Written by Sig Silber
Updated at 8:15 p.m. EDT October 19, 2019 to reflect the new Week 3 – 4 Forecast which does not support the November forecast issued on Thursday.
Here is the October 17, 2019 NOAA 15-month forecast for CONUS and Alaska including the Early Outlook for November and forecasts through January 2021. There are a fair number of changes since the forecast last month. The precipitation forecast is fairly complex. The Early Outlook for the single month of November may change again when it is updated at the end of October fourteen days after the current NOAA release.
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A. Focus on the NOAA Update
A note about terminology; the deviations from climatology/normal are color-coded but also labeled “A” for more than (above) normal and “B” for less than (below) normal. The area designated EC means Equal Chances of being more or less than normal. In my comments For the shorter-term maps, NOAA uses “N” instead of “EC” as they believe they can be more definitive with respect to shorter timeframes. So the words “warm”, “cool”, “wet”, “dry” should be generally interpreted as being relative to climatology/normal for that location and time of year.
First, we will take a look at the NOAA Early Outlook for November, 2019. It is called the Early Outlook because it will be updated at the end of October. Only the November Outlook will be updated at that time.
Temperature
Precipitation
We have nothing to compare these maps with as NOAA does not in their Update provide a forecast for each of the subsequent two months separate from their three-month forecast. Thus I do not have forecast maps for October from the previous NOAA Report to compare against. And the current month is not over so we can not really compare the forecast for next month against the actual for this month. It is probably best to just try to understand what NOAA is trying to convey about November*. For Temperature, it is warm all over except for an EC area in the Northwest and with respect to the warm anomaly the probabilities of being warmer than climatology are highest in Northern Alaska and CONUS Southwest. With respect to precipitation, Alaska and the Panhandle are wet and for CONUS it is mostly EC with a wet anomaly centered on Wyoming and Nebraska and two dry anomalies, one for Northern California and southern Oregon and a larger dry anomaly for the Gulf Coast states but extending to the next state north i.e. Arkansas and Tennessee.
* compared to normal/climatology for the indicated time of the year.
Visual Consistency Testing.
It is useful to see how the month forecast fits with the set of shorter forecasts that we have. The first two maps cover October (so they are less useful for this purpose) and the third map only extends the coverage through the first eight days of November. The Seasonal Outlook was issued fairly early this month since the third Thursday fell on October 17, 2019.
Perhaps we should have waited a day to publish this article but there were two NOAA releases today so we day to decide which to publish today and which tomorrow. I wanted our readers to get the new forecast ASAP. We will update this Visual Consistency Testing after the Week 3 – 4 forecast is issued on Friday October 18. We may not be able to do that until Saturday morning – but it will be done.
First Temperature
 |  |  |
| The new monthly forecast is to the right. Does it appear to be reflective of the three parts of the month for which we have forecasts? → |
| ↑ ← The full month forecast does not seem to fit well with the Week 3 – 4 forecast which now covers the first two weeks of November. We will also revisit this question at the end of October when the November forecast is updated. |
And then Precipitation
 |  |  |
| The new monthly forecast is to the right. Does it appear to be reflective of the three parts of the month for which we have forecasts? → |
| ↑ ← The full month forecast does not seem to fit well with the Week 3 – 4 forecast which now covers the first two weeks of November. We will also revisit this question at the end of October when the November forecast is updated. |
Now we consider the three-month Outlook.
Notice that the three-month periods are abbreviated e.g. November/December/January is shown as NDJ. You will see such abbreviations often in this report.
Prior Temperature Outlook for NDJ 2019 – 2020
New Temperature Outlook for NDJ 2019-2020
Prior Precipitation Outlook for NDJ 2019-2020
New Precipitation Outlook for NDJ 2019-2020
Now let us focus on the long-term situation.
First Temperature
Prior 14 Month Temperature Outlook: NDJ 2019/2020 – OND 2020
New 14 Month Temperature Outlook: DJF 2019/2020 – NDJ 2020/2021
To compare maps from one release to another, one needs to remember that the new release drops one three-month period and adds a later one. So to make the comparisons one has to shift the new maps to the right one position and that makes the map on the right drop down to become the left-most map in the next level. I do not have a computer software tool for doing that for you so you have to do it mentally. When I do the comparison, I print the two sets of maps and put them side by side and number the same three-month maps 1, 2, 3,…..,11 in both sets of maps to make it easier for me to easily compare the same three-month period in the new with the previous forecast. One uses the same procedure to compare the precipitation maps. Based on this procedure, I conclude that:
Now Precipitation
Prior 14 Month Precipitation Outlook: NDJ 2019/2020 – OND 2020
New 14 Month Precipitation Outlook: DJF 2019/2020 – NDJ 2020/2021
If you want larger versions of each map (temperature and precipitation) you can find them here. And then each of those maps can be clicked on to further enlarge them.
Sometimes it is useful to compare the three-month outlook to the forecast for the first of the three months. It shows how much the pattern changes over the three-month period.
One can mentally subtract the First-Month Outlook from the Three-month Outlook and create the Outlook for the last two months in the three-month period.
*The concept is that the probabilities of a deviation from climatology in the First Month and the combined Month Two and Three forecast that one derives must average out to the probabilities shown in the three-month maps.
Below is the NOAA Discussion (slightly reorganized) released by NOAA on October 17, 2019. Headings that are “Initial Cap” only rather than all caps were added by the Author of this Update Report for clarity. Also, we have organized the sequence of the sections of NOAA Discussion to first present the Atmospheric and Oceanic Conditions and then the Initial Month (November), the new NOAA Summary for NDJ, and finally the remainder of the 15-Month Forecast.
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
As noted in the summary, oceanic and atmospheric indicators show current ENSO-neutral conditions. The most recent Nino3.4 index is +0.4 degrees C, but there is variation in sea surface temperature (SST) anomalies along the equatorial Pacific from west of the Date Line to the South American coast. Greater than +1.0 degree C anomalies remain east of Papua-New Guinea while small negative SST anomalies are depicted in the eastern Pacific ocean. A review of the ocean sub-surface does depict cooler SSTs in the eastern portion of the Pacific basin are likely connected to the shoaling of an upwelling oceanic Kelvin wave in recent weeks. The subsurface ocean data also shows, however, a downwelling oceanic Kelvin wave shifting eastward at depth in the central Pacific. This wave is likely to reach the south American coast in coming weeks and moderate SSTs to some degree in the central and eastern Pacific in November to most likely weakly positive anomalies.
Two other areas of ocean anomalies need to be watched in the coming couple of months. One is a large area of positive SST anomalies ranging from 1-3 degrees C north of 20 N in the northeast Pacific Ocean. Extratropical SST anomalies, although often impressive in scale, can change rapidly due to mid-latitude wave activity and the associated variation in mean storm tracks. But this regional SST anomaly can be utilized, to some degree, as a predictor for the first lead of the current seasonal outlook package.
Also, a strong Indian Ocean Dipole (IOD) is currently in place with above-normal SSTs in the western Indian Ocean and below normal SSTs in the eastern Indian Ocean and waters in proximity to the Maritime continent. The atmosphere has responded to this boundary forcing with stationary enhanced convection observed for several weeks across Africa and the western Indian Ocean with stationary suppressed convection observed from the eastern Indian Ocean eastward across the Maritime continent into the west Pacific to near the Date Line. This is important because if suppressed convection persists in the western Pacific along with the absence of any organized, large scale enhanced convection further east in the Pacific, it may tend to favor more frequent periods of a retracted east Asian-Pacific jet and so in some ways mimic La Nina like conditions downstream – mainly during the few early leads in the forecast package.
Positive soil moisture anomalies remain quite high and in fact much of this area is observing values at or greater than the 99th percentile of the respective historical range. Flash drought conditions in the Southeast CONUS are favored to ease in coming weeks with favored above-normal rainfall during the second half of October. Moreover, as has been the cas e, SST anomalies range from +2.5 to +3.5 degrees C, or higher for waters surrounding Alaska.
PROGNOSTIC DISCUSSION OF SST FORECASTS
The CPC SST consolidation forecast, the NMME ensemble mean forecast and the official CPC / IRI probabilistic ENSO outlook for Nino3.4 all favor continued ENSO-neutral conditions through the upcoming winter 2019-2020 and spring 2020. There is, of course, considerable spread across the various model forecasts (statistical and dynamical) over the next 6 months. A few dynamical models favor a tendency toward bordering on weak La Nina (as characterized by Nino3.4) by late winter while the majority remain in ENSO-neutral territory or tend toward borderline weak El Nino over the same period. The expectation of ENSO-neutral conditions was utilized in making this month’s seasonal outlook package.
30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2019
The outlook for temperature and precipitation for November of 2019 is largely influenced by dynamical model and statistical tool guidance, and to a lesser degree antecedent conditions. Dynamical models inputs are from daily initializations of the CFS and those in the NMME suite.
For statistical tools, lagged temperature and precipitation conditions, based on observed soil moisture, have little skill in the cool season, so they were not considered in this outlook. Lagged impacts from MJO activity were considered, though the progression of the MJO across the Indian Ocean to the Maritime Continent, where teleconnections to North America are stronger, is highly uncertain with only the ECMWF predicting an amplified RMM2 state. Lagged impacts would favor more warmth over the Great Lakes and Mississippi Valley. Plots from recent initializations of the CFS 200-hPa height anomalies have some resemblance to lagged composites of MJO activity over the Indian Ocean. Therefore, the statistical predictors used in this outlook are trend (optimal climate normals, 15-year trends ),constructed analogs, and lagged composites of MJO activity.
Temperature
Trends would largely favor above normal temperatures, with the strongest signal from the Southwest to the Upper Great Lakes, with positive but weaker signals over much of the rest of the CONUS. Model output and MJO activity favor troughing inland over the Pacific Northwest and ridging over the Plains, allowing for periods of colder air to move from the Northern Plains to the Southern Appalachians. That pattern supports no signal over the Northwest and more uncertainty from the Northern Plains to the Tennessee Valley. Trends and model output strongly favor above normal temperatures form the Southwest to the Southeast, and from the Upper Great Lakes to the Northeast. Over Alaska, the sea ice edge is still far from the coast, so the probabilities for above normal temperatures are very high for the northern and northwestern coastal areas, decreasing to the south and east across the state.
Precipitation
The same 200-hPa pattern would support above normal precipitation for Alaska, with ridging over the Central Pacific implying a storm track into Alaska and a trough near the Pacific Northwest. Signals for below normal precipitation along portions of California were stronger in earlier CFS runs, and have weakened but not completely disappeared from recent runs, so a small area of slightly enhanced below normal precipitation probabilities is indicated over northern California and Oregon. Ridging over the central portions of the CONUS would favor drying downstream. Earlier model runs had large areas of drier than normal conditions for the Mississippi Valley to the Gulf Coast, but recent model runs and MJO composites are showing the ridge slightly further east. That shift in the pattern shifts the probabilities toward above normal precipitation in the Rockies and the Central Plains, while shrinking the area where below normal precipitation is favored over the Southeast.
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS (Focus on first three months)
Oceanic and atmospheric conditions in the equatorial Pacific Ocean reflect an ENSO-neutral state and these conditions are forecast to continue through the winter and spring of 2019-2020. Additional details regarding tropical conditions are provided below.
Here we focus on a summary of the first 3-month seasonal outlook for temperature and precipitation for the November-December-January (NDJ) season. Additional information related to the forecast for this season and subsequent 3-month overlapping seasonal outlooks through NDJ 2020-2021 are also given below.
Temperature
The NDJ 2019-2020 temperature outlook favors above-normal seasonal mean temperatures for Alaska and most of the contiguous U.S., with the greatest probabilities forecast for northwest Alaska and the Southwest U.S. where probabilities exceed 60% and 50% respectively. Odds for above-normal temperatures are more modest for most of the eastern U.S. and a small region in the upper-Mississippi valley is denoted Equal-Chances (EC) where climatological odds for either of the three categories (below-, near- or above-normal) is forecast.
Precipitation
The NDJ 2019-2020 precipitation outlook favors above-normal seasonal total precipitation amounts for Alaska (especially the Southwest portion of the state) and for a region from New Mexico northward to include the northern Rockies, northern and central Great Plains and the north-central Mississippi Valley. Smaller areas of favored below-normal seasonal precipitation amounts are highlighted for the central West coast and central Gulf Coast. Remaining areas of the forecast domain denote Equal-Chances (EC) where climatological odds for either of the three categories (below-, near- or above-normal) is forecast.
BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
The temperature and precipitation outlooks were based on currently depicted, organized, large scale SST anomaly patterns (i.e., ENSO-neutral, IOD, northeast Pacific SSTs, and near Alaska SSTs), both temperature and precipitation long term climate trends , bias-corrected and calibrated dynamical model forecasts from several sources, statistical forecast tools including the Constructed Analogue (CA) tool using near global SSTs as the primary predictor and an objective, historically skill weighted consolidation of (1) statistical tools only and (2) both statistical and dynamical forecast tools. Since ENSO is unlikely to provide a major influence on the mid-latitude circulation pattern, long term climate trends were weighted more heavily than normal during early and middle forecast leads.
PROGNOSTIC DISCUSSION OF OUTLOOKS – NDJ 2019 TO NDJ 2020
TEMPERATURE
The NDJ 2019-2020 temperature outlook depicts high coverage of above-normal temperatures across the forecast domain. This forecast was supported by most statistical and dynamical model forecast guidance and long term positive temperature trends . The warm northeast Pacific ocean also somewhat favors warmer air entering the western CONUS for this season especially early on in the 3-month period. The high uncertainty of any persistence of this regional feature substantially limits its predictive value thereafter. The greatest odds for above-normal seasonal mean temperatures are for western Alaska and the Southwest CONUS at a greater than 60% and 50% probability respectively. For western Alaska, strongly above-normal SSTs in part associated with declining long term trends in sea ice coverage, multi-year ice (thickness) and later freeze dates contribute to these higher forecast odds. More modest odds for above-normal temperatures are forecast for the remaining areas of the forecast domain where climate signals and forecast tool consistency were somewhat less.
A small region of Equal-Chances (EC) is denoted in the upper Mississippi Valley where some forecast tool information indicates somewhat less historical forecast skill and considerations are made for potentially increasing odds of below-normal temperatures at the end of this season. In this region the forecast is for no change from climatological odds (33%) for either above-, near- or below-normal seasonal mean temperatures.
Progressing through the winter and spring seasons (DJF 2019-2020 – MAM 2020), the evolution of the forecast is for continued favored above-normal temperatures (albeit at lower odds) for the western and southern CONUS as forecast tools, both statistical and dynamical guidance, support this forecast. Moreover, combining objectively the associated impact from the CPC consolidation Nino3.4 SST forecast and long term positive temperature trends for these seasons supports this evolution of above-normal temperatures as well as the increase in spatial coverage of forecast uncertainty as depicted by EC areas through MAM 2020.
Although odds are modest, elevated probabilities for below-normal temperatures are introduced in JFM 2020 in the northern Great Plains, increased in coverage in FMA 2020 (extended eastward to include the northern Great Lakes) and then decreased in areal extent in MAM 2020. Statistical guidance including negative long term temperature trends in some areas, especially in FMA 2020, along with enhanced odds of above-normal precipitation are the basis for the forecast. It is felt that the high probabilities of above-normal temperatures from most dynamical model guidance in this region may be overdone. Above-normal temperatures remained highly favored for Alaska peaking for the northwest coastal areas during MAM 2020 and again in SON 2020.
The remaining forecasts throughout 2020 across the CONUS are largely derived from an objective, historically skilled weighted combination of statistical forecast tools and support large coverage of favored above-normal temperatures for most, if not all, of the forecast domain over the period.
PRECIPITATION
The NDJ 2019-2020 precipitation outlook depicts above-normal seasonal total precipitation amounts for all of Alaska and for a region stretching from New Mexico northward to include the northern Rockies and the north-central Great Plains and Upper Mississippi Valley. For Alaska, dynamical model guidance, long term positive precipitation trends and overall warmer, more open waters (potentially wetter, stronger cyclones) around the state support the forecast. Across the CONUS, strong climate signals for precipitation departures from climatology were few. For NDJ and DJF 2019-2020, statistical guidance consolidation and long term positive precipitation trends are the primary basis for the forecast in these two seasons.
Modestly elevated odds for below-normal precipitation for small regions of the central West coast and central Gulf Coast are primarily based on dynamical model guidance and to a lesser extent long term negative precipitation trends .
Progressing from DJF 2019-2020 through AMJ 2020, forecast areas of favored above-normal precipitation along the northern tier of the CONUS slowly shift from the northern Rockies and Great Plains to parts of the Great Lakes, Ohio Valley and mid-Atlantic. In addition to statistical guidance consolidation and long term positive precipitation trends , support for these highlighted areas also includes dynamical model guidance from the NMME from JFM through MAM 2020. At the same time, the majority of forecast tools support migration of favored below-normal precipitation from Texas to the Southwest and central and southern California by MAM 2020. The remaining outlooks are based on long term precipitation trends in the absence of more clear, reliable climate signals such as a confident ENSO prediction.
New Drought Forecast
ENSO Considerations
We covered this in our October 11 article on the NOAA ENSO Status Update which can be read here. So I am not going to go into a lot of detail tonight. The NOAA Atmospheric and Oceanic Conditions section in the NOAA Discussion is excellent. We will be discussing any differences between the NOAA assessment of ENSO and JAMSTEC in our Sunday night article.
Here is the NOAA proprietary model.
And just to look ahead, here is the JAMSTEC one year forecast
And the CPC-IRI Probability Analysis.
B. Conclusion
There were a number of changes mostly related to the timing of the transition to ENSO Neutral and the timing of changes in the ENSO status over time.
We will provide a more detailed comparison when we compare the NOAA and JAMSTEC forecasts Sunday night.
