Seasonal Forecasts Issued January 16, 2020: Part I, NOAA Four-Season Forecast

Written by Sig Silber

Here is the January 16, 2020, NOAA 15-month forecast for CONUS and Alaska including the Early Outlook for February 2020 and forecasts out through April 2021. There are only slight changes since the forecast last month. NOAA is very sensitive about any discussion of how the Nino 3.4 Index is in or near El Nino Levels. That is temporary they say and we agree but temporary is a synonym for currently so we have somewhat less confidence in the early months of their forecast. And the MJO is difficult to forecast.

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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 February, 2020. It is called the Early Outlook because it will be updated at the end of January. Only the February 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 February 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 February*. For Temperature, it is mostly warm in northern and western Alaska, and for CONUS, the Southern Tier but extending way to the north in the West. There is a large cool anomaly centered on the Great Lakes but extending west, south, and east all the way into New England. With respect to precipitation, eastern Alaska is wet but the Panhandle is EC. For CONUS there are two wet anomalies, one for Montana and Wyoming and a bit farther south and the second for the Southeast and there are two dry anomalies one covering most of California and extending into Nevada and a bit into Oregon and a Central Mississippi (Indiana, Illinois, Missouri, and parts of Iowa and Kansas) dry anomaly that has a west to east orientation.

* 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 mostly January (so they are less useful for this purpose) and the third map only extends the coverage through the first fourteen days of February. The Seasonal Outlook was issued early this month since the third Thursday fell on January 16, 2020.  That is still not a solid basis for doing this visual consistency testing but it is the best we have to work with. It may tell us how the second half of the month should differ from the first half of the month for the full-month forecast to be accurate.

First Temperature

The new monthly forecast is to the right. Does it appear to be reflective of the parts of the month for which we have forecasts? →		↑ ← The full month forecast does seem to fit fairly well with the Week 3 – 4 forecast which only covers fourteen days of February as of when we published this article. We will also revisit this question at the end of January when the February forecast is updated.

And then Precipitation

The new monthly forecast is to the right. Does it appear to be reflective of the parts of the month for which we have forecasts? →		↑ ← The full month forecast does seem to fit well with the Week 3 – 4 forecast which only covers fourteen days of February as of when we published this article. We will also revisit this question at the end of January when the February forecast is updated.

Now we consider the three-month Outlook.

Notice that the three-month periods are abbreviated e.g. February/March/April is shown as FMA. You will see such abbreviations often in this report.

Prior Temperature Outlook for FMA 2020

New Temperature Outlook for FMA 2020

Prior Precipitation Outlook for FMA 2020

New Precipitation Outlook for FMA 2020

Now let us focus on the long-term situation.

First Temperature

Prior 14 Month Temperature Outlook: FMA 2020 – JFM 2021

New 14 Month Temperature Outlook: MAM 2020 – FMA 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: FMA 2020 – JFM 2021

New 14 Month Precipitation Outlook: MAM 2020 – FMA 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 January 16, 2020. 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 (February), the new NOAA Summary for FMA, and finally the remainder of the 15-Month Forecast.

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

ENSO-neutral conditions persist across the tropical Pacific Ocean. The Nino 3.4 index value peaked at +0.8 degrees C during the fall, but this was largely related to the Madden-Julian Oscillation (MJO). This index value has recently decreased to around +0.5 degrees C (for both the most recent week and the Oct-Dec 2019 season). Weekly sea-surface temperature (SST) index values remain the largest (near +1.0 degree C) in the westernmost Nino 4 region[Editor’s Note: JAMSTEC considers that to be Modoki like], and the smallest (near +0.2 degree C) off the South American coast in the Nino 1+2 region. A weakening of the low-level trade winds has resulted in westerly wind anomalies near the Date Line. These low-level westerly wind anomalies, in turn, often initiate the development of an oceanic Kelvin wave and associated downwelling. The result is an increase in both the magnitude of positive temperature departures at the sea surface, and the volume of warmer-than-normal sub-surface reservoir over the central and eastern Pacific. Equatorial subsurface temperature anomalies (averaged across 180 to 100 degrees W) re-bounded in accordance with this anticipated short-term warming. Despite this recent warmup of surface and subsurface temperatures in the Pacific, model guidance suggests this is only temporary and is not likely to result in the formation of an El Nino. OLR anomalies (used as a proxy for tropical convection) indicated enhanced convection was generally confined to an area west of the Date Line, and suppressed convection was noted over Indonesia and also east of the Date Line.

PROGNOSTIC DISCUSSION OF SST FORECASTS

The CPC SST consolidation forecast, which includes three statistical forecasts along with the CFS model, predicts a continuation of ENSO-neutral conditions through the early spring before the CFS and statistical models slightly diverge. The North American Multi-Model Ensemble (NMME) ensemble mean forecast for the Nino-3.4 SST anomaly is near +0.5 degrees C during mid-winter and then slowly decreases towards zero thereafter, reaching the zero anomaly line by April. Based on the latest observations and model forecasts, the CPC/IRI ENSO outlook favors ENSO-neutral conditions to persist through at least this spring.

30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2020  

The temperature and precipitation outlooks for February largely reflect dynamical model guidance, statistical relationships with modes of variability in the tropics, and some consideration for local sea surface temperatures. The Madden-Julian Oscillation is strong and likely to play a significant role in the upcoming month, which potentially means increased variability and a pattern flip in the middle of the month. The potential for escalated variability decreases the overall confidence in the outlooks.

Temperature

The temperature outlook for Alaska reflects model guidance in that above normal  temperatures are favored for western Alaska in all but 2 of the NMME models, though the probabilities are just slightly higher than the NMME models. The slight increase in probabilities is supported by more recent runs of the CFS and lagged composites of a currently strong MJO event pointing toward a warming in the middle of the month. A cooler signal is evident for eastern Alaska,  which contradicts some trends , so equal chances are specified there. A strong phase 5/6 of the MJO can also indicate a colder period for the eastern CONUS, approximately 15-30 days later. The colder period would not be expected to extend beyond about 15-20 days in length, as an active MJO would reverse the signal as it traversed the tropics. Given that potential MJO signal and consistent model support, below normal temperatures are favored from eastern Montana to the Northeast and southward to the Tennessee Valley. Probabilities  are highest where statistical measures and model forecasts agree. Trends are positive and signals  for below normal temperatures moderate for the Southeast, so equal chances are indicated, except over Florida, where above normal temperatures are favored. The area where above normal temperatures are favored extends westward from Florida across the immediate Gulf Coast, into Texas and the Central and Southern Rockies, terminating at the West Coast. Across the Great Basin, above normal temperatures are favored by trends  and some models, though signals  are weaker in the older model runs and much stronger in more recent runs.

Precipitation

The MJO would support the development of a trough near Baja California, which could limit the southern extent of a broad dry area in many of the NMME models. The pattern that would support the cold air would also support multiple frontal passages over the eastern CONUS with northerly flow in the wake of each passage, resulting in overall dry conditions in the from the Midwest to the Central Plains and potentially leaving dissipating fronts across the Gulf Coast, enhancing odds for precipitation over the Southeast. The precipitation outlook for Alaska is highly uncertain, though predicted above normal sea-surface temperatures in the Gulf of Alaska are likely associated with ridging there [Editor’s Note: This is an extremely important issue. Does a ridge of high pressure cause ocean warming? Does ocean warming cause a ridge of high pressure? This reminds me of the Blob and the RRR, the Rediculously Resiliant Ridge, which was farther south] and a storm track pushed into mainland Alaska, so above normal precipitation is slightly favored for central Alaska. Storms that are pushed northward into Alaska, would have less of an impact on California and Oregon, so below normal precipitation probabilities are elevated for central California, western Nevada, and southern Oregon. That same storm track could support more activity for the Northern Rockies, and MJO composites indicate conditions supportive of more upslope potential, so above normal precipitation is indicated from eastern Montana to Northern Colorado.

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

ENSO-neutral conditions continue across the equatorial Pacific Ocean, as represented in current oceanic and atmospheric observations. The official CPC ENSO forecast indicates that ENSO-neutral is most likely through the Northern Hemisphere spring 2020 (~60 percent chance) and summer 2020 (~50 percent chance).

Temperature

The February-March-April (FMA) 2020 temperature outlook favors above normal temperatures from central and southern portions of the West, across the southern tier of the CONUS, and the East Coast states. Increased chances for below normal temperatures during FMA are forecast across the northern Great Plains, the Upper Mississippi Valley, and the western half of the Great Lakes. Equal chances (EC) of above, near, or below normal temperatures are indicated across the remainder of the CONUS. Above normal temperatures are favored throughout much of Alaska, with the exception of EC over the extreme southeastern mainland and the Southeast Panhandle region.

Precipitation

The FMA 2020 precipitation outlook indicates enhanced probabilities of above normal seasonal total precipitation amounts east-southeastward from the northern Intermountain region and northern Rockies across the northern Plains, most of the Mississippi Valley, the Great Lakes region, and Ohio and Tennessee Valleys. Below normal seasonal precipitation amounts are favored across southwestern Oregon, California, much of Nevada, Arizona, New Mexico, and parts of West Texas. Equal chances (EC) are forecast among areas where seasonal precipitation amounts are expected to be similar to climatological probabilities. In Alaska, there are elevated probabilities of above normal seasonal total precipitation amounts from about the Alaska Range northward to the Arctic Coast, and EC for approximately the southern third of the state.  

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

The temperature and precipitation outlooks for FMA 2020 were based on dynamical model guidance and statistical tools that include global SST anomaly patterns and a canonical correlation analysis that uses the evolution of SST and sea-level pressure as predictors. During the next several leads, the seasonal outlooks were based largely on the calibrated probabilistic forecasts from the NMME and a consolidation forecast of dynamical and statistical tools. Long-term climate trends  were considered for all leads but were relied on more heavily from summer 2020 through the next winter 2020-21.

PROGNOSTIC DISCUSSION OF OUTLOOKS – FMA 2020 TO FMA 2021

TEMPERATURE

During FMA 2020 there are increased chances of above normal temperatures from central and southern portions of the West across the southern tier of the CONUS, and the East Coast states. This is based on the temperature consolidation tool (which includes the NMME), the CFS, the ENSO-OCN tool, and to some degree the CBaM. The latest outlook differs from the one issued last month (also valid for target season FMA) in that the Pacific Northwest/northern Rockies is now indicated as EC rather than favoring above normal, and trends support the highest probabilities for above normal temperatures over the Southwest to be shifted over/near New Mexico (in excess of 50%). The latest outlook also differs from the previous one for FMA over the Northeast/Upper Mid-Atlantic where indications generally show a slight westward shift of above normal temperatures. Increased chances for below normal seasonal mean temperatures during FMA are forecast across the northern Great Plains, the Upper Mississippi Valley, and the western half of the Great Lakes, which differs slightly from the previous outlook in that the eastern portion of the favored below normal temperatures (Lower Lakes region) now looks less convincing.  This is borne out by the temperature consolidation tool (which includes the NMME suite of forecasts), CCA, and OCN trends . The probabilistic NMME and the PAC predict enhanced odds of near normal temperatures for this region. Above normal temperatures are favored throughout much of Alaska, with the exception of EC over the extreme southeastern mainland and the Southeast Panhandle region, with this greater uncertainty indicated by the CFS and CBaM (which predict near to below normal temperatures), and the NMME-based solutions. Maximum probabilities for above normal temperatures are depicted over northwestern Alaska, in part related to the climatologically earlier breakup of sea ice near the coast, and historical temperature trends . For remaining areas of the CONUS and Alaska, where models and tools are either contradictory or predict weak signals , EC is favored.

For MAM and AMJ 2020 (leads 2 and 3) above normal temperatures are favored over all of Alaska, with the highest probabilities (in excess of 70% and 60%, respectively) focused over the northwest part of the state. This is supported by the climatological breakup of sea ice approximately a month earlier in recent decades, related historical temperature trends , the temperature consolidation tool, CCA, SST Constructed Analog (SST-CA) tool, and to some degree the CFS. Above normal temperatures are also favored for much of the CONUS, with the exception of the northern High Plains generally eastward across the northern half of the Mississippi Valley into the Great Lakes region. Most tools suggested a larger extent of above normal temperatures across the CONUS, but part of the reason for the extensive area of EC across the northern CONUS is the likelihood of an increasing contribution from soil moisture, with above normal precipitation forecast for FMA, MAM, and AMJ 2020.

For the remaining seasons, MJJ 2020 through FMA 2021, the seasonal outlooks were heavily tilted toward historical climate trends , as incorporated into the statistical consolidation tool (which does not include the NMME guidance).

 PRECIPITATION

The precipitation outlook for FMA 2020 favors above normal seasonal total precipitation amounts east-southeastward from the northern Intermountain region and northern Rockies across the northern Plains, parts of the Mississippi Valley, the Great Lakes region, and Ohio and Tennessee Valleys. Within this broad area, there are two separate areas of slightly higher probability (>40%); one in the northern High Plains, and the other in Kentucky/Tennessee. In-between these two probability maxima (in the unseasonably wet Dakotas & Upper Midwest), there are slightly lower probabilities for above normal precipitation, between 33% and 40%. The monthly precipitation outlook for February depicts below normal precipitation over portions of the Middle Mississippi Valley, which at first glance appears to conflict with the seasonal precipitation outlook. However, February is typically a drier month for this region, so this is consistent with short-term dryness and variability. The updated FMA outlook is supported by the precipitation consolidation tool (which includes the NMME), the CFS, and trends . The ENSO-OCN, which is often used as a first guess, depicts above normal precipitation over the northern High Plains and northern Rockies, and from the south-central Mississippi Valley northeast to the Great Lakes. Above normal precipitation is also favored over Alaska from about the Alaska Range poleward to the Arctic Coast, as supported by various models/tools. There are increased odds of below normal precipitation over southwestern Oregon, California, much of Nevada, Arizona, New Mexico, and parts of West Texas. This area of favored below normal precipitation has been shifted somewhat west and north from last month’s outlook (valid for FMA). Equal chances (EC) is indicated for those areas where seasonal precipitation amounts are expected to be similar to climatological probabilities.

For MAM and AMJ 2020 (leads 2 and 3), above normal precipitation continues to be favored for northern and central Alaska (north of the Alaska Range) based on the precipitation consolidation tool, the CBaM, NMME guidance, and the SST-CA. Over the CONUS, the large area of favored wetness in FMA gradually shifts eastward in MAM and AMJ, with the highest probabilities (>40%) depicted over the Ohio Valley, most of the Appalachians, and the Mid-Atlantic. This expected evolution generally parallels the precipitation consolidation and ENSO/OCN tool outputs during these seasons. By AMJ, the CFS and the SST-CA differ from the ENSO/OCN and consolidation by focusing the heaviest precipitation farther south and west over the Gulf Coast states. The area of favored below normal precipitation across the western CONUS gradually shifts northward by AMJ to include the Pacific Northwest, northern Intermountain region, and northern Rockies, signaling the transition from the climatological rainy season to the dry season.

 Coverage of favored areas for anomalous precipitation decrease during the summer as forecast confidence diminishes with a weakening signal among tools and convective precipitation becomes more dominant. The favored areas of below or above normal precipitation at later lead times are based largely on historical trends .

New Seasonal Drought Forecast

ENSO Considerations

Since the ENSO phase is not likely to change very much and since NOAA does not make it clear which forecasts for the NOAA Phase they rely on, we have decided to greatly abbreviate our coverage of that topic for the time being but it is discussed well in the NOAA Discussion so you can read their thoughts on the matter there. We are going to show the latest IRI-CPC meteorologist survey forecast of the probabilities, The mid-month computer model forecast has not yet been issued. 

So we are providing mostly the information we provided after the earlier IRI-CPC Update on January 9, 2020

Here is an update of the above.

I will add to the discussion the Australia BOM assessment of the situation.

And the JAMSTEC evaluation

Here is the short JAMSTEC discussion. We will discuss it a bit more on Sunday but suffice it to say the two agencies are not on the same page.

Jan. 17, 2020 Prediction from 1st Jan., 2020

ENSO forecast:

As predicted earlier, the El Niño Modoki-like state has been observed. The SINTEX-F predicts that a weak El Niño Modoki-like pattern will persist at least until boreal summer.

Indian Ocean forecast:

The strong positive Indian Ocean Dipole almost disappeared. However, the model predicts the evolution of another moderately positive Indian Ocean Dipole from boreal summer. There is a large uncertainty in the prediction at present due to the large spread in the prediction plumes of the dipole mode index. The Ningaloo Niño off the west coast of Australia has quickly emerged in December 2019. The model predicts that the Ningaloo Niño will persist until late austral summer. The strong negative Indian Ocean Subtropical Dipole has quickly emerged in September 2019, and then reached the peak in December. The model predicts that it will persist until late austral summer.

Regional forecast:

On a seasonal scale, the SINTEX-F predicts that most part of the globe will experience a warmer-than-normal condition in boreal spring. In boreal summer, almost all part of the globe will still experience a hotter-than-normal condition.

As regards to the seasonally averaged rainfall in boreal spring, a drier-than-normal condition is predicted for northern Brazil, most part of Southeast Asia, Indonesia, Philippines, and eastern Australia. In boreal summer, a wetter-than-normal condition is predicted for northwestern Brazil, southern part of West Africa, some parts of Southeast Asia, Philippines. In contrast, Mexico, northeastern Brazil, eastern Australia, northern part of West Africa, some part of India, northeastern China, and Indonesia will experience a drier-than-normal condition.

The model predicts most part of Japan will experience warmer and slightly drier-than-normal condition in the coming spring as a seasonal average. In summer, most part of Japan will be slightly warmer and wetter than-normal.

JAMSTEC calls the current pattern “El Niño Modoki-like state”

It is almost like there is a gag order at NOAA not to discuss that we are in somewhat El Nino Conditions or probably more correctly in ENSO Neutral but with an El Nino bias. Actually it is not almost like as I witnessed a more senior NOAA employee correcting a more junior NOAA employee who dared to mention this.

But we are not having El Nino weather. It is more like La Nina weather. The explanation may be that the warm area along the Equatorial Pacific is westerly displaced. So we consult the JAMSTEC Modoki Index.

It is clearly in El Nino territory and the Walker Cycle would be displaced to the west.

We may cover this more on Sunday but probably not in any great detail but will focus on any differences in the forecast.

Suffice it to say that we do not have total confidence in the NOAA forecast.

B. Conclusion

There were a number of fairly minor changes. The dynamic models do the best job of forecasting the next month so the new outlook issued each month is better able to forecast the next three months which last month was months JFM and now is FMA. There is always a lot of uncertainty in the forecasts and we see a lot of switching back and forth from month to month which probably is more related to how the conflicting or weak model results are resolved in the forecast rather than true changes in the forecast. So we may be seeing certain changes in the forecast maps which really reflect how the conflicting information is resolved that month rather than true changes in the forecast.

This month the thinking is that the MJO might become a lot more active. But an active MJO typically supports El Nino conditions.

All in all the forecast basically has not changed.