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Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

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   90day Prognostic
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    0.5mn OND 2020
    1.5mn NDJ 2020
    2.5mn DJF 2020
    3.5mn JFM 2021
    4.5mn FMA 2021
    5.5mn MAM 2021
    6.5mn AMJ 2021
    7.5mn MJJ 2021
    8.5mn JJA 2021
    9.5mn JAS 2021
   10.5mn ASO 2021
   11.5mn SON 2021
   12.5mn OND 2021
    0.5mn Oct 2020

Tools Used (see Discussion for explanation)
HOME> Outlook Maps>Seasonal Forecast Discussion
Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Sep 17 2020


The October 2020 monthly temperature and precipitation outlooks are primarily
based on consistent dynamical model forecast guidance within the context of
ongoing and likely strengthening La Nina conditions as we progress into the
autumn months. In addition, some areas of the forecast domain utilized current
land surface states and nearby ocean surface temperatures as input.

The MJO is also considered, but played a lesser role in the outlook as the
recent strong, coherent MJO activity has weakened some and is being disturbed
by higher frequency coherent, subseasonal tropical variability (atmospheric
Kelvin and equatorial Rossby wave activity) and evolving under strengthening La
Nina conditions. Consequently, it is unclear how coherent and robust the MJO
enhanced convective phase will emerge from the Maritime continent to the
Pacific Ocean during the second half of September. Also, statistically
significant impacts to higher latitudes from the MJO are often marginal during

The October 2020 temperature outlook favors above-normal monthly mean
temperatures for nearly all of the forecast domain except for areas in
southeast Alaska and the Pacific Northwest where Equal Chances (EC) is
forecast. Dynamical model forecast guidance and typical temperatures observed
during October under La Nina conditions support this outlook. Long term
positive temperature trends enhance odds for above-normal temperatures for
parts of the western CONUS as does dry surface conditions. Strong negative
trends in sea ice coverage and thickness and so warmer than normal ocean
surface temperatures in waters surrounding Alaska also favors higher odds for
above-normal temperatures for parts of western and northern Alaska.

La Nina conditions tend to favor near to below-normal temperatures in parts of
the Pacific Northwest, southeast Alaska and the Alaska Panhandle, but with
positive long term trends in some of these areas counteracting this generally
weak La Nina signal, EC is forecast for these areas. Long term positive
temperature trends , dynamical model forecast guidance, and to a lesser extent
near coast ocean surface temperatures and dry surface conditions support
slightly higher odds for above-normal temperatures for the Northeast and

For precipitation, consistent dynamical model forecast guidance and typical La
Nina conditions favors a region of below-normal precipitation stretching from
the Southwest and south-central Rockies eastward to include the central and
southern Plains and Mississippi Valley to parts of the Tennessee and Ohio River
Valley's. Potential tropical systems developing in the Gulf of Mexico and
northwestern Caribbean and their often northeast migration supports slightly
elevated odds for above-normal rainfall for parts of the extreme Southeast and
the state of Florida.

La Nina and consistent dynamical model forecast guidance favors above-normal
monthly total precipitation amounts for parts of the Pacific Northwest and
Alaska Panhandle. La Nina conditions typically support above-normal
(below-normal) precipitation for the west coast of Alaska (south-central
Alaska) respectively.

FORECASTER: Jon Gottschalck

The climatic normals are based on conditions between 1981 and 2010, 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 Wed September 30 2020

These outlooks are based on departures from the 1981-2010 base period.

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