This document discusses spectral analysis of Cyclone Hudhud from 2014. It provides background on the storm's formation and intensification as it traveled over the Andaman Sea and impacted eastern India and Nepal. Key details include:
- Hudhud reached peak intensity as a Category 4 storm with 135 mph winds before making landfall near Visakhapatnam, India.
- Radar images show the storm had an eye around 66 km in diameter shortly before landfall.
- Spectral analysis of radar signals can provide insights into tropical cyclone wind and wave generation using models like the Holland vortex model.
- IIR and FIR filters are used to suppress clutter in Doppler ultrasound images for analyzing tropical cyclone dynamics
1. A CASE STUDY ON SPECTRAL ANALYSIS OF CYCLONE HUDHUD
UNDER THE GUIDANCE OF
Dr.CH.SRINIVASU
A presentation by
V. SANTOSH(17981A04L6)
2. Cyclone Hudhud - The origin
• Extremely Severe Cyclonic Storm Hudhud was a strong tropical cyclone that
caused extensive damage and loss of life in eastern India and Nepal during
October 2014.
• Hudhud originated from a low pressure system that formed under the influence of
an upper-air cyclonic circulation in the Andaman Sea on October 6. Hudhud
intensified into a cyclonic storm on October 8 and as a Severe Cyclonic Storm on
October 9.
• Hudhud underwent rapid deepening in the following days and was classified as a
Very Severe Cyclonic Storm by the IMD.
3.
4. • Tropical Cyclone Hudhud powered ashore near Visakhapatnam, India
at 05 UTC (3 am EDT) Sunday as a Category 4 storm with sustained
winds of 135 mph.
• Wind observations from Visakhapatnam showed a peak sustained
wind of 73 mph at 9:44 am local time, with a peak gust of 119 mph at
10:30 am.
5. • On October 11, Hudhud underwent rapid intensification and developed an eye at
its center. In the following hours, the storm reached its peak intensity with a
minimum central pressure of 950 mbar (28.05 inHg) and three-minute average
windspeeds of 185 km/h (115 mph).
• Maintaining intensity, it made landfall over Visakhapatnam, Andhra Pradesh at
noon of October 12. The maximum wind gust recorded by the High Wind Speed
Recorder (HWSR) instrument of the Cyclone Warning Center in Visakhapatnam was
260 km/h (160 mph).
• Measured by the Doppler weather radar stationed in the city, the storm's eye was
66 km (41 mi) in diameter. The strength of the winds disrupted telecommunication
lines and damaged the radar, inhibiting further observations
6. As observed by ECHO - European
Community Humanitarian Aid
Office
8. Final image of
Tropical Cyclone
Hudhud as seen
by radar out of
Visakhapatnam,
India before it
failed at 12:51
am October 12,
2014.
At the time,
Hudhud was a
Category 4
storm with 135
mph winds.
9. dBZ
• dBZ stands for decibel relative to Z.
• It is a logarithmic dimensionless technical unit used in radar, mostly in weather radar,
to compare the equivalent reflectivity factor (Z) of a radar signal reflected off a
remote object (in mm6 per m3) to the return of a droplet of rain with a diameter of 1
mm (1 mm6 per m3)
• Reflectance of the surface of a material is its effectiveness in reflecting radiant
energy. It is the fraction of incident electromagnetic power that is reflected at an
interface.
11. Parametric Descriptions of Tropical
Cyclone Wind-Wave Generation
• Tropical cyclones, hurricanes, or typhoons represent the major
meteorological forcing events inmany tropical and sub-tropical
regions.
• The intense winds generated by the spatially compact and well-
formed vortex structures of such systems generate large and
potentially destructive ocean surface waves
12. • As the wind field varies rapidly in space and time (in both magnitude
and direction) in such systems, it would initially seem that
understanding the resulting wave fields would be a daunting task.
• It is true that such systems do represent a challenging test of our
understanding of the physical processes that are active.
13. HOLLAND MODEL
• The Holland wind field model (1) has been extensively used in many
wind and wavestudies, it has the limitation that it is, by definition, a
vortex not embedded in any background flow.
• In fluid dynamics, a vortex is a region in a fluid in which the flow
revolves around an axis line, which may be straight or curved
• As a result, at large values of r, the model tends to underestimate
observed winds. Thompson found that the performance of the
Holland model at large r could be improved by theaddition of a
second outer vortex of the same form as in model .
14. • The aim here is not to create a second tropical cyclone eye or eye
wall. Rather, there is a primary vortex with radius R1 and parameter
p01 which largely defines the vortex and then a second larger vortex
with radius R2 and parameter p02
• p0 is the central pressure and pn is the ambient atmospheric
pressure far from the storm
15. Tropical cyclone wind fields. (a) Left panel—calculated with
a single Holland vortex (1) and parameters, p0 = 950 HPa,
pn = 1005 HPa, R = 30 km
16. Schematic diagram showing the
generation of waves within a
translating northern hemisphere
tropical cyclone.
17. • For ultrasound color flow images with high quality, it is important to
suppress the clutter signals
• The class of filters that are used are finite impulse response (FIR),
infinite impulse response (IIR)
• IIR filters are one of two primary types of digital filters used in Digital
Signal Processing (DSP) applications (the other type being FIR). “IIR”
means “Infinite Impulse Response.”
Clutter filter
18. • The impulse response is “infinite” because there is feedback in the
filter; if you put in an impulse (a single “1” sample followed by many
“0” samples), an infinite number of non-zero values will come out
(theoretically.)
• DSP filters can also be “Finite Impulse Response” (FIR). FIR filters do
not use feedback, so for a FIR filter with N coefficients, the output
always becomes zero after putting in N samples of an impulse
response.
• In the above filtering IIR Doppler 8 filter is used.
