Seasonal forecasting of intense tropical cyclones over the North Atlantic and the western North Pacific basins

2016 ◽  
Vol 47 (9-10) ◽  
pp. 3063-3075 ◽  
Author(s):  
Woosuk Choi ◽  
Chang-Hoi Ho ◽  
Chun-Sil Jin ◽  
Jinwon Kim ◽  
Song Feng ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Seasonal Forecasting ◽  
The North ◽  
The North Atlantic

scholarly journals Seasonal Prediction of Tropical Cyclones over the North Atlantic and Western North Pacific

2021 ◽  
pp. 1-42
Author(s):  
Kevin I. Hodges ◽  
Antje Weisheimer
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Seasonal Prediction ◽  
Seasonal Forecasting ◽  
Forecasting Models ◽  
The North ◽  
Forecast Models ◽  
Coarse Model

Abstract In this study, Tropical Cyclones (TC) over the Western North Pacific (WNP) and North Atlantic (NA) basins are analysed in seasonal forecasting models from five European modelling centres. Most models are able to capture the observed seasonal cycle of TC frequencies over both basins; however, large differences for numbers and spatial track densities are found. In agreement with previous studies, TC numbers are often underestimated, which is likely related to coarse model resolutions. Besides shortcomings in TC characteristics, significant positive skill (deterministic and probabilistic) in predicting TC numbers and accumulated cyclone energy is found over both basins. Whereas the predictions of TC numbers over the WNP basin are mostly unreliable, most seasonal forecast provide reliable predictions for the NA basin. Besides positive skill over the entire NA basin, all seasonal forecasting models are skillful in predicting the interannual TC variability over a region covering the Caribbean and North American coastline, suggesting that the models carry useful information, e.g. for adaptation and mitigation purposes ahead of the upcoming TC season. However, skill in all forecast models over a smaller region centred along the Asian coastline is smaller compared to their skill in the entire WNP basin.

Are Tropical Cyclones Less Effectively Formed by Easterly Waves in the Western North Pacific than in the North Atlantic?

2008 ◽  
Vol 136 (11) ◽  
pp. 4527-4540 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Shih-Yu Wang ◽  
Ming-Cheng Yen ◽  
Adam J. Clark
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Monsoon Trough ◽  
Easterly Waves ◽  
The North ◽  
Easterly Wave ◽  
Monsoon Gyre ◽  
The North Atlantic

Abstract It has been observed that the percentage of tropical cyclones originating from easterly waves is much higher in the North Atlantic (∼60%) than in the western North Pacific (10%–20%). This disparity between the two ocean basins exists because the majority (71%) of tropical cyclogeneses in the western North Pacific occur in the favorable synoptic environments evolved from monsoon gyres. Because the North Atlantic does not have a monsoon trough similar to the western North Pacific that stimulates monsoon gyre formation, a much larger portion of tropical cyclogeneses than in the western North Pacific are caused directly by easterly waves. This study also analyzed the percentage of easterly waves that form tropical cyclones in the western North Pacific. By carefully separating easterly waves from the lower-tropospheric disturbances generated by upper-level vortices that originate from the tropical upper-tropospheric trough (TUTT), it is observed that 25% of easterly waves form tropical cyclones in this region. Because TUTT-induced lower-tropospheric disturbances often become embedded in the trade easterlies and resemble easterly waves, they have likely been mistakenly identified as easterly waves. Inclusion of these “false” easterly waves in the “true” easterly wave population would result in an underestimation of the percentage of easterly waves that form tropical cyclones, because the TUTT-induced disturbances rarely stimulate tropical cyclogenesis. However, an analysis of monsoon gyre formation mechanisms over the western North Pacific reveals that 82% of monsoon gyres develop through a monsoon trough–easterly wave interaction. Thus, it can be inferred that 58% (i.e., 82% × 71%) of tropical cyclones in this region are an indirect result of easterly waves. Including the percentage of tropical cyclones that form directly from easterly waves (∼25%), it is found that tropical cyclones formed directly and indirectly from easterly waves account for over 80% of tropical cyclogeneses in the western North Pacific. This is more than the percentage that has been documented by previous studies in the North Atlantic.

Tropical Cyclones in European Seasonal Forecast Models

2020 ◽  
Author(s):  
Kevin Hodges ◽  
Daniel Befort ◽  
Antje Weisheimer
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Seasonal Forecast ◽  
The North ◽  
Forecast Models ◽  
The North Atlantic ◽  
Stochastic Physics

<p>This study assesses the representation of Tropical Cyclones (TC) in an ensemble of seasonal forecast models from five different centres (ECMWF, UK Met Office, DWD, CMCC, Météo-France). Northern Hemispheric Tropical Cyclones are identified using a widely applied objective Tropical Cyclone tracking algorithm based on relative vorticity fields. Analyses for three different aspects are carried out: 1) assessment of the skill of the ensemble to predict  the TC frequencies over different ocean basins, 2) analyse the dependency between the model's ability to represent TCs and large-scale biases and 3) assess the impact of stochastic physics and horizontal resolution on TC frequency.</p><p>For the July to October season all seasonal forecast models initialized in June are skilful in predicting the observed inter-annual variability of TC frequency over the North Atlantic (NA). Similarly, the models initialized in May show significant skill over the Western North Pacific (WNP) for the season from June to October. Further to these significant positive correlations over the NA, it is found that most models are also able to discriminate between inactive and active seasons over this region. However, despite these encouraging results, especially  for skill over the NA, most models suffer from large biases. These biases are not only related to biases in the large-scale circulation but also to the representation of intrinsic model uncertainties and the relatively coarse resolution of current seasonal forecasts. At ECMWF model uncertainty is accounted for by the use of stochastic physics, which has been shown to improve forecasts on seasonal time-scales in previous studies. Using a set of simulations conducted with the ECMWF SEAS5 model, the effects of stochastic physics and resolution on the representation of Tropical Cyclones on seasonal time-scales are assessed. Including stochastic physics increases the number of TCs over all ocean basins, but especially over the North Atlantic and Western North Pacific.</p>

scholarly journals A Statistical Model to Predict the Extratropical Transition of Tropical Cyclones

2020 ◽  
Vol 35 (2) ◽  
pp. 451-466
Author(s):  
Melanie Bieli ◽  
Adam H. Sobel ◽  
Suzana J. Camargo ◽  
Michael K. Tippett
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Lead Time ◽  
Western North Pacific ◽  
Extratropical Transition ◽  
The North ◽  
Operational Forecasts ◽  
The North Atlantic ◽  
Better Than

Abstract This paper introduces a logistic regression model for the extratropical transition (ET) of tropical cyclones in the North Atlantic and the western North Pacific, using elastic net regularization to select predictors and estimate coefficients. Predictors are chosen from the 1979–2017 best track and reanalysis datasets, and verification is done against the tropical/extratropical labels in the best track data. In an independent test set, the model skillfully predicts ET at lead times up to 2 days, with latitude and sea surface temperature as its most important predictors. At a lead time of 24 h, it predicts ET with a Matthews correlation coefficient of 0.4 in the North Atlantic, and 0.6 in the western North Pacific. It identifies 80% of storms undergoing ET in the North Atlantic and 92% of those in the western North Pacific. In total, 90% of transition time errors are less than 24 h. Select examples of the model’s performance on individual storms illustrate its strengths and weaknesses. Two versions of the model are presented: an “operational model” that may provide baseline guidance for operational forecasts and a “hazard model” that can be integrated into statistical TC risk models. As instantaneous diagnostics for tropical/extratropical status, both models’ zero lead time predictions perform about as well as the widely used cyclone phase space (CPS) in the western North Pacific and better than the CPS in the North Atlantic, and predict the timings of the transitions better than CPS in both basins.

scholarly journals Continued Increases in the Intensity of Strong Tropical Cyclones

2020 ◽  
Vol 101 (8) ◽  
pp. E1301-E1303 ◽  
Author(s):  
James B. Elsner
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Base Period ◽  
The North ◽  
The North Atlantic

Abstract In a 2008 paper, using satellite-derived wind speed estimates from tropical cyclones over the 25-yr period 1981–2006, we showed the strongest tropical cyclones getting stronger. We related the increasing intensity to rising ocean temperatures consistent with theory. Oceans have continued to warm since that paper was published, so the intensity of the strongest cyclones should have continued upward as well. Here I show that this is the case, with increases in the upper-quantile intensities of global tropical cyclones amounting to between 3.5% and 4.5% in the period 2007–19 relative to the earlier base period (1981–2006). All basins individually show upward intensity trends for at least one upper quantile considered, with the North Atlantic and western North Pacific basins showing the steepest and most consistent trends across the quantiles.

Satellite-Derived Tropical Cyclone Intensity in the North Pacific Ocean Using the Deviation-Angle Variance Technique

2014 ◽  
Vol 29 (3) ◽  
pp. 505-516 ◽  
Author(s):  
Elizabeth A. Ritchie ◽  
Kimberly M. Wood ◽  
Oscar G. Rodríguez-Herrera ◽  
Miguel F. Piñeros ◽  
J. Scott Tyo
Keyword(s):  
Tropical Cyclone ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Deviation Angle ◽  
Intensity Estimation ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract The deviation-angle variance technique (DAV-T), which was introduced in the North Atlantic basin for tropical cyclone (TC) intensity estimation, is adapted for use in the North Pacific Ocean using the “best-track center” application of the DAV. The adaptations include changes in preprocessing for different data sources [Geostationary Operational Environmental Satellite-East (GOES-E) in the Atlantic, stitched GOES-E–Geostationary Operational Environmental Satellite-West (GOES-W) in the eastern North Pacific, and the Multifunctional Transport Satellite (MTSAT) in the western North Pacific], and retraining the algorithm parameters for different basins. Over the 2007–11 period, DAV-T intensity estimation in the western North Pacific results in a root-mean-square intensity error (RMSE, as measured by the maximum sustained surface winds) of 14.3 kt (1 kt ≈ 0.51 m s−1) when compared to the Joint Typhoon Warning Center best track, utilizing all TCs to train and test the algorithm. The RMSE obtained when testing on an individual year and training with the remaining set lies between 12.9 and 15.1 kt. In the eastern North Pacific the DAV-T produces an RMSE of 13.4 kt utilizing all TCs in 2005–11 when compared with the National Hurricane Center best track. The RMSE for individual years lies between 9.4 and 16.9 kt. The complex environment in the western North Pacific led to an extension to the DAV-T that includes two different radii of computation, producing a parametric surface that relates TC axisymmetry to intensity. The overall RMSE is reduced by an average of 1.3 kt in the western North Pacific and 0.8 kt in the eastern North Pacific. These results for the North Pacific are comparable with previously reported results using the DAV for the North Atlantic basin.

scholarly journals The Impact of Natural and Anthropogenic Climate Change on Western North Pacific Tropical Cyclone Tracks*

2015 ◽  
Vol 28 (5) ◽  
pp. 1806-1823 ◽  
Author(s):  
Angela J. Colbert ◽  
Brian J. Soden ◽  
Ben P. Kirtman
Keyword(s):  
Climate Change ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Anthropogenic Climate Change ◽  
The North ◽  
Steering Flow ◽  
The North Atlantic ◽  
The Impact

Abstract The impact of natural and anthropogenic climate change on tropical cyclone (TC) tracks in the western North Pacific (WNP) is examined using a beta and advection model (BAM) to isolate the influence of changes in the large-scale steering flow from changes in genesis location. The BAM captures many of the observed changes in TC tracks due to El Niño–Southern Oscillation (ENSO), while little change is noted for the Pacific decadal oscillation and all-India monsoon rainfall in either observations or BAM simulations. Analysis with the BAM suggests that the observed shifts in the average track between the phases of ENSO are primarily due to changes in the large-scale steering flow, with changes in genesis location playing a secondary role. Potential changes in TC tracks over the WNP due to anthropogenic climate change are also assessed. Ensemble mean projections are downscaled from 17 CMIP3 models and 26 CMIP5 models. Statistically significant decreases [~(4%–6%)] in westward moving TCs and increases [~(5%–7%)] in recurving ocean TCs are found. These correspond to projected decreases of 3–5 TCs per decade over the Philippines and increases of 1–3 TCs per decade over the central WNP. The projected changes are primarily caused by a reduction in the easterlies. This slows the storm movement, allowing more time for the beta drift to carry the storm northward and recurve. A previous study found similar results in the North Atlantic. Taken together, these results suggest that a weakening of the mean atmospheric circulation in response to anthropogenic warming will lead to fewer landfalling storms over the North Atlantic and WNP.

scholarly journals Objective Identification of Annular Hurricanes

2008 ◽  
Vol 23 (1) ◽  
pp. 17-28 ◽  
Author(s):  
John A. Knaff ◽  
Thomas A. Cram ◽  
Andrea B. Schumacher ◽  
James P. Kossin ◽  
Mark DeMaria
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Probability Of Detection ◽  
Linear Discriminant ◽  
The North ◽  
The North Atlantic ◽  
Special Algorithm ◽  
Central North Pacific

Abstract Annular hurricanes are a subset of intense tropical cyclones that have been shown in previous work to be significantly stronger, to maintain their peak intensities longer, and to weaken more slowly than average tropical cyclones. Because of these characteristics, they represent a significant forecasting challenge. This paper updates the list of annular hurricanes to encompass the years 1995–2006 in both the North Atlantic and eastern–central North Pacific tropical cyclone basins. Because annular hurricanes have a unique appearance in infrared satellite imagery, and form in a specific set of environmental conditions, an objective real-time method of identifying these hurricanes is developed. However, since the occurrence of annular hurricanes is rare (∼4% of all hurricanes), a special algorithm to detect annular hurricanes is developed that employs two steps to identify the candidates: 1) prescreening the data and 2) applying a linear discriminant analysis. This algorithm is trained using a dependent dataset (1995–2003) that includes 11 annular hurricanes. The resulting algorithm is then independently tested using datasets from the years 2004–06, which contained an additional three annular hurricanes. Results indicate that the algorithm is able to discriminate annular hurricanes from tropical cyclones with intensities greater than 84 kt (43.2 m s−1). The probability of detection or hit rate produced by this scheme is shown to be ∼96% with a false alarm rate of ∼6%, based on 1363 six-hour time periods with a tropical cyclone with an intensity greater than 84 kt (1995–2006).

scholarly journals Lightning in Eastern North Pacific Tropical Cyclones: A Comparison to the North Atlantic

2015 ◽  
Vol 144 (1) ◽  
pp. 225-239 ◽  
Author(s):  
Stephanie N. Stevenson ◽  
Kristen L. Corbosiero ◽  
Sergio F. Abarca
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Wind Shear ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
The North ◽  
The North Atlantic

Abstract As global lightning detection has become more reliable, many studies have analyzed the characteristics of lightning in tropical cyclones (TCs); however, very few studies have examined flashes in eastern North Pacific (ENP) basin TCs. This study uses lightning detected by the World Wide Lightning Location Network (WWLLN) to explore the relationship between lightning and sea surface temperatures (SSTs), the diurnal cycle, the storm motion and vertical wind shear vectors, and the 24-h intensity change in ENP TCs during 2006–14. The results are compared to storms in the North Atlantic (NA). Higher flash counts were found over warmer SSTs, with 28°–30°C SSTs experiencing the highest 6-hourly flash counts. Most TC lightning flashes occurred at night and during the early morning hours, with minimal activity after local noon. The ENP peak (0800 LST) was slightly earlier than the NA (0900–1100 LST). Despite similar storm motion directions and differing vertical wind shear directions in the two basins, shear dominated the overall azimuthal lightning distribution. Lightning was most often observed downshear left in the inner core (0–100 km) and downshear right in the outer rainbands (100–300 km). A caveat to these relationships were fast-moving ENP TCs with opposing shear and motion vectors, in which lightning peaked downmotion (upshear) instead. Finally, similar to previous studies, higher flash densities in the inner core (outer rainbands) were associated with nonintensifying (intensifying) TCs. This last result constitutes further evidence in the efforts to associate lightning activity to TC intensity forecasting.

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