Probabilistic Evaluation of the Dynamics and Prediction of Supertyphoon Megi (2010)

Abstract Supertyphoon Megi was the most intense tropical cyclone (TC) of 2010. Megi tracked westward through the western North Pacific and crossed the Philippines on 18 October. Two days later, Megi made a sharp turn to the north, an unusual track change that was not forecast by any of the leading operational centers. This failed forecast was a consequence of exceptionally large uncertainty in the numerical guidance—including the operational ensemble of the European Centre for Medium-Range Weather Forecasts (ECMWF)—at various lead times before the northward turn. This study uses The Observing System Research and Predictability Experiment (THORPEX) Interactive Grand Global Ensemble dataset to examine the uncertainties in the track forecast of the ECMWF operational ensemble. The results show that Megi's sharp turn is sensitive to its own movement in the early period, the size and structure of the storm, the strength and extent of the western Pacific subtropical high, and an approaching eastward-moving midlatitude trough. In particular, a larger TC (in addition to having a stronger beta effect) may lead to a stronger erosion of the southwestern extent of the subtropical high, which will subsequently lead to an earlier and sharper northward turn.

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Probabilistic Evaluation of Tibetan Plateau Mesoscale Vortex on 18 July 2013

Advances in Meteorology ◽

10.1155/2019/8302583 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13

Author(s):

Haiwen Liu ◽

Kaijun Wu ◽

Mengxing Du ◽

Ning Fu

Keyword(s):

Tibetan Plateau ◽

Heavy Rainfall ◽

Western Pacific Subtropical High ◽

Initial Time ◽

Baikal Lake ◽

Mesoscale Vortex ◽

Weather Forecasts ◽

Probabilistic Evaluation ◽

The Sichuan Basin

Tibetan Plateau (TP) mesoscale vortex (TPMV) was regarded as one of the most important rain bearing systems in China. Previous studies focused on the mechanisms of the TPMV in the viewpoint of deterministic forecast; however, few studies investigate the predictability of the TPMV using the Observing System Research and Predictability Experiment (THORPEX) Interactive Grand Global Ensemble (TIGGE) from the European Center for Medium Range Weather Forecasts (ECWMF). This paper investigates the location and the intensity of the larger-scale synoptic systems that influenced the development of the TPMV and its associated heavy rainfall by correlation and composite analysis. The case study on 18 July 2013 shows that stronger Balkhash Lake ridge, weaker Baikal Lake trough, and weaker western Pacific subtropical high (WPSH) are favorable to formation of TPMV over the Sichuan basin (SCB); otherwise, weaker Balkhash Lake ridge, stronger Baikal Lake trough, and stronger WPSH result in formation of TPMV to west of the SCB slightly. After the initial time, forecast for next 48 h of the geopotential height over the SCB can be viewed as a precursor of the subsequent time-averaged 90–108 h forecast of TPMV. TPMV had critical contributions to the heavy rainfall over the SCB on 18 July 2013.

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Sensitivity of the Track and Intensity Forecasts of Typhoon Megi (2010) to Satellite-Derived Atmospheric Motion Vectors with the Ensemble Kalman Filter

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-12-00020.1 ◽

2012 ◽

Vol 29 (12) ◽

pp. 1794-1810 ◽

Cited By ~ 18

Author(s):

Chanh Q. Kieu ◽

Nguyen Minh Truong ◽

Hoang Thi Mai ◽

Thanh Ngo-Duc

Keyword(s):

Kalman Filter ◽

Motion Vector ◽

The Philippines ◽

Intensity Change ◽

Track Forecast ◽

Recent Effort ◽

Low Level ◽

Sharp Turn ◽

Atmospheric Motion ◽

Upper Level

Abstract In this study, sensitivities of the track and intensity forecasts of Typhoon Megi (2010) to the Cooperative Institute for Meteorological Satellite Studies (CIMSS) University of Wisconsin satellite atmospheric motion vector (AMV) dataset are examined. Assimilation of the CIMSS AMV dataset using the local ensemble transform Kalman filter implemented in the Weather Research and Forecasting model shows that the AMV data can significantly improve the track forecast of Typhoon Megi, especially the sharp turn from west-northwest to north after crossing the Philippines. By broadening the western Pacific subtropical high to the west, the AMV data can help reduce the eastward bias of the track, thus steering the storm away inimical shear environment and facilitating its subsequent development. Further sensitivity experiments with separated assimilation of the low- to midlevel (800–300 hPa) and upper-level (300–100 hPa) AMV winds reveal that, despite the sparse distribution of the low-level AMV winds with most of the data points located in the periphery of Megi’s main circulation, the track forecasts tend to be more sensitive to the low-level than to the upper-level wind observations. This indicates that the far-field low-level observations can improve the large-scale environmental flow that storms are to move in, giving rise to a better representation of the steering flow and subsequent intensity change. While much of the recent effort in tropical cyclone research focuses on inner-core observations to improve the intensity forecast, the results in this study show that the peripheral observations outside the storm center could contribute considerably to the intensity and track forecasts and deserve attention for better typhoon forecast skills.

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Recent Intensification of the Western Pacific Subtropical High Associated with the East Asian Summer Monsoon

Journal of Climate ◽

10.1175/jcli-d-14-00569.1 ◽

2015 ◽

Vol 28 (7) ◽

pp. 2873-2883 ◽

Cited By ~ 30

Author(s):

Shinji Matsumura ◽

Shiori Sugimoto ◽

Tomonori Sato

Keyword(s):

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Asian Summer Monsoon ◽

East Asian ◽

Western Pacific Subtropical High ◽

Western Pacific ◽

Subtropical High ◽

The Past ◽

The North ◽

Asian Summer

Abstract The summer western Pacific subtropical high (WPSH) has intensified during the past three decades. However, the underlying mechanism is not yet well understood. Here, it is shown that baiu rainband activity in midsummer, which is part of the East Asian summer monsoon, plays an important role in recent intensification in the WPSH along the baiu rainband. In contrast with the WPSH, the summer Okhotsk high, which is located to the north of the baiu rainband, has weakened during the past three decades. The north–south contrasting changes between the two highs reflect a response to northward-moved and enhanced baiu heating, which intensifies the upper-tropospheric ridge, resulting in the baroclinic intensification of the WPSH. Regional climate model experiments also support the observational analysis. Therefore, baiu convective activity in midsummer can act as a major driver for the WPSH intensification. The results here suggest that the mechanism intensifying the summer North Pacific subtropical high clearly differs between the western and eastern Pacific.

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OBEST: An Observation-Based Ensemble Subsetting Technique for Tropical Cyclone Track Prediction

Weather and Forecasting ◽

10.1175/waf-d-15-0056.1 ◽

2016 ◽

Vol 31 (1) ◽

pp. 57-70 ◽

Cited By ~ 12

Author(s):

Lin Dong ◽

Fuqing Zhang

Keyword(s):

Tropical Cyclone ◽

Lead Times ◽

Track Forecast ◽

Forecast Errors ◽

Cyclone Track ◽

Tropical Cyclone Track ◽

Weather Forecasts ◽

Ensemble Mean ◽

Medium Range ◽

Environmental Prediction

Abstract An observation-based ensemble subsetting technique (OBEST) is developed for tropical cyclone track prediction in which a subset of members from either a single- or multimodel ensemble is selected based on the distance from the latest best-track position. The performance of OBEST is examined using both the 2-yr hindcasts for 2010–11 and the 2-yr operational predictions during 2012–13. It is found that OBEST outperforms both the simple ensemble mean (without subsetting) and the corresponding deterministic high-resolution control forecast for most forecast lead times up to 5 days. Applying OBEST to a superensemble of global ensembles from both the European Centre for Medium-Range Weather Forecasts and the National Centers for Environmental Prediction yielded a further reduction in track forecast errors by 5%–10% for lead times of 24–120 h.

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Hydrothermal activity in the Upper Permian Ravnefjeld Formation of central East Greenland – a study of sulphide morphotypes

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/ggub.v180.5090 ◽

1998 ◽

pp. 81-87

Author(s):

Jesper Kresten Nielsen ◽

Mikael Pedersen

Keyword(s):

Base Metal ◽

Early Period ◽

Sedimentary Basins ◽

Hydrothermal Activity ◽

Source Rocks ◽

Upper Permian ◽

Thermal Activity ◽

East Greenland ◽

The North ◽

Alum Shale

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kresten Nielsen, J., & Pedersen, M. (1998). Hydrothermal activity in the Upper Permian Ravnefjeld Formation of central East Greenland – a study of sulphide morphotypes. Geology of Greenland Survey Bulletin, 180, 81-87. https://doi.org/10.34194/ggub.v180.5090 _______________ Bituminous shales of the Ravnefjeld Formation were deposited in the subsiding East Greenland basin during the Upper Permian. The shales are exposed from Jameson Land in the south (71°N; Fig. 1) to Clavering Ø in the north (74°20′N) and have attracted considerable attention due to their high potential as hydrocarbon source rocks (Piasecki & Stemmerik 1991; Scholle et al. 1991; Christiansen et al. 1992, 1993a, b). Furthermore, enrichment of lead, zinc and copper has been known in the Ravnefjeld Formation on Wegener Halvø since 1968 (Lehnert-Thiel 1968; Fig. 1). This mineralisation was assumed to be of primary or early diagenetic origin due to similarities with the central European Kupferschiefer (Harpøth et al. 1986). Later studies, however, suggested base metal mineralisation in the immediately underlying carbonate reefs to be Tertiary in age (Stemmerik 1991). Due to geographical coincidence between the two types of mineralisation, a common history is a likely assumption, but a timing paradox exists. A part of the TUPOLAR project on the ‘Resources of the sedimentary basins of North and East Greenland’ has been dedicated to re-investigation of the mineralisation in the Ravnefjeld Formation in order to determine the genesis of the mineralisation and whether or not primary or early diagenetic base metal enrichment has taken place on Wegener Halvø, possibly in relation to an early period of hydrothermal activity. One approach to this is to study the various sulphides in the Ravnefjeld Formation; this is carried out in close co-operation with a current Ph.D. project at the University of Copenhagen, Denmark. Diagenetically formed pyrite is a common constituent of marine shales and the study of pyrite morphotypes has previously been successful from thermalli immature parts of elucidating depositional environment and thermal effects in the Alum Shale Formation of Scandinavia (Nielsen 1996; Nielsen et al. 1998). The present paper describes the preliminary results of a similar study on pyrite from thermally immature parts of the Ravnefjeld Formation which, combined with the study of textures of base metal sulphides in the Wegener Halvø area (Fig. 1), may provide an important step in the evaluation of the presence or absence of early thermal activity on (or below) the Upper Permian sea floor.

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Sub-seasonal east–west oscillation of the western pacific subtropical high in summer and its air–sea coupling process

Climate Dynamics ◽

10.1007/s00382-021-05893-8 ◽

2021 ◽

Author(s):

Yucheng Zi ◽

Ziniu Xiao ◽

Hongming Yan ◽

Jingjing Xu

Keyword(s):

Western Pacific Subtropical High ◽

Western Pacific ◽

Subtropical High ◽

Coupling Process ◽

The Western Pacific ◽

East West

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Probabilistic Forecasts Using Analogs in the Idealized Lorenz96 Setting

Monthly Weather Review ◽

10.1175/2010mwr3542.1 ◽

2011 ◽

Vol 139 (6) ◽

pp. 1960-1971 ◽

Cited By ~ 12

Author(s):

Jakob W. Messner ◽

Georg J. Mayr

Keyword(s):

Logistic Regression ◽

Systematic Errors ◽

Lead Times ◽

Model Output ◽

Weather Forecasts ◽

Probabilistic Forecasts ◽

Direct Model ◽

Nwp Model

Abstract Three methods to make probabilistic weather forecasts by using analogs are presented and tested. The basic idea of these methods is that finding similar NWP model forecasts to the current one in an archive of past forecasts and taking the corresponding analyses as prediction should remove all systematic errors of the model. Furthermore, this statistical postprocessing can convert NWP forecasts to forecasts for point locations and easily turn deterministic forecasts into probabilistic ones. These methods are tested in the idealized Lorenz96 system and compared to a benchmark bracket formed by ensemble relative frequencies from direct model output and logistic regression. The analog methods excel at longer lead times.

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Monthly Weather Forecasts in a Pest Forecasting Context: Downscaling, Recalibration, and Skill Improvement

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-082.1 ◽

2012 ◽

Vol 51 (9) ◽

pp. 1633-1638 ◽

Cited By ~ 3

Author(s):

Martin Hirschi ◽

Christoph Spirig ◽

Andreas P. Weigel ◽

Pierluigi Calanca ◽

Jörg Samietz ◽

...

Keyword(s):

Insect Pest ◽

Cydia Pomonella ◽

Codling Moth ◽

Lead Times ◽

Practical Applications ◽

Weather Forecasts ◽

Weather Information ◽

Agricultural Applications ◽

Resampling Procedure ◽

Skill Improvement

AbstractMonthly weather forecasts (MOFCs) were shown to have skill in extratropical continental regions for lead times up to 3 weeks, in particular for temperature and if weekly averaged. This skill could be exploited in practical applications for implementations exhibiting some degree of memory or inertia toward meteorological drivers, potentially even for longer lead times. Many agricultural applications fall into these categories because of the temperature-dependent development of biological organisms, allowing simulations that are based on temperature sums. Most such agricultural models require local weather information at daily or even hourly temporal resolution, however, preventing direct use of the spatially and temporally aggregated information of MOFCs, which may furthermore be subject to significant biases. By the example of forecasting the timing of life-phase occurrences of the codling moth (Cydia pomonella), which is a major insect pest in apple orchards worldwide, the authors investigate the application of downscaled weekly temperature anomalies of MOFCs for use in an impact model requiring hourly input. The downscaling and postprocessing included the use of a daily weather generator and a resampling procedure for creating hourly weather series and the application of a recalibration technique to correct for the original underconfidence of the forecast occurrences of codling moth life phases. Results show a clear skill improvement of up to 3 days in root-mean-square error over the full forecast range when incorporating MOFCs as compared with deterministic benchmark forecasts using climatological information for predicting the timing of codling moth life phases.

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