Written by Sig Silber
MJO plus a pattern shift soon as West-Coast High Pressure retrogrades (the same term used by astrologers) to the west (patterns usually move to the east) allowing a Low-Pressure trough to develop late in the week in the West. Also on Tuesday we get an updated NOAA forecast for November. So I have decided to use this lull (I am not very impressed by the Rex Block off the West Coast) to discuss the MJO so keep on reading.
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Let’s talk about the MJO
This article is a good resource. I extracted a part of the text. I took out the references to graphics and footnotes but the graphics are in the referenced article. After the extracted text, I provide two graphics that are identical to the ones in the B. Geerts and M. Wheeler article. The MJO is a classic meteorological pattern and the graphics are fairly standard and identical or similar graphics are used by all the people who write articles.
In the tropics weather is not as predictable as in mid-latitudes. That is because in mid-latitudes the weather variables (clouds, precipitation, wind, temperature, and pressure) are largely governed by the upper-tropospheric Rossby waves, which interact with surface weather in a process called baroclinic instability. In the tropics there is no such dominant instability or wave motion, and therefore the weather is less predictable for the 1-10 day period. Until recently it was believed that tropical weather variations on time scales less than a year were essentially random.
In 1971 Roland Madden and Paul Julian stumbled upon a 40-50 day oscillation when analyzing zonal wind anomalies in the tropical Pacific. They used ten years of pressure records at Canton (at 2.8 degrees S in the Pacific) and upper level winds at Singapore. The oscillation of surface and upper-level winds was remarkably clear in Singapore. Until the early 1980’s little attention was paid to this oscillation, which became known as the Madden and Julian Oscillation (MJO), and some scientists questioned its global significance. Since the 1982-83 El Niño event, low-frequency variations in the tropics, both on intra-annual (less than a year) and inter-annual (more than a year) timescales, have received much more attention, and the number of MJO-related publications grew rapidly.
The MJO, also referred to as the 30-60 day or 40-50 day oscillation, turns out to be the main intra-annual fluctuation that explains weather variations in the tropics. The MJO affects the entire tropical troposphere but is most evident in the Indian and western Pacific Oceans. The MJO involves variations in wind, sea surface temperature (SST), cloudiness, and rainfall. Because most tropical rainfall is convective, and convective cloud tops are very cold (emitting little longwave radiation), the MJO is most obvious in the variation of outgoing longwave radiation (OLR), as measured by an infrared sensor on a satellite.
Figure 1 (from Elleman 1997) [Editors Note: You can find this graphic in the referenced article but it is not necessary to understand this discussion] shows how the OLR anomalies in the eastern hemisphere propagate to the east at around 5 m/s. The OLR signal in the western hemisphere is weaker, and the recurrence interval for the eastward propagating OLR anomalies in the eastern hemisphere is about 30 to 60 days. How exactly the anomaly propagates from the dateline to Africa (i.e. through the western hemisphere) is not well understood. It appears that near the dateline a weak Kelvin wave propagates eastward and poleward at a speed exceeding 10 m/s.
Associated with the propagation of convective anomalies, the MJO involves variations in the global circulation. The MJO affects the intensity and break periods of the Asian and Australian monsoons and interacts with El Niño. Wet spells in the Australian monsoon occur about 40 days apart. Fairly weak correlations with the midlatitude rainfall patterns and jet stream characteristics have also been found (2).
Structure of a Madden-Julian wave
Within the center of suppressed convection, clear skies associated with a stronger-than-normal trade wind inversion allow more shortwave radiation to reach the ocean surface, causing a slight SST increase as the wave travels eastward. The Trade winds too are stronger than normal, explaining enhanced evaporation from the sea surface.
Easterly winds (and the evaporation rate) weaken near the western edge of the suppressed convection region, and this leads to low-level moisture convergence. This triggers deep convection, leading to the other half of the OLR oscillation, i.e. the region of enhanced convection. This region is comprised of one or more super cloud clusters (SCCs) that move eastward along with the MJ wave. Within the SCCs, westward-moving cloud clusters form at the eastern edge of the SCC and die at the western edge. These smaller clusters have a lifetime of one to two days. In turn, the individual mesoscale convective systems within these smaller clusters typically move eastward, usually by discrete propagation, and have a lifetime of 6-12 hours. The SCCs travel eastward at 5-10 m/s, not as a long-lived storm complex, but rather as a moving wave or oscillation, i.e. the MJO. The MJO has a wavenumber of 1-2, that is at any time there are one or two areas around the equator with enhanced convection, and one or two with suppressed convection.
Equatorially trapped waves (Kelvin and Rossby waves) that explain the evolution of an El Niño event are also the driving mechanism for the MJO. These waves occur in the entire troposphere from 30N to 30S, mainly in the eastern hemisphere. Surface air flows away from the suppressed convection in both zonal directions towards enhanced convection regions. In the upper troposphere, anomalous easterlies exit the west side of the enhanced convection. The strong westerlies from the east side of the enhanced convection flow into the region of suppressed convection. When suppressed convection is strong from the Indian Ocean to the middle Pacific Ocean, anomalous cyclonic gyres at 200 mb trail the region of suppressed convection. Similarly, anticyclonic gyres at 200 mb trail the enhanced convection region once it becomes strong in the Indian and western Pacific Oceans. Gyres in the opposite sense are produced at surface, but they are much weaker than the ones at the tropopause. The zonal circulation and horizontal gyres are important processes by which the MJO shuffles mass around the tropics.
The explanation above is simplistic, in that it idealises the oscillation, as it isolates it from other variations. As mentioned before, the speed and size are variable, and the MJO mainly affects rainfall patterns in Indonesia and surrounding areas. Not all of the elements of the MJO — convection, zonal wind, moisture convergence, and SST anomalies — are always visible. It is only when the 30-60 day oscillations are extracted from a series of MJO events that the idealised picture of the MJO emerges. Consecutive oscillations have varying amplitudes, periods, and wavelengths. The MJO exhibits the mixed Kelvin-Rossby wave structure over the eastern hemisphere, but over the western hemisphere, it only shows a Kelvin wave structure. It moves through the eastern hemisphere at around 5 m/s and through the western hemisphere at a higher speed (at least 10 m/s). The oscillation is stronger in the northern hemisphere winter. It is also in this season that the negative OLR anomalies are most likely to propagate along the equator from the Indian Ocean to the central Pacific Ocean. In the northern hemisphere summer, many of the anomalies veer away from the tropics before they make it to the central Pacific.
Now two key graphics that are identical to the ones in the above paper but not shown as these reproduce better. Everyone uses the same graphics.
NOAA Graphic Source and also for more information
One of many resources for tracking the MJO.
A. Now we focus on Alaska and CONUS (all U.S.. except Hawaii)
I am starting with a summary of small images of the three short-term maps first for temperature and then for precipitation This summary provides a quick look. I could have made it so you could click and enlarge the small images but for the moment I prefer that you go past the summary for the larger versions because if I set up such links, the chances increase that you will not back out of the link properly and get lost. For most people the summary with the small images will be sufficient. Later in the article for those with sufficient interest, you can find the larger maps and a discussion and for reference purposes I then also provide the forecast map for the current or soon to be current full month and the three-month forecast map. These are issued and updated less frequently than the first three maps shown.
There is also a full description of the factors determining the maps shown next and a detailed analysis of the ENSO situation which so dramatically impacts the forecasts below. This is a new approach to presenting information and we hope this is a useful way to do so. Let us know.
Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right →
It is fairly stagnant but not totally. Certainly the anomalies are more muted.
To the right is the week 3 and 4 Forecast.
There are now three warm anomalies and two cool anomalies. The MJO is in the mix. →
← The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems possible.
And then Precipitation
|Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right. →|
Pattern is fairly stagnant. The Rocky Mountain dry anomaly is moving around a bit but that may be artifact. Day 8 (November 7) is supposed to be significant.
To the right is the week 3 and 4 Experimental Forecast. →
Notice the wet Great Lakes Region and dry Southwest and southern West Coast but wet Northwest. La Nina plus MJO
← The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems to be feasible.
Let us focus on the Current (Right Now to 5 Days Out) Weather Situation.
This view of the past 24 hours provides a lot of insight as to what is happening.
You can see the moisture streaming in from the Pacific. It is not really intense.
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, Monday evening October 30, 2017, as I am looking at the above graphic, you can see the Northern Tier moisture mostly in Canada entering from the Pacific. And there is moisture entering the Southwest.
Looking at the current activity of the Jet Stream.
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.
One sees a trough that is not digging very far south. And there is also a disturbance off the coast of California. .
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
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.
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. .
Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 6. The Day 3 forecast can be found here. I used to present the Day 3 with a link to Day 6 but showing Day 6 may be more useful.
When I look at this Day 6 forecast, there is a huge High over Alaska, the Aleutians, and the Pacific. The surface central pressure is 1032 hPa. There is also a very strong Low over Kamchatka with surface central pressure of 980 hPa. But you can also see another Low just off the Northwest Coast with surface central pressure of 1010 hPa. The forecast is for the Blocking High west of that low to retrograde west creating space for that Low to form a trough. One also sees a High over the Northeast. Is this not fun or what?. If you do not like the forecast, wait a day and for most readers of this report, this graphic will have updated by the time you read it.
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.
Now looking at the Day 5 Jet Stream Forecast by one weather forecasting model.
You can again see both the Polar and to a limited extent the Southern Jet Streams. It appears to be zonal flow across CONUS. It could bring precipitation to California and more of the Southwest.
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.
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.
Here is the seven-day cumulative precipitation forecast. More information is available here.
We see mostly small pockets of heavy QPF in two areas one the West Coast and Northwest and the other an area running from Texas to the Great Lakes.
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. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.
Four- Week Outlook
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 October 30, 2017 was 4 out of 5
8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on October 30, 2017 was 3 out of 5).
Looking further out.
Reference Forecasts Full Month and Three Months.
Below is the Temperature Outlook for the month shown in the Legend. This map is first issued on the Third Thursday of the Month for the following month and then 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. Note that the three maps shown at the beginning of this discussion on temperature may cover a slightly different time period since they update as the month progresses and the map below covers a particular month shown in the Legend. It is useful if one wants to understand how that month is forecast to play out.
Below is the Temperature Outlook issued on the date and for the three-month period shown in the Map Legend. Again this is provided for reference only. It is the same map that is included in our Saturday night report that follows the NOAA third Thursday of the month Seasonal Outlook Update. It provides a longer time frame than the above maps. It uses a totally different methodology as it is not possible to use the dynamical models to project out three months. The dynamical models work by figuring out how the current conditions will evolve over a fairly short period of time. To look out three months or longer the approach is more statistical using the forecasted ENSO Phase and Climate Trends.
The theory behind using dynamical models for short-term forecasts (6 10 Days, 8 – 14 Days, and recently Weeks 3-4) and statistical models (Monthly and Three-Months) for longer-term forecasts makes perfect sense but sometimes we see that the short term forecasts and then the actuals do not match the statistical forecasts very well. This tells us that either the statistical forecasts were based on incorrect assumptions or that the actual weather patterns are different from what we might have expected.
Now – Precipitation
6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on October 30 was 4 out of 5)
8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on October 30, 2017 was 3 out of 5)
Looking further out.
Reference Forecasts Full Month and Three Months.
Below is the Precipitation Outlook for the month shown in the Legend. This map is first issued on the Third Thursday of the Month for the following month and then 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. Note that the three maps shown at the beginning of this discussion about precipitation may cover a slightly different time period since they update as the month progresses and the map below covers a particular month shown in the Legend. It is useful if one wants to understand how that month is forecast to play out.
Below is the Precipitation Outlook issued on the date and for the three-month period shown in the Map Legend. Again, this is provided for reference only. It is the same map that is included in our Saturday night report that follows the NOAA third Thursday of the month Seasonal Outlook Update. It provides a longer time frame than the above maps. It uses a totally different methodology as it is not possible to use the dynamical models to project out three months. The dynamical models work by figuring out how the current conditions will evolve over a fairly short period of time. To look out three months or longer, the approach is more statistical using the forecasted ENSO Phase and Climate Trends.
The theory behind using dynamical models for short-term forecasts (6 – 10 Days, 8 – 14 Days and recently Weeks 3-4) and statistical models for longer-term forecasts (Month and three months) makes perfect sense but sometimes we see that the short-term forecasts and then the actuals do not match the statistical forecasts very well. This tells us that either the statistical forecasts were based on incorrect assumptions or that the actual weather patterns are different from what we might have expected.
Here is the 6 – 14 Day NOAA discussion released today October 30, 2017 and the Week 3/4 discussion released Friday October 27, 2017
6-10 DAY OUTLOOK FOR NOV 05 – 09 2017
TODAY’S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN GOOD AGREEMENT ON 500-HPA FLOW PATTERN PREDICTED OVER THE FORECAST DOMAIN. A RIDGE IS PREDICTED OVER THE EASTERN BERING SEA AND WESTERN ALASKA, WHILE AN AMPLIFIED TROUGH IS EXPECTED OVER THE NORTHWESTERN CONUS. DOWNSTREAM, A RIDGE IS ANTICIPATED OVER THE EASTERN CONUS. ENSEMBLE SPREAD IS MODERATE OVER THE MAJORITY OF THE FORECAST DOMAIN. TODAY’S OFFICIAL 500-HPA MANUAL HEIGHT BLEND INDICATES ABOVE NORMAL HEIGHTS OVER ALASKA ALONG WITH THE SOUTH-CENTRAL AND EASTERN CONUS, WHILE NEAR TO BELOW NORMAL HEIGHTS ARE EXPECTED OVER THE WESTERN AND NORTH-CENTRAL CONUS.
BELOW NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL TEMPERATURES FOR THE WESTERN AND THE NORTH-CENTRAL CONUS. THE RIDGE OVER THE EASTERN CONUS WITH ABOVE NORMAL HEIGHTS, ENHANCE PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR THE SOUTH-CENTRAL AND EASTERN CONUS. ABOVE NORMAL HEIGHTS AND ABOVE NORMAL SEA SURFACE TEMPERATURES ENHANCE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR ALASKA AND THE ALEUTIANS EXCEPT THE BELOW NORMAL TEMPERATURE IN THE ALASKA PANHANDLE.
THE TROUGH FORECAST OVER THE WESTERN U.S. FAVORS ABOVE NORMAL PRECIPITATION FOR THE WESTERN AND NORTH-CENTRAL CONUS. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED ACROSS THE UPPER MISSISSIPPI VALLEY, THE GREAT LAKES REGION, THE OHIO AND TENNESSEE VALLEYS, AND THE NORTHEAST IN GOOD AGREEMENT WITH THE GEFS AND ECMWF CALIBRATED REFORECAST TOOLS. NEAR TO ABOVE NORMAL HEIGHTS ENHANCE PROBABILITIES FOR BELOW NORMAL PRECIPITATION FOR THE SOUTHEASTERN CONUS AND SOUTHERN TEXAS. PROBABILITIES OF BELOW NORMAL PRECIPITATION OVER THE CENTRAL GREAT PLAINS ARE RELATED TO THE WESTERLY, DOWN-SLOPE FLOW. ABOVE NORMAL PRECIPITATION IS FAVORED IN ALASKA ASSOCIATION WITH THE STORM TRACK WITH THE NORTHWESTERLY FLOW.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AGREEMENT ON THE EXPECTED FLOW PATTERN OVER MUCH OF THE FORECAST DOMAIN.
8-14 DAY OUTLOOK FOR NOV 07 – 13 2017
ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT TODAY FOR THE WEEK-2 PERIOD OVER MOST OF THE FORECAST DOMAIN. THE OVERALL CIRCULATION PATTERN IS QUITE SIMILAR TO THE 6-10 DAY PERIOD BUT LESS AMPLIFIED DURING WEEK-2. TODAY’S WEEK-2 BLENDED 500-HPA HEIGHT CHART INDICATES NEAR TO ABOVE NORMAL HEIGHTS OVER THE EASTERN AND SOUTH-CENTRAL CONUS AND ALASKA, WHILE NEAR TO BELOW NORMAL HEIGHTS ARE ANTICIPATED OVER THE NORTHWESTERN CONUS.
THE WEEK-2 TEMPERATURE OUTLOOK REFLECTS A STABLE PATTERN WITH SPATIAL COVERAGE OF FAVORED AREAS OF BELOW AND ABOVE-NORMAL TEMPERATURES QUITE SIMILAR TO DAYS 6-10. BELOW-NORMAL TEMPERATURES ARE MOST LIKELY ACROSS THE NORTHERN ROCKIES AND NORTHERN GREAT PLAINS WHERE LARGE NEGATIVE TEMPERATURE ANOMALIES ARE EXPECTED.
THE PRECIPITATION OUTLOOK IS FORECAST TO BE SIMILAR TO THAT OF THE 6-10 DAY PERIOD OVER ALASKA AND THE EASTERN CONUS. THE ONE NOTEWORTHY DIFFERENCE IN THE PRECIPITATION OUTLOOK FOR WEEK-2 COMPARED TO DAYS 6-10 IS NEAR TO BELOW-NORMAL PRECIPITATION FAVORED FOR SOUTHERN CALIFORNIA AND THE DESERT SOUTHWEST DUE TO THE PRECIPITATION SHIFTING EAST OF THE THESE AREAS BY DAY 8.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: AVERAGE, 3 OUT OF 5, DUE TO GENERALLY GOOD MODEL AGREEMENT, OFFSET BY MODERATE SPREAD AMONG INDIVIDUAL ENSEMBLE MEMBERS WITH RESPECT TO THE PACIFIC TROUGH.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON NOVEMBER 16
Week 3-4 Forecast Discussion Valid Sat Nov 11 2017-Fri Nov 24 2017
The Madden-Julian Oscillation (MJO) is currently active over the western Pacific Ocean. Concurrently, there is an ongoing La Nina watch. The active tropics are expected to have an impact on the climate of the North American region and the week 3/4 temperature and precipitation outlooks. The current week 3/4 outlook relies on operational dynamical model forecasts from the ECMWF, JMA, and CFSv2 ensemble prediction systems, as well as experimental forecasts from models of the Subseasonal Experiment (SubX), an experimental multi-model ensemble (MME) of both operational and experimental model systems, as well as statistical forecasts based on the current state of the MJO and ENSO, and considerations of continuity with week 2 forecasts.
Dynamical model forecasts for the week 2 period are characterized by a transition in the large-scale circulation pattern. Variability in the large-scale circulation continues into the week 3/4 period in dynamical model forecasts, increasing uncertainty in the temperature and precipitation outlooks. Despite a transition in the circulation pattern early in the period, model 500-hPa height forecasts for week 2 show good agreement on a prediction of a ridge over the North Pacific extending into western Alaska, and a trough downstream over the CONUS. Model forecasts over recent days have trended towards retrogression of a predicted trough from the central and eastern CONUS to an orientation from central Canada into the western CONUS, as indicated in the current week 2 forecast. Model forecasts for the week 3/4 period consistently predict a trough over North America with significant differences in the location and amplitude of the trough. The CFSv2 and ECMWF ensemble means are somewhat in agreement on an average height pattern for the week 3/4 period indicating de-amplification and westward retrogression of the trough from the week 2 period, such that negative 500-hPa height anomalies are predicted to be centered over western Canada and the Pacific Northwest, while the JMA ensemble mean predicts the mean location of the trough to be over the central CONUS. The SubX MME shows significant differences between component models, while the multi-model mean indicates the trough over the central CONUS.
The week 3/4 temperature outlook relies primarily on consolidated, calibrated probabilistic forecasts of the ECMWF, CFSv2 and JMA models, with some adjustments based on statistical regressions from the MJO RMM indices and experimental forecasts from the SubX MME. Both the consolidation of operational model forecasts and the consensus forecast of the SubX MME are consistent with impacts of the current phase of the MJO in the week 3/4 period, in predicting likely below normal temperatures for parts of the north-central CONUS. Below normal temperatures are most likely for parts of Montana into the Northern Plains, the Upper Mississippi Valley, and the western Great Lakes region, under the predicted trough and northerly flow. Above normal temperatures are most likely for California, the Southwest region, and southern Texas, where most models predict above normal 500-hPa heights during the week 3/4 period. Decadal temperature trends are also consistent with the forecast of likely above normal temperatures for the Southwest region. Above normal temperatures are also likely along the eastern seaboard, where most model forecasts predict anomalously southerly flow ahead of a predicted trough. Uncertainty in the large-scale circulation pattern leads to a forecast of equal chances (EC) for remaining areas of the CONUS.
Above normal temperatures are most likely for western Alaska, under the predicted ridge, and for northern Alaska, where decadal temperature trends are a significant component of variability during the transition season. Below normal temperatures are most likely for southeastern regions of Alaska and the Alaska Panhandle under predicted below normal mid-level heights.
Calibrated probabilistic model forecasts from the ECMWF ensemble support a forecast of likely above normal precipitation for the Pacific Northwest into the northern Rockies, as well as much of the Great Lakes region. The consensus forecast of the experimental SubX MME and statistical forecasts of the impact of the MJO in the week 3/4 period indicate likely above normal precipitation in much of the eastern CONUS, including parts of the Southeast. Statistical forecasts of the impacts of the strong MJO and the calibrated probabilistic consolidated forecast of the ECMWF, CFSv2 and JMA ensembles indicate likely below normal precipitation for central and southern California and the Southwest region into parts of the central and southern Plains. Below normal precipitation is likely for most western and interior regions of Alaska under a predicted ridge. Mixed signals from various forecast tools indicating greater uncertainty leads to a forecast of equal chances (EC) of above and below normal precipitation for other regions, including the Gulf and Atlantic coasts, as well as the southern coast of Alaska.
Hawaii is likely to experience above normal temperatures during the week 3-4 period, with persistent anomalously warm sea surface temperatures around the islands. Dynamical model precipitation forecasts are inconsistent across the islands, resulting in equal chances for above and below normal precipitation.
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.
|Nov 9, 1959||Neutral||+||+|
|Nov 10, 1959||Neutral||+||+|
|Nov 3, 1966||Neutral||–||+|
|Nov 2, 1967||Neutral||–||–|
|Nov 3, 1967||Neutral||–||–|
|Oct 20, 1981||Neutral||+||+|
|Oct 21, 1981||Neutral||+||+|
|Oct 9, 2006||El Nino||–||–|
|Oct 10, 2006||El Nino||–||–|
(t) = a month where the Ocean Cycle Index has just changed or does change the following month.
The spread among the analogs from October 9 to November 10 is 32 days which is a lot wider than last week. 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 October 25. These analogs are centered on 3 days and 4 days ago (October 26 or October 27). So the analogs could be considered to be in sync with respect to weather that we would normally be getting right now. For more information on Analogs see discussion in the GEI Weather Page Glossary.
There are two El Nino analogs (probably due to the MJO), seven Neutral Analogs and zero La Nina analogs. The phases of the ocean cycles of the analogs are consistent with McCabe Conditions C and B which are opposites. The NOAA 6 – 14 Day forecast is not very consistent with McCabe C but more consistent with McCabe B. which reduces my confidence in their forecast. NOAA lists the level of confidence as “4” for the “week one” and declining to “3” for what they call “week two”. I am thinking that their level of confidence might be a bit too high.
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.
Sometimes it is easier to work in black and white especially if you print this report so there is a black and white version from the later report by the same authors. Darker corresponds to red in the color graphic i.e. higher probability of drought.
|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.
Looking Out Beyond Three Months
On Saturday October 21, we published our Three to Four Season Outlook and compared the forecasts of NOAA and JAMSTEC for the first three seasons namely Fall, Winter, and Spring. This report can be accessed here. There will be a new Seasonal Outlook issued by NOAA on November 16 which we will report on November 18.
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.
Here is the 30 Days ending October 21, 2017
The precipitation and temperature patterns are similar but the temperature anomalies have moderated considerably. Remember, this is a 30 average so the most distant seven days are removed and the most recent seven days are added.
And the 30 Days ending October 28, 2017
Overall both the temperature and precipitation anomalies have moderated. There is a new dry area in the North Central states. Remember, this is a 30 average so the most distant seven days are removed and the most recent seven days are added.
B. Beyond Alaska and CONUS Let’s Look at the World which of Course also includes Alaska and CONUS
I will be including the above two graphics regularly as they really help with understanding why things are happening the way they are. I think the (at least intermediate) Source is The Weather Channel and I was able to download the full presentation with difficulty and you can attempt the same thing by clicking here. I think these two graphics are from a much larger set but these two really 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 November so we are 2/3rds between the set of positions shown above for July and the ones shown for January. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant. Notice the Summer position of the Pacific High.
Forecast for Today
Notice that below the map there is a tabulation of magnitude of the current anomalies by region. Overall it is warmer than climatology but less so than recently Eastern CONUS is warm. Both Poles are warm.
This graphic is actuals not anomalies as is the case in the temperature map. We again see the dry area from North Africa through Asia other than extreme Southeast Asia but including most of India. South America south of the ITCZ is wet until you get south of Brazil. Africa north and south of the Equator and the ITCZ is mostly dry. Australia is dry. Italy and Greece are wet.
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
Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader. Brazil is forecast to be warm. Not so much for Tibet. No change from last week.
Notice that in the Day 6 Forecast there is a huge Low south of Greenland. I do not see the Aleutian Low or the trough of the West Coast of CONUS forecast by NOAA.
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 change from the forecast last month due to a change from a consistently positive SOI to a near zero SOI. CONUS now looks like a north south divide with the southern tier wet. Eastern Africa is wet. Australia is slightly dry.
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.
And when we look at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.[NOAA may be having problems updating their daily SST Anomaly Report so I am working with the latest version that I have]
First the categorization of the SST anomalies.
|Mediterranean, Black Sea and Caspian Sea||Western Pacific||West of North America||North and East of North America||North Atlantic|
|Fairly Neutral.||Mostly slightly cool (from cyclones churning up the water)||Cool Kamchatka to south of Aleutians|
Slightly warm off Baja and West Coast of Mexico
|Warm off East Coast|
Warm around Scandinavia,
Fram Strait cool
Indian Ocean Warm west of 80E. Pacific cool east of 140E
|Africa||West of Australia||North, South and East of Australia|
West of South America
|East of South America|
Warm Gulf of Guinea and west of North Africa and Spain.
Cool south and southeast of Africa
Warm east of Madagascar
|Cool and extending way off-shore to the Northwest|
Warm east and southeast.
Cool east of 20S
Warm 30S to 50S
Then we look at the change in the anomalies. Here it gets a little tricky as red does not mean a warm anomaly but a warming of the anomaly which could mean more warm or less cool and blue does not mean cool but more cool or less warm.
|Mediterranean, Black Sea and Caspian Sea||Western North Pacific||West of North America||East of North America||North Atlantic|
Black Sea and Caspian Sea cooling. Western Mediterranean warming, Eastern Mediterranean cooling. This is the same as last week.
Cooling east of Asia.
Warming east of Arabian Peninsula.
Cooling South of Alaska.
Warming in Baja Area.
Warming offshore east of CONUS in a swath the runs mostly south.
Cooling further north and Hudson Bay and Great Lakes
Warming around Spain but again over a smaller area than shown last week.
|Equator||Pacific cooling east of 150W|
|Africa||West of Australia||North, South and East of Australia||West of South America||East of South America|
Warming west of North Africa
Warming south and east of Madagascar
Warming north and east
Cooling 30S and strong warming south of 40S
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)|
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.
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
The pattern now is cold water to the south of the Equator with warm water to the north of the Equator. That means ENSO Neutral.
The below table only looks at the Equator 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|
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)
|+0.5C to +1C (marginal)|
|These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator|
|0.5C or cooler Anomaly (warmish neutral)|
|0C or cooler Anomaly (coolish neutral)|
|These Rows Below Show the Extent of La Nina Impacts on the Equator.|
|-0.5C or cooler Anomaly|
|-1.0C or cooler Anomaly|
|-1.5C or cooler Anomaly|
|-2.0C or cooler Anomaly|
|-2.5C or cooler Anomaly|
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 October 30, in the afternoon working from the October 29 TAO/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||+0.4|
|B. 160W to 150W||-0.7||+0.3|
|C. 150W to 140W||-0.8||+0.0|
|D. 140W to 130W||-0.9||-0.4|
|E. 130W to 120W||-1.0||-0.5|
|Total divided by five i.e. the Daily Nino 3.4 Index||(-3.9)/5 = -0.8||(-0.2/5 = 0.0|
My estimate of the daily Nino 3.4 SST anomaly tonight is 0 which is dead neutral. NOAA has reported the weekly Nino 3.4 to be -05 which is a marginal La Nina value and much cooler than my estimate. Nino 4 is reported warmer at -0.2. Nino 3 is warmer at -0.8. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported the same at -1.4. 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. Notice that all the indices had been declining. The same data in table form but going back a couple of more years can be found here.
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. It is strange to me that the Asian forecasting services generally conclude that that this cool ENSO Phase is not a La Nina but a near La Nina and NOAA concludes it is a La Nina. It is the same ocean. The reported readings are very close but the Asian readings are generally slightly higher (less La Nina-ish) than the NOAA reading and their cut-off points for declaring a La Nina are a bit different and the parts of the Equator they look at are a bit different. It might be explained by what part of the ENSO pattern impacts their area of geography but it just seems to me that NOAA has been a bit over eager. And I wonder why.
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. Two weeks ago it looked a bit like the La Nina would have a short life with the anomaly having peaked, But not with today’s 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. It almost looks like a second Upwelling wave.
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).
Winds or currents are keeping most of the cool water just below the surface. There is cool water at depth from the 170W to LAND. The cool water is reaching the surface mostly east of 120W so it is not in the Nino 3.4 Measurement Area. We also see a pod of warm water at 140E to 130E. This may well signal the end of this La Nina but it will take quite a while for that warm water to arrive in the Nino 3.4 Measurement Area. .
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 175W to Land. To the west it is more than 200 meters deep. We now have the first sign of warm water intruding into the Eastern Nino 3.4 Measurement Area.|
|The 28C Isotherm is at 175W, the 27C Isotherm is at 170W, the 25C Isotherm is at 140W.|
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.
Low-Level Wind Anomalies near the Equator
Here are the low-level wind anomalies.
We now see easterly anomalies in the Nino 3.4 Measurement Area which means that the cool water below the surface will be rising to the surface as the water on the surface is blown to the west.
And now the Outgoing Long-wave Radiation (OLR) Anomalies which tells us where convection has been taking place.
The pattern has changed. We no longer see suppressed Outgoing Long Wave Radiation (OLR) at the Dateline (no longer dry) but we again see enhanced OLR at 120E ( wet)
And Now the Air Pressure which Shows up Mostly in 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 October 30 was reported as 10.93 which is a La Nina value. The 90 Day Average was reported at 6.84 which is a marginal La Nina 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 decline in the 90 Day average needs to be watched.
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.
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.
From Tropical Tidbits.com
The above is from a legacy “frozen” NOAA system meaning the software is maintained but not updated. Notice since mid-July the collapse of Nino 3.4 values from the range of 0.5C to 0.6C down to Zero C and then down to -0.9C but recently moved back closer to 0C.
The 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 is the October 12 and October 19 CPC/IRI ENSO Forecasts
As you can see there has been some recent change to limit the period where La Nina is favored to just the Fall and Winter. The CFS.v2 model holds the La Nina conditions for perhaps an additional two months.
Forecasts from Other Meteorological Agencies.
Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)
Discussion Issued October 24, 2017
La Niña WATCH activated
The El Niño Southern Oscillation (ENSO) is currently neutral. However, models suggest the tropical Pacific Ocean will continue to cool, making the chance of a La Niña forming in late 2017 at least 50%; around double the normal likelihood. While this means the Bureau’s ENSO Outlook has shifted to La Niña WATCH, rainfall outlooks remain neutral due to competing climate drivers.
Following a brief period of warming, tropical Pacific surface waters cooled significantly in the past fortnight, and hence the central to eastern tropical Pacific Ocean is now generally cooler-than-average. Atmospheric indicators of ENSO, including the Southern Oscillation Index (SOI), trade winds and cloudiness near the Date Line, are also approaching La Niña levels.
Seven of the eight international climate models surveyed by the Bureau suggest that sea surface temperatures will reach or exceed La Niña thresholds by November 2017. However, indicators need to remain at La Niña levels for at least three months to be considered an event. This is forecast by six of the eight models. If a La Niña does occur this year it is likely to be short and weak, as sea surface temperatures are forecast to warm again in early 2018, as the austral autumn is the time when La Niña events normally decay.
La Niña events typically bring above average rainfall to eastern Australia during late spring and summer. However, given the competing influence of other climate drivers (weakly warm waters to the north of Australia, and cooler waters in the eastern Indian Ocean), current climate outlooks do not favour widespread rainfall across Australia for November to January. Weak La Niña events in summer can also produce heatwaves in southeast Australia.
Late forming La Niña are rare, but not unheard of
Here is the new JAMSTEC forecast issued on October 1, 2017
The discussion is available in the Seasonal Outlook we published on October 21 which can be accessed here.
Indian Ocean IOD (It updates every two weeks)
The IOD Forecast is indirectly related to ENSO but in a complex way.
Discussion Issued October 24
Indian Ocean Dipole outlooks
The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 22 October was −0.11 °C. All of the climate models surveyed by the Bureau indicate that the IOD will remain neutral into early 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.
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 likely for this Winter and Spring. But the situation for next Summer is not yet clear.
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
Nothing to Report
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 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
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
With respect to relating analog dates to ENSO Events, the following table might be useful. In most cases this table will allow the reader to draw appropriate conclusions from NOAA supplied analogs. If the analogs are not associated with an El Nino or La Nina they probably are not as easily interpreted. Remember, an analog is indicating a similarity to a weather pattern in the past. So if the analogs are not associated with a prior El Nino or prior La Nina the computer models are not likely to generate a forecast that is consistent with an El Nino or a La Nina.
El Ninos and La Ninas
|Start||Finish||Max ONI||PDO||AMO||Start||Finish||Max ONI||PDO||AMO|
|DJF 1950||J FM 1951||-1.4||–||N|
|T||JJA 1951||DJF 1952||0.9||–||+|
|DJF 1953||DJF 1954||0.8||–||+||AMJ 1954||AMJ 1956||-1.6||–||+|
|M||MAM 1957||JJA 1958||1.7||+||–|
|M||SON 1958||JFM 1959||0.6||+||–|
|M||JJA 1963||JFM 1964||1.2||–||–||AMJ 1964||DJF 1965||-0.8||–||–|
|M||MJJ 1965||MAM 1966||1.8||–||–||NDJ 1967||MAM 1968||-0.8||–||–|
|M||OND 1968||MJJ 1969||1.0||–||–|
|T||JAS 1969||DJF 1970||0.8||N||–||JJA 1970||DJF 1972||-1.3||–||–|
|T||AMJ 1972||FMA 1973||2.0||–||–||MJJ 1973||JJA 1974||-1.9||–||–|
|SON 1974||FMA 1976||-1.6||–||–|
|T||ASO 1976||JFM 1977||0.8||+||–|
|M||ASO 1977||DJF 1978||0.8||N|
|M||SON 1979||JFM 1980||0.6||+||–|
|T||MAM 1982||MJJ 1983||2.1||+||–||SON 1984||MJJ 1985||-1.1||+||–|
|M||ASO 1986||JFM 1988||1.6||+||–||AMJ 1988||AMJ 1989||-1.8||–||–|
|M||MJJ 1991||JJA 1992||1.6||+||–|
|M||SON 1994||FMA 1995||1.0||–||–||JAS 1995||FMA 1996||-1.0||+||+|
|T||AMJ 1997||AMJ 1998||2.3||+||+||JJA 1998||FMA 2001||-1.6||–||+|
|M||MJJ 2002||JFM 2003||1.3||+||N|
|M||JJA 2004||MAM 2005||0.7||+||+|
|T||ASO 2006||DJF 2007||0.9||–||+||JAS 2007||MJJ 2008||-1.4||–||+|
|M||JJA 2009||MAM 2010||1.3||N||+||JJA 2010||MAM 2011||-1.3||+||+|
|JAS 2011||JFM 2012||-0.9||–||+|
|T||MAM 2015||AMJ 2016||2.3||+||N||JAS 2016||NDJ 2016||-0.8*||+||+|
*The GEI Weather and Climate Report does not accept this as a legitimate La Nina. It is not unusual for different Meteorological Agencies to maintain different lists of El Ninos and La Ninas. This is usually because the criteria for classification differ slightly. Obviously the GEI Weather and Climate Report has no standing but nevertheless for any analysis we do, we will either not include or asterisk this La Nina to indicate that NOAA has it on their list and we consider that to be Fake News. The alternative is to conclude that the other Meteorological Agencies are not able to measuring things correctly. .
ONI Recent History
The MJJ reading was adjusted downward from 0.3 to 0.2 a minor change and now back to +0.4. The JJA reading has been adjusted from -0.1 to +0.2 not an insignificant change but without significance re whether or not this cool event will qualify as a La Nina. We now have the JAS reading at -0.1 which remains an ENSO Neutral Reading. 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.
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.]
The above shows the geography of the Great Basin which is the route that winter storms take. The storm is pinned between the Sierra Nevada and Rocky Mountains. This explains why these troughs are so common. It also explains why points north get more precipitation than points south. These troughs have a long distance to travel/extend before they can impact the Southern Tier.
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