Dropsonde Observations of Intense Typhoons in 2017 and 2018 in the T-PARCII Project

2020 ◽  
Author(s):  
Kazuhisa Tsuboki ◽  
Hiroyuki Yamada ◽  
Tadayasu Ohigashi ◽  
Taro Shinoda ◽  
Kosuke Ito ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Maximum Wind Speed ◽  
Central Pressure ◽  
The South ◽  
Main Island ◽  
Maximum Wind ◽  
Typhoon Intensity

<p>Typhoon is a tropical cyclone in the western North Pacific and the South China Sea. It is the most devastating weather system in East Asia. Strong winds and heavy rainfalls associated with a typhoon often cause severe disasters in these regions. There are many cases of typhoon disasters even in the recent decades in these regions. Furthermore, future projections of typhoon activity in the western North Pacific show that its maximum intensity will increase with the climate change. However, the historical data of typhoon (best track data) include large uncertainty after the US aircraft reconnaissance of typhoon was terminated in 1987. Another problem is that prediction of typhoon intensity has not been improved for the last few decades. To improve these problems, in situ observations of typhoon using an aircraft are indispensable. The T-PARCII (Tropical cyclone-Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts) project is aiming to improve estimations and forecasts of typhoon intensity as well as storm track forecasts.</p><p>In 2017, the T-PARCII team performed dropsonde observations of intense Typhoon Lan in collaboration with Taiwan DOTSTAR, which was the most intense typhoon in 2017 and caused huge disaster over the central Japan. It was categorized as a supertyphoon by JTWC and as a very intense and huge typhoon by JMA. Typhoon Lan moved northeastward to the east of the Okinawa main island and it was located around 23 N on 21 and 28 N on 22 October. In these two days, we made dropsonde observations at the center of the eye and in the surrounding area of the eyewall. The observations showed that the central pressure of Lan slightly increases from 926 hPa on 21 to 928 hPa on 22 October with the northward movement. On the other hand, The JMA best track data indicate that the central pressure decreases from 935 hPa on 21 to 915 hPa on 22 October. The observations also showed a significant double warm core structure in the eye and the maximum wind speed along the eyewall. The dropsonde data were used for forecast experiments. The result shows an improvement of typhoon track prediction.</p><p>The T-PARCII team also made aircraft observations of Typhoon Trami during the period from 25 to 28 September 2018 in collaboration with the SATREPS ULAT group and DOTSTAR. Trami was almost stationary during the period to the south of the Okinawa main island. Then, it moved northward and finally made a landfall over the central part of Japan. This also caused a big disaster and electricity was shut down for several days in the central part of Japan. Typhoon Trami showed a drastic change of intensity from 25 to 26 September with a large change of eye size from about a diameter of 60 km to 200 km. Dropsonde observations showed the change of central pressure and maximum wind speed as well as the thermodynamic structure of the eye.</p>

scholarly journals A Pressure-Based Analysis of the Historical Western North Pacific Tropical Cyclone Intensity Record

2013 ◽  
Vol 141 (8) ◽  
pp. 2611-2631 ◽  
Author(s):  
Kenneth R. Knapp ◽  
John A. Knaff ◽  
Charles R. Sampson ◽  
Gustavo M. Riggio ◽  
Adam D. Schnapp
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
Ground Truth ◽  
Historical Record ◽  
Wind Pressure ◽  
Central Pressure ◽  
Typhoon Intensity ◽  
Annual Activity

Abstract The western North Pacific Ocean is the most active tropical cyclone (TC) basin. However, recent studies are not conclusive on whether the TC activity is increasing or decreasing, at least when calculations are based on maximum sustained winds. For this study, TC minimum central pressure data are analyzed in an effort to better understand historical typhoons. Best-track pressure reports are compared with aircraft reconnaissance observations; little bias is observed. An analysis of wind and pressure relationships suggests changes in data and practices at numerous agencies over the historical record. New estimates of maximum sustained winds are calculated using recent wind–pressure relationships and parameters from International Best Track Archive for Climate Stewardship (IBTrACS) data. The result suggests potential reclassification of numerous typhoons based on these pressure-based lifetime maximum intensities. Historical documentation supports these new intensities in many cases. In short, wind reports in older best-track data are likely of low quality. The annual activity based on pressure estimates is found to be consistent with aircraft reconnaissance and between agencies; however, reconnaissance ended in the western Pacific in 1987. Since then, interagency differences in maximum wind estimates noted here and by others also exist in the minimum central pressure reports. Reconciling these recent interagency differences is further exasperated by the lack of adequate ground truth. This study suggests efforts to intercalibrate the interagency intensity estimate methods. Conducting an independent and homogeneous reanalysis of past typhoon activity is likely necessary to resolve the remaining discrepancies in typhoon intensity records.

Potential Tropical Cyclone Disaster Loss Assessment based on Multiple Hazard Indicators

2020 ◽  
Author(s):  
Jian Li
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Storm Surge ◽  
Maximum Wind Speed ◽  
Central Pressure ◽  
Loss Assessment ◽  
Maximum Wind ◽  
Disaster Loss ◽  
Potential Loss

<p><span>Tropical cyclones could cause large casualties and economic loss in coastal area of China. It is of great importance to develop a method that can provide pre-event rapid loss assessment in a timely manner prior to the landing of a tropical cyclone. In this study, a pre-event tropical cyclone disaster loss assessment method based on similar tropical cyclone retrieval with multiple hazard indicators is proposed. Multiple indicators include tropical cyclone location, maximum wind speed, central pressure, radius of maximum wind, forward speed, Integrated Kinetic Energy (IKE), maximum storm surge, and maximum significant wave height. Firstly, the track similarity is measured by similarity deviation considering only the locations of tropical cyclone tracks. Secondly, the intensity similarity is measured by best similarity coefficient using central pressure, radius of maximum wind, maximum wind speed, moving speed, wind, storm surge, and wave intensity indices. Then, the potential loss of current tropical cyclone is assessed based on the retrieved similar tropical cyclones loss. Taking tropical cyclone Utor (2013) that affected China as an example, the potential loss is predicted according to the five most similar historical tropical cyclones which are retrieved from all the historical tropical cyclones. The method is flexible for rapid disaster loss assessment since it provides a relatively satisfactory result based on two scenarios of input dataset availability.</span></p>

scholarly journals Environmental influences on the intensity changes of tropical cyclones over the Western North Pacific

2013 ◽  
Vol 13 (12) ◽  
pp. 31815-31853
Author(s):  
Shoujuan Shu ◽  
Fuqing Zhang ◽  
Jie Ming ◽  
Yuan Wang
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
Environmental Conditions ◽  
North Pacific ◽  
Western North Pacific ◽  
The Other ◽  
Maximum Wind Speed ◽  
Composite Analysis ◽  
Maximum Wind ◽  
Intensity Changes

Abstract. The influence of environmental conditions on the intensity changes of tropical cyclones (TCs) over the western North Pacific (WNP) is investigated through examination of 37 TCs during 2000–2011 that interacted directly with the western North Pacific subtropical high (WNPSH). Comprehensive composite analysis of the environmental conditions is performed for two stages of storms: one is categorized as intensifying events (maximum wind speed increases by 15 kts over 48 h) and the other is categorized as weakening events (maximum wind speed decreases by 15 kts over 48 h). Comparison of the composite analysis of these two cases show that environmental conditions associated with the WNPSH play important roles in the intensity changes of TCs over the WNP. When a TC moves along the southern edge of the WNPSH, the relatively weaker easterly environmental vertical wind shear helps bring warm moist air from the south and southeast, which is favorable for the TC to intensify. On the other hand, when a TC moves along the western edge of the WNPSH, under the combined influences of the WNPSH and an upper-level westerly trough, a strong westerly vertical shear promotes the intrusion of dry environmental air associated with the WNPSH from the north and northwest, which may lead to the inhibition of moisture supply and convection over the west half of the TC and thus its weakening. The average sea surface temperature (SST) of 27.8 °C for the weakening events is also lower than an average of 28.9 °C for the strengthening events, but remains above the critical value of 27 °C for TC intensification, suggesting that the SST may be regarded as a less positive factor for the weakening events.

scholarly journals Comments on “Reexamination of Tropical Cyclone Wind–Pressure Relationship”

2008 ◽  
Vol 23 (4) ◽  
pp. 758-761 ◽  
Author(s):  
Shyamnath Veerasamy
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
Wind Pressure ◽  
Maximum Wind Speed ◽  
Central Pressure ◽  
Southwest Indian Ocean ◽  
Maximum Wind ◽  
The North ◽  
The North Atlantic

Abstract In their study on the wind–pressure relationship (WPR) that exists in tropical cyclones, Knaff and Zehr presented results of the use of the Dvorak Atlantic WPR for estimating central pressure and maximum wind speed of tropical cyclones. These show some fairly large departures of estimated central pressure and maximum surface winds from observed values. Based on a study carried out in the southwest Indian Ocean (SWIO), it is believed that improvements in the use of the Dvorak WPR can be achieved by using the size of a closed isobar (it is the 1004-hPa closed isobar in the SWIO) to determine whether to use the North Atlantic (NA), the western North Pacific (WNP), or a mean of the NA and WNP Dvorak WPR for estimating central pressure and maximum wind speed in tropical cyclones.

scholarly journals Initial Maintenance of Tropical Cyclone Size in the Western North Pacific

2010 ◽  
Vol 138 (8) ◽  
pp. 3207-3223 ◽  
Author(s):  
Cheng-Shang Lee ◽  
Kevin K. W. Cheung ◽  
Wei-Ting Fang ◽  
Russell L. Elsberry
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Surface Wind ◽  
Outer Core ◽  
Tropical Storm ◽  
Size Category ◽  
Near Surface ◽  
Low Level ◽  
Typhoon Intensity

Abstract A tropical cyclone (TC) size parameter, which is defined here as the radius of 15 m s−1 near-surface wind speed (R15), is calculated for 145 TCs in the western North Pacific during 2000–05 based on QuikSCAT oceanic winds. For the 73 TCs that intensified to typhoon intensity during their lifetimes, the 33% and 67% respective percentiles of R15 at tropical storm intensity and at typhoon intensity are used to categorize small, medium, and large TCs. Whereas many of the small TCs form from an easterly wave synoptic pattern, the monsoon-related formation patterns are favorable for forming medium to large TCs. Most of these 73 TCs stay in the same size category during intensification, which implies specific physical mechanisms for maintaining TC size in the basin. The 18 persistently large TCs from the tropical storm to the typhoon stage mostly have northwestward or north-northwestward tracks, while the 16 persistently small TCs either move westward–northwestward in lower latitudes or develop at higher latitudes with various track types. For the large TCs, strong low-level southwesterly winds exist in the outer core region south of the TC center throughout the intensification period. The small TCs are more influenced by the subtropical high during intensification. The conclusion is that it is the low-level environment that determines the difference between large and small size storms during the early intensification period in the western North Pacific.

Estimating Tropical Cyclone Intensity from Infrared Image Data

2011 ◽  
Vol 26 (5) ◽  
pp. 690-698 ◽  
Author(s):  
Miguel F. Piñeros ◽  
Elizabeth A. Ritchie ◽  
J. Scott Tyo
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
North Atlantic Ocean ◽  
Infrared Image ◽  
Ocean Basin ◽  
Maximum Wind Speed ◽  
Tropical Cyclone Intensity ◽  
Cyclone Intensity ◽  
Maximum Wind

Abstract This paper describes results from a near-real-time objective technique for estimating the intensity of tropical cyclones from satellite infrared imagery in the North Atlantic Ocean basin. The technique quantifies the level of organization or axisymmetry of the infrared cloud signature of a tropical cyclone as an indirect measurement of its maximum wind speed. The final maximum wind speed calculated by the technique is an independent estimate of tropical cyclone intensity. Seventy-eight tropical cyclones from the 2004–09 seasons are used both to train and to test independently the intensity estimation technique. Two independent tests are performed to test the ability of the technique to estimate tropical cyclone intensity accurately. The best results from these tests have a root-mean-square intensity error of between 13 and 15 kt (where 1 kt ≈ 0.5 m s−1) for the two test sets.

scholarly journals Comparative assessment of validity of gradient wind models for a translating tropical cyclone

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yuzuru Eguchi ◽  
Yasuo Hattori ◽  
Mitsuharu Nomura
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Wind Field ◽  
Comparative Assessment ◽  
Maximum Wind Speed ◽  
Observation Data ◽  
High Wind ◽  
Maximum Wind ◽  
Gradient Wind ◽  
The Difference

AbstractAccurate and conservative evaluations of the gradient wind in the free atmosphere are needed to account for high-wind hazards when designing wind resistance for critical infrastructure. This paper compared the validity of three existing gradient wind models to select an appropriate evaluation model, which enables us to accurately compute the asymmetric gradient wind field of a translating tropical cyclone under the condition of a symmetric pressure distribution and a constant translation velocity. The validity of the three models was assessed by evaluating the residuals in momentum conservation equations for the gradient wind under a specific tropical cyclone condition. The magnitude of the residuals was considered to be the measure of error in the gradient wind derived from each model. The results showed that the most frequently used model yielded the largest magnitude of residuals with the lowest maximum wind speed among the three models. The wind characteristics of the three models were validated using archived observation data of hurricanes. The physical reason for the difference in maximum wind speed among the three models was explained by the difference in the streamline feature of the gradient wind field. It was also revealed that the differences in maximum wind speed and magnitude of residuals became more pronounced as the translation speed and the intensity of a tropical cyclone increased. The comparative assessment of the three gradient wind models allowed us to identify the best model for use in conservative wind-resistant design and high-wind risk estimates.

scholarly journals A Study of the Effects of the Ice-Microphysics, Surface Friction, and Surface Heat Flux on Tropical Cyclone Formation§

2013 ◽  
Vol 7 (1) ◽  
pp. 110-118
Author(s):  
Masanori¶ Yamasaki
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Tropical Cyclone ◽  
Surface Heat Flux ◽  
Numerical Experiments ◽  
Surface Friction ◽  
Surface Heat ◽  
Maximum Wind Speed ◽  
Maximum Wind ◽  
Ice Microphysics

This paper describes results from numerical experiments which have been performed to understand the effects of the ice microphysics, surface friction, and surface heat flux on tropical cyclone (TC) formation. This study uses the author’s non-hydrostatic model that intends to resolve cumulus convection. However, the horizontal grid size is taken to be somewhat large; 2 km in an area of 600 km x 600 km. A non-uniform coarse grid is used in the surrounding area with 4,000-km square. Several buoyancy perturbations arranged in the west-east direction, and a weak vortex with the maximum wind speed of 5 m s–1 are given at the initial time of the numerical time integrations. It is confirmed from two numerical experiments with and without ice microphysics that the development of a vortex is slower, and TC formation is delayed, in the presence of ice microphysics. It is also confirmed that a vortex can develop even without surface friction. It is shown that a strong vortex with the maximum wind speed of 20~25 m s–1 can be obtained. As expected, however, no eye forms, and further development does not occur. That is, it is confirmed that surface friction is indispensable to eye formation and a very strong TC having an eye. As for the third concern of this study, it is shown that a vortex with the maximum wind speed of about 5 m s–1 does not develop in the absence of the surface heat flux. That is, the surface heat flux plays an important role even in a weak vortex. Important backgrounds and understandings that are concerned with these results are described, based on studies on TCs in the past 50 years.

Uncertainty of Tropical Cyclone Best-Track Information

2012 ◽  
Vol 27 (3) ◽  
pp. 715-729 ◽  
Author(s):  
Ryan D. Torn ◽  
Chris Snyder
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Maximum Wind Speed ◽  
Sea Level Pressure ◽  
Position Uncertainty ◽  
Maximum Wind ◽  
Intensity Information ◽  
Weather And Climate ◽  
The Mean ◽  
National Hurricane Center

Abstract With the growing use of tropical cyclone (TC) best-track information for weather and climate applications, it is important to understand the uncertainties that are contained in the TC position and intensity information. Here, an attempt is made to quantify the position uncertainty using National Hurricane Center (NHC) advisory information, as well as intensity uncertainty during times without aircraft data, by verifying Dvorak minimum sea level pressure (SLP) and maximum wind speed estimates during times with aircraft reconnaissance information during 2000–09. In a climatological sense, TC position uncertainty decreases for more intense TCs, while the uncertainty of intensity, measured by minimum SLP or maximum wind speed, increases with intensity. The standard deviation of satellite-based TC intensity estimates can be used as a predictor of the consensus intensity error when that consensus includes both Dvorak and microwave-based estimates, but not when it contains only Dvorak-based values. Whereas there has been a steady decrease in seasonal TC position uncertainty over the past 10 yr, which is likely due to additional data available to NHC forecasters, the seasonal TC minimum SLP and maximum wind speed values are fairly constant, with year-to-year variability due to the mean intensity of all TCs during that season and the frequency of aircraft reconnaissance.

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