The big question this week is what will happen to 99L (upgraded Sunday to TD9), But it may turn out that 91L which has been upgraded to TD8 may turn out to be at least as significant but for the Mid Atlantic not the Florida West Coast. And then there are the Pacific hurricanes that threaten Hawaii. For new readers, L is for the Atlantic and TD stands for tropical depression. Numbers designate the sequence. See longer description at end of article.
Please refer to the News Section of this Report for the links to articles that will explain more about the evolution of cyclonic activity this past week. But to avoid keeping you in suspense, the most recent chapter in this saga can be found at TD8 and TD9 Ready to Strike. And then just in new news: Hawaii may get hit also
Tropical Cyclones Everywhere
There are more East-Coast people in the path of TD8 and TD9 but the Pacific Hurricanes Madeline and Lester present a significant threat to Hawaii. The betting is that the Fujiwhara Effect will cause them to rotate around each other and if Hawaii remains in the geometric center of this projected maneuver, Global Warming will have been thwarted this time. We may discuss the increasing number of near misses to Hawaii in a future Weather and Climate Report. One wonders if and how TD8 and TD9 might interact.
Progress of Transition to Fall
From Thursday's Phoenix NWS Forecast Discussion.
Today and tonight...the overall atmospheric flow regime continues in its late September like pattern, with strong west and northwesterly flow aloft Replete with numerous trofs/shortwaves diving into the western states from Canada. The strong high pressure system that was suppose to build into Arizona from the west late yesterday and today stalled offshore, continuing the strong northwest flow aloft, I.E. Above 300 mb. A couple of disturbances are poised to move into central and northeast Arizona today, with a larger former Canadian trof [Editor's Note: "Trof" is Phoenix NWS-speak for "trough". Meteorologists are compulsive abbreviators. It may date back to when weather forecasts were sent out by Morse Code] moving into central Utah.
This is not a refutal of Global Warming but simply the way a La Nina-ish weather pattern behaves. When you start hearing about Canada in a forecast, it suggests that Fall is coming or here.
I do not usually quote from my friends in College Park Md., but I found this from their Friday discussion interesting.
WITH A DEEP TROUGH FORECAST NEAR THE WEST COAST, NEAR-NORMAL PRECIPITATION IS DEPICTED OVER THE SOUTHWEST, WHERE RAINFALL WOULD NOT RESULT FROM A CANONICAL MONSOONAL CIRCULATION.
Not exactly sure what they were trying to say here but it does make the point that the Southwest Monsoon is not the only driver of precipitation in the Southwest.
I just love the Phoenix NWS. They are so into science. This from Friday is long but worth reading. It is like reading a "whodunit".
What makes this pattern so interesting is, as the trof from western Canada slowly develops just west of AZ today, despite an increase in low level monsoon moisture, mid/upper level southwest winds show little cyclonicity nor with lateral shear. In other words, winds aloft become laminar, with mid level warm advection, and not really supportive for diurnal convection. Therefore any storms today will be thermodynamically driven, first in the mountains with possible descending outflows onto the central deserts. Secondary storm development is possible on the central deserts with outflows. Southeast CA and southwest AZ will mostly storm free this afternoon and evening.
Another remarkable thing about this developing mid/upper level trof in AZ is, the vertical structure of this system tilts to the northeast. In other words, by Saturday evening the 700 mb low center is positioned over northern Baja, the 500 mb circulation center just west of Needles CA, and the 300 mb center by Las Vegas. The entire trof wobbles eastward across AZ in this negative tilt orientation through the weekend. Vertically tilt trofs like this are storm killers or produce stable weather, and perhaps this is why the models forecast very little precip over south central AZ this weekend. Therefore the best chance of storms Saturday and Sunday will be thermodynamically driven, or heat of the day storms, and predominately over the mountains. Again, our forecast area in southeast CA and southwest AZ will be nearly storm free.
Next week we will have an update on the September Outlook from NOAA and the following week I will attempt to discuss the subject of Source versus Sink re the impact of precipitation on temperature and the impact of temperature on precipitation. This is important when discussing weather and also Global Warming.
Let's Now Focus on the Current (Right Now to 5 Days Out) Weather Situation.
A more complete version of this report with daily forecasts is available in Part II. This is a summary of that more extensive report. Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks will take you directly to that set of information but it may take a few seconds for your browser to go through the two-step process of getting to Page II and then moving to the Section within Page II that is specified by this link.
Characteristics of a Weekly Weather Column.
Many graphics in this report are auto-updated by the source of the graphic. It is always my choice as the writer to allow these graphics to auto-update or "freeze them" to what they looked like when I write the article. Generally speaking graphics in research themes which appear above this point do not auto-update as they come from published scientific papers. When I make the decision to allow certain graphics to auto-update, it creates two issues:
A. As the graphic updates, my commentary becomes out of sync with the new version of the graphic. This can be very extreme if for example you take a look at my report from months ago.
B. On rare occasions, source sites for graphics go down and the graphic does not appear in the article and you probably see white space. If you experience such an event and that graphic is important to your understanding of the report, please return later to view my weather and climate column. Sometimes the "outage" is only for several minutes, but often the duration can be a number of hours or even one or more days. We feel that this inconvenience is preferable to looking at "frozen" weather map images that do not update since I write the article on Monday evenings and you probably do not read it until Tuesday and perhaps later in the week. So I want you to have the advantage of seeing the most up-to-date graphics. If the source is down, the white space is the price paid for most of the time being able to see the latest available graphics.
First, 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 the link provided above.
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.
This graphic provides a good indication of where the moisture is. It is a bit different than just moisture imagery as it is quantitative.
Notice that unlike previous weeks, the "Atmospheric Rivers" right now are not originating from Mexico but from (a) possible cyclonic activity entering the Gulf of Mexico and a system arriving from the Atlantic Ocean that seems to be targeting Raleigh Durham NC. Plus Canada seems to want to send some moisture into CONUS.
Click Here for a World Precipitation Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the map only so to see it you have to click where I said "click here". You can adjust the settings to show Temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool!
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 general signifies equal chances for snow at sea level locations. I am leaving this explanation in the report but it may not be very significant until next October or so which now is less than two months away. .
Not sure one can rely on this graphic to locate the Four Corners High as it seems to be on vacation this Summer. If it showed up on this graphic, one could draw or imagine a one-inch or so in radius circle overlain on the Four Corners High with an arrow showing the wind pattern is clockwise (anticyclone). One can then imagine where moisture might be being drawn into the edge of the High Pressure System.
Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.
What you can see if a forecasted very deep trough in the West. That is quite impressive.
The MJO has had significant impacts this prior winter during the development of the El Nino but the impact on this September is not likely to be very noticeable other than alternatively accelerating and decelerating the development of the La Nina. It is forecast to be more significant in October. The forecasts of the MJO are all over the place and not suggesting a strong Active or Inactive Phase of the MJO any time soon. Thus it may be October or November before it really is able to be factored in.
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 in motion (last 24 hours) not a forecast.
The above is the Eastern Pacific again a 24hr loop of recent readings. It does a good job of showing what is going on right now. I wish I know how to join them and show them side by side. Below is the current water vapor Imagery.for North America.
Tonight, Monday evening August 29 (and this is the current situation not an animation of recent history), as I am looking at the above graphic,.there is some impact especially on Texas and Eastern New Mexico of the Southwest Monsoon but the action in the Caribbean appears to be of more potential interest as the week evolves. The storm off the East Coast does not appear to be very wet. The forecast implies that the cyclonic action in the Gulf of Mexico and some other factors will shift the Monsoonal Plume to the west a bit and that Arizona will get in on the action. We shall see.
This graphic updates automatically so it most likely will look different by the time you look at it as the weather patterns, except for the Southwest Monsoon, are moving from west to east .
Below is an analysis of projected tropical hazards and benefits over an approximately two-week period. This graphic is scheduled to update on Tuesday and I am reading the August 23, 2016 Version and looking at Week 2 of that forecast.
Mostly for the period August 31, 2016 to Sept 6, 2016, I see only minor impact of land areas. But when I look at the first week of the analysis it is very interesting. I usually do not comment on the first week as it has pretty much occurred by the time I go to press but you can see the area indicated as being a risk for the development of a tropical cyclone southeast of Florida.
For CONUS, the above graphic is more specific and near term with interpretation and has a focus on tropical storms. It does not cover as wide an area e.g. it does not cover the Western Pacific or the Atlantic far east of the U.S. It is actually a convenient graphic for tracking the Southwest Monsoon. As you can see, there continues to be a single band of tropical moisture and it is down by Southern Mexico and Central America. There is also tropical moisture west of the Gulf of Mexico which seems to be impacting Texas. In general the tropical storms origination off of the west coast of Central American are not curving around and coming aground but heading out to sea rapidly. There is subtropical moisture that creates the occasional thunderstorm. For now it is a minimal Monsoon (The Phoenix NWS refers to the Monsoonal situation as "High Grade", "Low Grade" and "No Grade". This is definitely somewhere between a "Low Grade" and a "No Grade" Monsoon at this point re Arizona and New Mexico. It is possible that there will be one more "Monsoonal Burst". I I had doubted that this would happen but there are so many factors right now that it may well happen this week. We should expect some minor intrusions of the Monsoonal Moisture Boundary (MMB) into CONUS but these events are likely to be brief and impact mostly the areas very close to Mexico and may favor Southern New Mexico and Western Texas.
Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 6 (the Day 3 forecast is available on Page II of this Report). This graphic also auto-updates.
The Aleutian Low is not the controlling factor during the summer. But it is quite visible right now and fairly strong.
The High Pressure off of California, the familiar RRR, is here and quite large and strong. The RRR continues to do a good job of protecting the West Coast from Pacific storms and also providing northerly winds for California. It is normal for this time of the year unlike during the winter. But it is so far north and offshore that one sees the Low (which has been a series of Lows) that has formed off California. That Low will have impacts. Recently, 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. For CONUS, we do not see a lot of strong Highs or Lows. You can look at the difference in the shown air pressure for the Highs and the Lows over CONUS and it is not a larger differential. Remember this is a forecast for Day 6. It is not the current situation.
Looking at the current activity of the Jet Stream.
The path of the current weather pattern is fairly clear from this graphic and it is across the Northern Tier of CONUS and over Canada and again is further south than usual for this time of the year. The sub-Jetstream level intensity winds shown by the vectors in this graphic are very important. Lately, they have tended to disrupt the generation of tall cumulus clouds in Arizona and New Mexico which are needed to have a significant precipitation from the Southwest Monsoon. West and Northwest winds sweeping into Southern California and Arizona and even extending into Northern Mexico are likely to be suppressing the Southwest Monsoon. This suggests that Fall is here. But you can see the southerly vectors in New Mexico and part of Texas so there may be some weak Monsoon activity in those places this week. Even weak storms when there is no steering current can create flooding conditions. So that is what is happening.
Re the above, H8 is the height of the 850 millibar level, 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.
Also the ideal situation is for the mid-level to be cooler than the Boundary Level. You need to have a steep decline in temperature at higher altitudes for the atmosphere to be unstable and create a significant number of healthy clouds and storms. The Devil is in the details. So there can be very higher PWATs i.e. the amount of moisture in the water column at a particular location but still no precipitation if there is no convection. A PWAT of 1.2 inches of water is sort of a summer trigger point, Levels much higher than 1.2 inches of water could lead to hail. But in the absence of instability, nothing happens. Those westerlies are one reason why there has been less instability than optimal for the Southwest Monsoon to be productive. And now with September almost here the PWAT's are down under 1.2 inches so we not only have a "low Grade Monsoon" we also have a "Dry Monsoon".
Below is the forecast out five days.
There is a continuation in the tendency to suppress the Monsoon even though this may not be showing up in the forecasts.You generally need a combination of moisture and dynamics and right now some of the moisture is coming from the Monsoon but the dynamics are coming from more Fall-like weather patterns. But now we have the cyclonic activity forecast to be in the Gulf of Mexico and a very deep trough coming down the Great Basin. So we can have some very interesting weather.
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. 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.
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.
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.
And when we look at Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.
Remember this discussion is all about anomalies not absolute temperatures...so it is deviation from seasonal norms.
The waters off of Japan especially between Japan and China remain warm. The Indian Ocean is now more cool than warm. The southern coast of Australia is especially cool but the Southeast Coast is a bit warm. Water northwest of Australia is warm but much less so than recently. The waters south of Africa are warm to the west but cool to the east.
The overall Northern Pacific is perhaps PDO Positive (the horseshoe pattern with the cool anomaly inside the horseshoe shape) but is not as obvious and may not record as PDO+ as the waters just off the West Coast are cool not warm. The cool anomaly now is a belt south of a large intense warm anomaly but it is less intense than recently. The Pacific Decadal Oscillation (PDO) Index rose to 2.4 in March which with El Nino fading may be significant. It was up to 2.62 in April but eased to 2.35 in May and then to +0.78 in June and now down to +0.18 for July. The question remains about the PDO. Is it acting independently of the El Nino or is this the change from PDO- to PDO+ that would signal a multi-decadal change in the Pacific. I anticipate that the PDO will turn negative as the La Nina gains control. Here is the list of PDO values.
The Black and Caspian seas are warm. So is the Persian Gulf.
The water directly west of South America is not showing much of a strong La Nina pattern even though El Nino is history. There is a narrow cool anomaly in the Pacific right along the Equator in the La Nina Measurement Area but it does not extend very far north or south of the Equator but may be beginning to do so. It is gradually stretching west. But the connection to Ecuador is weak. In fact the water off of Peru is a bit warm. It is a La Nina pattern but too weak yet to qualify as an official La Nina. It may ultimately turn out to be a La Nina Modoki i.e. shifted to the west more than the typical La Nina.The water off the West Coast of Central America is warm Further north, the Gulf of Alaska is quite warm. That really is the most impressive feature of the overall pattern.
The water off the East Coast of CONUS is very warm covering a large area and extending quite far to the east and we see the impact in terms of possible formation of tropical storms. The list of Atlantic Multidecadal Oscillation (AMO) values can be found here. Further north in the Atlantic east of Newfoundland the North Atlantic is becoming warmer than normal and the cool anomaly seems to be fading. The cool anomaly off shore of Northwest Africa is now a small warm anomaly. The waters north of Antarctica East of South America are uniformly colder than climatology but we see some warm anomalies north of that pattern and partially intruding into that pattern but less significant than recently. I have some additional commentary on this static analysis of the anomalies below where I examine the four-week change in these anomalies.
Since these are "departures" or "anomalies", it is not a seasonal pattern that is being shown it is the changes from what we would expect on a seasonal basis. It is important to understand that and interpret my comments above in the context of anomalies not absolute temperatures.
Below I show the changes over the last month in the Sea Surface Temperature (SST) anomalies.
Comparing a four-week graphic to a prior four-week graphic is always tricky since only 25% of the data has changed and I am not showing the former graphic (it is in last week's report). I add the new one to my draft report, compare and comment on the change and then delete the old one to keep this report to a manageable size. Also it is important to recognize that what you see in this graphic is the change in the anomaly. So blue means either cooler or less warm. Red means warmer or less cool. So you have to refer to the graphic above this one to really interpret this graphic as what we are seeing here is the change in the anomalies. What we see in this graphic is four weeks of change not the current absolute anomalies which are shown in the above graphic. It is not derivatives in the mathematical sense but deltas. They are somewhat similar. The graphic above this one has no time component. It is simply the deviation from climatology and this graphic below shows the four week change in the deviation from climatology. So it is a bit like the first (graphic above) and second (graphic below) derivatives but not exactly. I take it a step further by comparing this weeks version of the graphic to the prior week and report on the differences below.
What I see as I look at both last week's version of this graphic and the current one (before deleting the prior version) is a slightly different pattern of changes in the anomalies along the Equator in the Pacific. The anomalies are less cool between 145W and 90 which includes 145W to 120W which really makes me wonder about the NOAA ONI calculations. I think they are just flat out wrong. The Indian Ocean is indicating a moderation in the changes in anomalies. The waters of the U.S. West Coast are getting less warm or more cool you need to look at the actual anomalies up one graphic to figure out which it is. The Atlantic anomalies both North Atlantic and South Atlantic are pretty inconclusive except the area just north of South America is interesting. The Gulf of New Mexico is less cool or more warm and that is significant. The North/Central and Western Pacific four-week change in anomalies this week are less intense and perhaps the most significant feature that I see. Remember we are talking about changes in the anomalies something like a second derivative so you have to refer to the graphic above this one to know if blue is cool or less warm and if red is warm or less cool.
Four- Week Outlook
I am going to show the three-month SON Outlook (for reference purposes), the Early Outlook for the single month of September, the 6 - 10 Day and 8 - 14 Day Maps and the Week 3 - 4 Experimental Outlook.
First - Temperature
Here is the Three-Month SON Temperature Outlook issued on August 18, 2016:
Here is the Early Temperature Outlook for September Issued on August 18, 2016
6 - 10 Day Temperature Outlook
8 - 14 Day Temperature Outlook
Looking further out.
As I view these maps on August 29 (two of the five update each day and one updates every Friday), it appears that through September 23, the pattern during the first half of September will be a cool western third of CONUS and a warm Central and East. This then morphs into a 1/4 EC Northwest and North Central with everything else being warmer than climatology. The above week 3-4 graphic updates automatically on Fridays.
Last week we said that when it is updated on Friday, the cool anomaly shown at that time might no longer be shown and it all may be EC. It looks like we were correct about that.
Now - Precipitation
Here is the three-month SON Precipitation Outlook issued on August 18, 2016 21, 2016:
And here is the Early Outlook for September Precipitation Issued on August 18, 2016
6 - 10 Day Precipitation Outlook
8 - 14 Day Precipitation Outlook
As I view these maps on August 29 (two of the five update each day and one updates every Friday), it looks like precipitation leading up to September 23 is tending for the first half of September to be a north south La Nina-ish type of situation with a wet Northern Tier and Dry Southern Tier except for the impacts of the evolution of the tropical depression that appears to be ending up in the Gulf of Mexico and will probably land somewhere as a Tropical Storm or even Hurricane with the West Coast of Florida being the predicted landing area as I write this article. It is not clear how the first half of September morphs into the 3 - 4 Week Outlook shown above which updates automatically on Fridays. The wet anomaly in the North Central seems like a Canadian intrusion and that makes sense and the dry anomaly in the Southeast also to some extent seems like a continuation of the forecasted pattern for the first half of September. But the dry anomaly in the Northwest is a bit surprising. But that dry anomaly is in the full month forecast. So this may fit together better than it seems at first glance. But that dry anomaly in the Northwest does not seem to be very La Nina-ish.
Here is the NOAA discussion released today August 29, 2016.
6-10 DAY OUTLOOK FOR SEP 04 - 08 2016
TODAY'S 500-HPA MODEL SOLUTIONS ARE IN GOOD AGREEMENT IN DEPICTING A FAIRLY AMPLIFIED PATTERN OVER MUCH OF THE FORECAST DOMAIN. TROUGHS ARE FORECAST OVER THE NORTHERN ROCKIES AND WESTERN ALASKA WHILE RIDGING IS PREDICTED OVER THE NORTHEASTERN CONUS. SUBTROPICAL RIDGING IS FORECAST OVER PARTS OF THE SOUTH-CENTRAL CONUS. A WEAKNESS IN THE SUBTROPICAL RIDGE IS FORECAST BY THE GFS- AND ECMWF-BASED SOLUTIONS OVER PARTS OF THE SOUTHEAST. TODAY'S 6-10 DAY 500-HPA HEIGHT BLEND IS WEIGHTED MOST HEAVILY TOWARD THE ECMWF-BASED SOLUTIONS DUE PRIMARILY TO CONSIDERATIONS OF RECENT SKILL.
ABOVE-NORMAL TEMPERATURES ARE FAVORED OVER MOST OF THE CENTRAL AND EASTERN CONUS, WITH THE HIGHEST PROBABILITIES INDICATED NEAR THE ANOMALOUS RIDGE AXIS OVER THE NORTHEASTERN CONUS. HOWEVER, NEAR NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF THE SOUTHEAST DUE TO A PREDICTED WEAKNESS IN THE SUBTROPICAL RIDGE OVER THIS REGION. THERE ARE ENHANCED PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR MUCH OF THE WESTERN CONUS IN ASSOCIATION WITH A PREDICTED TROUGH. BELOW NORMAL TEMPERATURES ARE ALSO FAVORED FOR PARTS OF NORTHERN ALASKA UNDERNEATH PREDICTED CYCLONIC FLOW. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR SOUTHWESTERN ALASKA AND THE ALEUTIANS DUE IN PART TO ABOVE NORMAL SEA SURFACE TEMPERATURES IN ADJACENT WATERS.
THERE ARE ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION FOR MUCH OF THE NORTHWESTERN AND NORTH-CENTRAL CONUS IN ASSOCIATION WITH A MEAN TROUGH PREDICTED NEAR THE NORTHERN ROCKIES. BELOW MEDIAN PRECIPITATION IS FAVORED FOR MUCH OF THE EASTERN CONUS UNDERNEATH PREDICTED RIDGING. HOWEVER, NEAR TO ABOVE MEDIAN PRECIPITATION IS INDICATED FOR PARTS OF THE SOUTHEAST IN ASSOCIATION WITH A PREDICTED WEAKNESS IN THE SUBTROPICAL RIDGE AND POTENTIAL INFLUXES OF TROPICAL MOISTURE. THERE ARE ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION FOR PARTS OF SOUTHEASTERN TEXAS DUE TO POTENTIAL INFLUXES OF MOISTURE FROM THE GULF OF MEXICO. ABOVE MEDIAN PRECIPITATION IS ALSO FAVORED FOR PARTS OF THE SOUTHERN HIGH PLAINS AND SOUTHWEST DUE TO THE POTENTIAL FOR MOIST MONSOONAL FLOW TO AFFECT THESE REGIONS. PRECIPITATION ESTIMATES FROM THE GFS AND ECMWF ENSEMBLE MEMBERS FAVOR BELOW MEDIAN PRECIPITATION FARTHER TO THE NORTH FOR PARTS OF THE CENTRAL ROCKIES AND GREAT BASIN. NEAR TO ABOVE MEDIAN PRECIPITATION IS FAVORED FOR SOUTHERN ALASKA IN ASSOCIATION WITH PREDICTED SURFACE LOW PRESSURE. THERE ARE ENHANCED PROBABILITIES FOR NEAR TO BELOW MEDIAN PRECIPITATION FOR CENTRAL AND NORTHERN ALASKA TO THE NORTH OF THE PREDICTED MEAN STORM TRACK.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO FAIRLY GOOD AGREEMENT AMONG THE VARIOUS MODELS, OFFSET BY UNCERTAINTY IN THE PRECIPITATION OUTLOOK OVER THE SOUTHEAST.
8-14 DAY OUTLOOK FOR SEP 06 - 12 2016
TODAY'S WEEK TWO 500-HPA SOLUTIONS FROM THE ENSEMBLE MEANS ARE FAIRLY SIMILAR TO THAT PREDICTED FOR THE 6-10 DAY PERIOD OVER MUCH OF THE FORECAST DOMAIN. TROUGHS ARE PREDICTED OVER WESTERN ALASKA AND THE NORTHWESTERN CONUS WHILE RIDGING IS FORECAST OVER THE NORTHEAST. THE GREATEST DISAGREEMENT AMONG THE MODELS IS OVER THE SOUTHEAST DUE TO UNCERTAINTIES SURROUNDING A FORECAST WEAKNESS IN THE SUBTROPICAL RIDGE AND THE POTENTIAL FOR TROPICAL SYSTEMS TO AFFECT THIS REGION. DISAGREEMENTS ARE ALSO APPARENT AMONG THE DETERMINISTIC GFS SOLUTIONS AS RUN TO RUN CONTINUITY IS POOR OVER MUCH OF THE FORECAST DOMAIN. DUE TO THESE UNCERTAINTIES, TODAY'S WEEK TWO MANUAL HEIGHT BLEND IS BASED MOSTLY ON THE ENSEMBLE MEAN SOLUTIONS. THE GREATEST WEIGHTS WERE GIVEN TO THE GFS ENSEMBLE MEANS DUE, IN PART, TO RELATIVELY GOOD ANALOG CORRELATIONS, WHICH MEASURE HOW CLOSELY THE FORECAST PATTERN MATCHES CASES THAT HAVE OCCURRED IN THE PAST.
ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS MUCH OF THE EASTERN AND SOUTH-CENTRAL CONUS UNDER POSITIVE 500-HPA HEIGHT ANOMALIES. BELOW-NORMAL TEMPERATURES ARE FAVORED OVER A LARGE REGION OF THE WESTERN CONUS, IN ASSOCIATION WITH A PREDICTED TROUGH. THERE ARE ENHANCED PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR MUCH OF NORTHERN ALASKA UNDERNEATH CYCLONIC FLOW AND BELOW NORMAL HEIGHTS. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF SOUTHERN COASTAL ALASKA IN ASSOCIATION WITH ABOVE NORMAL SSTS.
FORECAST RIDGING LEADS TO ENHANCED PROBABILITIES FOR BELOW MEDIAN PRECIPITATION FOR PARTS OF THE EASTERN CONUS. HOWEVER, FAVORED NEAR MEDIAN PRECIPITATION IS INDICATED ALONG THE SOUTHERN ATLANTIC AND GULF COASTS DUE TO UNCERTAINTIES ASSOCIATED WITH POTENTIAL INFLUXES OF TROPICAL MOISTURE. ABOVE MEDIAN PRECIPITATION IS FAVORED FOR THE NORTHWESTERN AND NORTH-CENTRAL CONUS IN ASSOCIATION WITH A FORECAST TROUGH. THERE ARE ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHWEST AND FOR BELOW MEDIAN PRECIPITATION FOR PARTS OF THE CENTRAL ROCKIES CONSISTENT WITH GEFS REFORECAST GUIDANCE. ABOVE MEDIAN PRECIPITATION IS FAVORED FOR MUCH OF ALASKA UNDERNEATH PREDICTED CYCLONIC FLOW AND BELOW NORMAL HEIGHTS.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: BELOW AVERAGE, 2 OUT OF 5, DUE TO POOR RUN TO RUN CONTINUITY AMONG THE DETERMINISTIC GFS SOLUTIONS AS WELL AS UNCERTAINTIES SURROUNDING THE PRECIPITATION FORECAST OVER THE SOUTHEASTERN CONUS.
Some might find this analysis interesting as the organization which prepares it 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.
Sept 3, 1956
Aug 24, 1959
Aug 8, 1974
Aug 24, 1980
Aug 8, 1993
Sept 11, 1997
Aug 9, 2000
Following the MegaNino
Sept 2, 2002
El Nino Modoki Type I
Sept 3, 2004
El Nino Modoki Type II
(t) = a month where the Ocean Cycle Index has just changed or does change the following month.
One thing that jumped out at me right away was the spread among the analogs from August 8 to September 11 which is almost five week which is a large spread. 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 August 25. These analogs are centered on 3 days and 4 days ago (August 25 or 26). So the analogs could be considered pretty much in sync with the calendar.
I think NOAA would appreciate it if I said that these analogs are not a substitute for their very sophisticated forecasting software and I am not suggesting that they are. I present them partially for curiosity purposes but also to see how current conditions correlate with medium and low frequency cycles. The medium frequency cycle I track is ENSO and the two low- frequency cycles I track are the PDO and AMO. When I see that forecasts are consistent with the current phases of these cycles (as represented by the analogs), that seems very suggestive to me that our weather is probably fairly easy to forecast. If the analogs are all over the place then I have to wonder if the forecasts are good or if our weather is just not related to these cycles. That certainly can be the case. So I am doing some research here and you are seeing how I look at things. I hope you find it interesting.
There is this time three El Nino Analogs (why are there any?), two La Nina Analogs, and four ENSO Neutral Analogs. The phases of the ocean cycles in the analogs are suggestive of McCabe Condition C which is kind of opposite the forecasts except for the current batch of Southeast cyclones.So I definitely have less confidence in this 6 - 14 Day forecast than NOAA does.
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.
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.
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.
J FM 1951
Progress of the Cool ENSO Event
Let us start with the SOI.
Below is the Southern Oscillation Index (SOI) reported by Queensland, Australia. The first column is the tentative daily reading, the second is the 30 day moving/running average and the third is the 90 day moving/running average.
90 Day Average
The 30-day average, which is the most widely used measure, as of August 29 is reported at +4.62 which is up considerably from last week and still ENSO Neutral but very close to a La Nina level. The 90-day average at +3.82 is also up substantially from last week and but remains ENSO Neutral. Usually but not always the 90 day average changes more slowly than the 30 day average but it depends on what values drop out. The disparity between the two is one reason why we look at both. Different agencies use a different range to classify the SOI as being El Nino or La Nina. The strictest range is -5 for El Nino and +5 for La Nina. Some meteorological agencies sometimes use -8 or +8. So the range +5 to -5 is clearly neutral and above +8 is clearly La Nina and below -8 is clearly El Nino and between -8 and -5 and +5 to + 8 is somewhat marginal but suggestive of El Nino if negative and La Nina if positive.
The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource. August has not been particularly favorable for La Nina development and neither will be September in terms of the MJO. The MJO being Inactive is more favorable for La Nina than the MJO being Active. It is complicated in that some models predict a strong active MJO for September which normally means westerlies which is negative for the development of the La Nina. But the MJO goes back and forth from being Active, Inactive, strong and weak so in has mostly a short-term impact. Right now the impact is fairly muted. It tends to be more important when the situation is ENSO Neutral and the MJO can start the process of an El Nino getting started.
Low-Level Wind Anomalies
Here are the low-level wind anomalies.
There are mostly Easterly "anomalies" (for some reason NOAA assumes that "anomalous" means more rather than less which is strange to me as I speak English and "anomalous" in the English Language simply means "deviating from what is standard, normal, or expected." It appears from the legend on the right that this graphic is based on winds being Westerly and the color coding is the deviation from the expected levels of westerliness. Thus the browns are more westerly and the blues are less westerly as an anomaly meaning easterly. What we are observing here is probably mostly the MJO in action. These are small anomalies but not helping t he cool event to develop.
And now the Outgoing Longwave Anomalies which tells us where convection has been taking place.
In the above graphic, we see basically no convection along the Equator other than west of the Dateline. It s a cool event pattern but not very impressive.
Equatorial Subsurface Analysis
We are now going to change the way we look at a three dimensional view of the Equator and move from the surface view to the view from the surface down.
Current Sub-Surface Conditions. Notice the lag in getting this information posted so the current situation may be a bit different than shown.
And now the pair of graphics that I regularly provide and which as I publish are currently able to be accessed from the NOAA website. There was a period of time when that website was up and down but it appears to be functioning well recently. :
The above pair of graphics showing the current situation has an upper and lower graphic. 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.
The top graphic shows surface temperature anomalies. The coolest water at the surface shows up only in small isolated areas. Water of La Nina coolness but not very intense shows up along the Equator from 170W to the Coast of Ecuador. But there are pockets of water slightly warmer than -0.5C mixed in. The -1C water shows between 170W and 140W and that is a larger area than last week. But there is a large gap between 130W and 115W. That suggests the possibility that this will evolved into a cool Modoki pattern. The eastern part of the cool water pool is not that impressive. Notice that below 100 meters, there is not that much anomalously cool water. How is this cool event to be sustained?
The bottom half of the graphic (Absolute Values which highlights the Thermocline) is now more useful as we track the progress of this new Cool Event.
It shows the thermocline between warm and cool water. The 28C Isotherm is now located west of the Dateline. This graphic does not show a 27.5C anomaly which might more precisely indicate where convection is likely to occur. The 27C isotherm is now at 170W so we do not have ideal conditions for significant convection along the Equator east of the Dateline. The 25C isotherm is at about 150W. The 20C Isotherm has moved close to the surface but is not reaching the surface. But the amount of warm water just west of the Dateline is also not real impressive either but growing but staying fairly far east. It is clearly a transition state and all of this is important not just for tracking this cool event but thinking about when the next El Nino might be triggered. This graphic helps understand the logic behind some of the forecasts of the ONI. For the bast six weeks we pretty much had weak La Nina conditions both in terms of water temperatures and the SOI but it appears to be transitory in the sense of moving back to Neutral this week.
Here are the above graphics as a time sequence animation. You may have to click on them to get the animation going.
We now have to change our focus from tracking the El Nino to tracking the transition to ENSO Neutral and most likely to ENSO La Nina. So I have deleted many of the TAO/TRITON graphics to show how the El Nino developed except one which was close to the maximum. It was not the maximum but it was the one that I froze which was the closest to the maximum that I saved. It is useful for comparing the current situation with the pattern that prevailed near the peak of the El Nino this past winter.
And here is the current version of the TAO/TRITON Graphic.
Location Bar for Nino 3.4 Area Above and Below
Notice the intrusion of warm water from the south at about 120W
The below table which only looks at the Equator shows the extent of anomalies along the Equator. I had split the table to show warm, neutral, and cool anomalies. The top rows showed El Nino anomalies. When there were no more El Nino anomalies along the Equator, I eliminated those rows. The two rows just below that break point contribute to ENSO Neutral and after another break the rows are associated with La Nina conditions. I have changed the reference date to May 23, 1016.
Comparing Now to May 23, 2016
Subareas of the Anomaly
Degrees of Coverage
As of Today
May 23, 2016
As of Today
May 23 2016
As of Today
In Nino 3.4
May 23, 2016
These Rows Show the Extent of ENSO Neutral Impacts on the Equator
0.5C or cooler Anomaly*
0C or cooler Anomaly
These Rows Show the Extent of the La Nina Impacts on the Equator
-0.5C or cooler Anomaly
-1C or cooler Anomaly
-1.5C or cooler Anomaly*
* There is actually now some 0.5C+ water in the ONI measurement area especially south of the Equator between 130W and 120W but it is not right on the Equator.
** It is really 145W on the Equator but just south of the Equator it extends further west to 155W
If you just look on the Equator, there are 50 degrees of Longitude of Neutral to La Nina anomalies which is the maximum possible as the ONI Measurement Area is 50 degrees of Longitude wide and that also is the maximum possible since the ENSO Measurement Area only stretches for 50 degrees. There are 45 degrees of water anomalies cool enough to be a La Nina. Subtracting 45 degrees from the 50 degrees you end up with 5 degrees of ENSO Neutral and 45 degrees of water cool enough to qualify as La Nina i.e. temperature anomalies more negative than -0.5C. This is less La Nina-ish than last week. But there is zero water along the Equator in the ONI Measurement that is -1.5C or less which would be cool enough to be a strong La Nina when just looking at the Equator. But the ONI Measurement Area 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. Away from the Equator it is generally warmer when a La Nina is trying to get started. The water from 3N to 5N and from 3S to 5S had until recently remained relatively warm especially west of 150W. But now the warm area has shifted to being east of 135W especially south of the Equator. This inability to have sufficiently cool water throughout the ONI Measurement Area is why I describe this as a "Luke Cool" Event.
I calculate the ONI each week using a method that I have devised. To refine my calculation, I have divided the 170W to 120W ONI 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 August 29, in the afternoon working from the August 28 TAO/TRITON report, this is what I calculated.
Calculation of ONI from TAO/TRITON Graphic
A. 170W to 160W
B. 160W to 150W
C. 150W to 140W
D. 140W to 130W
E. 130W to 120W
Total divided by five subregions i.e. the ONI
(-1.87)/5 = -04
(-2.4).5 = -0.5
My estimate of the daily Nino 3.4 ONI has declined to -0.5 which is a borderline La Nina value. NOAA has reported the weekly ONI to be -0.6 which is a La Nina value but I question the accuracy of their calculation. Nino 4.0 is reported as being slightly cooler at -0.1. Nino 3 is being reported as unchanged at -0.5. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is being reported quite a bit cooler warmer at +02 down from 0.5. WE REMAIN IN ENSO Neutral BUT WE HAVE HAD OUR seventh LA NINA value of the ONI reported in the NOAA WEEKLY REPORT. But I again question the accuracy of the calculation this week. Quite frankly I think the NOAA ONI calculation have been incorrect for two weeks but we are talking about only a tenth of a degree Centigrade. The Australian Bureau of Meteorology has just announced that their estimate of the ONI for August was -0.4. IT IS THE SAME OCEAN. Someone is wrong. I believe my rough estimation approach is providing a more realistic ONI value right now. But we are quibbling over 0.1C which would not be an issue if this was clearly a La Nina. Seven weeks are not definitive (the NOAA criteria for declaring an El Nino or La Nina includes five overlapping three-month periods with the appropriate conditions) especially without confirmation from the SOI but it suggests the direction things are headed but other information suggests the ONI readings will soon (NOAA) or after September (Australia BOM) be less negative than they are this week. 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 graphical form but going back a couple of more years can be found here. NINO 1+ 2 stubbornly remains positive and determines the weather of Ecuador and Peru.
ONI Recent History
The official reading for May/Jun/Jul is now reported as +0.1. It was updated recently from the initial estimate of 0.2. So this El Nino is now officially over. I have discussed before the mystery of how the Nino 3.4 (ONI) CFSv2 values above get translated into the ERSST.v4 values shown below and if NOAA feels that working with two sets of books is a good way to operate, who am I argue. Many businesses do the same thing. As you can see this recent El Nino peaked in NDJ and has now ended and depending on what system you use it is either the 2nd or 3rd strongest El Nino since modern records were kept which is considered to be 1950. You could argue for it being #1 based on a week of readings but few are buying that argument. Still #2 or #3 means it is one of the strongest ever based on the way these events are measured. I will be writing more about that soon in a separate article. I believe the measurement system is inadequate re being useful in forecasting Worldwide weather impacts.
The full history of the ONI readings can be found here. The MEI index readings can be found here.
Although I did not discuss the Kelvin Waves earlier, now seems to be the best place to show the evolution of the subsurface temperatures which remains relevant. What we have is only the upwelling phase of the series of Kelvin waves last winter.
There is cool water from 175W to the coast of Ecuador. But the coolest water, however, is only reaching the surface from 165W to 140W which is a larger area than recently. There is also a huge gap in the coolest water between 130W and 110W. There are initial signs that this may evolve into a weak La Nina Modoki. We will get into the details in some future edition of this report if it becomes relevant but the key is the western part of the surface having more extreme cool anomalies than further east. It is something that happens as the El Nina matures and has not happened yet but the above graphic suggests that it might be possible. The eastern part of the cool anomaly is far less impressive than the western part. There is no comparison.
SST Surface Anomaly Hovmoeller
Here is another way of looking at it: Unlike the Upper Ocean Heat Anomaly Hovmoeller (I call it the Kelvin Wave Hovmoeller) which takes an average down to 300 meters, this just measures the surface temperature anomaly. It is the surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. 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 snap shots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event.
You read this Hovmoeller from bottom to top and you can clearly see how the El Nino ended and we are flirting with La Nina.
I do not usually show this NOAA Hovmoeller. It is similar to the above but reports the anomalies down to 300 meters but only on the Equator. If is useful in terms of estimating the subsurface cooling or warming that is in reserve. That heat content does not impact current weather but will impact future weather as it impacts the surface.
When I have shown it, I usually use the version that auto-updates but this version is a lot clearer. I use it mostly to show the Kelvin Waves. But I am showing it this time because it shows the deterioration of the cool anomaly. So the Upwelling phase of the prior Kelvin Wave is waning. That makes the La Nina call by some of the models suspect. I am showing last week's version above this text box followed by this week's version below this text box. You can clearly see the larger areas of lighter blue at the bottom which are the current readings. For the moment, this potential La Nina is dying. So the NOAA ONI readings are properly considered to be artifact.There is cool water from 180W to 140W along the Equator but that is not enough to have this coolish event labled a La Nina.
Here is the last week's version. I have condensed the vertical axis to take up less space.
And here is this week's version.
You can see a little blip just east of 130W. Perhaps that is the basis for NOAA's slightly higher ONI reading this week. It is ridiculous IMO. The cool anomaly is not getting stronger. It is getting weaker. Look at the two graphics and draw your own conclusions.
Recent CONUS Weather
Since it is not mid-Summer not Spring, I have decided to no longer show May.
Here is the 30 day period through July 3. It completes the month of June.
Adding the seven days and removing the first seven days changed the precipitation picture for Arizona and Nevada and Texas. It also did so for the Northeast. It still presents mostly a warm and dry assessment of June, 2016..
And now we track July. First we will take a look at the three-month history or at least a 90 day history which is basically May through July.
Re precipitation, it is a similar pattern but not nearly as extreme. The Temperature departures a a bit different as in July the heat anomaly extended to the East Coast.
Now let's look at the temperature and precipitation anomalies for the 30 days ending July 30, 2016
And now we start looking at August.
You can see the change from the 30 days ending July 30. It is actually a bit more of an El Nino pattern.
And now the 30 days ending August 20, 2016.
There is not much change from the prior week.
View from Australia
Below is the discussion just released. Notice the discussion re forecasting a La Nina for next winter. POAMA is not currently predicting a La Nina. POAMA is the Australian Bureau of Meteorology (BOM) proprietary forecasting model. BOM also consults the other international forecasting models and after that consultation is not forecasting a La Nina at this point in time as per below. Notice they use a different standard than NOAA namely + or - 0.8 rather than the + - 0.5 that NOAA sues. But even with the NOAA Standard, POAMA would not be forecasting a La Nina.even though right now the ONI is at a La Nina level based on NOAA criteria. But with NOAA criteria the duration must be five overlapping three month periods which is about the same as seven months but with some leeway to not meet the criteria for a particular month. Five weeks does not make a La Nina.
Negative Indian Ocean Dipole influencing Australia’s climate, while Pacific remains ENSO-neutral
In the tropical Pacific Ocean, the El Niño—Southern Oscillation (ENSO) remains neutral, but a late and weak La Niña remains possible. In the Indian Ocean, a negative Indian Ocean Dipole (IOD) continues, but has weakened from record July index values.
International climate models surveyed by the Bureau suggest the negative IOD will weaken during the southern hemisphere spring, and is likely to end in November. This means its influence on Australia’s spring rainfall may not be as strong as it has been during this winter, when wetter conditions prevailed in the east.
In the tropical Pacific Ocean, sea surface temperatures are cooler than average, though remain well short of La Niña levels. In the atmosphere, there has been little change in trade winds or cloudiness, indicating little or no coupling between the atmosphere and ocean. As a result, cool sub-surface temperatures have eased slowly towards normal. International climate models suggest neutral to weak La Niña levels for the remainder of the year. A La Niña WATCH remains in place.
During La Niña, northern and eastern Australia typically experience above average spring rainfall, with the first rains of the wet season typically arriving earlier than normal in northern Australia. Some La Niña-like effects can still occur even if thresholds are not exceeded.
IOD (Indian Ocean Dipole)
The graphic comes with only a very short discussion and here is that discussion:
Indian Ocean Dipole outlooks
The negative Indian Ocean Dipole (IOD) event continues. Although cool anomalies have eased back to average in the western Indian Ocean, and warm anomalies have declined in some parts of the eastern Indian Ocean, an are of significantly warmer than average water remains south of Indonesia and to the northwest of Australia. The weekly index value to 28 August was −0.69 °C.
The Indian Ocean Dipole (IOD) index has been below the −0.4 °C negative IOD threshold for fourteen weeks, peaking at −1.37 °C in early July. The July 2016 monthly IOD index value reported in the ERSSTv4 dataset was the strongest negative value in at least 50 years of record.
International climate models indicate the negative IOD will continue to steadily weaken during spring as is typical of the lifecycle of IOD events. This means its influence on Australian rainfall may lessen in the coming months.
A negative IOD typically brings above average rainfall to southern Australia during winter–spring, cooler than normal daytime temperatures to southern Australia, and warmer daytime and night-time temperatures to northern Australia.
Information on the impact of a negative IOD on Australia can be found here
Invests are designated by three separate forecast centers: the National Hurricane Center, Central Pacific Hurricane Center and Joint Typhoon Warning Center. The designation of a system as an invest does not necessarily correspond to any particular likelihood of development of the system into a tropical cyclone. Invests are numbered from 90 to 99, followed by L in the Atlantic, E and C in the East and Central Pacific respectively, or W in the West Pacific; the Joint Typhoon Warning Center also issues unofficial warnings for the Australian cyclone region, designating tropical invests with the "S" suffix when they form west of 135°E, and the "P" suffix when they form east of 135°E. Invests in the North Indian Ocean cyclone basin are also labeled by the JTWC, and are suffixed with "A" if they form in the Arabian Sea and with "B" if they form in the Bay of Bengal. Numbers are rotated within the season and are re-used as necessary (the next invest after 99 would be numbered 90). If the system develops into a tropical cyclone, it is reclassified as the next name/number on the list. [Editor's Note: That explains why we had 99L and then later we are informed of 91L]
This El Nino has ended in terms of currently satisfying the criteria. We are now speculating on the winter of 2016/2017 which now according to some of the models seems likely to be a La Nina or Neutral with a La Nina bias. But Australia and Japan do not see it that way and are not calling for a La Nina at this point in time. So NOAA is a bit the Odd Man Out but it is mostly a question of degree. NOAA is calling for a borderline La Nina and the others are forecasting a La Nina-ish event that does not quite meet the criteria for being labeled a La Nina and does not last long enough to meet the criteria.
The below is first the CPC/IRI (Early Month) forecast issued on August 11, 2016 followed by the (Late Month) forecast issued on August 18, 2016. It is important to remember that the first report in each month is based on a survey of meteorologists and the second report later in the month is based on the analysis of the forecast models. It is a minor difference but a difference.
First the Meteorologist Consensus Based Analysis. I assume they do it this way as to avoid forcing meteorologists to have to run their computers twice a month (some sarcasm expressed there).
And then the more recent Model-Based Forecast.
Notice that with this release, the probabilities for La Nina remain similar to the August 11 analysis until the FMA 2017 three-month period when relative likelihood of ENSO Neutral begins to gain on La Nina.
We have suggested that it is possible that some of the models and in particular NOAA's model will be wrong about how fast the Eastern Pacific Warm Pool moves back towards its La Nina location and it may well be that next winter will be more of a Neutral year or even have some characteristics of an El Nino Modoki and thus be wetter than a typical year as the Warm Pool may still be more in the Central Pacific than shifted all the way west to its La Nina position.
The mean of the NOAA model was until recently forecasting a fairly strong La Nina for next winter. The model gradually shifted to a weak La Nina Forecast and now to a marginal La Nina Forecast. Is the Mean of the forecast ensemble for the key periods NDJ and DJF below -0.5? It no longer seems to be right now. You can see the same thing in the Australian POAMA model and the August 1 JAMSTEC model run. The mean of the model ensemble for the ONI in the NOAA model has turned higher (less La Nina-ish actually on the El Nino side of Neutral) for the Spring of the coming winter as you can see. So this is forecast to be a short La Nina if it indeed actually meets the criteria to be recorded as a La Nina which remains to be seen. I doubt that this will be recorded as a La Nina since it most likely will only meet La Nina criteria for two or three overlapping three month periods not five. But it is forecasted to be so close that whether it officially is logged in as a La Nina or Neutral, probably has very little impact on the weather we will have.
But to save face as their forecasting model is shown to be not so good, NOAA may declare that La Nina "Conditions" are present. That is pretty much a judgment call and does not require that certain criteria were in fact met. But they may have missed their chance to do that as the forecasted ONI is clearly in Neutral territory. Of course forecasts are not actuals and the situation may change and we may have an actual La Nina.
We now have the JAMSTEC August 1 ENSO forecast.
The model shows ENSO Neutral for the next two years..The discussion below the graphic is far more nuanced. It has not changed since last week but it is informative so I am repeating it.
Aug. 17, 2016 Prediction from 1st Aug., 2016
The SINTEX-F model initialized with the SST condition observed on July 31st predicts a weak La Niña/La Niña Modoki state in coming months. [Editor's Note: This article is already running too long so we will not discuss La Nina Modoki tonight but here is a good article to read for those with an interest in the topic]. Although the NCEP GODAS shows an anomalously cold subsurface condition almost all the way from central Pacific to eastern Pacific along the equator in July, the prediction has not picked the strong La Niña/La Niña Modoki signal yet. This might be a model bias due to the simple SST data assimilation scheme used in the initialization. However, we have noted similar prediction results in several other climate models.
Indian Ocean forecast:
As predicted earlier, the negative Indian Ocean Dipole (IOD) has actually emerged in the June-July SST anomalies of the NCEP GODAS data. The model continues predicting the negative IOD for the boreal fall; this will bring a wetter-than-normal (drier-than-normal) condition over the eastern (western) side of the Indian Ocean. There is high possibility of floods in the region near Sumatra and Java, and drought in East Africa. The negative IOD seems to have brought temporary relief to a hot summer over East Japan normally expected in an evolving La Niña year.
In boreal fall, as a seasonally averaged view, most part of the globe will experience a warmer-than-normal condition, while northern Brazil will experience a colder-than-normal condition.
According to the seasonally averaged rainfall prediction, U.S., Korea, eastern China, Indo-China and East Africa will experience a drier condition during boreal fall, while most parts of Indonesia and northwestern South America (including Colombia, Ecuador, and western Brazil) will experience a wetter-than-normal condition; this may be mostly due to the negative IOD and the evolving weak La Niña. Also, because of those climate conditions in Indian and Pacific Oceans, Australia is expected to receive above normal rainfall during austral spring and summer. The active South Pacific Convergence Zone (SPCZ) may play a role in this, too However, we expect a weak dry condition in the southwestern coastal region of Western Australia because of the evolution of weak Ningaloo Niña. [ Editor's Note: Click for Explanation and even more detail on the Ningaloo Niña]
Most part of Japan will experience above normal temperature from summer through winter. We expect above normal precipitation in most part of Japan in September-October. However, it may be noted that the forecast skills in those mid- and high-latitudes on regional scales are still limited.
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 CONUS taking place has significantly increased. It may be in progress. It looks like it will require one more La Nina or ENSO Neutral event and this appears to be the way this might unfold. The AMO is pretty much neutral at this point 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..maybe as many as five.
TABLE OF CONTENTS FOR PART II OF THIS REPORT 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.
TABLE OF CONTENTS FOR PART 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.
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