Local Winter Outlook:
Temperaturausblick Winter 2022-23:
Locally, the odds have tilted slightly in the direction ofcolder than usual(not just a tenth of a degree colder than normal, but one of the coldest thirds of the 1991-2020 winters) in northeast Iowa, southeast Minnesota, and western Wisconsin.
Weilcolder than usual?
- Cheap things for a colder than normal winter.
- Weak LaNiñas (41% probability this winter) tend to prefer cooler, near-normal winters. Only 2 were among the warmest thirds.
- ModerateLa Niñas (27% probability this winter) tends to fall in the coldest third of winters. Of the 6 moderate La Niñas, 4 were in the coldest third and 2 were near normal. On the negative side, the last 2 winters have been temperate La Niñas and both have been near normal. Note that this is a small sample size.
- IsCFS-Version 2The climate model favors cooler than normal temperatures for this winter.
- Sea surface temperatures above normalin the North Pacific also favor cooler than normal temperatures in the north-central US and the Great Lakes. However, these sea surface temperature anomalies can change rapidly, so they are not always good for seasonal forecasts.
- Unfavorable things for a colder-than-normal winter.
- Very few winters have been in the coldest third (normal optimal climate) in the last decade. La Crosse had only 1 winter in the coldest third and Rochester had only 2 winters (2013-14 and 2018-19) in the coldest third.
- Since the late 1980s, LaNiña winters have varied widely in La Crosse. There were 4 warmer than normal, 4 almost normal and 5 colder (5) than normal. Rochester has now had more near-normal (6) winters than colder (3) or warmer (4) than normal winters.
Precipitation forecast winter 2022-23:
in the zonewetter than usual (not just a hundredth of an inch wetter than normal, but one of the wettest winters of 1991-2020)It is slightly favored throughout the upper Mississippi Valley. This was based on recent trends over the last decade.Meanwhile, there are just as many opportunities for northeastern Iowa and southeastern MinnesotaDryer-,Fence-, jwetter than usual.
Why wetter than normal?
- Cheap things for a wetter than normal winter.
- Dynamic climate models suggest much of Wisconsin is wetter than normal.
- In the last 15 years (normal optimum climate)La Crosse, WI had 8 winters that were wetter than normal winters, 4 winters with near normal precipitation, and 3 winters that were drier than normal. Rochester, MN had 9 winters that were wetter than normal, 5 winters with near normal precipitation, and only 1 winter that was drier than normal (2019-20).
- Unfavorable things for a wetter than normal winter
- La Niña can be very variable with rainfall. La Crosse has seen 8 in the wettest third, 8 near normal and 8 in the driest third. Rochester, meanwhile, had 10 near normals, with 7 in the wettest third and 7 in the driest third.
wetter than usualtutNOinevitably means there will be more snow than normal. Seasonal snowfall has varied widely during the 24 La Niñas since 1949-50.
- InLaCrosse WI, 8 were in the third with the most snow, 7 were almost normal and 9 were in the third with the least snow. 19.4" (1975-76) to 73.2" (1974-75): a very wide range.
- InRochester Min,13 were in the snowiest third, 9 were near normal, and 2 were in the lowest third for snow.Those winters averaged 48.9 inches of snowfall, which was 4.2 inches less than the 1991-2020 average of 53.1 inches.
Snowstorms occasionally occur this winter. However, the frequency, number, and intensity of these events cannot be predicted on a seasonal time scale.
What is the girl?:
what is the girl
23. October 2017
La Niña literally means "the little girl". in Spanish. La Niña is also sometimes called El Viejo (Old Man), anti-El Niño, or simply "a cold event" or "a cold episode." La Niña refers to unusually cold water temperatures in central and eastern equatorial waters (5°N-5°S, 120°-170
How is La Nina developing?
During La Niña, surface winds are stronger than normal over the tropical Pacific and most of the tropical Pacific is cooler than average. This is causing more cold water rising off the Peruvian coast, resulting in even colder waters in the central and eastern equatorial waters. Precipitation increases over Indonesia (where the water stays warm) and decreases over the central tropical Pacific (which is cold). There is more upward air movement and lower surface pressure over Indonesia. There is more air movement sinking over the cooler waters of the central and eastern Pacific.
Generalized Walker circulation anomaly (December-February) during the La Niña events overlaid on a map of mean sea surface temperature anomalies. Anomalous cooling of the ocean (blue-green) in the central and eastern Pacific and warming over the western Pacific amplifies the ascending limb of the Walker Circulation over the maritime continent and the descending limb over the eastern Pacific. Enhanced upward movement is also observed in northern South America, while anomalous downward movement is found in East Africa. Drawing from NOAA Climate.gov by Fiona Martin.
How long does La Niña usually last?
La Niña episodes typically last between 9 and 12 months. Both tend to develop in spring (March-June), peak in late autumn or winter (November-February), and then taper off in spring or early summer (March-June). It is common for La Niña. last two years or more. The longest La Niña lasted 33 months.
Global Impact of La Niña:
During La Nina winters, colder than normal temperatures prevail in western and central Canada, Japan, eastern China, southern Brazil, western and southern Africa, and Madagascar. Severe weather prevails in Indonesia, western and central Canada and in south-eastern Africa. Meanwhile, drier than normal conditions are being observed in central South America.
US. The effects of the girl:
There have been large variations in winter temperatures and precipitation patterns during La Niña, but some regions also have some clear trends of above or below normal temperature or precipitation.
The Girl Compositions:
Another way to examine the common features of La Niña winters is to create a composite map (an average of all these individual maps). This highlights the regions that frequently exhibit temperature or precipitation anomalies of the same sign. In terms of temperature, there is a strong trend of below average temperatures in parts of the west and north, particularly in the northern plains, with a weaker signal of above average temperatures in the south east, as shown in the figure below.
Differences in winter temperature from average (degrees F) during La Niña winters date back to the 1950's. Temperatures tend to be colder than average in the northern plains and warmer than average in the southern United States. Image from NOAA Climate.gov using data fromESRLjNCEI.
The differences in winter precipitation from the average (in inches) during La Niña winters date back to the 1950s. Rainfall tends to be below average in the southern United States and wetter than average in the Pacific Northwest and Ohio Valley. Image from NOAA Climate.gov using data fromESRLjNCEI.
The precipitation pattern shown above shows negative anomalies (indicating below-average precipitation) in the southern part of the country, with a weaker signal of above-average precipitation in the Ohio Valley and Pacific Northwest and northern Rocky Mountains.
However, these numbers are based on about 20 different La Niña episodes, many from the 1950s, 1960s, and 1970s, and we have not removed longer-term trends from the temperature and precipitation data used here. The trend is an important part of seasonal temperature forecasts. It's fairly trivial to halve the sample size and compare the temperature histories of the older half to the newer half. This paints a very different picture, with recent events being much warmer on average than previous ones. We can see this by comparing the image on the right below (more recent events) with the image on the left (older events).
Comparison of winter temperature differences from average (degrees F) between the first ten La Niña winters and the most recent ones dating back to 1950. Temperatures tend to be warmer across much of the country during the ten La Niña events during the first ten La Niñas. girls events. Image from NOAA Climate.gov using data fromESRLjNCEI.
This picture is consistent with long-term warming trends in the United States. These historical relationships along with guidance from a range of computer models play an important role in the final perspectives. The differences between the two periods for precipitation mixtures are much smaller and are therefore not shown here.
(1) The tertiles are technically the 33.33rd and 66.67th percentile positions in the distribution. In other words, they are the boundaries between the lower and middle thirds of the distribution and between the middle and upper thirds. These two limits define three categories: below normal, near normal, and above normal. On maps, CPC predictions show the likelihood of the favored categoryonly if there is a preferred category;otherwise they show EC ("Equal Opportunity"). Often the near-normal category remains at 33.33%, and the opposite of the preferred category is below 33.33% by the same amount as the preferred category is above 33.33%. When the probability of the preferred category becomes very large, such as 70% (which is very rare), the above rule for assigning the probabilities for the two unfavorable categories becomes different.
La Nina winter temperatures
Author:tom di liberto(6. October 2017)
If La Niña develops in the central/eastern tropical Pacific, it can affect areas thousands of miles away, including the United States. The effects are usually strongest in the northern hemisphere during winter. However, no two La Niña winters in the United States will have identical temperature and precipitation patterns.
The map series at right shows temperature patterns in the continental United States compared to the 1981-2010 average for each winter season (December through February) since 1950 that coincided with La Niña conditions in the equatorial Pacific. . The years are ranked by how below average the temperatures were.in the central/eastern tropical Pacific: stark(at least -1.5° Celsius colder than average),moderate (between -1° and -1.5°C) andweak(between -0.5° and -1°C colder than average).
In general, the stronger La Niña, the more reliable the effects in the United States. Typical US impacts are warmer and drier than average southern United States conditions, cooler than average North Central Plains conditions, and wetter than average Northwest Pacific stretching north. California.
However, as can be seen from these maps, there is wide variation even between strong La Niña events. For example, 8 of the 11 strong and moderate events show cold conditions in the northern Great Plains, most but not all of which are winter. This "failure" of the typical pattern occurs because La Niña is never thatSoloThing that affects the weather in the United States in winter. Other weather phenomena such as the Arctic Oscillation or the Madden Julian Oscillation as well as the random nature of the weather can also play a role in the outcome of winter.
Winter temperature (December-February) during strong, moderate and weak La Niña since 1950 (not including winter 2017-18)
Midwest La Niña Winter Average Temperature Variances (DJF) (24 winters of 1949-50)
La Niña winter precipitation
Author:tom di liberto(12. October 2017)
If La Niña develops in the central/eastern tropical Pacific, it can affect areas thousands of miles away, including the United States. The effects are usually strongest in the northern hemisphere during winter. However, no two La Niña winters will have identical precipitation patterns.
This map series shows precipitation patterns in the continental United States compared to the 1981-2010 average for each winter season (December through February) since 1950 that coincided with La Niña conditions in the equatorial Pacific. The years are ranked by how below average the temperatures weretropical eastern/central Pacific:stark(at least -1.5° Celsius colder than average),moderate(between -1° and -1.5°C) andweak(between -0.5° and -1°C colder than average).
In general, the stronger La Niña, the more reliable the effects in the United States. Typical US impacts are warmer and drier than average conditions in the southern United States, cooler than average conditions in the north-central plains, and wetter than average conditions in the Valley of Ohio and the Pacific Northwest. /Northern California.
However, as can be seen from these maps, there is wide variation even between strong La Niña events. And some effects are more reliable than others. For example, 9 of the 11 strong and moderate events in the Pacific Northwest show wet conditions above average, although the intensity of the anomaly varies, which is the case in most but not all winters. And 6 of the 11 events produced wet conditions in the Ohio Valley, which is a little over half but nowhere near a guarantee.
This "failure" of the typical pattern occurs because La Niña is never thatSoloThing that affects the weather in the United States in winter. Other weather phenomena such as the Arctic Oscillation or the Madden Julian Oscillation as well as the random nature of the weather can also play a role in the outcome of winter.
Winter (December-February) precipitation during strong, moderate, and weak La Niña since 1950 (not including winter 2017-18)
Midwest La Niña Winter Precipitation Performance (DJF) (24 winters of 1949-50)
La Nina seasonal snow
Author:Stefan Baxter(21. November 2017)
La Nina is connected to areceding jet stream over the North PacificOcean. Jet stream retreat is causing further blockage of high pressure systems simultaneously allowing cooler air into western and central Canada and parts of the contiguous northern US, storm track activity in the southern US - high pressure levels also favoring milder than normal temperatures. The storm's trail is again moving north across portions of the Ohio Valley and Great Lakes (2).
Based on climate analyzes (3) from this new snow dataset, we see that La Niña favors increased snowfall in the northwest and northern Rocky Mountains and the upper Great Lakes region of the Midwest. Reduced snowfall is seen in parts of the central and southern plains, southwest and mid-Atlantic.
Deviation of snowfall from the average for all La Niña winters (1950-2009). Blue shading shows
where snowfall is higher than average and brown shows where snowfall is lower than average.
Climate.gov figure based on CPC analysis usingRutgers rasterized snow data.
This La Niña print is pretty intuitive. Given the northward shift of the storm track, relatively cool and wet conditions are favored over the northern Rocky Mountains and northern plains, resulting in improved snowfall. Warmer, drier winters are more likely during La Niña in the southernmost states, and this is where seasonal snowfall is slowing (4). The stronger storm track and slight trend towards cooler temperatures in the northern US during La Niña slightly increases the likelihood of a relatively snowy winter.
snow and power
We can further subdivide the snow pattern and look at weaker and stronger La Niña events. The breakdown of La Niña events by magnitude reveals some interesting differences that are worth exploring further. In this preliminary analysis below, there is an indication that the weaker events in the NE and northern and central plains are snowier on average.
Deviation of average snowfall from the weakest La Niña winters (1950-2009). Blue shading shows
where snowfall is higher than average and brown shows where snowfall is lower than average.
Climate.gov figure based on CPC analysis usingRutgers rasterized snow data.
On the other hand, the strongest La Niña events (see below) are snowier in the Northwest, northern Rocky Mountains, western Canada and the Alaska Peninsula. Additionally, there is a trend for below-average snowfall over the mid-Atlantic, New England, and northern and central plains that is not seen during a weak La Niña.
Average snowfall performance for the strongest La Niña winters (1950-2009). Blue shading shows
where snowfall is higher than average and brown shows where snowfall is lower than average.
Climate.gov figure based on CPC analysis usingRutgers rasterized snow data.
In general, stronger La Niña events have a greater impact on winter weather patterns in western North America. Lesser events appear to be associated with widespread above-average snow across the northern United States. Since a weak La Niña means that the Pacific forcing is weaker than normal, it may mean that other mechanisms (such as the Arctic Oscillation) are at play and are worth further investigation.
The predictability of seasonal snowfall can be similar to precipitation in that one or two major events can drastically affect the seasonal average. Therefore, in general, the expected predictive power is likely to be lower than for temperature. However, since temperature also plays a role in snowfall, some predictability is still likely. And just like with seasonal temperatures and precipitation, knowing the state of ENSO is a pretty reasonable starting point.
Seasonal snowfall in west-central La Niña (24 winters of 1949-50)
- This new dataset is documented inKlüver et al. (2016)"Creation and Validation of a Complete 1° by 1° Daily North American Gridded Dataset for 1900-2009: Snowfall" in theMarine and Atmospheric Technology Magazine. The data set for this analysis goes back to 2009, so we're looking at winters from 1950/51 to 2008/09. Here all snow accumulation is used in the cold season from October to April.
- This is consistent with the temperature pattern: the storm trail strengthens where the temperature gradient is steeper than normal.
- Here we use a composite analysis to show snowfall. In this case we only take the La Niña years between 1950-51 and 2008-09 and calculate the mean. For strength composites, we divided the 18 La Niña winters between 1951 and 2009 into weak or strong cases. Hemedia ONI valueused to divide them is -0.95 °C on average from December to February (DJF). We must be careful not to draw too many conclusions based on greatly reducing our sample size. Composites also emphasize variance: regions with more year-to-year variability have higher amplitude composite signals.
- Areas in the south that favor below-average snowfall during La Niña are most evident when snowfall weather is relatively high. The signal is most likely to come through the noise there.
The AWSSI girl
Author:Midwest Regional Weather Center
The winter season has significant social implications across all sectors, from direct human health and mortality to commerce, transportation and education. The question "How severe was this winter?" has no easy answer. The severity of a winter depends at least on the intensity and persistence of the cold weather, the amount of snowfall, and the amount and persistence of the snow on the ground.The Cumulative Winter Season Severity Index (AWSSI) was developed to objectively quantify and describe the relative severity of the winter season.
The current season (2022-23) AWSSI can be foundHere.
How does AWSSI accumulate?
First measurable snowfall (>= 0.1 inch)
• Maximum temperature of 32°F or less
The winter season ends with the last occurrence of one of the following conditions:
• Last measurable snowfall (>= 0.1 inch)
Daily scores are calculated based on scores associated with temperature, snowfall, and snow depth thresholds. Daily scores are accumulated throughout the winter season, allowing for a running total of mid-season hardiness and a final cumulative value that characterizes the entire season. The cumulations of the temperature and snow components of the index are calculated separately and then added to the overall index. This allows for a comparison of each individual's relative contribution to the overall score.
The AWSSI was processed for 52 locations across the continental US to provide a variety of locations in different climate regimes for analysis. The AWSSI is calculated for each season from 1950-1951 to 2012-2013. The seasonal data is then quality checked and missing data from seasons that would account for 5% or more of the AWSSI seasons are removed. Means and standard deviations are calculated for daily temperature accumulations and snow levels, as well as the overall AWSSI. AWSSI data is collected hourly during the day.
Quintiles of AWSSI scores were determined for each site. Descriptive categories were assigned to each quintile as follows:
Example of an annotated score page:
CONUS AWSSI during La Niña (23 winters since 1954-55)
La Crosse, WIAWSSI during La Niña (23 winters since 1954-55)
Rochester, MNAWSSI during La Niña (23 winters of 1954-55)
Information sheet (2 pages) - pdf
Cumulative Winter Season Severity Index (AWSSI)
Barbara E Mayes Boustead, Steven D Hilberg, Martha D Shulski, and Kenneth G Hubbard. Journal of Applied Meteorology and Climatology, vol. 54, No. 8, August 2015: 1693-1712.
Abstract|full text |Pdf(2545 KB)
A cumulative winter season severity index. Barbara Mayes Boustead, NOAA/NWS, Valley, NE; and S. Hilberg, M.D. Shulski, and K.G. Hubbard. Presented at the 93rd Annual Meeting of the American Meteorological Society, January 2013.
A Cumulative Winter Season Severity Index (AWSSI).Webinar for the NWS Central Region, February 2017.
For further information please contact Barb Mayes Boustead (firstname.lastname@example.org) at the National Weather Service or Steve Hilberg (email@example.com).
The girl storm:
The girl storm:
Author:Michael K. Tippett and Chiara Lepore
27. April 2017
ENSOchanges the atmospheric circulation(especially theJet-Stream) in a way that affects winterTemperature and precipitation in the United StatesThe changes in spring (March-May) are similar to those in winter, but slightly weaker.
These changes are expected to affect thunderstorm activity as well: El Niño tends to move the jet stream further south across the US, trapping moisture from the Gulf of Mexico and reducing thunderstorm fuel. On the other hand, La Niña is associated with a more wavy and north-shifted jet stream that could increase severe weather activity to the south and southeast. In fact, historic tornadoes erupted1974,2008, and2011started under La Niña conditions.
However, tornado and severe weather activity is more variable ("louder" and harder to predict) than normal weather (think temperature and precipitation), and all ENSO signals are harder to spot. Until recently, there was only winter (January-March) when the ENSO signal is strongest but average tornado activity is relatively low (Cook & Schaefer, 2008).
A recipe for tornadoes
A clearer picture of the impact of ENSO can be obtained if we look at the ingredients that lead to the occurrence of tornadoes and thunderstorms (Allen et al., 2015a). Rather than just looking at individual weather events, it's important to consider the environmental signals of the severe weather outbreak.
Two important ingredients for tornadoes areatmospheric instability(e.g. warm, moist air near the surface and cool, dry air above) andvertical wind shear(Winds of different heights blowing in different directions or speeds). Measurements of these tornado-friendly ingredients can be combined into indices that are less noisy than actual tornado reports and allow us to see how ENSO periods make the environment more or less favorable for severe weather (footnote 1).
Across much of the United States, La Niña conditions have been associated with increases in these environmental factors and reports of tornadoes and hail. The largest signal is present in the south and southeast (including parts of Texas, Oklahoma, Kansas, Louisiana, Arkansas, and Missouri), except in Florida, where the opposite is observed. Positive values indicate increased activity and negative values decreased activity compared to the long-term average (1979-2015).
Figure 1. Sea surface temperature pattern showing the warm phase of the Pacific Decadal Oscillation (top). The state of the PDO between 1950 and this year, shown below, shows a predominantly positive phase from about 1978 to 1998 and a negative phase from about 1999. Image credit: Climate Impacts Group, University of Washington.
In the south and southeast, where the signal is strongest, we see a clear shift in activity with the ENSO phase, but with a huge range of variation, meaning some El Niño years still show severe weather activity and some La Niña years relatively are inactive. While increased tornado activity is generally associated with La Nina conditions, this year's high activity would be attributed to weak La Nina conditions to exaggerate the strength of the historical relationship (footnote 2).
Regional totals (100-90W, 31-36N) of tornado reports for March through May, hail events, a Tornado Environment Index (TEI) and a Hail Environment Index (HEI) expressed as a percentage of their 1979-2015 average and in the ONI conditioned. The edges of the box mark the 25Isand 75IsPercentiles and whiskers span 1.5 times the interquartile range. Figure from climate.gov; data of the authors.
1: The Tornado Environment Index (TEI) and Hail Environment Index (HEI) are functions of monthly averages of convective precipitation, available convective potential energy, and storm-related helicity. TEI and HEI are calibrated to match recent climatology for the number of tornadoes and hail events. See Tippett et al. (2012) and Allen et al. (2015b) for more details.
2: Inside Baseball: Further details of the ENSO relationship
In general, La Niña conditions are associated with increased tornado activity in the US, but more detailed aspects of ENSO may also be relevant (Lee et al., 2012). Sea surface temperature in the Gulf of Mexico is near the part of the US most severely affected by severe weather: Warm surface waters in the Gulf of Mexico in spring increase low-level moisture transport and southward flow and are associated with increased tornado and hail activity in the US (Molina et al., 2016). Gulf of Mexico sea surface temperature is negatively correlated with tropical Pacific sea surface temperature, meaning that when the tropical Pacific is cooler than average (La Niña), the Gulf of Mexico tends to be warmer than average.
The seasonal means (May-July) of the Gulf of Mexico SST can be predicted with some skill (Jung and Kirtman, 2016). Atmospheric angular momentum is related to ENSO and also shows the effects of tropical forcing on tornado activity (Gensini and Marinaro, 2016).
Local La Niña Statistics:
Statistics of past La Niña winters for the region:
In the following tablesRojorepresents a value in the upper third of winters,azulrepresents a value in the lower third of winter, andNegrorepresents a near normal value. For La Crosse, temperature and precipitation dates are from the winter of 1872-73 and snowfall is from 1895-96. For Rochester, temperature and precipitation dates are from the winter of 1886-87 and snowfall is from 1908-09.
|La Niña average monthly mean temperature for La Crosse, WI|
|The Girl Mean||21.1||16.2||20.4||19.2|
|The girl Max||29.2|
|The girl Min||6.4|
(1988-89 and 2020-21)
|La Niña Monthly total rainfall for La Crosse, WI|
|The Girl Mean||1.24||1.04||0,96||3.24|
|The girl Max||2.64|
|The girl Min||0,30|
|Total Monthly Snowfall for La Crosse, WI|
|Average monthly La Nina temperature for Rochester, MN|
|La Nina Monthly total rainfall for Rochester, MN|
|Nevada monthly total for Rochester, MN|
Climate variability: Arctic Oscillation (AO)
Author: LuAnn Dahlman
30. August 2009
The Arctic Oscillation (AO) refers to a pattern of atmospheric circulation in the middle and high latitudes of the Northern Hemisphere. The most obvious reflection of the phase of this oscillation is the north-south orientation of the mid-latitude jet stream that drives the storm. Therefore, AO can have a strong impact on weather and climate in major population centers in North America, Europe, and Asia, especially during winter.
IsAO positive Phaseit is characterized by below-average atmospheric pressure over the Arctic and above-average pressure over the Atlantic and North Pacific. The jet stream is farther north than average under these conditions, and storms can travel north of their usual paths. Therefore, in the mid-latitudes of North America, Europe, Siberia, and East Asia, there are generally fewer bouts of cold air than usual during the positive AO period.
Instead of this,negative phase of AOIt has above-average air pressure over the Arctic region and below-average pressure over the North Pacific and Atlantic. The jet stream moves toward the equator under these conditions, so the airflow surrounding the globe is south of its average position. Consequently, mid-latitude locations are more likely to experience bouts of cold polar air in winter when the AO is negative. In New England, for example, the higher frequencies of coastal storms known as "nor'easters" are associated with the negative phase of AO.
This chart shows the monthly values of the Arctic Oscillation Index.
The AO phases are analogous to the Southern Hemisphere Antarctic Oscillation (AAO), a similar pattern of air pressure anomalies and jet streams in the southern hemisphere. Viewed from above, these specimens show a characteristic ring shape or "ring-shaped" pattern; therefore AO and AAO are also referred to as Northern Annular Mode (NAM) and Southern Annular Mode (SAM), respectively.
MonthlyjDailyValues for the Arctic Oscillation Index are available from the NOAA Climate Prediction Center.
Thompson, D.W.J., S. Lee and M.P. Baldwin, 2002: Atmospheric Processes Determining the Northern Hemisphere Ring Mode/North Atlantic Oscillation. From the AGU monograph on the North Atlantic Oscillation, 293, 85-89.
Thompson, D.W.J. and J.M. Wallace, 2001: Regional climate impacts of the Northern Hemisphere ring mode. Science, 293, 85-89.
Thompson, D.W.J. and J.M. Wallace, 2000: Ring modes in the extratropical circulation. Part I: Month-to-month variability.J.Clima, 13, 1000-1016.
Thompson, D. W. J. and J. M. Wallace 1998: The signature of the Arctic oscillation in the winter temperature and geopotential height fields.Geophysics. Res. Latvian.25, 1297-1300.
Madden Julian Swing:
Climate variability: Madden-Julian Oscillation (MJO)
December 31, 2014
whileMadden-Julian-Oszillation (MJO)) is a lesser-known phenomenon, it can have dramatic effects in mid-latitudes. Several times a year, the MJO makes a major contribution to various extreme events in the United States, including arctic air outbursts during the winter months in the central and eastern parts of the United States.
So what is the MJO?
Think of ENSO as a person driving astationaryExercise bikes all day in the middle of a stage. Its immutable position is associated with ongoing changestropical rainand winds we havepreviously describedas associated with ENSO. Now imagine another cyclist entering the stage from the left and slowly pedaling across the stage, past the stationary bike (ENSO) and exiting the stage from the right. We're going to call this cyclist MJO and he'll be able to cross the stage from left to right multiple times throughout the show.
So unlike ENSO which is stationary, the MJO is amove eastClouds, rain, wind, and pressure disturbances that transit the planet in the tropics, returning to their original starting point in an average of 30 to 60 days. This atmospheric disturbance is distinct from ENSO, which, once established, is associated with persistent features lasting several seasons or longer over the Pacific Ocean basin. There can be multiple MJO events within a season, so the MJO is best described asinterseasonaltropical climate variability (i.e. varies from week to week).
The MJO was first developed in the early 1970s by Dr. Roland Madden and Dr. Paul Julian discovered while studying tropical wind and pressure patterns. They often found regular fluctuations in winds (defined by deviations from the mean) between Singapore and Canton Island in the west-central equatorial Pacific (Madden and Julian, 1971; 1972; Zhang, 2005).
The MJO consists of two parts, vizstages: One is the increase in precipitation (orconvective) and on the other hand the suppressed rain phase. Strong MJO activity often splits the planet in half: one half in the enhanced convection phase and the other half in the suppressed convection phase. These two phases create opposite changes in clouds and rain and all thatDipole(i.e. having two opposing main centers of action) spreads to the east. The location of convective phases is often divided into geographic stages, which climatologists number from 1 to 8, as shown in Figure 1.
illustration 1: Average precipitation difference for all MJO events from 1979-2012 for November-March for the eight phases described in the text. Green shading indicates above average precipitation and brown shading indicates below average precipitation. To first order, the green shaded areas correspond to the extent of the enhanced convective phase of the MJO and the brown shaded areas correspond to the extent of the suppressed convective phase of the MJO. Note the eastward shift of the shaded areas at each successive numbered phase when viewing the figure from top to bottom.
For the MJO to be considered active, this dipole of convectively enhanced/suppressed phases must be present and moving eastward over time. An animated illustration depicting the global extent and eastward spread of these two phases of the MJO is shown here (Fig. 2: Animation).
Figure 2.An animation illustrating the organization of the MJO into its phases of enhanced and suppressed convection during a spring 2005 MJO event. Green shading indicates favorable conditions for large-scale intensified rainfall and brown shading indicates unfavorable conditions for heavy rainfall. The MJO runs from late March to May, when green shading covers half the planet and the other half brown as these areas move west to east over time. Notice how the shader returns to the same spot in the order of about 45 days.
What's behind the pattern?
Let's dig a little deeper and look at some of the features within these two convective phases (Figure 3). In the enhanced convection phase, the surface winds converge and air is pushed up through the entire atmosphere. At the top of the atmosphere, the winds reverse (i.e., diverge). Such upward movement of air in the atmosphere tends to increase condensation and precipitation.
Figure 3:The structure of the surface and upper atmosphere of the MJO during a period in which the enhanced convection phase (thundercloud) is centered in the Indian Ocean and the suppressed convection phase is centered in the west-central Pacific. Horizontal arrows pointing to the left represent wind deviations from average coming from the east, and arrows pointing to the right represent wind deviations from average coming from the west. The entire system drifts eastward over time, eventually orbiting the globe and returning to its point of origin. Climate.gov drawing by Fiona Martin.
In the suppressed convective phase, the winds converge at the top of the atmosphere, forcing the air to descend, and later diverge at the surface (Rui and Wang, 1990). As air descends from high altitudes, it warms and dries out, which suppresses rain.
It is the overall dipole structure shown in Figure 3 that moves from west to east in the tropics over time, causing more cloud, rain, and even thunderstorms in the enhanced convection phase, and more sun and drought in the enhanced phase. suppressed convection.
The changes in precipitation and wind described above affect both the tropics and extratropics, making the MJO important for long-term weather and climate forecasting in the US and many other areas. MJO can modulate the timing and strength of monsoons (e.g. Jones and Carvalho, 2002; Lavender and Matthews, 2009), influence the number and strength of tropical cyclones in almost all ocean basins (e.g. Maloney and Hartmann, 2000) and resulting changes in the jet stream that can cause cold blasts, extreme heat events, and torrential rains in the United States and North America (Higgins et al. 2000, Cassou, 2008, Lin et al., 2009, Zhou et al., 2012, Riddle et al., 2013, Johnson et al., 2014).
The MJO can produce shocks similar to those of ENSO, but which only appear in weekly averages before changing, rather than persisting and therefore appearing in seasonal averages as ENSO does.
Future posts will focus on the details of how we monitor and assess the strength of the MJO, provide details on the impacts and the reasons for those impacts, and describe the current state of predictability of the MJO. Real-time MJO information updated daily or weekly can be found in the NOAA CPCMJO's website.
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Cassou, C., 2008: Intraseasonal Interaction between the Madden Julian Oscillation and the North Atlantic Oscillation.Nature,455, 523-527 doi:10.1038/nature07286 Carta
Higgins, W., J. Schemm, W. Shi und A. Leetmaa, 2000: Extreme Precipitation Events in the Western United States Related to Tropical Forcing.J.Clima,13, 793-820.
Nathaniel C. Johnson, Dan C. Collins, Steven B. Feldstein, Michelle L. L'Heureux, and Emily E. Riddle, 2014: Clever North American winter temperature forecasts for up to 4 weeks based on ENSO and MJO status*.Wea. forecast,29, 23–38.
Jones, C. and L. Carvalho, 2002: Active and rupture phases in the South American monsoon system.J.Clima,15, 905-914.
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Will 2022 be a rough winter? ›
Will 2022–2023 Be a Rough Winter? Generally, yes. Much of the country will deal with bone-chilling cold and loads of snow!Will there be an El Niño in 2023? ›
An El Niño is forecast for 2023 — but it's not certain
But according to the U.S. National Oceanic and Atmospheric Administration (NOAA), the climate is expected to transition to a neutral state by May 2023, and then possibly move into an El Niño phase, a period characterized by warmer sea conditions.
November 2022 to October 2023. Winter will be colder than normal, with near-normal precipitation and above-normal snowfall. The coldest periods will be early December, late January, and mid- to late February. The snowiest periods will be in early and late January and in February in the south.Is there going to be a winter 2022? ›
When Is the Winter Solstice? The first day of winter in the Northern Hemisphere is marked by the winter solstice, which occurs on Wednesday, December 21, 2022, at 4:48 P.M. EST. For the northern half of Earth (the Northern Hemisphere), the winter solstice occurs annually on December 21 or 22.How accurate is the Farmers Almanac 2022? ›
“Traditionally, we're 80 percent accurate … some years are better than other years,” says Tim Goodwin, the publication's associate editor. As for recent winters, The Old Farmer's Almanac claimed an overall accuracy rate of 72 percent for 2021 and 2022.Are winters getting colder? ›
But the scientific jury is still out. The data is clear: Rising global temperatures mean winters are getting milder, on average, and the sort of record-setting cold that spanned the country Friday is becoming rarer.Will there be a heatwave in 2023? ›
The return of the El Niño climate phenomenon later this year will cause global temperatures to rise “off the chart” and deliver unprecedented heatwaves, scientists have warned.Will january 2023 be cold? ›
Further fall in minimum temperatures by about 2°C very likely over many parts of Northwest & central India till 17th January and gradual rise by 3-5°C during 18th-21st January. Fall in minimum temperatures by 2-3°C very likely over East India till 17th and gradual rise by 2-3°C during 18th-21st January.Does El Niño mean more snow? ›
In general, El Niño conditions lead to wetter, snowier conditions in Amarillo and cooler maximum temperatures during the winter. La Niña conditions lead to drier and warmer temperatures overall, with notable extreme cold spells. In stronger El Niño or La Niña episodes, these trends are even greater.What is the winter forecast for Georgia? ›
November 2022 to October 2023. Winter will be colder than normal, with the coldest periods in early December and early and late January. Precipitation will be below normal, with above-normal snowfall in the north.
Will it be a cold winter 2022 in the US? ›
The typical U.S. impacts are warmer- and drier-than-average conditions across the southern tier of the United States, colder-than-average conditions across the north-central Plains, and wetter-than-average conditions in the Pacific Northwest stretching into northern California.What kind of winter is predicted for 2022 in Michigan? ›
November 2022 to October 2023. Winter will be colder than normal, with the coldest temperatures in early December and late January to mid-February. Both precipitation and snowfall will be above normal. The snowiest periods will be in late November to early December and early to mid-January.What kind of winter is predicted for 2022 in Pennsylvania? ›
November 2022 to October 2023. Winter will be colder than normal, with near-normal precipitation and above-normal snowfall. The coldest periods will be early December, late January, and mid- to late February. The snowiest periods will be in early and late January and in February in the south.