Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu Sep 19 2024 
 
 
30-DAY OUTLOOK DISCUSSION FOR OCTOBER 2024 
 
The October temperature and precipitation outlooks are characterized by low 
forecast probabilities and outlook coverage - not atypical for an October 
monthly outlook. Ongoing climate conditions in mid-September indicate a 
continued slow trend toward potential La Nina conditions later this autumn, a 
better organizing MJO as well as anomalous coastal sea surface temperatures 
(SSTs) - primarily for waters in proximity to Alaska. Although not impactful in 
a predictability context this late in the year, soil moisture continues to 
decrease in many areas across the CONUS, with the ongoing impactful drought in 
parts of the Ohio Valley and western mid-Atlantic continuing to worsen. 
 
Preparation of the October temperature and precipitation outlooks primarily 
utilized subseasonal dynamical and statistical model guidance, potential 
teleconnection associated with an active MJO, long term trends  as well as in 
some places coastal SSTs. Any potential impacts from slowly developing La Nina 
conditions are not considered in the October outlook to any large degree. 
 
The temperature outlook favors above-normal temperatures for the southwestern 
CONUS, the central and southern Rockies, and southern Texas, consistent with 
the majority of subseasonal dynamical model guidance and most of the NMME and 
C3S participant models. Strong warmer-than-normal temperature trends  and 
forecast model guidance elevates chances for above-normal monthly mean 
temperatures for the Northeast, mid-Atlantic and parts of the eastern Great 
Lakes. 
 
There is a large area of "Equal Chances" or EC forecast from the Pacific 
Northwest eastward to include the northern and central Plains, Mississippi 
Valley and Southeast. The above average coverage of EC in the outlook in these 
areas is associated with highly varying dynamical model guidance on the 
subseasonal time scale. This includes the latest ECMWF extended range forecast 
which depicts weak signals  in this region over the course of the month of 
October. 
 
Although associated impacts from anomalous tropical convection are less likely 
in autumn then during winter and early spring, that potential still exists and 
is at odds with much of the dynamical model guidance. Uncertainty in any 
mid-latitude teleconnection from the MJO further complicates the forecast in 
this area as MJO lagged composites of 200-hPa height and 850-hPa temperature 
for MJO RMM phases 6 and 7 support troughing and favored below-normal 
temperatures for parts of the western and central CONUS during the first half 
of October. A Multiple Linear Regression (MLR) forecast tool utilizing the MJO, 
ENSO and long-term trends  targeting the first two weeks of October indicates 
elevated odds for below-normal temperatures in parts of the north-central 
CONUS. 
 
For Alaska, anomalous SSTs and some forecast guidance supports favored 
above-normal (below-normal) temperatures for the northern Alaska (Southwest 
Alaska) portions of the state. 
 
The October precipitation outlook favors below-normal precipitation for an area 
from the Southwest U.S. and central Rockies eastward to include much of the 
central Plains and parts of the central Mississippi Valley. This forecast is 
primarily based on a high degree of agreement in bias-corrected and calibrated 
dynamical model guidance from the NMME and C3S model suites as well as the 
ECMWF extended range forecast. 
 
Elevated odds for above-normal precipitation is forecast for the central and 
eastern Gulf coast, parts of the Southeast, mid-Atlantic coast and much of the 
Northeast. Long term wetter-than-normal precipitation trends  (i.e., OCN) and 
some subseasonal dynamical model guidance support the forecast in the Northeast 
and mid-Atlantic areas. For the Southeast and Gulf coast areas, the outlook is 
driven by potential tropical moisture entering this region of the CONUS 
associated with the MJO entering RMM phases 8 and 1 during early October. 
Dynamical model guidance from some sources also supports this forecast, mainly 
for Florida and extreme Southeast coastal areas. In addition, a small area of 
enhanced odds for wetter-than-normal conditions is forecast for northern 
Washington state indicated in some forecast tools. 
 
For Alaska, model guidance is generally consistent with wet conditions for 
areas in western and northern Alaska, so above-normal precipitation slightly 
favored in those portions of the state. Large uncertainty associated with 
highly conflicting forecast tools any potential MJO impacts made EC the prudent 
forecast for most of the Ohio Valley and much of the Midwest at this time. 
 
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 Oct will be issued on Mon September 30 2024 
 
These outlooks are based on departures from the 1991-2020 base period. 
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