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Tropical Cyclone Research and Review  
  Tropical Cyclone Research and Review--2015, 4 (3-4)   Published: 2015-12-15
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An Observational Study of the Changes in the Intensity and Motion of Tropical Cyclones Crossing Luzon

WU Man-chi, CHOY Chun-wing
Tropical Cyclone Research and Review. 2015, 4 (3-4): 95;  doi: 10.6057/2015TCRRh3.01
Full Text: PDF (3769KB) ( 242 )
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Tropical cyclones (TCs) moving across Luzon from east to west are likely to affect Hong Kong. As such, it is
important for forecasters take into account the likely changes in intensity and movement characteristics of TCs
crossing Luzon. 50 TCs in the period 1980-2014 were examined to determine the effect of Luzon’s terrain on
their intensity and movement.
The results indicated that TCs generally weakened as they passed through the terrain of Luzon. The decrease
in the maximum sustained winds (MSW) for TCs with intensity of severe tropical storms or below was
normally < 10 knot. For typhoons, the decrease in the MSW was usually ≥10 knot. The study also showed that
TCs moving across Luzon were likely to accelerate (decelerate) as they approached (moved away) from Luzon.
Furthermore, while there was a slight bias for TCs to deflect leftwards on leaving Luzon, a significant negative
correlation was found between the deflection tendency before and after crossing Luzon. A TC deflected to the
right (left) before landfall was likely to deflect to the left (right) after leaving Luzon. Also, deflection upon/near
landfalling is found to be related to the intensity, moving speed and the direction of motion of a TC.

Application of Fuzzy Clustering Technique for analysis of North Indian Ocean Tropical Cyclone Tracks

Sankar Nath, S. D. Kotal and P. K. Kundu
Tropical Cyclone Research and Review. 2015, 4 (3-4): 110;  doi: 10.6057/2015TCRRh3.02
Full Text: PDF (4428KB) ( 244 )
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A fuzzy, c-means (FCM) clustering technique is explored to investigate the track of tropical cyclones over
the North Indian Ocean (NIO) for the period (1976-2014). A total of five clusters is objectively identified based
on partition index,partition coefficient, Dunn Index and separation index. The results obtained during analysis
emphasized that each cluster has the unique features in terms of their genesis location, landfall, travel duration,
trajectory, seasonality, accumulated cyclone energy and Intensity. Analysis of large scale environmental
parameters, constructed preceding day of genesis show some of these parameters to be potential precursors to
TC formation for almost all the clusters, most prominently, mid-tropospheric humidity, zonal wind,vorticity and
outgoing long wave radiation of the main developing regions. The individual clusters have the several distinct
features in their seasonal cycles.The cluster C5 shows distinct bimodal distributions where as other clusters
are formed throughout the year. ENSO influenced the cyclone frequency in two of the five clusters. The MJO
is found to play an important role in the genesis of the cyclone. The post monsoon season cyclone frequency
is more in MJO phase 2, 3 and 4. The technique (FCM) can be used as a guideline in terms of the probable
affected zone of TC Tracks by the operational forecasters.

An Introduction to the NASA East Pacific Origins and Characteristics of Hurricanes (EPOCH) Field Campaign

Amber E. Emory, Matthew McLinden, Mathias Schreier, Gary A. Wick
Tropical Cyclone Research and Review. 2015, 4 (3-4): 124;  doi: 10.6057/2015TCRRh3.03
Full Text: PDF (2261KB) ( 288 )
Show Abstract
Over the past five years, tropical activity in the East Pacific has increased, while declining in the Atlantic Basin.
In addition, during El Niño years, warmer than average sea surface temperatures further increase the likelihood
of tropical cyclone formation in the East Pacific. Hurricane field campaigns used the Ku-/Ka-band High-
Altitude Wind and Rain Airborne Profiler (HIWRAP) radar on the Global Hawk (GH) unmanned aircraft, in
GRIP (Genesis and Rapid Intensification Processes 2010), HS3 (Hurricane and Severe Storm Sentinel 2012-14),
and the NOAA Sensing Hazards with Operational Unmanned Technology (SHOUT 2015-16) field campaigns.
Although originally designed for the GH, the X-band high-altitude RADar (EXRAD) has yet to be integrated
and flown on an unmanned aerial vehicle. EXRAD will provide data with less attenuation of signal over deep
convection as well as better estimates of three-dimensional winds with its nadir-pointing beam. As part of the
NASA Hand On Project Experience (HOPE) Training Opportunity, our team proposed to fly the AV-6 GH aircraft
with the EXRAD radar, the High Altitude MMIC Sounding Radiometer (HAMSR), and NOAA Advanced
Vertical Atmospheric Profiling System (AVAPS) dropsondes to investigate genesis and/or rapid intensification
(RI) of an East Pacific hurricane by measuring both the environment and interior structures. Information on
planned activities primarily focused on the EXRAD high-altitude radar integration for the July-August 2017 science
flight will be presented.

A Multi-model Consensus Forecast Technique for Tropical Cyclone Intensity Based on Model Output Calibration

Hui Yu, Guomin Chen, Rijin Wan
Tropical Cyclone Research and Review. 2015, 4 (3-4): 132;  doi: 10.6057/2015TCRRh3.04
Full Text: PDF (1367KB) ( 259 )
Show Abstract
We analyzed the errors associated with forecasts of tropical cyclone (TC) intensity from 2010-2012 in the
western North Pacific region made by seven operational numerical weather prediction models. The results show
that the forecast error is significantly related to the initial error as well as the initial TC intensity, size, and translation
speed. Other factors highly related to the forecast error include the environmental sea surface pressure,
vertical wind shear and maximum potential intensity. We used stepwise regression to set up model forecast error
estimation equations, which were used to calibrate the model output. Independent experiments showed that
the calibrated model forecasts have significant skill compared to the original model output. Finally, a multimodel
consensus forecast technique for TC intensity was developed based on the calibrated model output; this
technique has 28% (15-20%) skill at 12 h (24-72 h) compared to the climatology and persistence forecasts of
TC intensity. This consensus technique has greater skill than the consensus forecast based on the original model
output and therefore it has the potential to be applied in operation.

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