Diagnosing the Pacific Tropical-Extratropical Pre-superstorm Environment

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Monday, 3 February 2014
Hall C3 (The Georgia World Congress Center )
Matthew G. Fearon, Desert Research Institute, Reno, NV; and M. L. Kaplan

Over the last two decades, researchers in the atmospheric and climate sciences have turned their attention to extreme storm events resulting from tropical-extratropical interaction. Extratropical cyclones fed by tropical moisture plumes (atmospheric rivers) or tropical cyclones that develop a mixed core (of warm and cold) are of particular interest because they appear to be a manifestation of imbalance(s) present in the atmosphere's general circulation and hence have the potential to become extreme events or so-called “superstorms”. Two events of interest include the “Perfect Storm” (October 1991) and Superstorm Sandy (October 2012), which decimated the Atlantic coastlines of New England and New Jersey, respectively. The earliest investigations on the origin of imbalance(s) in the general circulation stemming from the tropics involved studying the seasonal circulation patterns associated with El Niño - Southern Oscillation (ENSO). However, more recently intraseasonal variations, on timescales of 45 days or less, such as convectively coupled atmospheric and oceanic Kelvin waves associated with the Madden-Julian Oscillation (MJO), appear to be more representative (Roundy 2011). Even though Roundy et al. (2010) and others (e.g., Knippertz 2005; Kiladis 1998) have demonstrated that areas of anomalous tropical convection are associated with extratropical circulations, the characteristic features of the MJO itself have overshadowed its potential impacts. To this end, the proposed research aims to systematically examine the consequences of the MJO for intense storms that affect mid-latitudes such as the tropical-extratropical environment preceding the “Perfect Storm” and Superstorm Sandy, September 1 through October 31, 1991 and 2012, respectively. These case studies, like many other major extratropical storms that affect North America, indicate remarkable teleconnections over a broad swath of the northern hemisphere due to an active MJO. For example, a clear amplification of the Arctic Oscillation (AO) in the negative phase builds southward from north-central Canada into the central U.S. steering Superstorm Sandy westward into the New Jersey coastline on October 29, 2012. Strong similarities were also noted with the “Perfect Storm” of October 1991, where a hurricane was also steered into an extratropical storm near the New England coast. For these two extreme events, detailed analyses of the MJO and its modulation of the extratropics will be performed using a variety of tools such as the Weather Research and Forecasting (WRF) model, blended GOES satellite imagery products (e.g., visible, infared, vapor, and cloud track winds), and A-train (AIRS and CALIPSO) products.