Impact of Cyclone‐Cyclone Interaction on Lake‐Effect Snowbands: A False Alarm. Issue 2 (14th January 2023)

• Record Type: Journal Article
• Authors: Cao, Zuohao; Xu, Qin; Zhang, Da‐Lin
• Is Part Of: Journal of geophysical research. Volume 128:Issue 2(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-14
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2022JD037064
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: In this study, the impacts of two cyclone interactions with the environmental flow and with each other on a heavy winter snowfall event over the Great Lakes region are examined by applying a recently‐developed diagnostic tool to a lake‐effect snowstorm. This winter snowfall event was a false alarm by the Canadian operational model, in which the predicted lake‐effect snowfall at the lee side of Lake Erie doubles the observed. The false alarm involves the interactions of two cyclones, whose relative locations are poorly predicted, leading to inaccurate prediction of their induced winds and interactions over Lake Erie at both low and upper levels. In particular, at 1, 000 hPa, the cyclone‐induced winds and their interactions over Lake Erie caused colder and drier air over warm‐moist open‐water lake surface that is favorable for more latent heat flux deriving from the lake in the model than in the real atmosphere. At 500 hPa, the location errors of the model predicted cyclones reversed the cyclone‐induced winds over Lake Erie from mainly southerly to northerly, especially during the intense snowfall period. An analysis of the conditional symmetric instability (CSI) index over Lake Erie reveals that the operational model systematically over‐predicts CSI, more significantly during the intense snowfall period. As a result, the operational model prediction makes a false alarm of a lake‐effect snowfall event with large errors in precipitation intensity. Future improvements in operational model predictions are also suggested. Plain Language Summary: We have examined the impacts of two cyclone interactions on a heavy winter snowfall event over the Great Lakes region by applying a recently‐developed diagnostic tool to a lake‐effect snowstorm. This winter snowfall event was a false alarm by the Canadian operational model, with a prediction of doubled snowfall amount observed over Lake Erie. The false alarm involves the interactions of two cyclones, whose relative locations are poorly predicted, leading to inaccurate prediction of their induced winds and interactions over Lake Erie at both low and upper levels. At the low level, the cyclone‐induced winds and their interactions over Lake Erie caused colder and drier air over warm‐moist open‐water lake surface that is favorable for more latent heat flux deriving from the lake in the model than in the real atmosphere. At the upper level, the location errors of the model predicted cyclones reversed the cyclone‐induced winds over Lake Erie from mainly southerly to northerly, especially during the intense snowfall period. An analysis of the conditional symmetric instability (CSI) index over Lake Erie reveals that the operational model systematically over‐predicts CSI, more significantly during the intense snowfall period. Because of the above reasons, the false alarm of lake‐effect snowfall results. Key Points: Impacts of cyclone‐cyclone interactions on a false alarm with the prediction of doubled snowfall amount over Lake Erie are examined Positions of two cyclones are poorly predicted by the operational model, leading to errors in their induced winds over Lake Erie Over‐predictions of conditional symmetric instability result in the false alarm of the lake‐effect snowfall over Lake Erie