Written by Sig Silber
Updated at 2:20 am EST January 24, 2021, to incorporate the Week 3 – 4 Forecast issued on Friday
Here is the January 21, 2021, NOAA four-season forecast for CONUS and Alaska including the Early Outlook for February 2021. It covers a period that begins one month later than the forecast last month and extends one month longer. Also included is the updated three-month drought forecast. There is not a lot of change in the forecast from the one issued a month ago. NOAA is still ready to forecast an average Monsoon for this summer but one that does not reach Utah or Colorado. There is a warning that we could have a second La Nina next winter. That is something we need to watch carefully as it would be devastating.
Important Notice from NOAA:
1981-2010 base period means were implemented effective with the May 19, 2011 forecast release.
One might assume that the 1991-2020 base period will be implemented with the May 20, 2021 forecast release but at any rate, it is not in effect with this set of forecasts.
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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 for shorter time frames. 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 2021. 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 provide in their Update 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 warm for two-thirds of CONUS and the Aleutians in Alaska. But Southern Alaska, the Alaskan Panhandle, and the extreme Northwest are cool with EC conditions being a buffer between the cool anomaly area and the large warm anomaly that covers a large part of CONUS. With respect to precipitation, the Southern Tier is dry and the Northern Tier is wet from west to east but not including the Northeast which is EC. The Southern Tier is dry and the Northeast EC conditions extend west and separate the wet and dry anomalies.
* 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 with the second map extending to February 4, 2021, and the third map as of today covers through February 12. Thus only the third of the three maps (to a much lesser extent the second map) is useful for this purpose. The Seasonal Outlook was issued late this month since the third Thursday fell on January 21. the earliest possible issue of the forecast is on the 15th of the month. We are publishing on a Thursday so we do not have the updated Week 3-4 forecast. Twelve days is not a great basis for doing this visual consistency testing but it is worth looking at. There are only 28 days in February.
We have now updated the article on Saturday (we should have done the update on Friday) and now have 19 days which is fairly adequate for our purposes. So many readers will find the updated Week 3 – 4 forecast in this section and other readers can click on the article a second time to see how that forecast changed remembering it covers a different two-week period since it was issued a week later.
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? → |
| ↑ ←We updated this section to incorporate the Week 3 – 4 forecast issued on Friday, January 22, 2021. The Week 3-4 forecast fits somewhat with the full month forecast. The West Coast may turn out to be warmer than EC for the full month. That remains to be seen. We will revisit the forecast 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? → |
| ↑ ←We updated this section to incorporate the Week 3 – 4 forecast issued on Friday, January 22, 2021. The Week 3-4 forecast raises some questions about the fit with the full-month forecast. But we still only have short term forecasts for 19 of the 28 days in February. We will revisit the forecast at the end of January when the February forecast is updated. |
Sometimes it is useful to look at the Week 3-4 Discussion. We have added that discussion issued Friday afternoon January 22, 2022.
Week 3-4 Forecast Discussion Valid Sat Feb 06 2021-Fri Feb 19 2021
Several large-climate signals have potential to influence the current Week 3-4 Outlook. In the tropics, La Nina conditions persist with sea surface temperature (SST) anomalies observed just above -1 degree C in the Nino 3.4 region. While convective activity from the Madden Julian Oscillation (MJO) is currently weak, a signal is likely to emerge over the West Pacific in the coming days. In the extratropics, the anomalously weak stratospheric vortex, characteristic of a Sudden Stratospheric Warming, is forecast to strengthen again toward climatology by the start of the forecast period. So far, any attendant impacts on surface temperature have not noticeably manifested over North America and are not expected to over the forecast period. With these factors in mind, this week’s forecast is based on a blend of dynamical model guidance with additional considerations for La Nina related impacts.
Good agreement exists among the dynamical models (CFS, ECMWF, JMA and the SubX multi-model ensemble) regarding the anomalous 500-hPa height pattern over the Week 3-4 period. Models consistently indicate ridging over the Pacific and troughing from Alaska through the Northern Plains consistent with a La Nina-like signal. The largest discrepancy is with the strength and location of the trough with stronger anomalies shifted further west in the JMA. Anomalous ridging is also forecast in the Northeast with the JMA and ECMWF extending those positive height anomalies to the Southeast.
As a result of the anomalous ridging over the Northeast, the temperature forecast tilts broadly toward above-normal probabilities throughout the Eastern US with slightly higher probabilities extending from the Northeast to the Florida panhandle. Increased probabilities of below normal temperatures are forecast from the Northern Plains to the Pacific Northwest as well as eastern Alaska and the panhandle in association with the aforementioned troughing pattern. Equal chances are carved out throughout the western and southwestern regions of the CONUS where height anomalies are favored to be weak.
Below normal precipitation is most likely across the southeast with the highest probabilities found along much of the Gulf Coast consistent with La Nina conditions. Anomalous wetness is favored across the Midwest and Great Lakes regions. Equal chances are forecast across much of Alaska, but changes for below normal precipitation are increased along the southern coast and along the panhandle.
SST anomalies around Hawaii remain above normal, suggesting an increased chance of above normal temperatures throughout the forecast period. Dynamical model guidance also consistently suggests equal chances to slightly below normal precipitation values.
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 2021
New Temperature Outlook for FMA 2021
Now Precipitation.
Prior forecast for FMA 2021
New Precipitation Outlook for FMA 2021
I can make the comparison easier by showing the prior forecast and the current forecast side by side.
| Prior Forecast | New Forecast | |
| Temperature | | |
| Precipitation | | |
Now let us focus on the long-term situation.
First Temperature
Prior 14 Month Temperature Outlook: FMA 2021 – JFM 2022
New 14 Month Temperature Outlook: MAM 2021 – FMA 2022
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 2021 – JFM 2022
New 14 Month Precipitation Outlook: MAM 2021 – FMA 2022
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 months.
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 months.
*The concept is that the probabilities of a deviation from climatology in the First Month and the combined Month Two-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 21, 2021. 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 NOAA Summary for FMA, and finally the remainder of the 15-Month Forecast.
BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
Tropical oceanic and atmospheric observations reflect ongoing La Nina conditions. During the past 30-days, an area of negative sea-surface temperature (SST) anomalies was located from about 160 deg E to the coast of South America. SST anomalies for the period ranged between 0.5 deg C to 1.5 deg C over most of this region, with the strongest anomalies from 170-150 deg W. Some warming has occurred recently, east of 135W. Subsurface temperatures were colder-than-average for the same region, down to a depth of about 175 meters. The Oceanic Nino 3.4 Index (ONI) for the latest observed season (OND 2020) is -1.3 deg C, which qualifies as a moderate La Nina at this time. Atmospheric observations reflect enhanced easterly trade winds at 850-hPa from the western to the east-central equatorial Pacific, westerly wind anomalies at 200-hPa over most of the Pacific, and suppressed tropical convection over the western and central Pacific. The atmospheric conditions reflect a canonical La Nina response.
PROGNOSTIC DISCUSSION OF SST FORECASTS
The CPC Nino3.4 SST consolidation depicts negative SST anomalies weakening (so warming) through the remainder of the winter and spring of 2021. The consolidation forecast predicts the ONI value will cross the -0.5 deg C threshold into ENSO-neutral territory during FMA 2021, and reach the zero anomaly line by AMJ 2021. This is slightly warmer than last month’s SST CON. The NMME ensemble mean SST plume for the Nino 3.4 region reaches the -0.5 deg C threshold by April 2021, and continues to warm slightly through summer 2021. The C3S (Copernicus) SST plume reaches the ENSO-neutral threshold slightly earlier, in Feb, then remains at or about -0.5 deg C until June. The CPC-IRI consensus predicts the likelihood of La Nina will drop to the same likelihood of ENSO-neutral by about AMJ 2021. The official ENSO forecast calls for approximately a 95% chance for La Nina to continue through Northern Hemisphere winter, with a potential transition during the spring 2021 (~55% chance of ENSO Neutral during AMJ 2021).
30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2021
The February 2021 temperature and precipitation outlooks are based on Weeks 3 to 4 forecasts from the CFS and ECMWF models, the North American Multi-Model Ensemble (NMME), typical influences from the ongoing La Niña, and decadal trends. Below average sea surface temperatures (SSTs) across the equatorial Pacific along with a strong coupling with the atmosphere represent La Niña conditions. Although dynamical models depict a strengthening Madden-Julian Oscillation (MJ0) during late January into early February, La Niña is likely to be the major tropical forcing due to the well-established anomalous enhanced (suppressed) convection over the Maritime Continent (equatorial Central Pacific).
Despite high latitude blocking with a persistent negative Arctic Oscillation (AO), 30-day temperatures since mid-December have averaged above normal for nearly all of the CONUS. This mild temperature pattern was due in part to enhanced Pacific flow overspreading the higher latitudes of North America and cross polar flow generally limited to the Eastern Hemisphere. Week-2 model guidance (Jan 28-Feb 3) remains consistent that an amplified and full-latitude 500-hPa ridge becomes centered over the Aleutians and extends poleward. The Week 3-4 ECMWF model indicates this anomalous ridging persisting through at least early February, which is likely to promote cross polar flow and result in below normal temperatures across parts of Alaska. Based on good model continuity with this feature and support from a number of inputs to the NMME, below normal temperatures are favored for southeastern Mainland Alaska and the Alaska Panhandle. Although the source region is expected to become more favorable for Arctic air to shift south across the western and north-central CONUS during the next month, the NMME supports equal chances (EC) of below, near, or above normal temperatures for much of the West and Northern Great Plains. Sparse snow cover across the Canadian Prairies and Northern Great Plains may be a limiting factor to anomalously cold temperatures heading into February. Below normal temperatures are slightly favored for parts of the Pacific Northwest and Northern Rockies, due to the predicted close proximity of anomalous cold during the first half of February and this is also consistent with La Niña composites.
The largest probabilities (above 50 percent) of above normal temperatures are forecast from the Rio Grande Valley eastward to the Gulf Coast, based on the week 3-4 model guidance, calibrated NMME, and La Niña composites. Although a high latitude block over the Davis Strait and negative phase of the NAO are forecast to promote periods of below normal temperatures along the East Coast during the remainder of January, the GFS ensemble members depict a transition to a neutral or even positive phase of the NAO by the beginning of February. As the negative NAO diminishes during the next two weeks, La Niña is expected to become a more dominant factor which increases probabilities of above normal temperatures across the Southeast. Above normal temperatures are only slightly favored for the Northeast, Great Lakes, and Upper Mississippi Valley due to lower forecast confidence and the potential for a variable temperature pattern during February. It remains unclear when or even if the recent stratospheric warming event would influence temperatures across the CONUS and this will be reassessed for the updated outlook released on January 31.
The precipitation outlook for February is consistent with La Niña composites and supported by the NMME. Below normal precipitation is most likely across the southern tier of the CONUS, while above normal precipitation is favored from the Pacific Northwest eastward to the Upper and Middle Mississippi Valley and Great Lakes. Elevated probabilities of below normal precipitation, forecast for southeastern Mainland Alaska and the Alaska Panhandle, are consistent with below normal temperatures favored for these areas. A majority of inputs to the NMME support increased probabilities of above normal precipitation across the Aleutians. Probabilities throughout the forecast domain are tempered due to large uncertainties during this monthly outlook time range.
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS (Focus on FMA 2021
La Nina conditions are present across the equatorial Pacific Ocean, as indicated by current oceanic and atmospheric observations. La Nina is expected to continue through the Northern Hemisphere winter (~95% chance), with a potential transition to ENSO-neutral (~55% chance) during April-May-June 2021.
Temperature
The February-March-April (FMA) temperature outlook favors below normal seasonal mean temperatures for the southern half of mainland Alaska, the Alaska Panhandle, and from the Pacific Northwest eastward to the Northern Rockies. Above normal seasonal mean temperatures are favored across parts of northern and western Alaska, and for most of the CONUS, except portions of the Northern Plains, Northern Rockies, Southern Oregon, and Northern California. Maximum probabilities for above normal temperatures exceed 60% across parts of the Southwest and Southern Great Plains.
Precipitation
The FMA precipitation outlook favors above normal precipitation for most of the northern tier of the CONUS, extending from the Pacific Northwest to the Great Lakes, then southward across eastern portions of the Middle Mississippi Valley, the Ohio Valley, and the Central and Northern Appalachians. Above normal precipitation is also favored for northern and western portions of Alaska. Maximum probabilities for above normal precipitation exceed 50% over the Ohio Valley. From central and southern California across the Great Basin to the Central and Southern Plains, below normal precipitation is favored. Below normal precipitation is the most favored outcome across portions of the Southeast, as well as along the southern coast of mainland Alaska and for the Alaska Panhandle.
Equal Chances (EC) are forecast for areas where probabilities for each category of seasonal mean temperatures or seasonal total precipitation amounts are predicted to be similar to climatological probabilities.
BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
Given a very high likelihood of the persistence of La Nina conditions, the seasonal outlooks utilized canonical impacts during past observed La Nina events as guidance for many areas of the forecast domain through at least MAM 2021. This guidance included regressions of temperature and precipitation relative to the CPC consolidation forecasts of the Nino3.4 region and via “bridging” techniques utilizing statistical relationships between dynamical model forecasts of the Nino 3.4 index and observed temperature and precipitation. Dynamical model guidance from the North American Multi-Model Ensemble (NMME) and the model suite from the Copernicus program are a significant component of guidance for the temperature and precipitation outlooks through JJA 2021. Beyond JJA 2021, the consolidation of various statistical tools, including decadal trends , was the primary basis for the outlooks, with little remaining influence from ENSO or other reliable large-scale signals of climate variability for these forecast leads. Predicted low soil moisture conditions as a result of predicted precipitation totals over already dry areas, influenced the temperature outlooks for the spring and early summer 2021 over the Central Plains and Southwest. At later leads, decadal trends in temperature and precipitation were the primary tool used in creating the seasonal outlooks.
PROGNOSTIC DISCUSSION OF OUTLOOKS – FMA 2021 TO FMA 2022
TEMPERATURE
The temperature outlook for FMA 2021 reflects current model guidance, blended with likely impacts of La Nina and trends . The favoring of below normal temperatures across portions of mainland Alaska, the Alaska Panhandle, and the Pacific Northwest reflect La Nina conditions. The outlook is slightly warmer than last month’s outlook but colder than the recent model guidance for this region. The FMA outlook for the Northern Great Plains is warmer than last month’s lead 2 outlook, reflecting the ongoing lack of snow cover and more recent model guidance, though probabilities are modest at best from North Dakota to Illinois. Odds for above normal temperatures were also increased across the Lower Mississippi, Gulf Coast, and Florida, reflecting recent model guidance and likely La Nina impacts. The outlooks for later spring and summer 2021 reflect recent model guidance and trends , with the lowest probabilities in the central portions of the CONUS where variances are highest, model skill lowest, and trends are small to negative. Outlooks for next autumn were unchanged, as the reasoning behind the outlooks has not changed for those periods, and trends are the most reliable tool. Some outlooks are calling for a second La Nina winter, which would not be unprecedented since 1950, and the outlooks for next winter are already aligned for that possibility.
PRECIPITATION
La Nina is the primary physical driver behind the subsequent FMA and MAM precipitation outlooks, so only minor adjustments were needed to the corresponding outlooks made last month. In MAM, the amplitude of La Nina and its associated precipitation impacts are expected to begin to decline. In AMJ 2021, below normal precipitation amounts are forecast to diminish in spatial coverage across the southern CONUS, and be centered over most of the southwestern quarter of the CONUS. After AMJ, with a predicted ENSO Neutral, trends are more highly factored, which favors below normal precipitation for portions of the Northern and Central Rockies during summer months, shifting southward during the winter. East of the Mississippi, summer and early autumn months have a wet trend. By next winter, Dec-Jan-Feb 2021-22, the only remaining signal is the trend for above normal precipitation over the Northern Plains.
We will discuss this more when we compare the JAMSTEC to the NOAA forecast. But it is useful to look at the JAMSTEC discussion especially as it applies to Spring and Summer since their raising the issue that this is somewhat of a La Nina Mokoki raises questions about the use of statistical analysis in these forecasts. We will address this in more detail when we publish our NOAA v JAMSTEC comparison. NOAA hardly recognizes an El Nino Modoki let alone a La Nina Modoki. Fortunately, the major impact of a La Nina Modoki is seen in the Western Pacific as it impacts the track of cyclones headed west. But what heads west frequently turns north and then returns east at higher latitudes and impacts North America in that way but perhaps in a more subtle way. Below is the JAMSTEC discussion.
Jan. 15, 2021
Prediction from 1st Jan., 2021
ENSO forecast:
Observation now shows a La Niña Modoki-like state, as predicted earlier. The SINTEX-F continues to predict that this La Niña Modoki-like state will persist in this boreal winter. Then, it will start to decay from boreal spring. We need to be careful of its impact as it may be different from that of a canonical La Niña.
Indian Ocean forecast:
Observation shows that the tropical Indian Ocean is a neutral state. The ensemble mean prediction suggests that the present condition will persist in the first half of this year.
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 (austral autumn) except for Alaska, western Canada, northern part of the South American Continent, western Australia, Indochina Peninsula, and India.
As regards to the seasonally averaged rainfall in boreal spring (austral autumn), a drier-than-normal condition is predicted for U.S.A., La Plata Basin, southwestern Africa, southern Europe facing the Mediterranean Sea, some part of the Middle East, eastern China, and Indonesia. In contrast, Canada, most part of Brazil, Philippines, Indochina Peninsula, India, Sri Lanka, and western China will experience a wetter-than-normal condition.
The model predicts most part of Japan will experience a warmer-than-normal condition in spring as a seasonal average. As regards to the seasonally averaged rainfall, most part of Japan (except for Kyushu and Okinawa) will experience a slightly wetter-than-normal condition.
Drought Forecasts
These two forecasts (Monthly and Season) are issued by the same agency but to obtain them you need to access two different links here (for the single month forecast which comes out at the end of the month and here for the forecast issued with the Seasonal Outlook.
Here is the Three-Month Drought Forecast which was issued on January 21, 2021
Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for February (Feb) 2021 and February through April (FMA) 2021, various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), the Week 3-4 outlooks and tools from CPC, dynamical models at the monthly and seasonal time scales, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for Feb and FMA, and initial conditions for parameters such as soil moisture. Existing drought areas on the forecast are based on the January 19 U.S. Drought Monitor. Conditions currently reflect the presence of a moderate La Niña, with a 95% chance for La Niña to persist through the Northern Hemisphere winter (end of March 2021), and the potential for a transition to ENSO-neutral during the Spring 2021 (55 percent chance during April-June).
The ongoing La Niña event unfortunately favors subnormal precipitation and above-normal temperatures across the southern tier of States where drought is currently severe to exceptional (D2-D4) levels. SNOTEL basin Snow Water Content (SWC) values are less than 75% of normal across much of the southern half of the West, and under 50% in southern Utah, Arizona, and New Mexico, including below 25% in most of Arizona and southwestern New Mexico. In contrast, where near to above normal precipitation and seasonable temperatures have occurred (Northwest), SWC values are better across the northern half of the West, with basins in Washington, northeastern Oregon, northern Idaho, western Montana, and northwestern Wyoming close to normal or slightly above. For the next 2 weeks, however, a change in the long-term weather pattern should bring welcome precipitation and subnormal temperatures to the West, including the Southwest, before the Week 3-4 and 1- and 3-month LLFs revert back to the “typical” La Niña anomaly pattern. This brief favorable weather pattern in the Southwest is likely not enough to make any significant improvements in the long run (end of April), thus persistence was made for much of the Southwest, with development in southern California. In contrast, the Northwest should continue receiving above-normal precipitation and (probably) seasonable temperatures, continuing a wet trend from this Fall for additional improvements in the Northwest. The improvement in northwestern California was based upon recent heavy rains the past 30-days, more heavy precipitation expected during the next 2-3 weeks, and a wet climatology with equal chances (EC) of below, normal, or above precipitation in both the 1- and 3-month precipitation LLFs.
Forecast confidence is moderate to high for the Western region.
In the northern Plains, although the 6-10 day ERF, Week 3-4, and 1- & 3-month LLFs tilt toward above-normal precipitation, the past 30-60 days have been quite dry and very mild there, which has led to minimal or no snow cover. Plus, with climatology quite dry during February and March, any surplus precipitation in the Dakotas most-likely would not eliminate the accumulated deficits and impacts of the past 1-2 months. Thus, persistence (not improvement) is forecast for the northern Plains. In addition, development was not added in South Dakota since the forecasts showed potential for above-normal precipitation. Improvement might have been depicted if this SDO was for MAM or AMJ as the precipitation climatology is much wetter then. Farther south, with the ongoing La Niña, the 3-month LLF favors subnormal precipitation in Colorado, Kansas, and Nebraska, thus persistence for existing drought areas and some development along the eastern drought border (southern Kansas) was drawn.
Forecast confidence is moderate for the High Plains region.
The past 30-days brought surplus precipitation to western parts of the Midwest, with subnormal totals in Wisconsin, Illinois, Indiana, Michigan, western Ohio, and Kentucky. Temperatures have also averaged above normal, leading to diminished snow cover. With the 7-day QPF limiting moderate precipitation to southern sections (Kentucky), only light amounts should occur for much of the region. The 6-10 day ERF favors above-normal precipitation, but by 8-14 days, the odds call for near to below-normal precipitation (with seasonable ERF temperatures). With the Week 3-4, 1- and 3-month LLFs favoring above-normal precipitation, improvement is expected in Illinois and Indiana and northern Minnesota. In western Iowa, with only a weak signal for improvement, a rather dry February and March climatology, and the drought being long-term, persistence was the safest forecast.
Forecast confidence is moderate to high for the Midwest region.
Surplus precipitation, including snow, has fallen on most of the South (Texas, Oklahoma, Louisiana, Arkansas) during the past 30-60 days, prompting drought improvement across most of Texas, Oklahoma, and Arkansas recently. The 7-day QPF continued the ample precipitation across central and eastern Texas, Arkansas, and most of Louisiana, Mississippi, and Tennessee, although drier weather is expected by 8-14 day ERF and into the Week 3-4 forecast. The upcoming rains should be enough to remove the small D1 areas in western Tennessee and northern Mississippi. The 1- and 3-month LLFs favor subnormal precipitation for southern and western sections of the South (and above-normal temperatures), with a southwestward dip of above-normal precipitation probabilities from the Ohio Valley into the lower Mississippi Valley in the FMA precipitation LLF. With subnormal precipitation expected in southern Texas and along the central and eastern Gulf Coast, development was depicted in these areas – but not along the western Gulf Coast where the precipitation outlooks are closer to normal.
Forecast confidence is moderate for the South region.
Mostly dry conditions have enveloped parts of the Southeast the past 30-60 days, namely the central and eastern Gulf and southern Atlantic Coasts and eastern Tennessee Valley, although a band of surplus precipitation did fall from Apalachicola, FL area northeastward into the Carolinas and southeastern Virginia. Currently, only a few areas of D0 were found on the Jan. 19 USDM in the Southeast. However, the 7-day QPF predicts heavy precipitation (1-4 inches) across much of the Southeast – except drier right along the Gulf Coast and Florida. Then, the extended range forecasts expect precipitation to gradually decrease, with the 8-14 day ERF favoring subnormal precipitation across the region. Similarly, the Week 3-4, 1- and 3-month LLFs also expect subnormal precipitation (thanks to La Niña) mainly along the Gulf Coast – thus, development is expected along (most of) the central and eastern Gulf and southern Atlantic Coasts (including all of Florida) by the end of April.
Forecast confidence is moderate for the Southeast region.
A wet winter pattern has dramatically improved conditions and stream flows across New England, with only a few small D1 areas left. The 7-day QPF showed light precipitation, 6-10 & 8-14 day ERFs have a slight tilt toward below-normal precipitation, and temperatures will be seasonable out to 2 weeks. The Week 3-4 hinted at above-normal precipitation, while the 1- and 3-month LLFs favored above-normal precipitation in western areas and EC toward eastern areas (above-normal temperatures for both time periods). With minimal soil moisture loss during the winter (low temperatures, no evaporation, frozen ground) and future moisture infiltration (e.g. snow pack), most winter precipitation that occurs should contribute to decent spring moisture conditions by the end of April. Thus, the remaining D1 areas should be gone by the end of April.
Forecast confidence is moderate to high for the Northeast region.
In Hawaii, a La Niña typically brings above-normal rainfall during their climatologically wet winter season, particularly later in the season (Jan-Mar), thus improvement is expected across the islands. In Alaska, no changes are anticipated during their frigid winter hibernation. In Puerto Rico, recent dryness in the north (D0 and D1) may expand somewhat by the end of April based upon some model guidances forecasting subnormal Feb and FMA precipitation; therefore some development was added in north-central sections.
Forecast confidence is high for Alaska and Hawaii, moderate for Puerto Rico.
ENSO Considerations
We have covered some of this when we reported on the IRI/CPC analysis on January 14, 2021. We may discuss it again when we do the NOAA/JAMSTEC Comparison.
Now let us look at the NOAA ENSO Update
More information can be found here.
NOAA depends a lot on the IRI-CPC analysis.
It is useful to see how the view has changed if at all which is shown below
This compares the new forecast to the one made last month. The first forecast in each month is based on a survey of meteorologists and the second is based on climate models so they are not totally comparable. But there is not much change through MAM but AMJ is more evenly balanced between La Nina and ENSO Neutral than the forecast in Mid-December and the chances of an El Nino getting started soon have been reduced.
NOAA has their own proprietary model which they rarely use. It is not exactly clear why they shun their own model.
In most cases, I freeze the models as of the date of publication but for this one, I am going to just let the above model run so if you refer to the article in the future, the values in the above may not relate well to the discussion. But I am doing that so if you refer to this article in say two weeks, you will see if there has been any change in the forecast from this model.
Comparison models would include JAMSTEC
And the JAMSTEC Modoki Index
And the Australian BOM
And here is one more graphic that I created from a different NOAA source. It is a cross-section of the Pacific Equator from the surface down to 450 meters. What is shown in this graphic is the temperature anomalies not the absolute temperature. ENSO is measured at the surface since only the surface interacts with the atmosphere. But the future of the surface often is impacted by the water below the surface. At some point, NOAA will update the normal values for this area as they do that every five years but they have not done so yet. See the note at the beginning of this article.
Currently
| Two Months Ago | Last Month |
 |
|
The Southern Oscilation Index or SOI being above 7 confirms that the Atmosphere is in tune with the Sea Surface Temperatures in the Pacific along the Equator. This is another graphic that we have not frozen.
B. Conclusion
We are now in a La Nina. There may be an issue as to how westerly oriented this La Nina will be and what if any will be the impacts of it having some characteristics of a Modoki as JAMSTEC suggests.
NOAA has introduced the concept of a double-dip La Nina. That is not unusual but it is the first mention of this possibility as far as I know. It would be devastating for the West.
