NOAA Updates The Outlook For January, 2021 – Mega-Change, Happy New Year

Written by Sig Silber

Updated at 8:00 pm January 1, 2021 to reflect the new Week 3-4 Report. It adds more nuance and partially contracts the Monthly Report issued yesterday. The Week 3 – 4 Report at this point in time represents half of January but it is the second half so it gets weighted less when making the full month forecast and probably was not available at the time the full month report was issued. It is clear that the forecast for January has a lot of factors which can change the actual weather for the month.

At the end of every month, NOAA issues an update to their Early Outlook for the following month which was issued as usual on the Third Thursday of December. Today, fourteen days later, NOAA has issued their Updated Outlook for January. There are some very significant changes. The changes raise questions about the three-month forecast.

Some housekeeping: On December 19, 2020, we published Part I of our analysis of the NOAA and JAMSTEC Three- to Four- Season Outlook and that can be accessed here. In that report, the January 2020 Early Outlook was issued. This article presents the NOAA update of their Early temperature and precipitation Outlooks for January and the most recent Drought Forecast update for the month of January.

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I am trying to understand the reason for the major change in the forecast. The updated forecast is always different from the Early Look but this month it is a really significant change.

First a few comments on a possible La Nina Modoki. First we look at the Equator from the surface down to 450 meters. We are looking for temperature anomalies i.e. deviations from normal. We expect the surface to be warmer and it to be colder at depth. What counts is the deviation from normal.

A month ago	Currently

Here is a different view the surface and I have not frozen this graphic so it will continue to update daily in this article.

Now, we will compare the NOAA Early Outlook for January 2021 with the newly issued update.

Early Outlook Temperature

Updated Temperature Forecast

Early Outlook Precipitation

Updated Precipitation Forecast

Here is the discussion released with the forecast.

30-DAY OUTLOOK DISCUSSION FOR JANUARY 2021

The updated outlook for January 2021 for temperature and precipitation is largely based on recent instances of official NOAA products, model guidance, and the status of major climate oscillations. La Nina is likely to persist through January, with the most recent Nino 3.4 value at -0.9 deg C. There is some uncertainty associated with the MJO, as some models have a signal emerging in phase 3, and other models have no signal. Lagged impacts from a phase 3-4 propagation would be associated with negative (positive) temperature anomalies over Alaska and into the Western CONUS (centered on the Great Lakes). Some models are showing a weakened polar vortex, though none explicitly show a sudden stratospheric warming (SSW) at this point. The weakened polar vortex could set the stage for colder air into the eastern CONUS, though uncertainty about any SSW activity is high.

The temperature outlook reflects current model guidance, with the incorporation of official outlooks for the near term, though the probabilities are moderated compared to the model guidance to account for MJO and SSW related uncertainties. The temperature outlook favors above normal temperatures from the Northern Great Plains (largely from early in the month), to the Northeast (consistent signal for the entire month) to the Gulf Coast. A negative Arctic Oscillation and high latitude blocking across eastern Canada is another reason why probabilities for above normal temperatures in the Northeast/Great Lakes are not as high as most model guidance. Across Alaska, model guidance is indicating high uncertainty, with cold temperatures for western Alaska to start the month, but mitigated by the well below normal sea ice and a moderating pattern by the middle of January.

The precipitation outlook reflects a predicted wet start to the month for the West Coast, with the most consistent signals from Central California to Oregon, and inland to the Central Rockies as the storms track that way. Some signal for dryness remains over the Southwest and Rio Grande Valley, but it’s weak compared to the mid-month outlook. Above normal precipitation is favored from the Great Plains to the East Coast, with early month moisture predicted to surge northward from the Gulf of Mexico. A phase 3 MJO would result in troughing over the Rockies, seeding downstream storminess, though a SSW with cold air into the east would mitigate that, so probabilities are modest. Signals are mixed for most of Alaska, but some moderate signals remain for above normal precipitation across the Alaska Peninsula with dryness across interior Alaska.

Visual Consistency Testing.

It is useful to see how the full-month forecast fits with the set of partial-month forecasts that we have. These will continue to update in this article. It is important to remember that with the partial-month forecasts, we generally have about 25 days of the subsequent month to look at when we do this at the end of the month as we are doing now. It depends on what day of the week the month ends. So this month, which ended on a Thursday, we were missing a forecast that included seven of the last nine days of the month. So we were only in fair shape for the visual consistency testing this month. We have since updated this article after the next week 3 – 4 forecast was issued on Friday and will now have almost the full picture.

First Temperature

The new monthly forecast is to the right. Does it appear to be reflective of the four parts of the month for which we have forecasts? →			↑ ← The Week 3 – 4 forecast was updated on Friday, January 1. At this point, we have forecasts for 29 days of the 31 days in January, and the fit looks fair. Florida may be cooler for the month than indicated. So may the West Coast.

And Precipitation

The new monthly forecast is to the right. Does it appear to be reflective of the four parts of the month for which we have forecasts? →			↑ ←The Week 3 – 4 forecast was updated on Friday, January 1, 2021 At this point, we have forecasts for 29 days of the 31 days in January, and the fit is only fair Alaska looks wrong, and the Southern Tier seems insufficiently dry.

Here is the recently issued discussion with the new Week 3-4 Report

Week 3-4 Forecast Discussion Valid Sat Jan 16 2021-Fri Jan 29 2021

Many large-scale climate drivers are likely to influence this Week 3-4 Outlook. In terms of tropical teleconnections, La Nina persists while the Madden-Julian Oscillation (MJO) is generally incoherent. What enhanced MJO signal does exist is likely over the Atlantic at present, destructively interfering with the low frequency state. At higher latitudes, models continue to advertise a stratospheric warming event in the coming days. The trouble with leveraging these warmings for North American sensible weather is that historically the only significant impacts from such events occurs across Northern Eurasia where the vortex, and associated cold weather, is favored to be situated. Dynamical models also have great difficulty in establishing the response (i.e. split versus displacement) of the polar vortex to stratospheric warmings, let alone where the associated impacts set up. As a result of these factors, consensus among dynamical model guidance is the primary basis of this forecast, with secondary considerations of long-term trends and La Nina.

Dynamical model forecasts consistently feature the positive phase of the Pacific-North American teleconnection over the Pacific, while also highlighting a negative Arctic Oscillation despite some inconsistencies in its North Atlantic center of action. Models all feature some degree of anomalous 500-hPa troughing over North America (ECMWF from the Great Plains through North Atlantic, JMA from the Rockies through Ohio Valley, and the CFS being slightly below-normal over the Lower Mississippi Valley). This troughing location is tied to the upstream anomalous ridging over the Pacific and how far it extends inland over the West (the least in the JMA, relative to other guidance).

The resulting temperature forecast broadly favors above-normal temperatures for much of the country. Confidence is highest for above-normal temperatures across the West and near the Canadian border, although probabilities were damped somewhat relative to guidance across the Northern Tier for the uncertain stratospheric state. Even with some degree of anomalous troughing over the CONUS anticipated in model guidance, these are likely to be offset by long-term trends or La Nina favoring above-normal conditions across much of the southern CONUS. Some equal chances are carved out over the Southeast where these factors destructively interfere, while sea surface temperatures (SSTs) over the Gulf of Mexico and off the Mid-Atlantic and Southeast are below-normal at present. Above-normal temperatures are favored for much of Alaska tied to anomalous ridging being forecast, with equal chances for the Aleutians and southwestern mainland which could be near the anomalous trough axis.

Below-median precipitation is favored across much of the country. The biggest exception is across northern parts of the High Plains, where a slight shift toward above-median precipitation is forecast tied to shortwave activity descending from Canada to the east of the anomalous ridge. The fate of these systems appears highly variable once over the Plains, resulting in equal chances for much of the Great Lakes, Midwest, and Ohio Valley. Below-median precipitation is also favored for the West (anomalous ridging), South (La Nina and long-term trends) and East Coast (either behind anomalous trough axis in the ECMWF or influenced by anomalous ridging in the CFS and JMA). An anomalous ridge axis forecast near the Alaskan/Canadian border favors below-median precipitation for much of Alaska, with the exception of equal chances for the Aleutians.

SST anomalies remain positive in the vicinity of Hawaii, resulting in elevated chances of above-normal temperatures. Dynamical model guidance shows a slight tilt toward below-median precipitation across the islands.

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.

And with respect to drought, this was also issued on December 31, 2020

Latest Monthly Assessment – The moderate La Niña event is likely to continue through the Northern Hemisphere winter 2020-2021 (a 95% chance during January-March), with a potential transition during the Spring 2021 (50% chance of Neutral conditions during April-June). La Niña winter impacts in the U.S. typically (but not always) include above-normal temperatures and below-normal precipitation across the southern tier of States, below-normal temperatures and above-normal precipitation in the Northwest, below-normal temperatures in southeastern Alaska the northern Rockies and Plains, and above-normal precipitation in the Ohio Valley and Hawaii. Nearly half (48.99%) of the contiguous U.S. is designated with drought as of December 29, 2020. The worst drought conditions continue across Arizona and Utah where extreme (D3) to exceptional (D4) drought covers more than 90 percent of those states. Widespread precipitation (more than 10 inches, liquid equivalent) was observed across the coastal Pacific Northwest and the Cascades with small improvements noted during December. Above normal precipitation since late November resulted in widespread improvement or removal of drought throughout the Northeast.

The updated monthly outlook favors above average precipitation from the Pacific Northwest south to northern California, supporting drought improvement by the end of January. Drought persistence is likely throughout the remainder of the West where long-term drought exists and improvement is not expected on a monthly time scale. A wet end to December and enhanced probabilities of above normal precipitation during early January support improvement or removal for the Midwest and eastern parts of the southern to central Great Plains. Elsewhere, across the high Plains, a dry climatology favors persistence. The Northeast is forecast to be drought-free by January 31, 2021.

No drought is indicated or expected to develop across Alaska for January. Drought persistence is likely for Puerto Rico as they enter the dry season. Across Hawaii, drought improvement is likely with enhanced trades due to La Niña conditions plus dynamical model forecasts favor increased precipitation across the leeward portions of the islands.

This is a relief especially for the West given the history in 2020. It is not a huge improvement but it is an improvement.

Current Status of Drought

Change in Drought in December

Looking back on November to relate the forecast for December to the actuals in November

First November Temperature (29 out of 30 days).

And then November Precipitation (29 out of 30 days).

We then show the new forecast and the prior month’s actuals (less one day) side by side.

Conclusion

The purpose of this article was to present the updated Outlook for January 2021 and compare it with the Early Outlook. It is not to critique the updated Outlook for January based on our opinions but we point out possible inconsistencies if we find them and we have. We have assessed the extent to which the monthly outlook seems to fit with the other forecasts provided by NOAA. In reality, all forecasts are obsolete when issued as the situation changes day by day or six hours by six hours i.e. each new model run. In our other articles, we continually examine the current forecasts from NOAA including Day 1- 5, 6-10, 8-14, and Week 3 and 4. So we are continually looking at approximately 25 days into the future.

On January 14, 2021, IRI/CBC will issue their ENSO forecast and we will present that and critique it. What they present on January 14 is likely to begin to impact the forecasts for the next three months and should shed some light on Spring. It is an ongoing process and we attempt to provide our readers with the best current assessment of the next approximately 25 days (except when we cover the Four-Season Analysis or medium-frequency cycles such as ENSO in which cases we are looking further out than 25 days), so our analysis is pretty much ongoing. We also publish a “LIVE” Weather Article which updates in real-time to reflect NOAA Weather Headlines and for those interested provides detailed information down to current warnings in place. All of our reports including past versions of these reports can be located via the Directory/Archive which can be accessed here.