Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu May 16 2024 
 
 
30-DAY OUTLOOK DISCUSSION FOR JUNE 2024 
 
During the first half of May 2024, the transition from El Nino to ENSO neutral 
continues as shown by both oceanic and atmospheric indicators. A further 
transition to La Nina remains favored to occur sometime during the summer 
months. The MJO is currently not well organized. Although some model forecasts 
of the RMM index do indicate some improvement in the signal over the next 
couple of weeks, it seems potentially transient in nature with high 
uncertainty. Also, given the time within the seasonal cycle, there is low 
confidence in any reliable impacts to the U.S. and so the MJO did not play any 
substantial role in the monthly outlook. Soil moisture anomalies, coastal sea 
surface temperatures (SSTs) and long-term temperature trends  are considered in 
preparation of the June 2024 outlook. 
 
The June 2024 temperature outlook depicts elevated odds for above-normal 
monthly mean temperatures for a region from eastern mainland Alaska to the 
Pacific Northwest and northern Rockies south and east to the Southwest CONUS 
and eastward to include the southern Plains and Southeast. Subseasonal model 
guidance (ECMWF, GEFS, among others) favors mean ridging for the west-central 
CONUS northward across western Canada to eastern Alaska in early June. The 
potential ridging elevates odds for warmer than normal conditions for the first 
third of June for much of this area with dry soil moisture conditions adding 
support for areas in the Pacific Northwest, northern Rockies and parts of the 
Southwest and southern High Plains. The majority of the NMME and C3S monthly 
model predictions also indicate above-normal temperatures for this region. 
Subtropical ridging along the southern tier of the U.S. supports elevated odds 
for above-normal temperatures for the southern Plains, Gulf coast and 
Southeast. Highest odds are forecast for the eastern Southwest and Texas where 
ridging, dry surface conditions and positive long-term temperature trends  
co-exist. 
 
Below-normal monthly mean temperatures are favored for two small areas for 
coastal central and southern California and also for parts of southwest Alaska. 
Cooler than normal ocean surface temperatures contribute to these forecasts 
with favored mean forecast troughing near and along the southern half of the 
West coast also supporting below-normal temperatures for the California region. 
 
A dipole forecast for enhanced odds for below-normal (above-normal) 
temperatures was considered for parts of the Midwest, Ohio Valley and 
mid-Atlantic (northern Great lakes and New England) respectively. Conflicting 
model forecast guidance, soil moisture conditions and long-term temperature 
trends, however, made highlighting these areas in the outlook a low confidence 
forecast at the current time. Therefore, Equal Chances (EC) for either above-, 
near- or below-normal temperatures is forecast for the mid-month outlook and 
reevaluated for the end of the month update. 
 
For precipitation, elevated odds for above-normal monthly total precipitation 
amounts are forecast for a region from the central Plains eastward across the 
Ohio Valley to the mid-Atlantic. Both subseasonal and monthly model predictions 
indicate the tendency for a mean frontal zone in the interior of the CONUS from 
the Atlantic seaboard westward to the central CONUS. The location of this 
wetter than normal area is quite variable amongst the model solutions so the 
forecast area is generally placed in the most likely region after considering 
all the available information. 
 
Drier than normal monthly precipitation amounts are forecast for eastern areas 
of the Southwest as well as parts of the Pacific Northwest and northern 
Rockies. NMME and C3S model monthly predictions are in very good agreement this 
month similar to last several monthly forecast cycles for below-normal 
precipitation for the eastern Southwest, south-central Rockies and much of 
Texas implying a later and/or weaker southwest monsoon onset. Subseasonal model 
guidance in early June indicates positive 500-hPa height anomalies in the 
northeast Pacific ocean implying a northward shifted storm track and so 
elevated odds for below-normal precipitation is forecast in the Pacific 
Northwest and northern Rockies. Some NMME and C3S model guidance also supports 
this forecast. 
 
Favored forecast ridging in western Canada can sometimes enhance warm season 
precipitation for far east-central mainland Alaska so a slight tilt toward 
above-normal precipitation is highlighted in this area for June 2024. 
 
Remaining areas depicted in white are forecasts of EC for either above-, near- 
or below-normal precipitation amounts due to weak climate signals  and/or low 
historical forecast skill or reliability. 
 
FORECASTER: Jon Gottschalck 
 
The climatic normals are based on conditions between 1991 and 2020, following 
the World Meteorological Organization convention of using the most recent 3 
complete decades as the climate reference period.  The probability anomalies 
for temperature and precipitation based on these new normals better represent 
shorter term climatic anomalies than the forecasts based on older normals. 
 
An updated monthly outlook... for Jun will be issued on Fri May 31 2024 
 
These outlooks are based on departures from the 1991-2020 base period. 
$$