Written by Sig Silber
I am working with the fine output of the Queensland Australia Department of Science which is associated with the Australian BOM. Queensland figured out that it is not just the level of ENSO (in their work they focused on the SOI Index) that counts but also the trend. I think we are seeing this play out. La Nina has peaked and is starting its decline and that is what I believe will significanly influence our weather. But the next 25 days, which is what we focus on, will be impacted mostly by the MJO which in itself is a sign that La Nina is on its way out. To undestand the impact on our weather, you need to read the full report.
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December started warm all over but the Arctic Blast at the end skewed the monthly data (actually this only covers Days 2 -31 as it is a 30 day average)
What next? On New Years Eve I expressed skepticism about the NOAA forecast for January, especially the precipitation forecast, and also what that meant for February and March. Weather is a slow process and ENSO phases linger but this La Nina is fading fast. It starts with the ocean heat reserve and the cool anomaly that defines a La Nina is crashing (up). We do not have an El Nino in our future but we do have ENSO Neutral and fairly soon.
This was the 8 – 14 Day Precipitation Outlook published today January 2, 2018
Here is the full-month forecast they just released a day ago.
This is the six-hour snow forecast.
Image Credit: Getty Images. Full story from The Sun here.
I am sure there has been plenty of media coverage of this event which was well forecast. Very good for sellers of winter clothing. Not necessarily well located for a large part of the upscale ski industry. Did not do much for the overall drought situation of the U.S. THE PATTERN MAY BE CHANGING BUT IT CONTINUES TO BE THE CURRENT PATTERN so we continue our snow coverage.
NOAA Snow Forecast looking ahead to Days 4,5 (top Row) 6 and 7 (bottom row). When you view these graphics you can click on them to enlarge them.
A. Now we return to our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii)
I am starting with a summary first for temperature and then for precipitation of small images of the three short-term maps. You can click on these maps to see larger versions. The easiest way to return to this report is by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. Larger maps are available later in the article with the discussion and analysis.
For most people, the summary with the small images will be sufficient. Later in the article for those with sufficient interest there is a full description of the factors determining the maps shown here with a detailed analysis of the ENSO situation which so dramatically impacts the forecasts below.
First Temperature
And then Precipitation
Let us focus on the Current (Right Now to 5 Days Out) Weather Situation.
Water Vapor.
This view of the past 24 hours provides a lot of insight as to what is happening.
You can still see the split in the Jet Stream. There is a storm off the West Coast. What will happen to it is the question of the week.
Below is the same graphic as above but without the animation to show the current situation with respect to water vapor imagery for North America. It also covers more of CONUS.
Tonight, Tuesday evening January 2, 2018, as I am looking at the above graphic, you see some clouds entering Washington State and also some moving through Central California and Southern Nevada.
This graphic is about Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events. You can convert this graphic into a flexible forecasting tool by clicking here. One can obtain views of different geographical areas by clicking here.
Day One CONUS Forecast | Day Two CONUS Forecast |
There is snow forecast for the Great Lakes and also along the East Coast. Earlier I have provided snow forecasts for day 4 through 7 and a link to earlier days. These graphics update and can be clicked on to enlarge but my brief comments are only applicable to what I see on Tuesday night prior to publishing. |
60 Hour Forecast Animation
Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below. The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.
You can enlarge the below daily (days 3 – 7) weather maps for CONUS by clicking on Day 3 or Day 4 or Day 5 or Day 6 or Day 7. These maps auto-update so whenever you click on them they will be forecast maps for the number of days in the future shown.
What is Behind the Forecasts? Let us try to understand what NOAA is looking at when they issue these forecasts.
Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 7. The Day 3 forecast can be found here. the Day 6 Forecast can be found here. Actually all the small graphics below can be clicked on to enlarge them.
When I look at this Day 7 forecast, there is a large strong Low centered over the western Aleutians with surface central pressure of 968 hPa. This Low would appear to be well positioned to pump moisture into the West Coast especially the Northwest. There is another Low furher west off of Kamchatka with surface central pressure of 984 hPa. It may be two centers of the same pattern rather than two distinct lows. There is a High centered over Saskatchewan with surface central pressure of 1032 hPa. Looking at this graphic it would seem that any significant precipitation would be directed north of CONUS or remain near the West Coast. However there is a Low off of California that is not very strong with surface central pressure of 1008 but with access to moist air. That appears to be the main source of the forecast precipitation for the Day 8 – 14 Period. All in all, the pattern still seems further to the north than usual for January.
I provided this K – 12 write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 6. It is not the current situation.
The table below showing the Day 3, Day 4, Day 5, Day 6 and Day 7 of this graphic can be useful in thinking about how the pattern of Highs and Lows is expect to move during the week.
Looking at the current activity of the Jet Stream. The below graphics and the above graphics are very related.
Not all weather is controlled by the Jet Stream (which is a high altitude phenomenon) but it does play a major role in steering storm systems especially in the winter The sub-Jet Stream level intensity winds shown by the vectors in this graphic are also very important in understanding the impacts north and south of the Jet Stream which is the higher-speed part of the wind circulation and is shown in gray on this map. In some cases however a Low-Pressure System becomes separated or “cut off” from the Jet Stream. In that case it’s movements may be more difficult to predict until that disturbance is again recaptured by the Jet Stream. This usually is more significant for the lower half of CONUS with the cutoff lows being further south than the Jet Stream. Some basic information on how to interpret the impact of jet streams on weather can be found here and here. I have not provided the ability to click to get larger images as I believe the smaller images shown are easy to read.
Current | Day 5 |
You can see that early in the week a trough is anticipated to impact Central CONUS and later the pattern becomes meridional and is further south. |
Putting the Jet Stream into Motion and Looking Forward a Few Days Also
To see how the pattern is projected to evolve, please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.
This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.
When we discuss the jet stream and for other reasons, we often discuss different layers of the atmosphere. These are expressed in terms of the atmospheric pressure above that layer. It is kind of counter-intuitive to me. The below table may help the reader translate air pressure to the usual altitude and temperature one might expect at that level of air pressure. It is just an approximation but useful.
Re the above, H8 is a frequently used abbreviation for the height of the 850 millibar level (which is intended to represent the atmosphere above the Boundary Layer most impacted by surface conditions), H7 is the 700 mb level, H5 is the 500 mb level, H3 is the 300 mb level. So if you see those abbreviations in a weather forecast you will know what they are talking about.
Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on “earth” adjusting the parameters and then clicking again on “earth” to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns. This amazing graphic covers North and South America. It could be included in the Worldwide weather forecast section of this report but it is useful here re understanding the wind circulation patterns.
500 MB Mid-Atmosphere View
The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA’s latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Because “Thickness Lines” are shown by those green lines on this graphic, it is a good place to define “Thickness” and its uses. The 540 Level generally signifies equal chances for snow at sea level locations. Thickness of 600 or more suggests very intensely heat and fire danger. Sometimes Meteorologists work with the 500 mb heights which provide somewhat similar readings to the “Thickness” lines but IMO provide slightly less specific information. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.
Here is the seven-day cumulative precipitation forecast. More information is available here.
Four- Week Outlook: Looking Beyond Days 1 to 5, What is the Forecast for the Following Three + Weeks?
I use “EC” in my discussions although NOAA sometimes uses “EC” (Equal Chances) and sometimes uses “N” (Normal) to pretty much indicate the same thing although “N” may be more definitive.
First – Temperature
6 – 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on January 2, 2018 was 4 out of 5
8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on January 2, 2018 was 4 out of 5).
Looking further out.
Now – Precipitation
6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on January 2, 2018 was 4 out of 5)
8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on January 2, 2018 was 4 out of 5)
Looking further out.
.
Here is the 6 – 14 Day NOAA discussion released today January 2, 2018 and the Week 3/4 discussion released Friday December 29, 2017
6-10 DAY OUTLOOK FOR JAN 08 – 12 2018
TODAY’S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE PREDICTED 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN. AN AMPLIFIED RIDGE IS FORECAST OVER ALASKA, ASSOCIATED WITH SIGNIFICANTLY POSITIVE HEIGHT ANOMALIES. THIS RIDGE IS FORECAST TO EXTEND SOUTH TO NEAR THE PACIFIC NORTHWEST. AN ANOMALOUS TROUGH IS PREDICTED OFF THE CALIFORNIA COAST. A LARGE, LONGWAVE TROUGH IS ANTICIPATED OVER MUCH OF THE EASTERN TWO-THIRDS OF THE CONUS. HOWEVER THERE’S A GOOD DEAL OF UNCERTAINTY REGARDING HOW DEEP THIS TROUGH WILL BE. OVER THE PAST COUPLE OF DAYS THE ENSEMBLE MEAN SOLUTIONS HAVE TRENDED TOWARDS BUILDING POSITIVE HEIGHT ANOMALIES IN THE EASTERN CONUS, WHILE TODAY’S DETERMINISTIC GFS AND ECMWF RUNS PREDICT A DEEP TROUGH AND LARGE NEGATIVE HEIGHT ANOMALIES IN THIS REGION DURING THE 6-10 DAY PERIOD. THE HIGHER BLEND WEIGHTS WERE GIVEN TO THE ENSEMBLE MEAN SOLUTIONS DUE TO SUBSTANTIALLY HIGHER 500-HPA ANOMALY CORRELATIONS IN THE PAST 60 DAYS, FOLLOWED BY THE 0Z DETERMINISTIC ECMWF RUN, AND THEN THE 0Z AND 6Z DETERMINISTIC GFS RUNS. ENSEMBLE SPREAD (AT 5760 M) IS LOW TO MODERATE OVER THE CONUS, AND MODERATE OVER THE EASTERN PACIFIC. [Editor’s Note: But they are highly confident even as their models are bouncing all over the place]
LARGE POSITIVE HEIGHT ANOMALIES ASSOCIATED WITH AN EXPECTED RIDGE OVER ALASKA STRONGLY FAVOR ABOVE NORMAL TEMPERATURES FOR MOST OF THE STATE, EXCEPT FOR PARTS OF SOUTHEAST MAINLAND ALASKA AND THE PANHANDLE, WHERE NORTHEASTERLY SURFACE FLOW IS PREDICTED TO FAVOR NEAR TO BELOW NORMAL TEMPERATURES. A RIDGE FORECAST IN THE WESTERN CONUS INCREASES THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES FOR MOST AREAS WEST OF THE CONTINENTAL DIVIDE, THE CENTRAL HIGH PLAINS, MOST OF THE SOUTHERN PLAINS, AND LOUISIANA. ANOMALOUSLY COLD AIR, SLIDING SOUTH FROM CANADA INTO THE TROUGH PREDICTED IN THE EASTERN HALF OF THE CONUS, ENHANCES THE CHANCES FOR BELOW NORMAL TEMPERATURES FROM THE NORTHERN PLAINS AND EASTERN NEBRASKA EASTWARD ACROSS THE NORTHERN HALF OF THE MISSISSIPPI VALLEY, THE GREAT LAKES REGION AND OHIO VALLEY, THE NORTHERN AND CENTRAL APPALACHIANS, AND THE ATLANTIC COAST STATES FROM MAINE TO MARYLAND AND NORTHERN VIRGINIA. THE TEMPERATURE OUTLOOK FOR THE 6-10 DAY PERIOD IS LARGELY BASED ON THE AUTOMATED TEMPERATURE FORECAST, THE GEFS AND ECMWF CALIBRATED REFORECAST TOOLS, AND DYNAMICAL MODEL TEMPERATURE FORECASTS.
SEVERAL CYCLONIC SYSTEMS ARE FORECAST TO MOVE ACROSS THE ALEUTIANS AND INTO WESTERN MAINLAND ALASKA DURING THE 6-10 DAY PERIOD, FAVORING ABOVE NORMAL PRECIPITATION FOR THAT REGION. THE EASTERN MAINLAND OF ALASKA, AND THE PANHANDLE ARE EXPECTED TO BE EAST OF THE MEAN RIDGE AXIS, UNDER NORTHEASTERLY ANOMALOUS FLOW, WHICH FAVORS DRIER THAN NORMAL CONDITIONS. A PREDOMINANTLY WET PATTERN IS ANTICIPATED OVER THE CONUS, DUE TO MOISTURE STREAMING OUT AHEAD OF THE TROUGH NEAR THE CALIFORNIA COAST, AND ALSO ASSOCIATED WITH SHORTWAVES THAT ARE EXPECTED TO MOVE THROUGH THE LONGWAVE TROUGH OVER THE EAST-CENTRAL CONUS.
THE PRECIPITATION OUTLOOK FOR THE 6-10 DAY PERIOD IS LARGELY BASED ON THE AUTOMATED PRECIPITATION FORECAST, THE GEFS AND ECMWF CALIBRATED REFORECAST TOOLS, DYNAMICAL MODEL PRECIPITATION FORECASTS, AND INSPECTION OF STORM TRACKS AS DEPICTED BY TODAY’S 12Z DETERMINISTIC GFS RUN.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AGREEMENT AND AGREEMENT AMONG THE TOOLS, OFFSET BY SOME UNCERTAINTY IN THE STRENGTH OF THE EASTERN TROUGH.
8-14 DAY OUTLOOK FOR JAN 10 – 16 2018
BY THE WEEK-2 PERIOD, MODELS ARE IN FAIRLY GOOD AGREEMENT THAT RIDGING WILL CONTINUE ACROSS ALASKA, BUT WEAKEN ACROSS THE SOUTHERN PORTION OF THE STATE, AS A DEEPENING TROUGH UNDERCUTS THE RIDGE. OVER THE CONUS, 500-HPA HEIGHTS ARE FORECAST TO BUILD OVER APPROXIMATELY THE NORTHWESTERN QUARTER OF THE COUNTRY. ABOVE NORMAL TEMPERATURES ARE FAVORED ACROSS ALL OF ALASKA, AND ALL AREAS WEST OF THE CONTINENTAL DIVIDE. THE TROUGH ANTICIPATED OVER THE EAST-CENTRAL CONUS IS PREDICTED TO EXTEND FROM ABOUT THE GREAT LAKES REGION TO THE SOUTHERN PLAINS. THIS FEATURE LEADS TO INCREASED ODDS OF BELOW NORMAL TEMPERATURES IN THIS REGION. OUT AHEAD OF THIS TROUGH, RESIDUAL WARMTH IS POSSIBLE ACROSS THE SOUTHERN ATLANTIC COAST STATES. AS WITH THE 6-10 DAY FORECAST PERIOD, A PREDOMINANTLY WET PATTERN IS INDICATED FOR MOST OF THE CONUS. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED IN THE SOUTHWEST CONUS, INCLUDING CALIFORNIA, EARLY IN THE PERIOD, WHICH APPEARS COUNTER-INTUITIVE TO THE PREDICTED 500-HPA RIDGE BUILDING ACROSS THIS REGION. HOWEVER, THIS PRECIPITATION IS ANTICIPATED TO MOVE QUICKLY ACROSS AND OUT OF THE SOUTHWEST CONUS DURING THE EARLY STAGES OF THE WEEK-2 PERIOD. PRONOUNCED ONSHORE FLOW ACROSS SOUTHERN ALASKA LEADS TO ELEVATED ODDS OF ABOVE NORMAL PRECIPITATION, WHILE RIDGING AND ASSOCIATED POSITIVE HEIGHT ANOMALIES LEAD TO INCREASED ODDS OF DRIER THAN NORMAL CONDITIONS IN NORTHERN ALASKA. THE POTENTIAL FOR UPSLOPE PRECIPITATION, AND A DEVELOPING BAROCLINIC ZONE WITH MIXED PRECIPITATION TYPES, WARRANTS A 50 PERCENT PROBABILITY AREA FOR ABOVE NORMAL PRECIPITATION ACROSS CENTRAL AND EASTERN PORTIONS OF THE CONUS.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AGREEMENT AND AGREEMENT AMONG THE TOOLS, OFFSET BY SOME UNCERTAINTY IN THE STRENGTH OF THE EASTERN TROUGH.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON JANUARY 18.
Week 3-4 Forecast Discussion Valid Sat Jan 13 2018-Fri Jan 26 2018 [Editors’ Note: Things are changing fast so this may be out of date at this point not sure.]
The current Week 3-4 outlook continues to suggest a substantial evolution of the large-scale pattern over North America. At present, bitterly cold Arctic air is spread over the eastern half of the CONUS, while persistent anomalous warmth has remained over Alaska. The current circulation appears somewhat tied to the active phase of the Madden-Julian Oscillation, which presently extends across the Western Hemisphere. Lagged composites of the MJO in Phase 7 (over the West Pacific) supports anomalous cold air descending from the Northern Plains through the eastern U.S., along with the anomalous ridging for Alaska that is currently being observed. The MJO presence over the Western Hemisphere is less favorable for extratropical teleconnections, but if the convective envelope reaches the Indian Ocean, as is forecast in the next few days, extratropical responses again become favored via interactions with the East Asian waveguide. As such, the Week 3-4 outlook follows a blend of dynamical model guidance along with empirical guidance relating lagged responses from an MJO signal over the Indian Ocean. These would suggest extension of the Pacific Jet (troughing over Alaska, ridging north of Hawaii) and ridging building across the east; each a substantial departure from recent observations. The response to an MJO event in Phase-2 also favors anomalous negatively-tilted troughing from the Pacific Northwest through Southern Rockies, which the dynamical model guidance supports to varied extents. The current outlook is based predominantly on empirical guidance related to the MJO and La Nina coupled with dynamical model guidance that is consistent among prediction systems and with the aforementioned statistical guidance.
Dynamical model forecasts spanning the Week 3-4 period are somewhat mixed, with general consensus between the CFS, JMA, and most of the Sub-X models supporting: anomalous troughing over Alaska, ridging over California and the eastern Seaboard (associated with the positive phase of the North-Atlantic Oscillation), and either a weakness in anomalous ridging or slight anomalous troughing focused on the Northern Rockies through Southern Plains. The ECMWF is an outlier this week, with blocking over Alaska that projects strongly onto the positive phase of the North Pacific Oscillation-West Pacific (NPO-WP) pattern. This is a reversal from the ECMWF outlook last week, which previously forecast the negative NPO-WP structure now favored by the CFS and JMA. Given the ECMWF’s inconsistency over the last week and its atypical evolution of the Northern Hemisphere circulation relative to the expected MJO response, it was discounted in this outlook compared to the other dynamical models.
The highest forecast probabilities relating to temperature in the current outlook are for above-normal values over the eastern CONUS. A warming trend is apparent here in the evolution between the 6-10 and 8-14 day periods and is anticipated to continue throughout the Week 3-4 timeframe given the typical MJO response and consistent ridging placed here by the dynamical model guidance. The anomalous warmth is also forecast with lesser probabilities to extend across the Southern Plains and into the Southwest, consistent with Week-2 and ridging forecast near the Pacific coastline. A small area of below-normal temperatures is forecast over the Northern Rockies during Week 3-4 in line with the lagged MJO response from the Multiple-Linear Regression tool, MJO composites, and weakness in the forecast height fields among the model guidance. The background La Nina state would also suggest enhanced odds for anomalously cold temperatures across the Northern Rockies, giving further support for inclusion of these potential below-normal temperatures.
With extension of the jet across the Pacific favored in this outlook, the majority of model guidance places above-normal precipitation into the Alaska Panhandle and portions of the Pacific Northwest. There is some uncertainty among the exact orientation of the jet, which limits confidence in these forecast probabilities. Much of California and the Southwest is favored to experience below-normal precipitation given the favored jet placement being north of the region, and the background La Nina state favoring anomalous dryness. Model guidance is consistent in forecasting above-normal precipitation from the Midwest through the Mid-Atlantic in association with shortwave features digging through the weakness in the height field forecast across the West. Below-normal rainfall is also forecast for Florida and parts of the Southeast, given the robust La Nina footprint for the region and the anticipated storm track being north of this area. Lastly, a relatively small portion of southern mainland Alaska is favored for below-normal precipitation with the jet anticipated to be south of the region.
The Hawaiian outlook for Week 3-4 remains highly uncertain as with the prior week. Sea-surface temperature anomalies are now negative across much of the immediate vicinity, though dynamical forecasts for Week 3-4 favor a slight tilt toward above-normal 2-meter temperatures with anomalous ridging forecast near the islands. Given the latest bias-corrected Week-2 guidance, and the lower-frequency nature of climate variability in the tropics, a slight tilt toward below-normal temperatures is indicated across the entire archipelago. Dynamical model guidance suggests enhanced precipitation probabilities further east in the island chain, in line with the greater positive SST anomalies for this region. As such, below-normal rains are forecast in the West with slightly enhanced rainfall probabilities for Hilo.
Some might find this analysis which you need to click to read interesting as the organization which prepares it focuses on the Pacific Ocean and looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of ENSO events.
Analogs to the Outlook.
Now let us take a detailed look at the “Analogs” which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. “Analog” means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 – 14 day Outlook.
Here are today’s analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the Outlook but I have not been regularly analyzing this second set of information. The first set which is what I am using today applies to the 5 and 7 day observed pattern prior to today. The second set, which I am not using, relates to the correlation of the forecasted outlook 6 – 10 days out with similar patterns that have occurred in the past during the dates covered by the 6 – 10 Day Outlook. The second set of analogs may also be useful information but they put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so.
Centered Day | ENSO Phase | PDO | AMO | Other Comments |
Dec 30, 1956 (2) | Neutral | – | – | |
Dec 19. 1985 | Neutral | + | – | |
Dec 20, 1985 | Neutral | + | – | |
Dec 24, 1985 | Neutral | + | – | |
Dec 28 1985 | Neutral | + | – | |
Dec 13, 1988 (2) | La Nina | – | – | |
Dec 24, 1993 | Neutral | + | – | |
Dec 26, 1993 | Neutral | + | – |
(t) = a month where the Ocean Cycle Index has just changed or does change the following month.
The spread among the analogs from December 13 to December 30 is 17 days which is quite tight. I have not calculated the centroid of this distribution which would be the better way to look at things but the midpoint, which is a lot easier to calculate, is about December 22. These analogs are centered on 3 days and 4 days ago (December 29 or December 30). So the analogs could be considered to be out of sync with respect to weather that we are likely to be getting being similar to some extent to what we would expect to have a week earlier in the winter. For more information on Analogs see discussion in the GEI Weather Page Glossary. For sure it iis a rough measure as there are so many historical patterns but not enough to be a perfect match with current conditions. I use it mainly to see how our current conditions match against somewhat similar patterns and the ocean phases that prevailed during those prior patterns. If everything lines up I have my own measure of confidence in the NOAA forecast. Similar initial conditions should lead to similar weather. I am a mathematician so that is how I think about models.
Including the duplicates, there are eight Neutral Analogs, two La Nina analogs and zero El Nino Analogs. The phases of the analogs again this week favor McCabe conditions A and B. McCabe A and B are consistent with the forecast adding support to the level of confidence indicated by NOAA. But the analogs are all associated with AMO – and currently the AMO is in its positive phase raising other questions.
The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. Water Planners might usefully pay attention to the low-frequency cycles such as the AMO and the PDO as the media tends to focus on the current and short-term forecasts to the exclusion of what we can reasonably anticipate over multi-decadal periods of time. One of the major reasons that I write this weather and climate column is to encourage a more long-term and World view of weather.
In color | Black and White same graphics |
McCabe Condition | Main Characteristics |
A | Very Little Drought. Southern Tier and Northern Tier from Dakotas East Wet. Some drought on East Coast. |
B | More wet than dry but Great Plains and Northeast are dry. |
C | Northern Tier and Mid-Atlantic Drought |
D | Southwest Drought extending to the North and also the Great Lakes. This is the most drought-prone combination of Ocean Phases. |
You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.
Historical Anomaly Analysis
When I see the same dates showing up often I find it interesting to consult this list.
Recent CONUS Weather
This is provided mainly to see the pattern in the weather that has occurred recently.
Looking Out Beyond Three Months
On Saturday December 23, 2017 we published our monthly Seasonal Outlook Update and you can access that here. Also on Sunday December 31 we published the January Update and you can access it here. There will be a new Seasonal Outlook issued by NOAA on January 18 which we will report on January 20.
Reference Forecasts Full Month and Three Months.
Below are the Temperature followed by the Precipitation Outlooks for the month and three months shown in the Legend. These map are issued on the Third Thursday of the Month. The maps for the following month (but not the three-month maps) are updated on the last day of the month. The 6 – 10 day and 8 – 14 Day update daily and the Week 3/4 Map Updates every Friday so usually these are more up to date. Also the three shorter-term maps will generally cover a slightly different time period since they update daily as the month progresses. But these reference maps are sometimes useful if one wants to understand how the current month was originally forecast to play out.
B. Beyond Alaska and CONUS Let’s Look at the World which of Course also includes Alaska and CONUS
It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel. They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming. We are now moving into early January and should be to the set of positions shown above for January. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant. Notice the Winter position of the Pacific High.
Forecast for Today (you can click on the maps to enlarge them)
Additional Maps showing different weather variables can be found here.
Forecast for Day 6 (Currently Set for Day 6 but the reader can change that)
World Weather Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the control panel and embed it into my report so that you could use the tool within my report. But if you visit it Click Here and you will be able to use the tool to view temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool. Return to this report by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. It may require hitting it a few times depending on how deep you are into the BOM tool. Below are the current worldwide precipitation and temperature forecasts for six days out. They will auto-update and be current for Day 6 whenever you view them. If you want the forecast for a different day Click Here
Temperature | Precipitation |
Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader. |
And now we have experimental forecasts from the U.S. NAEFS Model.
Temperature | Precipitation |
We see a cold Northeastern North American | You definitely see the La Nina pattern for North America. |
Looking Out a Few Months
Here is the precipitation forecast from Queensland Australia:
It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. Notice the continuance of the underlying driver of the SOI having been consistently positive. CONUS except for the Northwest looks fairly wet, Eastern Australia is wet.
JAMSTEC Forecasts
One can always find the latest JAMSTEC maps by clicking this link. You will find additional maps that I do not general cover in my monthly Update Report. Remember if you leave this page to visit links provided in this article, you can return by hitting your “Back Arrow”, usually top left corner of your screen just to the left of the URL box.
Sea Surface Temperature (SST) Departures from Normal for this Time of the Year i.e. Anomalies
My focus here is sea surface temperature anomalies as they are one of the two largest factors determining weather around the World. If we want to have a good feel for future weather we need to look at the oceans as our weather mostly comes from oceans and we need to look at
- Surface temperature anomalies (weather develops from the ocean surface and
- the changes in the temperature anomalies since that may provide clues as to how the surface anomalies will change based on the current trend of changes. This is not that easy to do since the oceans are deep, there are many currents, winds have an impact etc. Two ways that are available to use are to look at the change in the situation today compared ot the average over a period of time and NOAA also produces a graphic of monthly changes. I use both. The first set of graphics is simply looking at the average compared to today and that is below.
Three Month Average Anomaly | Current Anomaly |
La Nina shows up | La Nina is more intense |
And when we look in more detail at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.
This may be a good time to show the recent values to the indices most commonly used to describe the overall spacial pattern of temperatures in the (Northern Hemisphere) Pacific and the (Northern Hemisphere) Atlantic and the Dipole Pattern in the Indian Ocean.
Most Recent Six Months of Index Values | PDO Click for full list | AMO click for full list. | Indian Ocean Dipole (Values read off graph) | |
October | -0.68 | +0.39 | -0.3 | |
November | +0.84 | +0.40 | 0.0 | |
December | +0.55 | +0.34 | -0.1 | |
January | +0.10 | +0.23 | 0.0 | |
February | +0.04 | +0.23 | +0.2 | |
March | +0.12 | +0.17 | +0.0 | |
April | +0.52 | +0.29 | +0.2 | |
May | +0.30 | +0.32 | +0.2 | |
June | +0.19 | +0.31 | 0.0 | |
July | -0.54 | +0.31 | 0.0 | |
August | -0.64 | +0.31 | +0.4 | |
September | -0.26 | +0.35 | +0.2 | |
October | -0.64 | +0.44 | 0.0 | |
November | -0.52 | +0.35 | 0.0 | |
December 2017 |
Switching gears, below is an analysis of projected tropical hazards and benefits over an approximately two-week period.
* Moderate Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend. ** High Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.
Tropical Activity Possibly Impacting CONUS.
When there is activity and I have not provided the specific links to the storm of “immediate” interest, one can obtain that information at this link. At this point in time, no (new) tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update.
Now let us look at the Western Pacific in Motion.
The above graphic which I believe covers the area from the Dateline west to 100E and from the Equator north to 45N normally shows the movement of tropical storms towards Asia in the lower latitudes (Trade Winds) and the return of storms towards CONUS in the mid-latitudes (Prevailing Westerlies). This is recent data not a forecast. But, it ties in with the Week 1 forecast in the graphic just above this graphic. Information on Western Pacific storms can be found by clicking here. This (click here to read) is an unofficial private source but one that is easy to read.
C. Progress of ENSO
A major driver of weather is Surface Ocean Temperatures. Evaporation only occurs from the Surface of Water. So we are very interested in the temperatures of water especially when these temperatures deviate from seasonal norms thus creating an anomaly. The geographical distribution of the anomalies is very important. To a substantial extent, the temperature anomalies along the Equator have disproportionate impact on weather so we study them intensely and that is what the ENSO (El Nino – Southern Oscillation) cycle is all about. Subsurface water can be thought of as the future surface temperatures. They may have only indirect impacts on current weather but they have major impacts on future weather by changing the temperature of the water surface. Winds and Convection (evaporation forming clouds) is weather and is a result of the Phases of ENSO and also a feedback loop that perpetuates the current Phase of ENSO or changes it. That is why we monitor winds and convection along or near the Equator especially the Equator in the Eastern Pacific.
Starting with Surface Conditions.
TAO/TRITON GRAPHIC (a good way of viewing data related to the part of the Equator and the waters close to the Equator in the Eastern Pacific where we monitor to determining the current phase of ENSO. It is probably not necessary in order to follow the discussion below, but here is a link to TAO/TRITON terminology.
And here is the current version of the TAO/TRITON Graphic. The top part shows the actual temperatures, the bottom part shows the anomalies i.e. the deviation from normal.
Location Bar for Nino 3.4 Area Above and Below
———————————————— | A | B | C | D | E | —————– |
The below table only looks at the Equator (and starting this week I am including large anomalies just off the Equator also) and shows the extent of anomalies along the Equator. The ONI Measurement Area is the 50 degrees of Longitude between 170W and 120W and extends 5 degrees of Latitude North and South of the Equator so the above table is just a guide and a way of tracking the changes. The top rows show El Nino anomalies. The two rows just below that break point contribute to ENSO Neutral.
Subareas of the Anomaly | Westward Extension | Eastward Extension | Degrees of Coverage | Total by ENSO Phase | |
Total | Portion in Nino 3.4 Measurement Area | ||||
These Rows below show the Extent of El Nino Impact on the Equator | |||||
1C to 1.5C (strong) | NA | NA | 0 | 0 | 0 |
+0.5C to +1C (marginal) | NA | NA | 0 | 0 | |
These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator | |||||
0.5C or cooler Anomaly (warmish neutral) | 170E | 175E | 5 | 0 | 15 |
0C or cooler Anomaly (coolish neutral) | 175E | 155W | 30 | 15 | |
These Rows Below Show the Extent of La Nina Impacts on the Equator. | |||||
-0.5C or cooler Anomaly | 155W135W | 145W120W | 25 | 25 | 35 |
-1.0C or cooler Anomaly | 145W120W | 135W115W | 15 | 10 | |
-1.5C or cooler Anomaly | 115W | 110W | 5 | 0 | |
-2.0C or cooler Anomaly | 110W | LAND | 15 | 0 | |
-2.5C or cooler Anomaly | LAND | LAND | 0 | 0 | |
This week only 35 degrees of Longitude along the Equator in the Nino 3.4 Measurement Area registers La Nina values. The other 15 degrees register Neutral. That is not the case for the full +5N and +5S width of the Nino 3.4 Measurement Area but in this analysis we are just looking at the Equator. |
My Calculation of the Nino 3.4 Index
I calculate the current value of the Nino 3.4 Index each Monday using a method that I have devised. To refine my calculation, I have divided the 170W to 120W Nino 3.4 measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.
So as of Monday January 2 in the afternoon working from the January 1TAO/TRITON report [Although the TAO/TRITON Graphic appears to update once a day, in reality it updates more frequently.], this is what I calculated.
Calculation of Nino 3.4 from TAO/TRITON Graphic
Anomaly Segment | Estimated Anomaly | |
Last Week | This Week | |
A. 170W to 160W | -0.5 | -0.1 |
B. 160W to 150W | -0.7 | -0.4 |
C. 150W to 140W | -1.4 | -0.6 |
D. 140W to 130W | -1.3 | -0.6 |
E. 130W to 120W | -1.0 | -0.7 |
Total | -4.9 | -2.4 |
Total divided by five i.e. the Daily Nino 3.4 Index | (4.9)/5 = -1.0 | (-2.4)/5 = -0.5 |
My estimate of the daily Nino 3.4 SST anomaly tonight is -0.5 which is a borderline ENSO La Nina value. NOAA has reported the weekly Nino 3.4 to be -0.6 which is a weak La Nina value. Nino 4 is reported a bit warmer this week at -0.2. Nino 3 is much warmer at -0.9. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported a bit warmer at -1.3. It was up there close to 3 at one time so this index has been declining quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. The same data in graphic form but going back a couple of more years can be found here. The full table of values can be found here.
This graphic brings the Nino 3.4 up to date and is easy to read.
This is probably the best place to AGAIN express the thought that this way of measuring an ENSO event leaves a lot to be desired. Only the surface interacts with the atmosphere and is able to influence weather. The subsurface tells us how long the surface will remain cool (or warm). Anomalies are deviations from “Normal”. NOAA calculates and determines what is “Normal” which changes due to long ocean cycles and Global Warming. So to some extent, the system is “rigged”. Hopefully it is rigged to assist in providing improved weather forecasts. But to assume that any numbers reported can be assumed to be accurate to a high level of precision is foolhardy.
This overlaps with the next topic but I will show it here.
The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2016. We may be at Peak La Nina but it has now only a few months to run and we are starting our La Nina Demise Count Down. But we are not yet ready to predict the end of La Nina readings. Perhaps we are. Let’s say that his Active MJO Phase will temporarily put the Nino 3.4 Index in Neutral Territory. It will rebound to La Nina Territory and the La Nina be over by March but perhaps late February. I was planning to try to graph the slope of the decline to make a prediction as to when it reaches -0.5C. But it already has. It would seem easier to do it that way than to run dollars of machine time to run the NOAA models but I am very old fashioned. The problem is the Nino 3.4 index is measured at the surface so I need to get the correlation of the subsurface cool reservoir to the surface Nino 3.4 Measurements. I think that is what the models do but anything a model can do, one can do with a straight edge. That is Sig Silber’s rule. For most purposes the World is linear. The CDAS graphic which we also show is another way to do the same thing as is the BOM SOI graphic.
Sea Surface Temperature and Anomalies
It is the ocean surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. So we are interested in the actual ocean surface temperatures and the departure from seasonal normal temperatures which is called “departures” or “anomalies”. Since warm water facilitates evaporation which results in cloud convection, the pattern of SST anomalies suggests how the weather pattern east of the anomalies will be different than normal.
A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snapshots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event. I have decided to use the prettied-up version that comes out on Mondays rather that the version that auto-updates daily because the SST Departures on the Equator do not change rapidly and the prettied-up version is so much easier to read. The bottom of the Hovmoeller shows the current readings. Remember the +5, -5 degree strip around the Equator that is being reported in this graphic. So it is the surface but not just the Equator.
This next graphic is more focused on the Equator and looks down to 300 meters rather than just being the surface.
The bottom of the Hovmoeller shows the current situation.
Let us look in more detail at the Equatorial Water Temperatures.
We are now going to look at a three-dimensional view of the Equator and move from the surface view and an average of the subsurface heat content to a more detailed view from the surface down This graphic provides both a summary perspective and a history (small images on the right).
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Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east.
Now for a more detailed look. Below is the pair of graphics that I regularly provide. The date shown is the midpoint of a five-day period with that date as the center of the five-day period. The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters. At different times I have discussed the difference between the actual values and the deviation of the actual values from what is defined as current climatology (which adjusts every ten years except along the Equator where it is adjusted every five years) and how both measures are useful for other purposes.
There is cold water from the Dateline to Land. At the west end of the cool anomaly it is now not quite 200 meters deep and indeed is moving closer to the 150 meter depth. We now have warm water developing west of the Dateline and crossing the Dateline at depth. It is now intruding into the Eastern Pacific Nino 3.4 Measurement Area but at depth not at the surface. La Nina’s days are numbered but in terms of months not weeks or days. |
The 28C Isotherm is at the Dateline, the 27C Isotherm is at the 175W, the 25C Isotherm is at 150W and the 20C Isotherm has reached the surface at about 110W which is not in the Nino 3.4 Measurement area. |
The flattening of the Isotherm Pattern is an indication of ENSO Neutral just as the steepening of the pattern indicates La Nina or El Nino depending on where the slope shows the warm or cool pool to be. That flattening has occurred and we have gone to a Weak La Nina thermocline.
Tracking the change.
Here are the above graphics as a time sequence animation. You may have to click on them to get the animation going.
And now Let us look at the Atmosphere.
And Now the Air Pressure to Confirm that the Atmosphere is Reacting to the Sea Surface Temperature Pattern. The most Common way to do that is to use an Index called the SOI.
This index provides an easy way to assess the location of and the relative strength of the Convection (Low Pressure) and the Subsidence (High Pressure) near the Equator. Experience shows that the extent to which the Atmospheric Air Pressure at Tahiti exceeds the Atmospheric Pressure at Darwin Australia when normalized is substantially correlated with the Precipitation Pattern of the entire World. At this point there seems to be no need to show the daily preliminary values of the SOI but we can work with the 30 day and 90 day values.
Current SOI Readings
The 30 Day Average on January 2, 2018 was reported as -3.00 which is clearly NOT a La Nina value. The 90 Day Average was reported at 5.47 which is a Neutral ENSO value. Looking at both the 30 and 90 day averages is useful and right now both are in agreement with the 90 day lagging the 30 day as one would expect. But the 30 day SOI is no longer confirming that we have La Nina Conditions nor is the 90 Day. The trend: October/November/December is down i.e. less La Nina-ish and almost a transition to El Nino. So Queensland in their forecast is basing it on a declining SOI and that forecast is shown elsewhere in this report.. |
SOI = 10 X [ Pdiff – Pdiffav ]/ SD(Pdiff) where Pdiff = (average Tahiti MSLP for the month) – (average Darwin MSLP for the month), Pdiffav = long term average of Pdiff for the month in question, and SD(Pdiff) = long term standard deviation of Pdiff for the month in question. So really it is comparing the extent to which Tahiti is more cloudy than Darwin, Australia. During El Nino we expect Darwin Australia to have lower air pressure and more convection than Tahiti (Negative SOI especially lower than -7 correlates with El Nino Conditions). During La Nina we expect the Warm Pool to be further east resulting in Positive SOI values greater than +7).
To some extent it is the change in the SOI that is of most importance. The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Ocean Equatorial Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.
Forecasting the Evolution of ENSO
Here is the primary NOAA model for forecasting the ENSO Cycle. | The CDAS model is a legacy “frozen” NOAA system meaning the software is maintained but not updated. We find it convenient to obtain this graphic from Tropical Tidbits.com |
This model is forecasting a La Nina. It probably is the most aggressive model re being so definitive about the ENSO Phase for this Fall and Winter. Click here to see a month by month version of the same model but without some of the correction methodologies applied. It gives us a better picture of the further out months as we are looking at monthly estimates versus three-month averages. | Notice that since mid-October, the Nino 3.4 Index has been in a declining channel. But it looks like that downward trend has stopped and the Index has bottomed and may be rising soon. The CDAS data It is not in conflict with the primary NOAA model but shows daily values rather then smoothing them out like the CFSv2 Model does. |
he CFS.v2 is not the only forecast tool used by NOAA. The CPC/IRI Analysis which is produced out of The International Research Institute (IRI) for Climate and Society at Columbia University is also very important to NOAA. Below are the November 9 and November 20 CPC/IRI ENSO Forecasts
First let’s look at the November reports
And now the December Reports
This is the discussion
CPC/IRI ENSO Update Published: December 14, 2017
El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued jointly by the Climate Prediction Center/NCEP/NWS and the International Research Institute for Climate and Society
ENSO Alert System Status: La Niña Advisory
Synopsis: La Niña is likely (exceeding ~80%) through the Northern Hemisphere winter 2017-18, with a transition to ENSO-neutral most likely during the mid-to-late spring.
La Niña strengthened during the past month, as indicated by an increasingly prominent pattern of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean (Fig. 1). The latest weekly Niño-3.4 index value was -0.8°C, with the easternmost Niño-3 and Niño-1+2 indices at or below -1.0°C during much of the month (Fig. 2). Sub-surface temperature anomalies weakened slightly during November, but remained significantly negative (Fig. 3) due to the anomalously shallow depth of the thermocline across the central and eastern Pacific (Fig. 4). The atmospheric circulation over the tropical Pacific Ocean also reflected La Niña, with convection suppressed near the International Date Line and enhanced over Indonesia (Fig. 5). The low-level trade winds were stronger than average over the western and central Pacific, with anomalous westerly winds at upper-levels. Overall, the ocean and atmosphere system reflects La Niña.
La Niña is predicted to persist through the Northern Hemisphere winter 2017-18 by nearly all models in the IRI/CPC plume (Fig. 6) and in the North American Multi-Model Ensemble (NMME; Fig. 7). Based on the latest observations and forecast guidance, forecasters favor the peak of a weak-to-moderate La Niña during the winter (3-month Niño-3.4 values between 0.5°C and 1.5°C). In summary, La Niña is likely (exceeding ~80%) through the Northern Hemisphere winter 2017-18, with a transition to ENSO-neutral most likely during the mid-to-late spring (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).
La Niña is anticipated to affect temperature and precipitation across the United States during the upcoming months (the 3-month seasonal temperature and precipitation outlooks will be updated on Thursday December 21st). The outlooks generally favor above-average temperatures and below-median precipitation across the southern tier of the United States, and below-average temperatures and above-median precipitation across the northern tier of the United States
This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog.
The next ENSO Diagnostics Discussion is scheduled for 11 January 2018. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: [email protected].
Forecasts from Other Meteorological Agencies.
Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)
And the ENSO Outlook Discussion Issued on January 3, 2018:
La Niña persists in the tropical Pacific
Pacific Ocean climate patterns indicate a weak La Niña persists in the tropical Pacific. The event is expected to be short-lived, and end in the southern autumn of 2018.
The latest sea surface temperatures in the central to eastern tropical Pacific remain around La Niña levels (0.8 °C below average), while in the atmosphere, cloud patterns also remain typical of La Niña. A recent weakening in the trade winds, and a fall in the Southern Oscillation Index (SOI), are likely to be the result of a Madden–Julian Oscillation (MJO) event, and are not considered a signal of an early La Niña breakdown. However, a build-up of warmer water beneath the surface of the western Pacific may be a precursor to the end of this event in the coming months.
International climate models surveyed by the Bureau indicate that some further cooling of the equatorial Pacific sea surface temperatures is expected over the remainder of the southern summer. Five of the eight models remain within La Niña thresholds during March 2018. However, only one out of eight international climate models remain at La Niña levels by the end of autumn (May). In order for 2017-18 to be considered an event, La Niña conditions need to persist for at least three months.
The Bureau’s model POAMA suggests that sea surface temperatures in the equatorial Pacific will remain within La Niña thresholds throughout summer but begin warming back to borderline neutral levels during autumn.
La Niña typically brings above average rainfall to eastern Australia during summer, particularly in northern New South Wales and Queensland. However, with a weak event expected, this typically means less influence on Australian rainfall. La Niña events can also increase the likelihood of prolonged warm spells for southeast Australia.
Here is the most recent JAMSTEC forecast issued on December 1, 2017
And here is the short discussion.
Dec. 22, 2017 Prediction from 1st Dec., 2017
ENSO forecast:
The La Niña-like condition will persist until late winter of next year. Then the tropical Pacific will return to a normal state by summer.
Indian Ocean forecast:
A normal state in the tropical Indian Ocean will persist until spring of next year.
Regional forecast:
On a seasonal scale, most part of the globe will experience a warmer-than-normal condition, while some parts of northern/eastern U.S., northern Brazil, central Africa, and India will experience a colder-than-normal condition in boreal winter. As regards to the seasonally averaged rainfall, a wetter-than-normal condition is predicted for some parts of Philippine, East Australia, and northern Brazil during boreal winter, whereas most parts of Indonesia, West Australia, southern Europe, western U.S, and eastern China will experience a drier condition during boreal winter. Those are partly due to the La Niña-like condition.
In winter, most parts of Japan might experience somewhat warmer- and drier-than-normal conditions.
Indian Ocean IOD (It updates every two weeks)
Indian Ocean Dipole Outlook Discussion Issued January 3, 2018
The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 31 December was −0.4 °C. All six of the climate models surveyed by the Bureau indicate that the IOD will remain neutral into autumn 2018.
The influence of the IOD on Australian climate is weak during December to April. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents the IOD pattern from being able to form.
The IOD Forecast is indirectly related to ENSO but in a complex way. It is important to understand how and where the IOD is measured.
IOD Positive is the West Area being warmer than the East Area (with of course many adjustments/normalizations). IOD Negative is the East Area being warmer than the West Area. Notice that the Latitudinal extent of the western box is greater than that of the eastern box. This type of index is based on observing how these patterns impact weather and represent the best efforts of meteorological agencies to figure these things out. Global Warming may change the formulas probably slightly over time but it is costly and difficult to redo this sort of work because of long weather cycles.
D. Putting it all Together.
At this time it would seem a La Nina is here for this Winter and Spring with La Nina Conditions already in place. But the situation for next Summer is not yet clear. However, we are getting very close to being able to forecast the end of this La Nina event. But it may only be a temporary end for the Summer and next Fall as it may return for next Winter or Spring. But that is now looking less likely with ENSO Neutral highly likely.
Forecasting Beyond Five Years.
So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast.
The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS. It includes decade by decade predictions through 2050. Predicting a particular year is far harder.
The odds of a climate shift for the Pacific taking place has significantly increased. It may be in progress. The AMO is pretty much neutral at this point (but more positive i.e. warm than I had expected) so it may need to become a bit more negative for the “McCabe A” pattern to become established. That seems to be slow to happen so I am thinking we need at least a couple more years for that to happen. So our assessment is that the standard time for Climate Shifts in the Pacific are likely to prevail and it most likely will be a gradual process with a speed up in less than five years but more than two years. The next El Nino may be the trigger.
E. Relevant Recent Articles and Reports
Weather in the News
Weather Research in the News
Nothing to report
Global Warming in the News
It could give a Global Warming Advocate Indigestion
F. Table of Contents for Page II of this Report Which Provides a lot of Background Information on Weather and Climate Science
The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.
1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)
2. Medium Frequency Cycles such as ENSO and IOD
3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.
4. Computer Models and Methodologies
5. Reserved for a Future Topic (Possibly Predictable Economic Impacts)
G. Table of Contents of Contents for Page III of this Report – Global Warming Which Some Call Climate Change.
The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.
2. Climate Impacts of Global Warming
3. Economic Impacts of Global Warming
4. Reports from Around the World on Impacts of Global Warming
H. Useful Background Information
The current conditions are measured by determining the deviation of actual sea surface temperatures from seasonal norms (adjusted for Global Warming) in certain parts of the Equatorial Pacific. The below diagram shows those areas where measurements are taken.
NOAA focuses on a combined area which is all of Region Nino 3 and part of Region Nino 4 and it is called Nino 3.4. They focus on that area as they believe it provides the best correlation with future weather for the U.S. primarily the Continental U.S. not including Alaska which is abbreviated as CONUS. The historical approach of measurement of the impact of the sea surface temperature pattern on the atmosphere is called the Southern Oscillation Index (SOI) which is the difference between the atmospheric pressure at Tahiti as compared to Darwin Australia. It was convenient to do this as weather stations already existed at those two locations and it is easier to have weather stations on land than at sea. It has proven to be quite a good measure. The best information on the SOI is produced by Queensland Australia and that information can be found here. SOI is based on Atmospheric pressure as a surrogate for Convection and Subsidence. Another approach made feasible by the use of satellites is to measure precipitation over the areas of interest and this is called the El Nino – Southern Oscillation (ENSO) Precipitation Index (ESPI). We covered that in a weekly Weather and Climate Report which can be found here. Our conclusion was that ESPI did not differentiate well between La Nina and Neutral. And there is now a newer measure not regularly used called the Multivariate ENSO Index (MEI). More information on MEI can be found here. The jury is still out on MEI and it it is not widely used.
The below diagram shows the usual location of the Indo-Pacific Warm Pool. When the warm water shifts to the east we have an El Nino; to the west a La Nina.
Interaction between the MJO and ENSO
This Table is a first attempt at trying to relate the MJO to ENSO
El Nino La Nina MJO Active Phase MJO Inactive Phase Relationship of MJO and ENSO Eastern Pacific Easterlies Western Pacific Westerlies MJO Active Phase MJO Inactive Phase
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Table needs more work. Is intended to show the interactions. What is more difficult is determining cause and effect. This is a Work in Progress.
History of ENSO Events as measured by the ONI
The new SON reading of -0.7 is the first La Nina Reading. These would have to extend through JFM 2018 for this to be recorded as a La Nina. The chances of this are about 50:50. The full history of the ONI readings can be found here. The MEI index readings can be found here.
Four Quadrant Jet Streak Model Read more here This is very useful for guessing at weather as a trough passes through. It would apply to the states that are at the apex of the trough.
If the centripetal accelerations owing to flow curvature are small, then we can use the “straight” jet streak model. The schematic figure directly below shows a straight jet streak at the base of a trough in the height field. The core of maximum winds defining the jet streak is divided into four quadrants composed of the upstream (entrance) and downstream (exit) regions and the left and right quadrants, which are defined facing downwind.
Isotachs are shaded in blue for a westerly jet streak (single large arrow). Thick red lines denote geopotential height contours. Thick black vectors represent cross-stream (transverse) ageostrophic winds with magnitudes given by arrow length. Vertical cross sections transverse to the flow in the entrance and exit regions of the jet (J) are shown in the bottom panels along A-A’ and B-B’, respectively. Convergence and divergence at the jet level are denoted by “CON” and “DIV”. “COLD” and “WARM” refer to the air masses defined by the green isentropes.
[Editor’s Note: There are many undefined words in the above so here are some brief definitions. Isotachs are lines of equal wind speed. Convergence is when there is an inflow of air which tends to force the air higher with cooling and cloud formation. Divergence is when there is an outflow of air which tends to result in air sinking which causes drying and warming, Confluence is when two streams of air come together. Diffluence is when part of a stream of air splits off.]