements in Oklahoma; moderate to extreme (D1-D3) and abnormal dryness improvements in eastern Texas; and abnormal dryness improvements in Arkansas, Louisiana and Mississippi. Conversely, drought and abnormal dryness was expanded in western Texas due to lack of rain, precipitation deficits, drying soils and degrading streamflow in the area…

Looking Ahead

The National Weather Service Weather Prediction Center has forecasted a significant ice storm (valid January 30 – February 2) is forecasted to bring freezing rain, sleet, and ice accumulations over portions of the Southern Plains and Mid-South. The storm is expected to bring prolonged power outages and cause treacherous travel conditions. Moving into next week (valid February 4 – February 8), very chilly conditions are expected across the Northeast as cold air and gusty winds settle in under upper-level troughing. Dangerous wind chills and possibly new daily temperature records are in store for much of the Northeast region. Temperatures could stay below zero all day in parts of Maine and in the single digits in much of northern New England. This cold airmass is expected to sink further south along the Eastern Seaboard leading to temperatures 10-20F below normal. Temperatures are expected to rebound across the East as warmer temperatures over the central U.S. migrate eastward after the weekend. The West however could stay around 5-10F below average especially in terms of highs underneath upper troughing. A frontal system could spread some light snow to the Midwest/Great Lakes regions and Northeast this weekend, and amounts could be enhanced downwind of the Great Lakes. Light precipitation is possible along the Eastern Seaboard while the West could expect generally light to moderate precipitation in the form of lower elevation rain and higher elevation snow. At 8 – 14 days, the Climate Prediction Center Outlook (valid February 9 – February 15) calls for below-normal temperatures across much of the West, from the Pacific Northwest to the Southwest, and much of Alaska. Near-normal temperatures are expected in parts of the Northwest, northern and central Rockies and southern Plains, including southwest and eastern Alaska, while the eastern half of the contiguous U.S. and the Alaska Panhandle have the greatest probability of warmer-than-normal temperatures. Most of the U.S. can expect above-normal precipitation with the probability of near-normal precipitation occurring in much of the Northwest, the Florida Peninsula and northern Alaska and in parts of southern Texas.