Spatial Distribution and Evolution of Extratropical Cyclone Errors over North America and its Adjacent Oceans in the NCEP Global Forecast System Model

Colle, Brian A.; Charles, Michael E.

doi:10.1175/2010waf2222422.1

Cited by 13 publications

(9 citation statements)

References 24 publications

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“…The relation of forecast skill and atmospheric predictability to large-scale flow anomalies (AO, NAO, ENSO, and others) is an issue of some importance, since the onset and persistence of certain atmospheric flow regimes can have significant effects on model performance (Ferranti et al, 2002;Simmons and Hollingsworth, 2002;Archambault et al, 2008), and on reliability in forecasts of extreme and high-impact weather events including mid-latitude extratropical cyclone activity (Colle and Charles, 2011).…”

Section: P U B L I S H E D B Y T H E I N T E R N a T I O N A L M E T mentioning

confidence: 99%

Recent Northern Hemisphere mid-latitude medium-range deterministic forecast skill

Langland¹,

Maue²

2012

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C T A multi-model archive of global deterministic forecasts and analyses from three operational systems is constructed to analyse recent Northern Hemisphere mid-latitude forecast skill from 2007 to 2012 and its relation to large-scale atmospheric flow anomalies defined by the Arctic Oscillation (AO) index. We find that the anomaly correlation coefficient (ACC) in 120-hr forecasts of 500 hPa geopotential height has similar variability on synoptic, monthly, and seasonal time scales in each of the three forecast systems examined here: the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Prediction Global Forecast System, and the U.S. Navy Operational Global Atmospheric Prediction System. The results indicate that forecast skill as measured by the ACC is significantly correlated with the AO index and its transitions between negative and positive phase. Intervals of exceptionally high ACC skill during the 2009Á2010 and 2010Á2011 winters are associated with periods in which the AO remained in a persistent negative phase pattern. Episodes of low ACC, including so-called 'forecast skill dropouts' most frequently occur during transitions between negative and positive AO index and with positive AO index. The root mean square error (RMSE) of 120-hr forecast 500 hPa height is also modulated by the AO index, but to a lesser extent than the ACC. In two recent winters, the RMSE indicates lower 120-hr forecast accuracy during periods with negative AO index, which is opposite to 'skill' patterns provided by the ACC. These results suggest that the ACC is not in all situations an optimal metric with which to quantify model forecast skill, since the ACC can be higher when the large-scale atmospheric flow contains strong anomalies even if there is no actual improvement in model forecasts of that atmospheric state.

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Section: P U B L I S H E D B Y T H E I N T E R N a T I O N A L M E T mentioning

confidence: 99%

Recent Northern Hemisphere mid-latitude medium-range deterministic forecast skill

Langland¹,

Maue²

2012

Tellus A: Dynamic Meteorology and Oceanography

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“…The hypothesis to be tested is as follows: given a reasonably selected set of targeted observations, forecasts that incorporate the assimilation of these additional observations will be significantly more skillful than forecasts that do not, and the extra observations will be especially important for cases with anticipated highimpact weather, often associated with rapidly developing cyclones and the rapid growth of forecast error. Examples of cases in which large forecast errors are associated with deepening cyclones are presented in Colle and Charles (2011). Further, we hypothesize that the impact of the targeted observations will be larger in specific downstream ''verification regions'' focused on the expected area with high-impact weather and that the impact will be smaller when evaluated over continental-sized areas.…”

Section: Introductionmentioning

confidence: 99%

Impact of Targeted Winter Storm Reconnaissance Dropwindsonde Data on Midlatitude Numerical Weather Predictions

Hamill

Yang

Cardinali

et al. 2013

Monthly Weather Review

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The impact of assimilating data from the 2011 Winter Storm Reconnaissance (WSR) program on numerical weather forecasts was assessed. Parallel sets of analyses and deterministic 120-h numerical forecasts were generated using the ECMWF four-dimensional variational data assimilation (4D-Var) and Integrated Forecast System. One set of analyses was generated with all of the normally assimilated data plus WSR targeted dropwindsonde data, the other with only the normally assimilated data. Forecasts were then generated from the two analyses. The comparison covered the period from 10 January to 28 March 2011, during which 98 flights and 776 total dropwindsondes were deployed from four different air bases in the Pacific basin and the United States. The dropwindsondes were deployed in situations where guidance indicated the potential for high-impact weather and/or the potential for large subsequent forecast errors. Downstream target verification regions where the high-impact weather was expected were identified for each case. Forecast errors around the target verification regions were evaluated using an approximation to the total-energy norm. Precipitation forecasts were also evaluated over the contiguous United States using the equitable threat score and bias.Forecast impacts were generally neutral and thus smaller than reported in previous studies, most from over a decade ago, perhaps because of the improved forecast and assimilation system and the somewhat denser observation network. Target areas may also have been undersampled in this study. The neutral results from 2011 suggest that it may be more beneficial to explore other targeted observation concepts for the midlatitudes, such as assimilation of a denser set of cloud-drift winds and radiance data in dynamically sensitive regions.

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“…The skill of numerical weather prediction models in forecasting extratropical cyclones varies regionally and temporally (Charles and Colle 2009;Colle and Charles 2011;Froude et al 2007). The skill of numerical weather prediction models in forecasting extratropical cyclones varies regionally and temporally (Charles and Colle 2009;Colle and Charles 2011;Froude et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Ensemble Sensitivity Tools for Assessing Extratropical Cyclone Intensity and Track Predictability

Zheng

Chang

Colle

2013

Weather and Forecasting

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This paper applies ensemble sensitivity analysis to a U.S. East Coast snowstorm on 26-28 December 2010 in a way that may be beneficial for an operational forecaster to better understand the forecast uncertainties. Sensitivity using the principal components of the leading empirical orthogonal functions (EOFs) on the 50-member European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble identifies the sensitive regions and weather systems at earlier times associated with the cyclone intensity and track uncertainty separately. The 5.5-day forecast cyclone intensity uncertainty in the ECMWF ensemble is associated with trough and ridge systems over the northeastern Pacific and central United States, respectively, while the track uncertainty is associated with a short-wave trough over the southern Great Plains. Sensitivity based on the ensemble mean sea level pressure difference between two run cycles also suggests that the track's shift between the two cycles is linked with the initial errors in the short-wave trough over the southern Great Plains. The sensitivity approach is run forward in time using forward ensemble regression based on short-range forecast errors, which further confirms that the short-term error over the southern plains trough was associated with the shift in cyclone position between the two forecast cycles. A coherent Rossby wave packet originated from the central North Pacific 6 days before this snowstorm event. The sensitivity signals behave like a wave packet and exhibit the same group velocity of ;298 longitude per day, indicating that Rossby wave packets may have also amplified uncertainty in both the cyclone amplitude and track forecast.

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Spatial Distribution and Evolution of Extratropical Cyclone Errors over North America and its Adjacent Oceans in the NCEP Global Forecast System Model

Cited by 13 publications

References 24 publications

Recent Northern Hemisphere mid-latitude medium-range deterministic forecast skill

Recent Northern Hemisphere mid-latitude medium-range deterministic forecast skill

Impact of Targeted Winter Storm Reconnaissance Dropwindsonde Data on Midlatitude Numerical Weather Predictions

Ensemble Sensitivity Tools for Assessing Extratropical Cyclone Intensity and Track Predictability

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