Increasing vertical resolution in US models to improve track forecasts of Hurricane Joaquin with HWRF as an example

The atmosphere−ocean coupled Hurricane Weather Research and Forecast model (HWRF) developed at the National Centers for Environmental Prediction (NCEP) is used as an example to illustrate the impact of model vertical resolution on track forecasts of tropical cyclones. A number of HWRF forecasting experiments were carried out at different vertical resolutions for Hurricane Joaquin, which occurred from September 27 to October 8, 2015, in the Atlantic Basin. The results show that the track prediction for Hurricane Joaquin is much more accurate with higher vertical resolution. The positive impacts of higher vertical resolution on hurricane track forecasts suggest that National Oceanic and Atmospheric Administration/NCEP should upgrade both HWRF and the Global Forecast System to have more vertical levels.

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Impact of the Different Components of 4DVAR on the Global Forecast System of the Meteorological Service of Canada

Monthly Weather Review ◽

10.1175/mwr3408.1 ◽

2007 ◽

Vol 135 (6) ◽

pp. 2355-2364 ◽

Cited By ~ 33

Author(s):

Stéphane Laroche ◽

Pierre Gauthier ◽

Monique Tanguay ◽

Simon Pellerin ◽

Josée Morneau

Keyword(s):

Data Assimilation ◽

Positive Impact ◽

Weather Forecast ◽

Forecast Model ◽

Variational Data Assimilation ◽

Global Forecast System ◽

Forecast System ◽

Medium Range Weather Forecast ◽

Medium Range ◽

The Impact

Abstract A four-dimensional variational data assimilation (4DVAR) scheme has recently been implemented in the medium-range weather forecast system of the Meteorological Service of Canada (MSC). The new scheme is now composed of several additional and improved features as compared with the three-dimensional variational data assimilation (3DVAR): the first guess at the appropriate time from the full-resolution model trajectory is used to calculate the misfit to the observations; the tangent linear of the forecast model and its adjoint are employed to propagate the analysis increment and the gradient of the cost function over the 6-h assimilation window; a comprehensive set of simplified physical parameterizations is used during the final minimization process; and the number of frequently reported data, in particular satellite data, has substantially increased. The impact of these 4DVAR components on the forecast skill is reported in this article. This is achieved by comparing data assimilation configurations that range in complexity from the former 3DVAR with the implemented 4DVAR over a 1-month period. It is shown that the implementation of the tangent-linear model and its adjoint as well as the increased number of observations are the two features of the new 4DVAR that contribute the most to the forecast improvement. All the other components provide marginal though positive impact. 4DVAR does not improve the medium-range forecast of tropical storms in general and tends to amplify the existing, too early extratropical transition often observed in the MSC global forecast system with 3DVAR. It is shown that this recurrent problem is, however, more sensitive to the forecast model than the data assimilation scheme employed in this system. Finally, the impact of using a shorter cutoff time for the reception of observations, as the one used in the operational context for the 0000 and 1200 UTC forecasts, is more detrimental with 4DVAR. This result indicates that 4DVAR is more sensitive to observations at the end of the assimilation window than 3DVAR.

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Predictability of ECMWF Cubic Octahedral Nature Run (ECO1280) using Finite-Volume Cubed-Sphere Global Forecast System (FV3GFS) Compared to Real-World Predictability

10.5194/egusphere-egu2020-2012 ◽

2020 ◽

Author(s):

Sean Casey ◽

Lidia Cucurull ◽

Andres Vidal

Keyword(s):

Finite Volume ◽

Real World ◽

Forecast Model ◽

Global Forecast System ◽

Forecast System ◽

Weather Forecasts ◽

Global Nature ◽

System Assessment ◽

Cubed Sphere ◽

Environmental Prediction

<p>Under the Quantitative Observing System Assessment Program, the National Oceanic and Atmospheric Administration's (NOAA's) Atlantic Oceanographic and Meteorological Laboratory (AOML) is preparing to utilize the 9-km-resolution European Centre for Medium-Range Weather Forecasts (ECWMF) Cubic Octahedral grid global Nature Run (ECO1280) for observation simulation and conducting Observing System Simulation Experiments (OSSEs). &#160; As part of the OSSE calibration, and before experiments can be run, it needs to be shown that the forecast model used in the OSSEs does not do a better job in predicting the Nature Run meteorology than it does in predicting the real world. Otherwise, the conclusions from the OSSEs in such a configuration may misstate the potential impact of a given instrument. In this presentation, the predictability of the new global OSSE system being developed at NOAA will be discussed. The NOAA/National Centers for Environmental Prediction (NCEP) Finite-Volume Cubed-Sphere Global Forecast System (FV3GFS) is used to test predictability over the first two months of ECO1280 (October-November 2015), comparing forecasts using simulated observations with added errors to real-world observations.&#160; Only conventional observations will be utilized in both cases. &#160;</p>

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Intensidade do vento de dois ciclones tropicais obtida por diferentes conjuntos de dados

Revista Brasileira de Geografia Física ◽

10.26848/rbgf.v13.1.p067-075 ◽

2020 ◽

Vol 13 (1) ◽

pp. 067

Author(s):

Christie Andre Souza ◽

Michelle Simões Reboita

Keyword(s):

Tropical Cyclones ◽

The Other ◽

Data Sets ◽

Global Forecast System ◽

Forecast System ◽

Wind Intensity

Os ciclones tropicais quando atingem ventos com intensidade igual ou superior a 119 km/h desenvolvem uma estrutura conhecida como olho em seu centro. Já os ventos mais intensos do sistema são encontrados imediatamente após o olho. Num estudo recente para os ciclones Haiyan e Haima foi levantada a questão da qualidade dos dados do Global Forecast System (GFS) em representar os ventos uma vez que os ventos máximos apareceram no olho do sistema. Diante disso, esse estudo tem como objetivo avaliar como diferentes conjuntos de dados (GFS, ERA5, ERA-Interim e CCMP) representam os ventos nesses dois ciclones tropicais. A ERA5 e o GFS mostram ventos mais intensos nos ciclones do que os outros dois conjuntos de dados. Todos, exceto o GFS, mostram claramente ventos mais fracos no olho dos ciclones. Wind intensity of two tropical cyclones obtained by different data sets A B S T R A C TWhen the tropical cyclones reach winds with intensity equal or higher than 119 km/h, they develop a structure known as the eye at its center. The strongest winds in the system are found immediately after the eye. In a recent study for Haiyan and Haima cyclones, the question of the quality of the Global Forecast System (GFS) data in representing the winds once the maximum winds appeared in the system eye was raised. Therefore, this study aims to evaluate how different data sets (GFS, ERA5, ERA-Interim and CCMP) represent the winds in these two tropical cyclones. ERA5 and GFS show cyclones with more intense winds than the other datasets. Except the GFS, the other data clearly show weaker winds in the cyclone eye.Keywords: analyzes; cyclones; meteorology; reanalysis

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High-Resolution Ensemble HFV3 Forecasts of Hurricane Michael (2018): Rapid Intensification in Shear

Monthly Weather Review ◽

10.1175/mwr-d-19-0275.1 ◽

2020 ◽

Vol 148 (5) ◽

pp. 2009-2032 ◽

Cited By ~ 3

Author(s):

Andrew T. Hazelton ◽

Xuejin Zhang ◽

Sundararaman Gopalakrishnan ◽

William Ramstrom ◽

Frank Marks ◽

...

Keyword(s):

Tropical Cyclones ◽

Early Stage ◽

Vertical Wind Shear ◽

Vertical Shear ◽

Rapid Intensification ◽

Forecast System ◽

The Mean ◽

Cubed Sphere ◽

Environmental Prediction ◽

The Relationship

Abstract The FV3GFS is the current operational Global Forecast System (GFS) at the National Centers for Environmental Prediction (NCEP), which combines a finite-volume cubed sphere dynamical core (FV3) and GFS physics. In this study, FV3GFS is used to gain understanding of rapid intensification (RI) of tropical cyclones (TCs) in shear. The analysis demonstrates the importance of TC structure in a complex system like Hurricane Michael, which intensified to a category 5 hurricane over the Gulf of Mexico despite over 20 kt (10 m s−1) of vertical wind shear. Michael’s RI is examined using a global-nest FV3GFS ensemble with the nest at 3-km resolution. The ensemble shows a range of peak intensities from 77 to 159 kt (40–82 m s−1). Precipitation symmetry, vortex tilt, moisture, and other aspects of Michael’s evolution are compared through composites of stronger and weaker members. The 850–200-hPa vertical shear is 22 kt (11 m s−1) in the mean of both strong and weak members during the early stage. Tilt and moisture are two distinguishing factors between strong and weak members. The relationship between vortex tilt and humidification is complex, and other studies have shown both are important for sheared intensification. Here, it is shown that tilt reduction leads to upshear humidification and is thus a driving factor for intensification. A stronger initial vortex and early evolution of the vortex also appear to be the key to members that are able to resist the sheared environment.

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The Impact of Air–Sea Interactions on the Simulation of Tropical Intraseasonal Variability

Journal of Climate ◽

10.1175/2008jcli2180.1 ◽

2008 ◽

Vol 21 (24) ◽

pp. 6616-6635 ◽

Cited By ~ 49

Author(s):

Kathy Pegion ◽

Ben P. Kirtman

Keyword(s):

Intraseasonal Variability ◽

Intraseasonal Oscillation ◽

Coupled Model ◽

Coupled Simulation ◽

Maritime Continent ◽

Forecast System ◽

Climate Forecast System ◽

Environmental Prediction ◽

The Impact ◽

The Western Pacific

Abstract The impact of coupled air–sea feedbacks on the simulation of tropical intraseasonal variability is investigated in this study using the National Centers for Environmental Prediction Climate Forecast System. The simulation of tropical intraseasonal variability in a freely coupled simulation is compared with two simulations of the atmospheric component of the model. In one experiment, the uncoupled model is forced with the daily sea surface temperature (SST) from the coupled run. In the other, the uncoupled model is forced with climatological SST from the coupled run. Results indicate that the overall intraseasonal variability of precipitation is reduced in the coupled simulation compared to the uncoupled simulation forced by daily SST. Additionally, air–sea coupling is responsible for differences in the simulation of the tropical intraseasonal oscillation between the coupled and uncoupled models, specifically in terms of organization and propagation in the western Pacific. The differences between the coupled and uncoupled simulations are due to the fact that the relationships between precipitation and SST and latent heat flux and SST are much stronger in the coupled model than in the uncoupled model. Additionally, these relationships are delayed by about 5 days in the uncoupled model compared to the coupled model. As demonstrated by the uncoupled simulation forced with climatological SST, some of the intraseasonal oscillation can be simulated by internal atmospheric dynamics. However, the intraseasonally varying SST appears to be important to the amplitude and propagation of the oscillation beyond the Maritime Continent.

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A Comparison of the Downstream Predictability Associated with ET and Baroclinic Cyclones

Monthly Weather Review ◽

10.1175/mwr-d-17-0083.1 ◽

2017 ◽

Vol 145 (11) ◽

pp. 4651-4672 ◽

Cited By ~ 4

Author(s):

Ryan D. Torn

Keyword(s):

Standard Deviation ◽

Indian Ocean ◽

Tropical Cyclones ◽

North Pacific ◽

Western North Pacific ◽

Ensemble Forecast ◽

Latent Heat Release ◽

Propagation Characteristics ◽

Forecast System ◽

The Impact

The impact of the extratropical transition (ET) of tropical cyclones and baroclinic cyclogenesis in the western North Pacific (WNP), Atlantic, and southern Indian Ocean (SIO) basins on the predictability of the downstream midlatitude flow is assessed using 30 years of cases from the Global Ensemble Forecast System (GEFS) Reforecast, version 2. In all three basins, ET is associated with statistically larger 500-hPa geopotential height forecast standard deviation (SD) compared to the forecast climatology. The higher SD values originate from where the TC enters the midlatitudes and spread downstream at the group velocity of the associated wave packet. Of the three basins, WNP ET is associated with the largest amplitude and longest-lasting SD anomalies. Forecasts initialized 2–4 days prior to the onset of ET have larger SD anomalies compared to forecasts initialized during or after the onset of ET. By contrast, the region of positive SD anomaly associated with winter baroclinic cyclones is confined to the upstream trough, with fall cyclones exhibiting some downstream propagation characteristics similar to ET. The ET cases with the larger downstream SD anomaly are characterized by a more amplified ridge downstream of the TC as it enters the midlatitudes. By contrast, ET cases with an upstream trough, large TC position variability at the onset of ET, latent heat release, or upper-tropospheric PV advection by the irrotational wind are not characterized by significantly larger downstream SD compared to cases without an upstream trough or smaller values of these quantities.

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Impact of Boreal Summer Intra-Seasonal Oscillations on the Heavy Rainfall Events in Taiwan during the 2017 Meiyu Season

Atmosphere ◽

10.3390/atmos10040205 ◽

2019 ◽

Vol 10 (4) ◽

pp. 205 ◽

Cited By ~ 1

Author(s):

Wan-Ru Huang ◽

Pin-Yi Liu ◽

Jen-Her Chen ◽

Liping Deng

Keyword(s):

Heavy Rainfall ◽

Boreal Summer ◽

Economic Losses ◽

Global Forecast System ◽

Forecast System ◽

Rainfall Events ◽

The Impact ◽

Meiyu Season ◽

Heavy Rainfall Events ◽

Seasonal Oscillations

During May and June (the Meiyu season) of 2017, Taiwan was affected by three heavy frontal rainfall events, which led to large economic losses. Using satellite observations and reanalysis data, this study investigates the impact of boreal summer intra-seasonal oscillations (BSISOs, including a 30–60 day ISO mode named BSISO1 and a 10–30 day ISO mode named BSISO2) on the heavy rainfall events in Taiwan during the 2017 Meiyu season. Our examinations show that BSISO2 is more important than BSISO1 in determining the formation of heavy rainfall events in Taiwan during the 2017 Meiyu season. The heavy rainfall events generally formed in Taiwan at phases 4–6 of BSISO2, when the enhanced southwesterly wind and moisture flux convergence center propagate northward into the Taiwan area. In addition, we examined the forecast rainfall data (at lead times of one day to 16 days) obtained from the National Centers for Environmental Prediction Global Forecast System (NCEPgfs) and the Taiwan Central Weather Bureau Global Forecast System (CWBgfs). Our results show that the better the model’s capability in forecasting the BSISO2 index is, the better the model’s capability in forecasting the timing of rainfall formation in Taiwan during the 2017 Meiyu season is. These findings highlight the importance of BSISO2 in affecting the rainfall characteristics in East Asia during the Meiyu season.

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Potential Impacts of the Saharan Air Layer on Numerical Model Forecasts of North Atlantic Tropical Cyclogenesis

Weather and Forecasting ◽

10.1175/2008waf2007090.1 ◽

2009 ◽

Vol 24 (2) ◽

pp. 420-435 ◽

Cited By ~ 13

Author(s):

Aaron S. Pratt ◽

Jenni L. Evans

Keyword(s):

Tropical Cyclones ◽

North Atlantic ◽

Forecast Accuracy ◽

Tropical Cyclogenesis ◽

Atlantic Basin ◽

Easterly Waves ◽

Saharan Air Layer ◽

The North ◽

Gfs Model ◽

Environmental Prediction

Abstract Tropical cyclones have devastating impacts on countries across large parts of the globe, including the Atlantic basin. Thus, forecasting of the genesis of Atlantic tropical cyclones is important, but this problem remains a challenge for researchers and forecasters due to the variety of weather systems that can lead to tropical cyclogenesis (e.g., stalled frontal boundaries, African easterly waves, and extratropical cyclones), as well as the role of the surrounding environment in promoting or inhibiting the development into a tropical depression and beyond. In the North Atlantic, the effects of the Saharan air layer (SAL), a hot, dry dusty layer that moves into the eastern Atlantic basin, must be taken into account when forecasting whether genesis will occur. There are several characteristics of SAL that impact tropical cyclones (decreased midtropospheric moisture, increased midlevel shear, and enhanced stability). The purpose of this study is to examine the forecasting skill of the National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) model for the 2002 and 2003 Atlantic hurricane seasons, with particular regard paid to possible SAL effects on model genesis forecast accuracy. Cyclone phase space analyses of GFS 6-hourly forecasts were divided into three possible outcomes: S (successful forecasts that verified in cyclogenesis), F1 (cyclogenesis events that were not forecast to occur), and F2 (forecasted cyclogenesis that did not occur). The spatial variabilities of these outcomes for the early, middle, and late season were analyzed for both years, as well as the background environmental conditions. The large number of F2 forecasts that were seen in both years can be partly explained by the GFS model not capturing the detrimental effects of the SAL on cyclogenesis.

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Assessing the Performance of an Ensemble Forecast System in Predicting the Magnitude and the Spectrum of Analysis and Forecast Uncertainties

Monthly Weather Review ◽

10.1175/2010mwr3439.1 ◽

2011 ◽

Vol 139 (4) ◽

pp. 1207-1223 ◽

Cited By ~ 7

Author(s):

Elizabeth Satterfield ◽

Istvan Szunyogh

Keyword(s):

Ensemble Spread ◽

Forecast System ◽

Forecast Uncertainty ◽

Total Magnitude ◽

Real Atmosphere ◽

Grid Points ◽

Ensemble Transform Kalman Filter ◽

Environmental Prediction ◽

The Impact ◽

Data Assimilation System

The ability of an ensemble to capture the magnitude and spectrum of uncertainty in a local linear space spanned by the ensemble perturbations is assessed. Numerical experiments are carried out with a reduced resolution 2004 version of the model component of the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS). The local ensemble transform Kalman filter (LETKF) data assimilation system is used to assimilate observations in three steps, gradually adding more realistic features to the observing network. In the first experiment, randomly placed, noisy, simulated vertical soundings, which provide 10% coverage of horizontal model grid points, are assimilated. Next, the impact of an inhomogeneous observing system is introduced by assimilating simulated observations in the locations of real observations of the atmosphere. Finally, observations of the real atmosphere are assimilated. The most important findings of this study are the following: predicting the magnitude of the forecast uncertainty and the relative importance of the different patterns of uncertainty is, in general, a more difficult task than predicting the patterns of uncertainty; the ensemble, which is tuned to provide near-optimal performance at analysis time, underestimates not only the total magnitude of the uncertainty, but also the magnitude of the uncertainty that projects onto the space spanned by the ensemble perturbations; and finally, a strong predictive linear relationship is found between the local ensemble spread and the upper bound of the local forecast uncertainty.

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