Verification of Extratropical Cyclones within the NCEP Operational Models. Part I: Analysis Errors and Short-Term NAM and GFS Forecasts

Abstract

This paper verifies extratropical cyclones around North America and the adjacent oceans within the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) and North American Mesoscale (NAM) models during the 2002-07 cool seasons (October-March). The analyzed cyclones in the Global Forecast System (GFS) model, North American Mesoscale (NAM) model, and the North American Regional Reanalysis (NARR) were also compared against sea level pressure (SLP) observations around extratropical cyclones. The GFS analysis of SLP was clearly superior to the NAM and NARR analyses. The analyzed cyclone pressures in the NAM improved in 2006-07 when its data assimilation was switched to the Gridpoint Statistical Interpolation (GSI).The NCEP GFS has more skillful cyclone intensity and position forecasts than the NAM over the continental United States and adjacent oceans, especially over the eastern Pacific, where the NAM has a large positive (underdeepening) bias in cyclone central pressure. For the short-term (0-60 h) forecasts, the GFS and NAM cyclone errors over the eastern Pacific are larger than the other regions to the east. There are relatively large biases in cyclone position for both models, which vary spatially around North America. The eastern Pacific has four to eight cyclone events per year on average, with errors .10 mb at hour 48 in the GFS; this number has not decreased in recent years. There has been little improvement in the 0-2-day cyclone forecasts during the past 5 yr over the eastern United States, while there has been a relatively large improvement in the cyclone pressure predictions over the eastern Pacific in the NAM.

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…As noted earlier in section , ETCs are of importance to the U.S. East Coast. A substantial body of work has examined aspects of East Coast winter storms, which have major societal impacts ranging from commerce to public safety over the mid‐Atlantic and northeastern United States (e.g., Brennan & Lackmann, ; Charles & Colle, , ; Evans & Jurewicz, ; Ganetis & Colle, ; Hirsch et al, ; Kocin & Uccellini, ; Kumjian & Lombardo, ; Nicosia & Grumm, ; Novak et al, ; Novak & Colle, ; Root et al, ; Sanders & Bosart, ; Zhang et al, ). In fact, the oldest study identified in this review paper is related to cyclogenesis over the East Coast, which is relevant to the modeling and forecasting of such storms (Miller, ).…”

The Climatology and Characteristics of Rossby Wave Packets Using a Feature-Based Tracking Technique

“…Souders et al (2014) describe the details of the RWP tracking approach so only a brief overview is provided below. The method uses a hybrid approach to track RWPs, by combining a point-based object identification similar to the cyclone-tracking scheme of Charles and Colle (2009), and an feature-based tracking approach similar to methods used in the tracking of tropical convective clouds (Arnaud et al 1992). A minimum WPA threshold (14 m s 21 ), a minimum object size (40 grid points from 2.58-resolution data), and a search range for track continuity (208N/S, 308W, and 908E) were chosen.…”

Using model analysis and satellite data to assess cloud and precipitation in midlatitude cyclones

“…A number of recent studies have analysed how well midlatitude cyclones are forecast by operational centres. Initial mean errors in position, speed and minimum sea level pressure are found to be < 100 km, 10 km h −1 and ∼1 mb, respectively (Froude et al , 2007; Charles and Colle, 2009; Froude, 2010). These mean errors are typically found to triple over three days due to a combination of effects from the interaction of dynamical representation and physical parametrizations.…”