scholarly journals Landfalls of Tropical Cyclones with Rapid Intensification in the Western North Pacific

2019 ◽  
Author(s):  
Jie Yang ◽  
Meixiang Chen
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Intensity Change ◽  
Moderate Intensity ◽  
Rapid Intensification ◽  
Southern Chinese ◽  
Chinese Coast ◽  
The Mean ◽  
Definition Of

Abstract. This study statistically investigates the seasonal and decadal variation of tropical cyclones (TCs) underwent rapid intensification (RI) and their landfalling cyclone energy in the western North Pacific using the satellite-era best track data from 1986 to 2017. Totally 31.2 % TCs have underwent at least one RI processes (RI TCs) and 341 made landfalls after RI from 946 historical TCs, using the definition of 95th percentile from the accumulative probability distribution of over-water 24-h TC intensity change. The frequent-occurrence region of RI is found in sea areas to the east of Philippines, and the mean genesis and on-set locations of landfalling TCs underwent RI had westward components compared with the ones did not made landfalls. The Philippine coast, the southern Chinese coast and the coast along the southern Japan are the three main regions affected by the landfalling RI TCs. The coasts in the latter two regions have increased trend of cyclone energy since 1986, which possibly correlates with the poleward migration of the mean latitude where TCs reach their lifetime maximum intensities (LMI). The frequency of the landfalling RI TCs have a significant upward trend with insignificant increase in their LMI, while both the LMI and landfalling cyclone energy by TCs that didn't undergo RI in the western North Pacific show downward trends in the period during 1986–2017. The changes of the LMI distribution in the western North Pacific are related tightly with these two types of TCs with different intensification rates: strong TCs are found become stronger mainly due to more active RI processes, while weak TCs have weakened in majority of moderate intensity TCs, which didn't experience RI processes.

scholarly journals Satellite Air–Sea Enthalpy Flux and Intensity Change of Tropical Cyclones over the Western North Pacific

2016 ◽  
Vol 55 (2) ◽  
pp. 425-444 ◽  
Author(s):  
Si Gao ◽  
Shunan Zhai ◽  
Long S. Chiu ◽  
Dong Xia
Keyword(s):  
Heat Flux ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Sensible Heat Flux ◽  
Vertical Wind Shear ◽  
Intensity Change ◽  
Rapid Intensification ◽  
Sea Temperature

AbstractAn improved high-resolution satellite enthalpy flux dataset is employed to study the composites of initial (i.e., t = 0 h) latent heat flux (LHF), sensible heat flux (SHF), and their bulk variables associated with four intensity-change categories of tropical cyclones (TCs) over the western North Pacific Ocean—rapidly intensifying (RI), slowly intensifying, neutral, and weakening—in a vertical wind shear–relative coordinate system with horizontal dimensions normalized by the radius of maximum wind. Results show that RI TCs are associated with significantly higher LHF and SHF in all TC environments than non-RI TCs, which are mainly attributable to the air–sea humidity difference (DQ) and the air–sea temperature difference (DT), respectively. Higher DQ and DT are primarily due to significantly higher sea surface temperature (SST) underlying RI TCs, emphasizing the crucial role of SST in supplying more energy to TCs that undergo rapid intensification, in which LHF plays a more important role than SHF. Relative to non-RI TCs, LHF and SHF for RI TCs show a more symmetric pattern. The magnitude and pattern of air–sea enthalpy flux could serve as potential predictors for rapid intensification of TCs.

scholarly journals Ending Storm Version of the 7-day Weighted Analog Intensity Prediction Technique for Western North Pacific Tropical Cyclones

2017 ◽  
Vol 32 (6) ◽  
pp. 2229-2235 ◽  
Author(s):  
Hsiao-Chung Tsai ◽  
Russell L. Elsberry
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Storm Events ◽  
Training Set ◽  
Intensity Prediction ◽  
Prediction Technique ◽  
The Mean ◽  
Forecast Interval ◽  
Intensity Spread

Abstract The weighted analog intensity prediction technique for western North Pacific (WAIP) tropical cyclones (TCs) was the first guidance product for 7-day intensity forecasts, which is skillful in the sense that the 7-day errors are about the same as the 5-day errors. Independent tests of this WAIP version revealed an increasingly large intensity overforecast bias as the forecast interval was extended from 5 to 7 days, which was associated with “ending storms” due to landfall, extratropical transition, or to delayed development. Thus, the 7-day WAIP has been modified to separately forecast ending and nonending storms within the 7-day forecast interval. The additional ending storm constraint in the selection of the 10 best historical analogs is that the intensity at the last matching point with the target TC track cannot exceed 50 kt (where 1 kt = 0.51 m s−1). A separate intensity bias correction calculated for the ending storm training set reduces the mean biases to near-zero values and thereby improves the mean absolute errors in the 5–7-day forecast interval for the independent set. A separate calibration of the intensity spreads for the training set to ensure that 68% of the verifying intensities will be within the 12-h WAIP intensity spread values results in smaller spreads (or higher confidence) for ending storms in the 5–7-day forecast intervals. Thus, some extra effort by the forecasters to identify ending storm events within 7 days will allow improved intensity and intensity spread forecast guidance.

scholarly journals Water Budget and Intensity Change of Tropical Cyclones over the Western North Pacific

2017 ◽  
Vol 145 (8) ◽  
pp. 3009-3023 ◽  
Author(s):  
Si Gao ◽  
Shunan Zhai ◽  
Baiqing Chen ◽  
Tim Li
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Water Budget ◽  
Western North Pacific ◽  
Precipitable Water ◽  
Moisture Flux ◽  
Intensity Change ◽  
Surface Evaporation ◽  
Total Precipitable Water

Three satellite observational datasets and a reanalysis dataset during the period 2001–09 are used to examine four water budget components (total precipitable water, surface evaporation, precipitation, and column-integrated moisture flux convergence) associated with western North Pacific tropical cyclones (TCs) of different intensity change categories: rapidly intensifying, slowly intensifying, neutral, and weakening. The results show that surface evaporation plays an important role in storm rapid intensification (RI) and the highest evaporation associated with rapidly intensifying TCs is associated with the highest sea surface temperature. Total precipitable water in the outer environment, where moisture is mainly provided by surface evaporation, is also vital to storm RI because RI is favored when there is less dry air intruded into the storm circulation. The roles of surface evaporation and total precipitable water in storm RI are related to the enhanced convective available potential energy by moistening and warming the boundary layer. The largest amount of column-integrated moisture flux convergence associated with weakening TCs, which results in the heaviest precipitation, is because their strongest mean intensity promotes moisture transport. It is suggested that different water budget components play different roles in TC intensity change. The results agree with the notion that TC intensity change results from a competition between surface moisture and heat fluxes and low-entropy downdrafts into the boundary layer.

A Definition of Rapid Weakening for Tropical Cyclones Over the Western North Pacific

2019 ◽  
Vol 46 (20) ◽  
pp. 11471-11478 ◽  
Author(s):  
Zhanhong Ma ◽  
Jianfang Fei ◽  
Xiaogang Huang
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Definition Of

scholarly journals Changes in Characteristics of Rapidly Intensifying Western North Pacific Tropical Cyclones Related to Climate Regime Shifts

2018 ◽  
Vol 31 (19) ◽  
pp. 8163-8179 ◽  
Author(s):  
Haikun Zhao ◽  
Xingyi Duan ◽  
G. B. Raga ◽  
Philip J. Klotzbach
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Wind Shear ◽  
Western North Pacific ◽  
Regime Shift ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Climate Regime ◽  
Climate Regime Shift

A significant increase in the proportion of tropical cyclones undergoing rapid intensification at least once during their lifetime (RITCs) over the western North Pacific (WNP) is observed since 1998 when an abrupt climate regime shift occurred. Changes of large-scale atmospheric and oceanic conditions affecting TC activity are compared between two subperiods: one before and one since 1998. Results suggest that both a significant decrease in the number of TCs and a nearly unchanged number of RITCs since 1998 caused a significant increase in the frequency of RITCs. The decrease in TC numbers is likely driven by considerably increased vertical wind shear and decreased low-level vorticity. In contrast, the unchanged RITC counts and thus increased ratio of RITCs during the recent decades are largely attributed to the dominance of a more conducive ocean environment with increased TC heat potential and warmer sea surface temperature anomalies. These associated decadal changes are closely associated with the recent climate regime shift. During the recent decades with a mega–La Niña–like pattern, stronger easterly trade winds have caused increased vertical wind shear and a weakened monsoon trough, thus hampering TC formation ability over the WNP. In addition, a steeper thermocline slope that hampered the eastward migration of warm water along the equatorial Pacific has generated a more favorable thermodynamic environment supporting TC rapid intensification over the WNP.

scholarly journals Impact of Storm Size on Prediction of Storm Track and Intensity Using the 2016 Operational GFDL Hurricane Model

2017 ◽  
Vol 32 (4) ◽  
pp. 1491-1508 ◽  
Author(s):  
Morris A. Bender ◽  
Timothy P. Marchok ◽  
Charles R. Sampson ◽  
John A. Knaff ◽  
Matthew J. Morin
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Numerical Models ◽  
Storm Track ◽  
Eastern Pacific ◽  
Lead Times ◽  
Rapid Intensification ◽  
Forecast Lead Time ◽  
The Impact

Abstract The impact of storm size on the forecast of tropical cyclone storm track and intensity is investigated using the 2016 version of the operational GFDL hurricane model. Evaluation was made for 1529 forecasts in the Atlantic, eastern Pacific, and western North Pacific basins, during the 2014 and 2015 seasons. The track and intensity errors were computed from forecasts in which the 34-kt (where 1 kt = 0.514 m s−1) wind radii obtained from the operational TC vitals that are used to initialize TCs in the GFDL model were replaced with wind radii estimates derived using an equally weighted average of six objective estimates. It was found that modifying the radius of 34-kt winds had a significant positive impact on the intensity forecasts in the 1–2 day lead times. For example, at 48 h, the intensity error was reduced 10%, 5%, and 4% in the Atlantic, eastern Pacific, and western North Pacific, respectively. The largest improvements in intensity forecasts were for those tropical cyclones undergoing rapid intensification, with a maximum error reduction in the 1–2 day forecast lead time of 14% and 17% in the eastern and western North Pacific, respectively. The large negative intensity biases in the eastern and western North Pacific were also reduced 25% and 75% in the 12–72-h forecast lead times. Although the overall impact on the average track error was neutral, forecasts of recurving storms were improved and tracks of nonrecurving storms degraded. Results also suggest that objective specification of storm size may impact intensity forecasts in other high-resolution numerical models, particularly for tropical cyclones entering a rapid intensification phase.

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