Prognostic Discussion for Monthly Outlook
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Jun 15 2023


30-DAY OUTLOOK DISCUSSION FOR JULY 2023

The July 2023 temperature and precipitation outlooks are based on the North 
American Multi-Model Ensemble (NMME), CPC's statistical tools, consolidations 
of those inputs, the Copernicus (C3S) model systems data for July, the week 3-4 
model solutions, and antecedent soil moisture conditions. An El Niño advisory 
was recently issued, though the ocean-atmosphere coupling is not yet strong 
enough to contribute majorly to the variability over Alaska and the Contiguous 
United States (CONUS) during July. The Madden-Julian Oscillation (MJO) remains 
active with its enhanced phase over the Maritime Continent. The MJO is forecast 
to weaken by many of the global models. Typically in July, the main pathway of 
MJO related influence on the mid-latitude circulation pattern is through 
modulation of tropical cyclone activity. An MJO contributing to a relative 
burst in East Pacific tropical cyclone activity could result in moisture surges 
into the Southwest, and later more tropical cyclone activity in the Atlantic, 
though July is relatively a quiet time of year for tropical activity in the 
Atlantic.

Above normal temperatures are favored from the Four Corners region, across the 
central and southern Great Plains, the Southeast, and the Northeast. The 
highest odds are across the Rio Grande Valley and the Northeast, where NMME and 
statistical tool outputs are aligned. From Southern California to the Great 
Basin, Northern Rockies and portions of the northern Great Plains, the NMME and 
C3S solutions were much cooler than the statistical tools, and recent soil 
moisture conditions are quite anomalous in those regions, so uncertainty is 
higher there compared to other parts of the forecast domain. Trends (Optimal 
Climate Normals) in those regions also show patterns opposite of many other 
tools, so OCN are discounted in favor of Equal Chances of above, near, and 
below Normal Temperatures (EC). Across Alaska, most modeling systems and 
statistical tools favored above normal temperatures, with the highest odds 
across the southern portions of Mainland Alaska. Recent below-normal sea 
surface temperatures (SSTs) and late season sea ice breakup mitigate odds near 
the west coast of Alaska. 

A weakened monsoon during July across eastern Arizona and New Mexico is 
predicted in many of the NMME input systems and some of the statistical tools, 
so that signal makes it into the final consolidation. Again, trends are showing 
opposite signals across the Great Basin and portions of the Rockies, so 
forecast probabilities are a bit muted, and the trends are largely discounted. 
NMME output favors above-normal precipitation across the Rio Grande while 
statistical tools have a signal further east, so the official outlook is a 
compromise between those two. Upper-level height anomalies from the NMME imply 
a strong subtropical ridge, which would favor above-normal precipitation from 
the southern Great Plains northward and into the Mid-Atlantic. The mid-latitude 
portion of the NMME signal would also favor a storm track across the northern 
Great Plains and into the Ohio River valley, so above-normal precipitation is 
favored across those two regions. The NMME has strong signals for below-normal 
precipitation across Northern Mainland Alaska, with a weak storm track further 
south. Many of the statistical tools have low skill during July in Alaska, and 
the coupling to the tropics is not influential in Alaska during the summer, so 
the NMME had a larger influence on the outlook.

FORECASTER: Matthew Rosencrans

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 Jul will be issued on Fri June 30 2023

These outlooks are based on departures from the 1991-2020 base period.
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