Accessibility navigation

Linking rapid forecast error growth to diabatic processes

Sánchez, C. ORCID:, Methven, J. ORCID:, Gray, S. ORCID: and Cullen, M. (2020) Linking rapid forecast error growth to diabatic processes. Quarterly Journal of the Royal Meteorological Society, 146 (732). pp. 3548-3569. ISSN 0035-9009

Text - Accepted Version
· Please see our End User Agreement before downloading.


It is advisable to refer to the publisher's version if you intend to cite from this work. See Guidance on citing.

To link to this item DOI: 10.1002/qj.3861


The predictability of high impact weather events over the North Atlantic is controlled by synoptic‐scale systems and the mesoscale structures embedded within them. Despite forecast uncertainty being greatest at small scales at the initial time, forecast error projects strongly onto synoptic and larger scales within days. Different stages of error growth have previously been identified including: convective instability, baroclinic instability and the influence of divergent outflow on the tropopause position, and interactions between disturbances at tropopause level. Evidence is presented for “predictability barriers” (PBs) identified with events on certain validation dates during the North Atlantic Waveguide and Downstream impact Experiment (NAWDEX) where ensemble spread grows more quickly than usual, but ensemble mean forecast error grows even faster. An advective mechanism for diabatic influence on the development of tropopause ridges is hypothesised to be linked to the PB events. A semi‐geostrophic balance tool is used to attribute the response of the 3‐D ageostrophic flow to geostrophic and diabatic forcing, enabling a novel diagnostic for Diabatically‐Induced Ageostrophic Advection of potential vorticity (DIAA). It is shown that predictability barriers are linked to events with strong diabatic influence on tropopause advection during the NAWDEX period. Error growth exceeds ensemble spread rate by approximately 4/3 during strong DIAA events, showing that predictive skill is considerably lower in these situations.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:91525


Downloads per month over past year

University Staff: Request a correction | Centaur Editors: Update this record

Page navigation