Operational transition of novel statistical–dynamical forecasts for tropical subseasonal-to-seasonal drivers

Subseasonal-to-seasonal (S2S) has emerged as one of the great frontiers for atmospheric
predictability. These time scales of weeks-to-months are at the heart of the mission for NOAA’s
Climate Prediction Center (CPC), which has been particularly focused on expanding and
improving their 3–4-week forecasts. Dynamical S2S models have improved significantly over
recent years, but they have yet to fully tap the potential predictability of coherent tropical modes
like the Madden–Julian Oscillation (MJO).

A unique approach to this problem has been implemented on NCICS.org/mjo. This website takes
recent observations and appends them with 45-day forecasts from the Climate Forecast System
version 2 (CFSv2). The combined data are then Fourier filtered in space and time for some of the
dominant modes of S2S variability in the tropics: the MJO, convectively coupled equatorial waves,
and low-frequency variability like the El Niño–Southern Oscillation (ENSO). This filtering
highlights the most predictable aspects of the S2S system. The website includes numerous maps,
Hovmöllers, and indices for identifying and predicting these modes. It has been updating daily
since 2011 with several upgrades and iterations over the years. These diagnostics have become
routine inputs for CPC’s Global Tropical Hazards (GTH) outlook.

NCICS.org/mjo has reached a level a maturity (Readiness Level 7) where it is a prime candidate
to be transitioned fully into operations at CPC. This proposal outlines that transition. It also
includes some modest development work that will use proven methods to further tailor these
diagnostics to CPC’s goals. Once these processes have been transferred to CPC, future work could
easily expand them to other models that CPC is already ingesting.

The proposed project is directly to the MAPP/NOAA Climate Test Bed competition because it
takes a demonstrated research product and transitions it into operations at NOAA’s CPC. In
particular, the proposal leverages a newly proved methodology to improve key forecast products
like the Weeks 3-4 outlooks. Transitioning this product to operations will help NOAA fulfill its
long-term climate goals by expanding CPC’s capabilities for monitoring and prediction using
existing models and observations. These diagnostics are already used by a number of public,
private, academic, and international users to provide them the climate intelligence they need for
resilience against climate variability.