Skillful empirical subseasonal prediction of landfalling atmospheric river activity using the Madden–Julian oscillation and quasi-biennial oscillation

Abstract

Upon landfall, atmospheric rivers (ARs)-plumes of intense water vapor transport-often trigger weather and hydrologic extremes. Presently, no guidance is available to alert decision makers to anomalous AR activity within the subseasonal time scale (~2-5 weeks). Here, we construct and evaluate an empirical prediction scheme for anomalous AR activity based solely on the initial state of two prominent modes of tropical variability: the Madden-Julian oscillation (MJO) and the quasi-biennial oscillation (QBO). The MJO-the dominant mode of intraseasonal variability in the tropical troposphere-modulates landfalling AR activity along the west coast of North America by exciting large-scale circulation anomalies over the North Pacific. In light of emerging science regarding the modulation of the MJO by the QBO-the dominant mode of interannual variability in the tropical stratosphere-we demonstrate that the MJO-AR relationship is further influenced by the QBO. Evaluating the prediction scheme over 36 boreal winter seasons, we find skillful subseasonal "forecasts of opportunity" when knowledge of the MJO and the QBO can be leveraged to predict periods of increased or decreased AR activity. Certain MJO and QBO phase combinations provide empirical subseasonal predictive skill for anomalous AR activity that exceeds that of a state-of-the-art numerical weather prediction model. Given the wide-ranging impacts associated with landfalling ARs, even modest gains in the subseasonal prediction of anomalous AR activity may support decision making and benefit numerous sectors of society.

Prediction of Northern Hemisphere Regional Surface Temperatures Using Stratospheric Ozone Information

“…Figure highlights within the locations of statistically useful relationships (e.g., high regression beta values), the predictions can remain consistent over a few years past the regression model end date within the regions that have a well‐resolved signal in the model. Further, although prediction of the absolute values appears feasible in some cases (Figures c and f over 2021–2022), prediction of the sign of the anomaly may be more broadly applicable (Figure e), and represents one approach to testing skill (Mundhenk et al, ). The next section analyzes to what degree a simple empirical model based on March TCO can predict the sign of the surface temperature anomaly over regions where the model is not well resolved.…”

Circulation Drivers of Atmospheric Rivers at the North American West Coast

“…Additionally, while predictability of AR landfalls in the extended range (2-4 weeks) has so far proven elusive (Wick et al, 2013;, excepting possible forecasts of opportunity associated with joint MJO/quasi-biennial oscillation phase considerations (Mundhenk et al, 2018), it is possible there could be improved skill on these timescales for predicting favorable versus unfavorable circulation types, which would have value for water resource management and flood prevention. Although beyond the scope of this work, quantifying links between the seasonal prevalence of important circulation features identified here and subseasonal-to-decadal climate variability modes such as the MJO, ENSO, and PDO could lead to improved seasonal and subseasonal AR predictability.…”

“…Upper-level circulation observed during AR landfalls in Northern California (Neiman et (Neiman et al, 2008) feature a prominent high-low couplet with a gradient parallel to the coast, which acts to channel wind and moisture onshore. Recent work highlighted links between regional AR activity and circulation features associated with common teleconnection patterns such as the Pacific North American Pattern (PNA; Guan & Waliser, 2015), Arctic Oscillation (Guan et al, 2013), El Niño Southern Oscillation (ENSO; Ryoo et al, 2013;Kim & Alexander, 2015;Kim et al, 2017), Pacific Decadal Oscillation (PDO; GSR'17), Madden-Julian Oscillation (MJO; Guan & Waliser, 2015), and the MJO jointly with the quasi-biennial oscillation (Baggett et al, 2017;Mundhenk et al, 2018). Recent work highlighted links between regional AR activity and circulation features associated with common teleconnection patterns such as the Pacific North American Pattern (PNA; Guan & Waliser, 2015), Arctic Oscillation (Guan et al, 2013), El Niño Southern Oscillation (ENSO; Ryoo et al, 2013;Kim & Alexander, 2015;Kim et al, 2017), Pacific Decadal Oscillation (PDO; GSR'17), Madden-Julian Oscillation (MJO; Guan & Waliser, 2015), and the MJO jointly with the quasi-biennial oscillation (Baggett et al, 2017;Mundhenk et al, 2018).…”

A Cautionary Note on the Long‐term Trend in Activity of the Madden‐Julian Oscillation During the Past Decades

“…Due to its intermediate period of 30-60 days, the MJO has been considered one of the primary subseasonal predictability sources beyond the deterministic weather forecasts (e.g., Gottschalck et al, 2010;Vitart et al, 2012;Waliser, 2012). The continuous improvement of MJO prediction skill in the recent decades has promoted great enthusiasm in the community in exploring potentials for the extended range prediction of extreme weather activities (e.g., Baggett et al, 2018;Jiang et al, 2018;Lee et al, 2018;Lin, 2018;Mundhenk et al, 2018;Vitart & Robertson, 2018;Wang et al, 2018;Xiang et al, 2015;Xiang et al, 2019).…”