Written by Sig Silber
Updated at 10 pm EDT Friday June 19 2020 to reflect the Week 3 – 4 Forecast.
Here is the June 18, 2020, NOAA 15-month forecast for CONUS and Alaska including the Early Outlook for July 2020 and forecasts out through September 2021. It covers a period that begins one month later than the forecast last month and extends one month longer. There is essentially no change in the overall forecast. The prior forecast included the Early Outlook for June and this forecast has the Early Outlook for July. So that is new information, as is the three-month drought 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 July, 2020. It is called the Early Outlook because it will be updated at the end of June. Only the July 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 July 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 July*. For Temperature, it is warm all over and the Northeast and greater Southwest have high probabilities for being warmer than climatology. For precipitation, there is a large wet anomaly for the Southeast extending north through the MidAtlantic and west over to eastern Texas. There is a dry anomaly centered on Wyoming. Western and northern Alaska are wet.
* 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 June (two days of July) so only the third of the three maps is really useful for this purpose. The third map extends the coverage through the first 10 days of July. The Seasonal Outlook was issued early this month since the third Thursday fell on June 18, 2020. Ten days of shorter forecasts is not an acceptable basis for doing this visual consistency testing but it is what we have to work with and there are thirty-one days in July. The report is not updated to reflect the new Week 3 – 4 Forecast which extends our shorter forecast through July 17 which is not ideal but a big improvement over what we had last night
First Temperature
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| 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 now have shorter forecasts through July 17, 2020. That is not ideal but there seems to be pretty good agreement with the full month forecast except in the Northwest. So we will be looking to see if the second half of the month is indeed warm in the Northwest. We will also revisit the forecast at the end of June when the July 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 now have shorter forecasts through July 17, 2020. That is not ideal but there seems to be better agreement with the full month forecast except in the Northeast and Arizona. [See forecaster discussion shown below] So we will be looking to see if the second half of the month is sufficiently different in those areas to make the full month work out as forecast. We will also revisit the forecast at the end of June when the July forecast is updated. ← |
Here is today’s Week 3 – 4 Discussion
Week 3-4 Forecast Discussion Valid Sat Jul 04 2020-Fri Jul 17 2020
The global tropical convective pattern continues to be dominated by Kelvin wave activity masquerading as an MJO by some metrics. The active region of a Kelvin wave has moved over the East Pacific this week and is expected to continue circumnavigating the globe over the next two weeks. Most of the dynamical models show an increase in RMM amplitude, embedded within an otherwise noisy RMM forecast, during this time period as the Kelvin wave projects onto an MJO-like upper-level wind signal. Regardless of the state of the tropics, the meridional PV gradient is weak throughout the Northern Hemisphere, in typical summer fashion. Therefore, it’s difficult for any tropical modes to have substantial impacts on the midlatitude flow pattern and today’s forecast is mostly influenced by our calibrated dynamical model guidance.
The CFS, JMA, and ECMWF dynamical models feature a low amplitude 500-hPa height pattern over North America. Both the CFS and JMA have moderate amplitude anomalous ridges over the northeastern U.S. All three models hint at a weakness in the height field over the Northwest; the CFS is most aggressive with an anomalous trough forecast over the region. Today’s temperature forecast features its highest probabilities of above normal temperatures, 60-70%, over the Great Lakes, Northeast, and Southwest where soil moisture is anomalously low and there is good model agreement regarding above normal temperatures.
Most dynamical guidance supports near to above normal height anomalies over Alaska, where a 60-70% chance of above normal temperatures is forecast. There is weak evidence from the CFS that the Panhandle will be below normal, but this forecast isn’t supported by the ECMWF and JMA. SSTs are above normal north and west of Hawaii and below normal to the southeast. The CFS forecasts this pattern to persist over the next few weeks, and dynamical guidance supports above normal temperatures throughout the state, so a 70% chance of above normal temperatures is forecast over Hawaii.
As mentioned above, there is model agreement regarding anomalous ridging over the Great Lakes and Northeast U.S. Models are also in agreement that these areas will experience below normal precipitation during Weeks 3-4, so a 50-55% chance of below normal precipitation is forecast from eastern Montana to the Northeast Coast, with an embedded 55-60% chance extending from western Minnesota and Iowa eastward. There is also good agreement regarding delayed Southwest monsoon onset, so a 50-60% chance of below normal precipitation is forecast over most of Arizona and western New Mexico. There is also good agreement supporting above normal precipitation throughout most of the Southeast, although this could be largely convective in nature and therefore much of that rainfall will likely be localized.
The forecast anomalous precipitation signal over Alaska is weak, which is consistent with a nearly climatological forecast height pattern, so equal chances are forecast. Models suggest equal chances of below and above normal rainfall over the southeastern Hawaiian islands and a slight tilt to above normal rainfall over the northwestern islands.
Now we consider the three-month Outlook.
Notice that the three-month periods are abbreviated e.g. July/August/September is shown as JAS. You will see such abbreviations often in this report.
Prior Temperature Outlook for JJA 2020
New Temperature Outlook for JJA 2020
Now Precipitation.
Prior forecast for JJA 2020
New Precipitation Outlook for JJA 2020
Now let us focus on the long-term situation.
First Temperature
Prior 14 Month Temperature Outlook: JAS 2020 – JJA 2021
New 14 Month Precipitation Outlook: ASO 2020 – JAS 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: JAS 2020 – JJA 2021
New 14 Month Precipitation Outlook: ASO 2020 – JAS 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 June 18, 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 (July), the new NOAA Summary for JAS, and finally the remainder of the 15-Month Forecast.
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
Oceanic and atmospheric observations across the equatorial Pacific indicate ENSO-neutral conditions persisted into June. Observed SSTs, for the previous 30 days, showed average or positive anomalies west of the Date Line and negative anomalies from 160 degrees W longitude eastward to near the coast of South America. Positive subsurface temperature anomalies continued to be confined to the western Pacific with increasing negative temperature anomalies below the surface of the eastern Pacific. Integrated upper-ocean heat anomalies declined rapidly since earlier this spring and remain significantly negative. Easterly low-level wind anomalies were present east of the Date Line during the previous 30 days with westerly upper-level wind anomalies along the equator over the central and east-central Pacific Ocean. Positive outgoing longwave radiation (OLR) anomalies, during this same time period, show suppressed convection across the western and central equatorial Pacific.
PROGNOSTIC DISCUSSION OF SST FORECASTS
The CPC SST Consolidation for the Nino 3.4 region indicates a steady decline into increasing negative anomalies to -0.5 degrees C by JAS with negative anomalies peaking during the early winter. The SST canonical correlation analysis (CCA), constructed analog (CA), and Markov statistical models indicate a persistence of ENSO-neutral conditions through the summer and fall into winter. The CPC/IRI consensus forecast favors a continuation of ENSO-neutral conditions (with about a 60 percent chance) during the Northern Hemisphere summer with the chances decreasing through the autumn (to 40-50 percent) and approximately an equal chance (40-50 percent) of developing La Nina conditions.
30-DAY OUTLOOK DISCUSSION FOR JULY 2020
Temperature
The July 2020 temperature outlook depicts elevated probabilities for above-normal monthly mean temperatures for the entire forecast domain. Nearly all information considered in preparing the temperature outlook pointed to warmer than normal conditions at varying degrees for Alaska and the CONUS. Current land surface conditions, dynamical model forecast guidance, statistical based tools as well as long term positive temperature trends in most areas supported the outlook. In addition, potential persistent enhanced convection in the Indian Ocean tends to favor positive 500-hPa heights for considerable areas of the CONUS during the summer months and so further tilts the odds toward warmer potential conditions in July.
The greatest odds for above-normal temperatures are forecast for a region in the south-central Rockies where dynamical model guidance, long term trends and extreme drought conditions favor above-normal temperatures. Both dynamical model guidance and long term trends supported the forecast for most of the western CONUS along with considerably drier than normal conditions in many areas. Similar factors also supported above-normal temperatures for the Northeast, eastern Great Lakes and the mid-Atlantic region for the month of July.
As is often the case, the interior portion of the country shows considerable uncertainty, lower confidence and so lower forecast probabilities. The temperature forecast from the CFS favors near to below-normal temperatures for much of the central CONUS. This is considered overdone given recent conditions and forecast factors for July from other sources and forecast tools so was considered an outlier and ignored. Even so, the northern portion of this area, which stretches from the western Great Lakes and upper Mississippi Valley to the Gulf coast, had less forecast guidance consistency along with elevated soil moisture conditions so odds for above-normal temperatures are considerably tempered in some of these areas. Anomalous land surface wetness and favored above-normal precipitation for the month of July also reduce odds for above-normal temperatures in the lower Mississippi Valley, Tennessee Valley and Gulf coast states.
Elevated probabilities for above-normal temperatures are also forecast for Alaska due to consistent forecast tools as well as current above-normal sea surface temperatures in the Bering Sea and other nearby waters which result in slightly higher odds for above-normal temperatures for areas of western Alaska.
Precipitation
For precipitation, the July 2020 outlook indicates considerable uncertainty, lower forecast confidence and so reduced forecast coverage. Above-normal precipitation is favored for the Gulf Coast, Southeast, Tennessee Valley to the mid-Atlantic. This forecast is driven by potential influences from current subseasonal coherent tropical variability (MJO, atmospheric Kelvin wave activity, etc.) and any subsequent tropical disturbances and moisture as well as the majority of dynamical model guidance from the NMME, data from the IMME predecessor, Copernicus data, as well as some statistical forecast guidance. The CFS precipitation forecast was considered an outlier and was discounted. Week 3-4 model guidance was mixed in this region as well so probabilities are quite modest for this half-month lead outlook.
Support for below-normal precipitation for the north-central Rockies to the northern Plains is modest, but is included due to long term negative precipitation trends , some support from dynamical model guidance, and anomalously dry conditions potentially limiting local recycling of precipitation. There remains a high degree of uncertainty for the timing and strength for the start of the Southwest U.S. monsoon this year.
There is a modest tilt in the odds for above-normal precipitation for western Alaska based on model guidance and above-normal sea surface temperatures in nearby waters. Equal-chances (EC) is designated in remaining areas where the forecast probabilities are not effectively different from climatological probabilities for either above-, near- or below-normal monthly total precipitation amounts.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
Tools used for the seasonal outlooks included dynamical model guidance such as the North American Multi-Model Ensemble (NMME) and the Calibration, Bridging, and Merging (CBaM) version of the NMME. Current soil moisture conditions played a role in the JAS temperature outlook, primarily across the Great Plains and Four Corners region. The seasonal consolidation tool, which includes dynamical model input from the NMME and various statistical tools such as regressions of observed temperature and precipitation on the CPC Nino 3.4 SST consolidation, was used especially at later leads. The likelihood that either ENSO-neutral or La Nina will be present later this summer through the autumn and winter seasons played a role in both temperature and precipitation outlooks. During the 2021 warm season decadal trends were the primary source of climate signals .
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS (Focus on July/August/September
The July-August-September (JAS) 2020 temperature outlook predicts likely above normal temperatures across Alaska and most of the contiguous U.S. (CONUS), with the exception being some areas near the Central Mississippi Valley, where equal chances (EC) of below, near and above normal temperatures are indicated. The JAS precipitation outlook predicts above normal precipitation to be likely for southern regions of Alaska, including the Aleutian Islands and the Alaska Panhandle. Above normal precipitation is also likely for much of the eastern CONUS from parts of the eastern Great Plains eastward across the Central and Lower Mississippi Valley to the Mid-Atlantic and Southeast regions and southward to the entire Gulf Coast from Texas to Florida. Below normal precipitation is favored for much of the Pacific Northwest, the Northern Rockies, and extending southeastward into the Central Rockies, parts of the northern Great Basin, and northeast regions of the Four Corners region. Equal chances (EC) of below, near and above normal precipitation are indicated for northern Alaska, as well as remaining areas of the Southwest CONUS, the western Great Plains, the Upper Mississippi Valley, the Great Lakes region, and the Northeast.
During the late summer and early fall season, increased chances of above normal temperatures expand to include the entirety of the CONUS with the largest probabilities over the Southwest and Northeast. Chances of above normal precipitation remain elevated across much of the Midwest, Southeast, and mid-Atlantic into August-September-October, while elevated chances of below normal precipitation shift southeastward from the Pacific Northwest into northern areas of the Southwest region. In autumn 2020 elevated chances of above normal precipitation are introduced into the Pacific Northwest and expand into the northern to central Great Plains in winter 2020-2021, then shift eastward into the Midwest by spring 2021. Increased chances of below normal precipitation expand across the southern tier of the CONUS in September-October-November 2020 through November-December-January 2020-2021.
Equal chances (EC) are forecast in areas where the likelihood of seasonal mean temperatures or seasonal accumulated precipitation amounts are expected to be similar to climatological probabilities.
PROGNOSTIC DISCUSSION OF OUTLOOKS – JAS 2020 TO JAS 2021
TEMPERATURE
Above normal temperatures are likely across almost the entire CONUS and Alaska during JAS with the largest probabilities forecast across the West and Northeast, based on excellent agreement among dynamical and statistical forecast tools including a strong decadal signal. Probabilities of above normal temperatures were increased from eastern Nevada into the Four Corners region from the previous JAS outlook following the latest model guidance, consistent with an increasing signal for below normal precipitation for much of this region, and ongoing low soil moisture conditions. Conversely, high soil moisture is one of the factors for equal chances of below, near or above normal temperatures forecast for parts of the Central Mississippi Valley in JAS. Beginning in ASO, increased chances of above normal temperatures expand through the central U.S. as the effect of anomalous soil moisture wanes and decadal trends support a larger signal for above normal temperatures. From JAS through OND 2020, changes from the previous outlook were to slightly increase probabilities of above normal temperatures for the Southwest and to decrease probabilities of above normal temperatures for the Pacific Northwest to northern Rockies. These minor changes were based on the latest consensus among dynamical and statistical tools and influenced by the equal chances of La Nina ans ENSO neutral conditions and low probability of El Nino. An expected lack of sea ice due to decadal trends elevates the probabilities for above normal temperatures across northern Alaska during the autumn season. The temperature outlook for the longer lead times following the spring of 2021 are based largely on decadal timescale trends .
PRECIPITATION
The precipitation outlooks are based primarily on the latest dynamical model guidance through DJF, along with statistical models, including the signal due to decadal trends , through JAS 2021. Compared to the previous outlook for JAS, a slight northeastward shift was made in the area of enhanced chances of below normal precipitation over the Four Corners region, as some model guidance such as from the CBaM Bridging component related to ENSO impacts, indicate potential enhanced precipitation over southwestern areas of the Southwest monsoon region. Consistent with the NMME and consolidation tool, probabilities above 40 percent for above normal precipitation were expanded from the eastern Gulf Coast into the Central Mississippi and Ohio Valleys. Elevated probabilities of above normal precipitation were indicated for southern Alaska, as supported by dynamical model guidance. Elevated chances of above normal precipitation were introduced into the Pacific Northwest in autumn and early winter, compared to previous outlooks, following dynamical model guidance and potentially associated with the equal likelihood of ENSO neutral or La Nina. A signal for below normal precipitation continues throughout the southern tier of the CONUS through autumn into early winter. No changes were made to the precipitation outlook from JFM 2021 onward, as the future evolution of interannual variability and ENSO remain uncertain.
At the longer leads, MJJ through JAS 2021, the tilt in the odds towards above normal precipitation across parts of the central and eastern U.S. is consistent with decadal trends . The area of favored below normal precipitation for parts of the Southwest during the spring 2021 is consistent with decadal trends
We will discuss this more when we compare the JAMSTEC to the NOAA forecast in a couple of days but it is useful to look at their discussion especially as it applies to summer.
June 10, 2020 Prediction issued on June 1, 2020
ENSO forecast:
Observation shows that a weak La Niña is developing at present. The SINTEX-F predicts that the weak La Niña-like condition will persist in the latter half of this year.
Indian Ocean forecast:
Observation shows that the western tropical Indian Ocean is warmer-than-normal at present. The model predicts the evolution of a moderately positive Indian Ocean Dipole (IOD) from boreal summer. The predicted IOD will quickly decay in boreal autumn, in which a typical IOD usually matures. However, there is a large uncertainty in the prediction (15% of the ensemble members actually predict a negative IOD event).
The strong negative Indian Ocean Subtropical Dipole still persists. The model predicts that it will disappear from austral winter.
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 summer and autumn.
As regards to the seasonally averaged rainfall in boreal summer, a drier-than-normal condition is predicted for most part of the South American Continent, South Africa, West Africa, central China, and western Indonesia. In contrast, most part of southern U.S.A., Mexico, India, Southeast Asia, Philippines, eastern Indonesia, eastern China, and the Korean Peninsula will experience a wetter-than-normal condition. In boreal autumn, a wetter-than-normal condition is predicted for northwestern coastal area of Canada, India, Southeast Asia, Philippines, and Indonesia. In contrast, eastern U.S.A., western part of the South American Continent, eastern part of South Africa, some part of West Africa, southeastern Europe facing the Mediterranean Sea will experience a drier-than-normal condition.
The model predicts most part of Japan will experience hotter-than-normal condition in summer as a seasonal average. In autumn, most part of Japan will experience hotter- and wetter-than-normal condition.
New Seasonal Drought Forecast (It is not set up to auto-update but you can always find the new forecast here) But it will not update until July 16, 2020.
Latest Seasonal Assessment – Drought coverage rapidly developed and intensified across the southern Great Plains and eastern New Mexico since May, due to insufficient rainfall, above normal temperatures, and periods of enhanced winds. Improvement or removal is slightly favored for parts of Oklahoma and northwest Texas due in part to an expected increase in rainfall during the latter half of June. Farther to the west across the Texas Panhandle and eastern New Mexico, that improvement is related to a relatively wet climatology, associated with the Southwest Monsoon. Nearly half of the annual precipitation typically occurs during July-August-September across eastern New Mexico. Drought is likely to persist and expand across the West and northern to central High Plains through the summer. A major factor in the drought expansion is the likelihood of above normal temperatures during the outlook period.Although drought is not forecast to develop across the Corn Belt and Midwest at the seasonal time scale, these areas will be closely monitored this summer for shorter-term but high impact drought on agriculture. Short-term drought may develop across parts of New England during late June into the beginning of July, but it is highly uncertain if this drought would persist through the end of September.
Drought is favored to gradually improve across Puerto Rico during the next few months. Conversely, drought development is forecast across the leeward sides of the Hawaiian Islands. Alaska is forecast to remain drought-free through the end of September.
ENSO Considerations
Here is what NOAA released last Thursday which is the official time for them to make that release.
ENSO Update
Best to look at the next three slides.
This (my slide but NOAA showed something similar) seems to say that ENSO Neutral is more likely through summer and then Neutral and La Nina are about equally likely. Is that what the report above says? Pick which sentence you like.
This shows the new forecast by the meteorologists compared to the prior forecast by the models. And they are quite a bit different. Darts anyone?
It looks like La Nina to me. This is just a slice along the equator but if you look at 170W to 120W it is not between +0.5C and -0.5C. It may be warmer away from the Equator as the measurement zone extends 5 degrees north and south. I could check that out and will with the Seasonal Outlook next week but for now I wonder what they are smoking. NOAA says at the surface it averages out to -0.4C. It might be time to get a new thermometer.
It is useful to see what some other agencies think. We will go into this more in a couple of days but this is the JAMSTEC forecast
And here is what the Bureau of Meteorology BOM in Australia things
NOAA has their own proprietary model which they rarely use.
B. Conclusion
There were essentially no changes to the forecast. The specific forecast for July is new information but it is very similar to the current and prior three-month forecast.
