An Evaluation of Sea Level Cyclone Forecasts Produced by NMC's Nested-Grid Model and Global Spectral Model

Smith, Bruce; Mullen, Steven L.

doi:10.1175/1520-0434(1993)008<0037:aeoslc>2.0.co;2

Cited by 16 publications

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“…12b), eastern Canada ( 1, 4, and 6). This same bias was prevalent in NCEP operational models 10-15 yr ago (Smith and Mullen 1993), which suggests that lee cyclogenesis is still occurring too far north in these models on average even though the model terrain has Fig. For the NAM, the displacement is significant at the 90% level to the south for all years, 1 and to the east in 2002-03 and 2006-07.…”

Section: B Displacement Errors For 2002-07mentioning

confidence: 64%

“…For the NAM, the displacement is significant at the 90% level to the south for all years, 1 and to the east in 2002-03 and 2006-07. Smith and Mullen (1993) showed very similar results for both the GFS and NAM. There was little position bias in the GFS for region 1 during 2006-07, which suggests that it may now be better simulating these upstream terrain effects than the NAM.…”

Section: B Displacement Errors For 2002-07mentioning

confidence: 92%

“…It has been several years since a large number of extratropical cyclones have been verified around North America within the National Centers for Environmental Prediction (NCEP) operational models. Smith and Mullen (1993) found that the NGM, in the 1987-88 and 1989-90 cool seasons at forecast hours 24 and 48, slightly overdeepened weak and continental cyclones (2-4 mb), and underdeepened deep and oceanic cyclones (2-6 mb in the Pacific and 2-4 mb in the Atlantic). They found that the LFM underdeepened Atlantic and Pacific cyclones by 6-10 mb at forecast hour 48, and overdeepened cyclones to the east of the Rockies through the eastern United States by up to 4 mb.…”

Section: A Backgroundmentioning

confidence: 99%

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

Charles

Colle

2009

Weather and Forecasting

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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.

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Section: B Displacement Errors For 2002-07mentioning

confidence: 64%

Section: B Displacement Errors For 2002-07mentioning

confidence: 92%

Section: A Backgroundmentioning

confidence: 99%

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

Charles

Colle

2009

Weather and Forecasting

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“…Phenomenologically driven studies strive to gain insight into the nature of model errors for particular phenomena. For example, numerous studies are available concerning cyclone tracks and development, with lee cyclogenesis receiving particular attention (e.g., Mullen and Smith 1993;Smith and Mullen 1993;Schultz and Doswell 2000). Other studies examine how well models can forecast surface trough passages (Colle et al 2001) and tropical storms (e.g., Powell and Aberson 2001).…”

Section: Introductionmentioning

confidence: 99%

Field Significance Revisited: Spatial Bias Errors in Forecasts as Applied to the Eta Model

Elmore

Baldwin

Schultz

2006

Monthly Weather Review

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The spatial structure of bias errors in numerical model output is valuable to both model developers and operational forecasters, especially if the field containing the structure itself has statistical significance in the face of naturally occurring spatial correlation. A semiparametric Monte Carlo method, along with a moving blocks bootstrap method is used to determine the field significance of spatial bias errors within spatially correlated error fields. This process can be completely automated, making it an attractive addition to the verification tools already in use. The process demonstrated here results in statistically significant spatial bias error fields at any arbitrary significance level.To demonstrate the technique, 0000 and 1200 UTC runs of the operational Eta Model and the operational Eta Model using the Kain-Fritsch convective parameterization scheme are examined. The resulting fields for forecast errors for geopotential heights and winds at 850, 700, 500, and 250 hPa over a period of 14 months (26 January 2001-31 March 2002) are examined and compared using the verifying initial analysis. Specific examples are shown, and some plausible causes for the resulting significant bias errors are proposed.

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“…The cyclone displacement error is the distance between the forecast position and the observed cyclone. Previous operational models, such as the Nested Grid Model, and earlier versions of the GFS (i.e., the Aviation Model), also had this problem (Mullen and Smith 1990;Smith and Mullen 1993). 5 shows the position-error histograms of GFS cyclone displacement over the WA, C, and EP regions.…”

Section: Resultsmentioning

confidence: 99%

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

Colle

Charles

2011

Weather and Forecasting

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Short-to medium-range (1-5 day) forecasts of extratropical cyclones around North America and its adjacent oceans are verified within the Global Forecast System (GFS) model at the National Centers for Environmental Prediction (NCEP) during the 2002-07 cool seasons (October-March). Cyclones in the immediate lee of the Rockies and U.S. Great Plains have 25%-50% smaller pressure errors than other regions after hour 36. The central pressure and displacement errors are largest over the central and eastern Pacific for the 42-72-h forecast, while the western and central Atlantic pressure errors for 96-120 h are similar to the central and eastern Pacific. For relatively strong cyclones, the western Atlantic and central/eastern Canada pressure errors are larger than those for the Pacific by 108-120 h. There are large spatial variations in the central pressure biases at 72-120 h, with overdeepened GFS cyclones (negative errors) extending from the northern Pacific and Bering Strait eastward to western Canada, while underdeepened GFS cyclones (positive errors) occur across northeast Canada and just east of the U.S. east coast. GFS cyclone tracks and spatial composites using the daily NCEP reanalysis are used to illustrate flow patterns and source regions for some of the large GFS cyclone errors and biases. Relatively large central pressure errors over the central Pacific early in the forecast (30 h) spread eastward over Canada by 66 h and the eastern United States by 84 h. The underdeepened GFS cyclone errors (.1.5 standard deviations) at day 4 over the western Atlantic are associated with an anomalous ridge over the western United States and trough over the eastern United States, and most of the underdeepening occurs with cyclones tracking east-northeastward across the Gulf Stream. Many of the overdeepened cyclones have tracks more parallel to the U.S. east coast. The underdeepened cyclones over the central and eastern Pacific tend to occur farther south (358-458N) than the overdeepened events.

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An Evaluation of Sea Level Cyclone Forecasts Produced by NMC's Nested-Grid Model and Global Spectral Model

Cited by 16 publications

References 0 publications

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

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

Field Significance Revisited: Spatial Bias Errors in Forecasts as Applied to the Eta Model

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

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