Written by Sig Silber

Updated at 6:25 pm EDT July 16 to reflect the new Week 3- 4 forecast and to include the JAMSTEC discussion. We will compare the JAMSTEC and NOAA forecasts soon.

This July 15, 2021, NOAA four-season forecast for CONUS and Alaska – including the Early Outlook for August, 2021 – 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. The main changes seem to be that we are going from a good Monsoon in July to an average Monsoon in August to a transition to dryness in September.  That last part is my interpretation, not totally clear from the NOAA material. Then we appear to have something like La Nina Conditions in Fall and possibly Winter.  The level of confidence is not high on this; particularly the Winter aspect. I did not have enough time to really study the longer term – I may add some additional commentary tomorrow when I update the Week 3 – 4 Forecast.

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The most signficant statement from the NOAA Discussion.

I encourage everone to read the full NOAA Discusssion. They do a good job of explaining how they have made the forecast. That makes it possible to critique their forecast if one disagrees with their assumptions and methodology. I am not suggesting that readers should do that but I am suggesting that the NOAA maps provide the synthesized forecast while the NOAA discussion provides additional information on why and how the forecast may differ from the maps presented. So looking at the maps is great but reading the NOAA discussion and then looking at the maps provides additional understanding of how this forecast may play out. NOAA is pretty sure that the update of August at the end of July will have some major changes. 

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 August 2021. It is called the Early Outlook because it will be updated at the end of July. Only the August 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 August from the previous NOAA Report to compare against. The current month is not over so we can not really compare the forecast for next month against the actual for this month. If we do the comparison with JAMSTEC, we have been receiving monthly forecasts for the first three months so we may be comparing the NOAA and JAMSTEC forecasts for August but I have not yet received the forecast from JAMSTEC so I do not know if I will. We will see. It is probably best in this article to just try to understand what NOAA is trying to convey about August*. For Temperature, west and southwest Alaska are cool and most of CONUS is warm but there is both a large south/central EC area with even a small cool anomaly in eastern Texas but also impacting Louisiana, SE Oklahoma and Arkansas. With respect to precipitation, eastern Alaska is wet and Montana and surrounding states are dry. The Southwest Monsoon is shown as normal in August. There is a large wet anomaly that streatched from eastern Texas to New Jersey. SE of that wet swath it is forecast to be EC.

Listen up all those planning to play the Monsoon Fantasy Game describe at the end of this article. It will be time to get your August forecasts in soon.  You might want to pay attention to the August forecast.

* 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 only July and the third map as of today covers through July 9. Thus only the third of the three maps is at all useful for this purpose. The Seasonal Outlook was issued early this month since the third Thursday fell on July 15. 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. 6 days is not an adequate basis for doing this visual consistency testing. There are 31 days in August.

We have updated this article and we will now have have 13 days which is marginally adequate for our purposes.

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? →		↑ ← 13 days of data is not enought to validate the full month forecast but it is enough to raise some questions about the validity of the forecast. We will revisit the forecast at the end of July when the August 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? →		↑ ← 13 days of data is not enought to validate the full month forecast but it is enough to raise some questions about the validity of the forecast. We will also revisit the forecast at the end of July when the August forecast is updated.

Sometimes it is useful to look at the Week 3-4 Discussion. We will add that when it is issued Friday afternoon July 16, 2021.

Week 3-4 Forecast Discussion Valid Sat Jul 31 2021-Fri Aug 13 2021

ENSO-neutral conditions are currently present across the Pacific Ocean. Equatorial sea surface temperatures (SSTs) are near average across most of the Pacific Ocean with upper level westerly wind anomalies across the central and east-central equatorial Pacific Ocean. The RMM indices indicate the intraseasonal signal remains over the Indian Ocean during the last week. Dynamical models continue to favor eastward propagation of the MJO at a low amplitude across the Indian Ocean and the Maritime Continent during week-1, but the RMM mean solutions diverge among the models by week-2. The Week 3-4 temperature and precipitation outlooks are based primarily on dynamical guidance including the GEFS, CFS, Canadian, ECMWF, JMA, the Subseasonal Experiment (SubX) multi-model ensemble (MME) of experimental and operational ensemble prediction systems, with additional considerations for MJO, ENSO-neutral, decadal climate trends, and soil moisture conditions, as well as the predicted evolution of the pattern from Week-2 forecasts.

Good agreement exists among the dynamical models regarding the anomalous 500-hPa height pattern over the Week 3-4 period. Dynamical model 500-hPa height anomaly forecasts during Week 3-4 show a fairly consistent evolution from the forecast state during Week-2. Most dynamical models feature anomalous ridging with above normal 500-hPa heights over south of Bering Sea and a weak trough with below normal 500-hPa heights is forecast over Alaska. A trough is also forecast over the eastern North Pacific centered near the coast of western North America, while ridging is predicted over the western and central CONUS. Near to above normal 500-hPa height anomalies are likely over Hawaii.

Above normal temperatures are expected across the western and central CONUS, extending eastward to the Upper and Middle Mississippi Valley as well as the eastern Upper Great Lakes, under the predicted above normal 500-hPa heights. Below normal temperatures are favored over most of the eastern CONUS excerpt for parts of the Northeast where above normal temperatures are indicated. The highest confidence for below normal temperatures lies across the Lower Mississippi Valley, consistent with the manual blend tool. Decadal trends lead to predicted above normal temperatures for northern Mainland Alaska, the Aleutians and the Alaska Panhandle, supported by most of the dynamical tools.

The dynamical model guidance is in reasonably good agreement on the spatial pattern of anomalous precipitation during the Week 3-4 period. Consistent with the forecast ridging, below-average precipitation is favored for the Northwest and Northern Plains. Most of the dynamical model guidance also extends enhanced chances for below-average rainfall southward across the Plains into Texas. Dynamical models continue to show enhanced monsoon precipitation across the Four Corners, with the highest probabilities across Arizona. Enhanced chances for above-average precipitation extend into the Great Basin. Above normal precipitation is favored throughout most of the eastern CONUS, except for Florida Peninsula, where below normal precipitation is indicated, consistent with most of the dynamical and statistical guidance. Anomalous troughing and several shortwave disturbances lead to enhanced probabilities of above normal precipitation over Mainland Alaska, supported by most of the dynamical tools.

A multi-model ensemble mean of the Subseasonal Experimental (SubX) guidance depicts high probabilities for above-normal temperatures across most of Hawaii. The SubX MME anomaly forecast indicates likely equal chances for below- and above-average precipitation for Hawaii for the Week 3-4 period.

Now we consider the three-month Outlook.

Notice that the three-month periods are abbreviated e.g August/September/October is shown as ASO. You will see such abbreviations often in this report.

Prior Temperature Outlook for ASO 2021

New Temperature Outlook for ASO 2021

Now Precipitation. 

Prior forecast for JAS 2021

New Precipitation Outlook for ASO 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: ASO 2021 – JAS 2022

New 14 Month Temperature Outlook: SON 2021 – ASO 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.

I am now showing them side by side in addition to one after another. It is easier to make the comparison this way but to do it I have to make the maps smaller and readers have to remember how to compare two sets of maps when one starts a month later than the other. Here goes:

Forecast Issued Last Month	Forecast Issued This Month

Based on this procedure, I conclude that:

Now Precipitation

Prior 14 Month Precipitation Outlook: ASO 2021 – JAS 2022

New 14 Month Precipitation Outlook: SON 2021 – ASO 2022

I am also going to show the two graphics side by side. It is tricky because the array for the current month starts one month later. So you have to follow the instructions I provided with the temperature array of maps. So you can compare the forecast maps by looking at the large ones which are shown with the prior month forecast followed by the forecast this month or you can look at them side by side.

Last Month	This Month

If you want larger versions of each newly issued 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 July 15, 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 (August), the NOAA Summary for ASO, and finally the remainder of the 15-Month Forecast.

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

The coupled oceanic and atmospheric observations reflect ENSO-neutral conditions. Sea surface temperatures (SSTs) are near climatological averages across most of the equatorial Pacific Ocean. Positive subsurface temperature anomalies persisted across most of the Pacific Ocean, while negative temperature anomalies emerged at depths of 50 to 200 meters in the eastern equatorial Pacific Ocean. Integrated upper-ocean heat anomalies, that have been positive since March, are now near zero. Convection is suppressed near the Date Line and enhanced near the Maritime Continent, while low-level easterlies and upper-level westerlies are near climatological averages over much of the equatorial Pacific Ocean.

PROGNOSTIC DISCUSSION OF SST FORECASTS

Dynamical models of the NMME predict weak Nino 3.4 SST anomalies between zero and -0.5 C in the next three months, followed by larger anomalies below -0.5 C, the threshold for potential La Nina conditions, later in autumn and through winter. Statistical models generally predict ENSO-neutral conditions, with Nino 3.4 SST anomalies between -0.5 and +0.5 C over the same period. The CPC SST Consolidation, a skill weighted combination of dynamical and statistical models, tracks more closely to the dynamical model forecasts with the probability of La Nina increasing through autumn into winter. The Copernicus (C3S) international, multi-model ensemble system, in contrast to the NMME, predicts a greater persistence of weak negative Nino 3.4 SST anomalies through autumn, reflecting ENSO-neutral conditions. The official CPC/IRI consensus ENSO outlook calls for greater than a 50 percent probability of La Nina through five overlapping seasons from SON 2021 through JFM 2022, consistent with the historical tendency for a second winter of La Nina following the first La Nina winter, and predictions from the North American Multi-Model Ensemble.  

30-DAY OUTLOOK DISCUSSION FOR AUGUST 2021

The August 2021 temperature and precipitation outlooks are based on dynamical model guidance including the North American Multi-Model Ensemble (NMME) and Copernicus Multi-Model Ensemble (C3S), statistical tools, current soil moisture conditions, and potential influences from modes of tropical variability. The Madden-Julian Oscillation (MJO) weakened during early July due to interference with an equatorial Rossby wave and a couple of atmospheric Kelvin waves. Dynamical models depict the MJO resuming an eastward propagation during the latter half of July and this could eventually lead to a more favorable large-scale environment for tropical cyclone (TC) development across the east Pacific and Atlantic basins later next month. The MJO evolution and its associated modulation of TC development will be reevaluated at the end of July.  

Temperature

Anomalous 500-hPa ridging over the middle to high latitudes of western North America has persisted since early June which resulted in much above normal temperatures and record-setting heat across the western and north-central CONUS. Periodic amplification of a downstream trough over the eastern CONUS is a common feature this summer along with a weakness in the subtropical ridge along the Gulf Coast. Although the anomalous ridging and associated above normal temperatures are forecast to shift eastward during week-2 (Jul 22-28), the week 3-4 dynamical models  depict a retrogression of the ridge axis to western North America heading into August Therefore, the temperature outlook for the CONUS closely resembles observations during the past 30 days. Above normal temperatures are favored throughout the western and north-central CONUS and also along the East Coast. The largest probabilities (above 60 percent) of above normal temperatures are forecast across the Northern Rockies and Northern High Plains, due to very low soil moisture (below the 5th percentile) and good model agreement. Conversely, high soil moisture (above the 90th percentile) across parts of the Southern Great Plains, Lower Mississippi Valley, and Western Gulf Coast supports elevated probabilities of below normal temperatures for those areas. Also, favored wetness during August is consistent with this forecast. Based on dynamical models  and decadal trends , above normal temperatures are favored for Southwest Mainland Alaska along with the Aleutians and Alaska Peninsula. Probabilities of above normal temperature are reduced slightly for the Alaska Peninsula due to negative sea surface temperature anomalies to its south.

Precipitation

The NMME and a lagged precipitation outlook from soil moisture support elevated probabilities of below normal precipitation from the Northern Rockies east to parts of the Northern to Central Great Plains. Based on decadal trends  and the NMME, above normal precipitation is favored for the Mid-Atlantic, Eastern Corn Belt, Tennessee Valley, and Lower Mississippi Valley. Although week 3-4 dynamical models depict an enhanced Monsoon during early August, equal chances (EC) of below, near, or above normal precipitation are forecast for the Desert Southwest ad Four Corners Region due to weak signals  among the monthly tools. Elsewhere across the CONUS, EC is necessary at this half month time lead for the monthly precipitation outlook and adjustments are anticipated for the updated outlook, released on July 31. The elevated probabilities of above normal precipitation, forecast across northeast Mainland Alaska, are based on the NMME and consistent with decadal trends .

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS  (Focus on August through October)

ENSO-neutral conditions persist across the equatorial Pacific Ocean, as indicated by current oceanic and atmospheric observations. The CPC/IRI ENSO consensus forecast predicts that ENSO-neutral conditions are likely to persist through the next three-month season, while La Nina conditions are more likely in autumn and winter. By winter there is approximately an equal chance of weak La Nina conditions, moderate-to-strong La Nina conditions, or ENSO-neutral conditions. El Nino is the least likely scenario through winter.   

Temperature

The August-September-October (ASO) 2021 temperature outlook favors above normal temperatures for the western half of the CONUS, the Midwest, and the eastern quarter of the CONUS, with the largest probabilities exceeding 60 percent over parts of the Great Basin and Central Rockies as well as the Northeast. The ASO 2021 precipitation outlook predicts enhanced probabilities of below normal precipitation across much of the western half of the CONUS, excluding parts of the Pacific Northwest, as well as the Northern Plains and western Great Lakes region. Above normal precipitation is likely for the central and eastern Gulf Coast region and from the Appalachians to the Atlantic Coast, excluding the Florida Peninsula. Above normal precipitation is slightly favored for the southern coast, eastern interior, and North Slope of Mainland Alaska, as well as the northern Alaska Panhandle. Equal chances (EC) are indicated for areas where probabilities for each category of seasonal mean temperatures and seasonal accumulated precipitation are expected 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

Dynamical model forecasts from the North American Multi-Model Ensemble (NMME) and Copernicus (C3S) multi-model ensemble systems are used extensively for the first six leads when they are available. The ENSO-OCN statistical forecast tool was used for the OND 2021 through FMA 2022 seasons to determine expected climate impacts of likely La Nina conditions, as predicted by the CPC ENSO outlook and CPC SST consolidation forecast, in addition to decadal climate trends. The objective, skill weighted consolidation, that combines both dynamical and statistical forecast tools, was used for all leads.

Anomalously wet soil moisture conditions across the Southern Plains and Lower Mississippi Valley and anomalous dry soil moisture conditions across the western CONUS and Northern Plains were factors in the temperature outlook for late summer and early fall. At longer leads, decadal climate trends  in temperature and precipitation, as represented by the OCN tool, are the primary climate signal in the seasonal outlooks.

 PROGNOSTIC DISCUSSION OF OUTLOOKS – ASO 2021 TO ASO 2022

 TEMPERATURE

 Above normal temperatures are likely throughout a majority of the forecast domain during ASO, except for parts of the Southern and Central Plains and the Lower and Middle Mississippi Valley, where equal chances (EC) of below, near, or above normal temperatures are forecast. This EC area corresponds to weaker signals in the dynamical model temperature forecasts, as well as areas with persistent abnormally wet soil moisture conditions. A reduction in above normal temperature probabilities for this area relative to last month’s outlook is seen for both ASO and SON. Probabilities of above normal temperatures are increased relative to last month’s outlook across the Northern Rockies and Northern Plains, as indicated by the NMME dynamical model forecasts and due in part to continued dry soil moisture conditions. Above normal temperatures are likely for most of Alaska in ASO, with an expanded area of EC for southeastern Mainland Alaska and the Panhandle, as indicated by dynamical model forecasts.  

For SON, above normal temperatures are favored across the entire CONUS, corresponding to dynamical model forecasts and the decreased impact of anomalous soil moisture conditions. For OND 2021 through MAM 2022, the seasonal outlook represents the enhanced likelihood of La Nina. Positive decadal temperature trends  across most of the domain are moderated by the impacts of temperature variability due to La Nina. Areas of EC expand across southern Alaska and the northern tier of the CONUS in OND 2021 through MAM 2022, including the Pacific Northwest, Northern and Central Plains, and western Great Lakes regions. Below normal temperatures are more likely for parts of the Pacific Northwest in DJF through FMA 2022, and across the northern tier into parts of the Northern Plains in FMA. Below normal temperatures are also favored for parts of southeastern Mainland Alaska and the Alaska Panhandle in JFM and FMA 2022, due to potential La Nina impacts.

For AMJ 2022 and thereafter, the forecast pattern primarily reflects decadal trends with above normal temperatures favored for much of the West and across the southern and eastern CONUS through next spring and summer. Probabilities of above normal temperatures peak in the summer of next year across the West and along the Atlantic coast, consistent with the seasonal influence of decadal climate trends . Decadal trends  favor above normal temperatures for northwestern areas of Alaska next spring, related to long term changes in sea ice cover during this season, and across the state by summer of 2022.  

PRECIPITATION

Dynamical model forecasts from the NMME support slightly elevated probabilities of below normal precipitation for much of the West into the Northern Plains and western Great Lakes region, excluding parts of the Pacific Northwest, in the ASO seasonal outlook. Dynamical model forecasts favor above normal precipitation in ASO for much of the central and eastern Gulf Coast region, excluding the Florida Peninsula, and from the Appalachians eastward to the Atlantic coast. Probabilities for above normal precipitation are enhanced for eastern areas of the Alaska Mainland, consistent with decadal trends , the SST constructed analog forecast, and dynamical model forecasts from the NMME and C3S. Enhanced probabilities for below normal precipitation persist for much of the Southwest and across the Great Plains in SON, while enhanced probabilities of above normal precipitation continue for the Mid-Atlantic, as supported by the NMME. Below normal precipitation for the Southwest in early autumn is consistent with the increasing possibility of La Nina conditions, and the potential inhibition of tropical activity in the eastern Pacific. Beginning in the OND seasonal outlook, the precipitation pattern begins to evolve to reflect the increasing likelihood of La Nina. Below normal precipitation is generally favored across southern regions of the CONUS from Southern California to the Southeast by winter. Above normal precipitation is more likely for parts of the Pacific Northwest for NDJ and DJF and for southeastern Mainland Alaska in DJF and JFM 2022.

From next winter into next spring and summer the precipitation pattern forecast increasingly reflects decadal precipitation trends . Enhanced probabilities of below normal precipitation persist for much of the Southwest through MAM 2022, while probabilities of above normal precipitation are enhanced for parts of the Mississippi and Ohio Valleys from JFM through AMJ 2022 and for parts of the Mid-Atlantic in AMJ through ASO 2022. Decadal trends  are the primary signal for above normal precipitation for the North Slope of Alaska in NDJ 2021 through FMA 2022 and for parts of eastern interior Alaska in JJA through ASO 2022.

We will discuss this more when we compare the JAMSTEC to the NOAA forecast. But it is useful to look at the JAMSTEC discussion. But we have not received it yet. If we receive it soon, I will add it to the report.

It was received and here it is.

ENSO forecast:

Observation shows that the tropical Pacific is in a neutral state. The SINTEX-F predicts that a weak La Niña Modoki-like state will appear in boreal  autumn.

Indian Ocean forecast:

As predicted earlier, observation shows occurrence of a negative Indian Ocean Dipole. The SINTEX-F ensemble mean predicts that the Indian Ocean will return to a neutral state in boreal autumn. However, there is a large uncertainty in the predictions, and the SINTEX-F2-3DVAR, which predicted most recent IOD events, predicts that a weakly negative Indian Ocean Dipole will persist in boreal autumn.

Regional forecast:

On a seasonal scale, the SINTEX-F predicts that most parts of the globe will experience a hotter-than-normal condition in boreal autumn (austral spring) except for northern parts of the South American Continent. In boreal winter (austral summer), the model still predicts most parts of the globe will experience a warmer-than-normal condition, except for northern parts of the South American Continent and some parts of Europe.

As regards to the seasonally averaged rainfall in boreal autumn (austral spring), a drier-than-normal condition is predicted for California, southern parts of the South American Continent, most parts of southern Africa, some parts of West Africa, some parts of Europe, some parts of Indochina, and most parts of China. In contrast, most parts of Alaska, the western coastal area of Canada, Central America, northern parts of the South American Continent, some parts of Central Africa, India, Philippines, and Indonesia will experience a wetter-than-normal condition. Some parts of West Africa will also experience a wetter-than-normal condition due to the evolving Atlantic Niño. Extremely wetter-than-normal conditions in Indonesia will be mostly due to the evolving negative Indian Ocean Dipole. In boreal winter (austral summer), a wetter-than-normal condition is predicted for Alaska, northern parts of the South American Continent, Philippines, and Indonesia. In contrast, most parts of Australia, some parts of southern Africa, and some parts of Europe will experience a drier-than-normal condition.

The model predicts most parts of Japan will experience a warmer-than-normal condition in autumn and winter as a seasonal average. As regards to the seasonally averaged rainfall, the model predicts almost neutral conditions over most parts of Japan in autumn. In winter, Okinawa and southern parts of Japan will experience a drier-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 that was issued on July 15, 2021

We can compare the new forecast to the prior forecast recognizing that the new forecast is for a three-month period that begins one month later.

Prior Forecast	New Forecast

There are two versions of the discussion of the seasonal drought outlook: long and short and this month I am providing the long version.

Discussion for the Seasonal Drought Outlook

Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for August and August through October 2021 (ASO), 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 related 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 the ASO season, and initial conditions such as soil moisture. The USDM valid on July 13 was used for initial drought conditions.

Drought remains firmly entrenched across the western conterminous U.S., with nearly the entire Western Region experiencing drought conditions (D1 or worse) according to the US Drought Monitor valid on July 13, 2021. An unprecedented heat wave baked the Northwest in late June, with daytime temperatures climbing near 30 deg. F above normal. New all-time record high temperatures were established at numerous locations, including Seattle WA (108F), Portland OR (116F), and Salem OR (117F). Quillayute, in far western Washington, hit 110F — more than ten degrees higher than their previous all-time record. In Lytton, British Columbia (about 200 miles northeast of Seattle), temperatures climbed to 121F, easily setting a new all-time high temperature record for Canada. Most areas of Idaho and Montana are now D2-D3, with some D4 in central Idaho. Farther south, conditions are even more extreme, with D3-D4 encompassing large sections of eastern Washington, interior Oregon, California, Nevada, Utah, Arizona, and adjacent western Colorado and western New Mexico. There is good news in the short-term across the Southwest, where monsoon rains should be abundant until about the end of July. Conditions are more uncertain thereafter, and the 3-month ASO outlook favors subnormal precipitation. Late summer is the wettest time of year in this region, and the July moisture should bring drought improvement that will likely not reintensify between August and the end of October. Part of east-central Arizona could record over 4 inhces of rain by July 22. One-third to one-half of the annual precipitation total in Arizona, southern Utah, and New Mexico falls during July through September. Over the rest of the West, annual precipitation totals are not as dominated by the late summer monsoon, and the ASO outlook favors less precipitation than normal everywhere except Washington, north and west Oregon, north Idaho, and adjacent northwest Montana. Above-normal temperatures are expected regionwide. Based on these considerations, drought is expected to persist or intensify outside the desert Southwest, with drought covering the entire region except westernmost Washington by the end of October.

Forecast confidence is high in the West Coast States, where precipitation is climatologically low until autumn, and moderate for the desert Southwest, Utah, Idaho, and Montana.

In the High Plains region, drought is entrenched across northern and western sections (i.e., the Dakotas, Wyoming, and western Colorado) like it is across most of the West Region. In sharp contrast, Nebraska, Kansas, and the eastern half of Colorado contain few areas of drought. Climatologically, ASO as a whole is a drier time of year across Wyoming, but for the rest of the region, precipitation climatologically wanes as August progresses into autumn. The third week of July could bring a couple inches of precipitation to eastern Kansas, but the short-term looks drier elsewhere, and the ASO outlook favors deficient precipitation everywhere but the east half of Kansas and extreme southeastern Nebraska. Drought persistence or intensification is the only reasonable forecast in areas of existing drought, and drought is expected to expand across all of Wyoming, northeastern Colorado, western Nebraska, and adjacent South Dakota by the end of October. Recent surplus precipitation should preclude drought from extending into more of eastern Colorado and Kansas.

Forecast confidence is medium for the High Plains Region.

Precipitation during the last few weeks has almost entirely removed drought from the Southern Region. Only parts of the western Big Bend of Texas and small patches of northwest Oklahoma remain in drought. The monsoonal showers and thunderstorms that should bring some relief to the southern Rockies should also bring improvement to western Texas despite the ASO outlook favoring subnormal precipitation. In Oklahoma, the isolated patches of lingering drought are expected to be removed by the end of October, though with much less confidence.

Forecast confidence in the Southern Region is low to moderate across western Oklahoma, and high elsewhere.

In the areas of drought across the Midwest Region (most of Minnesota, central and northern Iowa, southern Wisconsin, and adjacent locales), the forecast has to weigh short-term wetness against enhanced chances for subnormal ASO precipitation. This inherently makes for an uncertain forecast, but the short-term looks wettest across most of Iowa and points east, which is where some improvement or removal is forecast. Farther north across Minnesota and small parts of adjacent states – where significant precipitation is not expected as July plays out – drought is forecast to persist.

Forecast confidence in the Midwest Region is low.

The Southeast Region is drought-free, and is expected to remain so through the end of October. Only parts of the western Carolinas are experiencing any abnormal dryness. Precipitation looks unremarkable in the short-term, and odds favor surplus precipitation for ASO through most of the region outside the Florida Peninsula. Even there, in the absence of any compelling reason to expect markedly below-normal precipitation, drought development is not expected

Forecast confidence is moderate to high for the Southeastern Region.

In the Northeast Region, drought is restricted to parts of Cape Cod, and from northernmost New York eastward through west-central Maine. With surplus ASO precipitation favored, drought should be on the decline if not removed altogether. The forecast for Cape Cod is less certain, with drier weather expected in the short-term and existing groundwater shortages. But even there, ASO precipitation should bring the region out of drought by the end of the period.

Forecast confidence is moderate for Cape Cod, and high for the rest of the Northeast Region.

There is some dryness in southern and eastern Alaska, but drought development is not expected there by the end of October. The lingering drought in southern Puerto Rico is expected to dissipate as ASO is the wettest time of year climatologically, and the expected enhanced tropical activity further argues for a forecast of removal. In contrast, ASO is expected to be drier than normal across Hawaii, which should cause drought to persist or intensify, with some expansion expected in the Big Island, O’ahu, and Kaua’i.

Forecast confidence is high in Puerto Rico and Hawaii, and moderate in Alaska.

ENSO Considerations

Now let us look at the NOAA recent ENSO Update. This happens every month on the second Thursday. I show this because it is the information that NOAA works from in producing the Four-Season Forecast. We have covered some of this when we reported on the IRI/CPC analysis on July 8, 2021. We may discuss it again when we do the NOAA/JAMSTEC Comparison.

ENSO UPDATE

This is a NOAA graphic but not part of the release of information on July 8, 2021. My interpretation of this graphic is that we are NOT in La Nina right now. It is a cross-section of the Equatorial Pacific. What counts is the surface temperature and this only shows the Equator and the actual calculation is based on the temperature anomaly from 170W to 120W but inducing 5 degrees north and south of the Equator. I have a different graphic that shows that but this one is probably more accurate for the area shown. The water is anomalously cold east of 100W. But west of 150W it is certainly not as cold as -0.5C. So we are definitely in ENSO Neutral the question being what is next and when will there be a change.

But now I freeze the graphic and focus on the top part which shows the temperature anomalies.

Below is the graphic above but also one issued five days later. (I believe these images are five-day averages centered on the date shown.)

Prior Version	Updated Version

The Southern Oscillation Index or SOI being above 7 confirms that the Atmosphere is in tune with the Sea Surface Temperatures in the Pacific along the Equator. At least temporarily the SOI Index is in neutral territory. This is another graphic that we have not frozen.

Here is the BOM (Australia Bureau of Meteorology) Nino3.4 tracker.

Here is their current forecast.

B. Conclusion

From the perspective of NOAA, we not in a La Nina but will be soon. There is an issue as to how long we remain in that La Nina condition. The tools NOAA uses to forecast the state of ENSO has introduced the concept of a possible to probably double-dip La Nina. That is not unusual.

Special Appendix

Play for fun and to increase your knowledge of the North American Monsoon (NAM). But there are prizes: two of them actually

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