October 1966 Robert W. Fett 605
LIFE CYCLE OF TROPICAL CYCLONE JUDY
AS REVEALED BY ESSA II AND NIMBUS II
MAJOR ROBERT W. FETT
Southeast Asia Tactical Forecast Center, Saigon, Viet Nam
ABSTRACT
Three ESSA I1 views and a Nimbus I1 view of tropical cyclone Judy illustrate an important general charac-
teristic of tropical cyclone development. This is the tendency of the apparent center of circulation, as seen in satellite
photographs, to move from the edge of major overcast cloudiness in the weaker stages t o a more central position
as the storm intensifies, and to become almost symmetrical t o the main cloud shield in the most intense stages. As
the storm decreases in intensity the center of circulation again msumes an asymmetric relationship to the major
overcast cloud area. Some aspects of the physical plausibility of this relationship are briefly discussed.
1. INTRODUCTION
In an earlier paper Fett [l] described an important
characteristic of the formative stage of tropical cyclone
development revealed clearly for the first time by mete-
orological satellites. This was that the center of circula-
tion of tropical depressions, generally with maximum sus-
tained surface wind speeds of less than 30 kt., tends to be
defined by convective cloud bands of rather narrow width,
located along the edge of the major overcast cloud area.
With further intensification the center of circulation
becomes obscured and the overcast cloud shield appears
to expand about the storm center. Satellite views of the
more intense storms have generally indicated that the
center of circulation, or in these cases the eye of the storm,
is in a position very nearly symmetrical to the main cloud
shield. Some excellent examples of this condition have
recently been published by Fritz et al. [2]. I t may be
concluded from these examples that a progressive tendency
for the center to assume a more and more central position
with respect to major cloudiness during the process of
intensification is inherent in typhoon development
Another aspect, occasionally viewed, is a tendency for
the storm to “run down” in tbe same manner that it
intensifies [3]. A fern rare pictures of decaying storms
that were not obscured by land or frontal effects show
the circulation center of the storm again in a more
asymmetrical position near the edge of major overcast
cloudiness.
In all prior studies, no single storm was viewed during
all stages t o illustrate adequately this tendency. With
the recent advent of ESSA 11, the new Automatic Picture
Transmission (APT) satellite, and &limbus 11, the com-
plete development and decay of typhoon Judy was
monitored by equipment a t Tan Son Nhut AFB, Saigon.
For the first time a single storm was observed in all
stages a t the appropriate times. The views obtained
indicate that Judy exemplified the qualities described
above.
9. TROPICAL DEPRESSION JUDY, MAY 25,1966
On this day a tropical depression in the South China
Sea mas viewed by both ESSA I1 and Nimbus 11: Figure 1
shows the Nimbus view obtained on pass 131 at 0326 GMT.
Low-level cloud banding in the northwest quadrant tends
to define a circulation center near 15’ N., 116’ E. The
initial depression advisory by the Joint Typhoon Warning
Center (JTWC) at Guam placed a center a t 14.0° N.,
116.5’ E. at 0600 GMT approximately 2:h hr. after the
Nimbus photo. This position is in reasonable agreement
with the estimate derived through the satellite photo
which was gridded to an accuracy of plus or minus 30 n.mi.
Maximum sustained surface wind speeds were indicated
by Guam to be 30 kt. From the Nimbus photo one can
see that the apparent center of circulation lies in a more
open area northwest of the major overcast convective
cloudiness associated with the storm system. The de-
pression a t this time conforms to the Stage C, “Comma
Configuration, ” described in a previous paper [l]. Maxi-
mum sustained surface wind speeds in this stage of de-
velopment have normally been found to fall within the
range of 20 to 30 kt., in close agreement with the JTWC
estimate and with available surface reports plotted in
figure 1. From Manila’s 200-mb. 0000 GMT wind report
plotted near 15.3’ N., 120.5’ E. and from the indications
of upper wind direction denoted by cirrus plumes (dashed
arrows) one can deduce that even in this early stage of
development an anticyclone or ridge had formed aloft
over the overcast, area. A comparison of Manila’s 200-
mb. wind with thal from station 663 on the southern
coast of China (near 22’ N., 112’ E.) reveals that a broad
606 MONTHLY WEATHER REVIEW Vol. 94, No. 10
FIGURE 1.-A Nimbus 11 view of tropical depression Judy on May 25, 1966.
Surface and 200-mb. winds for 0000 GMT in the deprcssion area are plotted.
the alignment of cirrus striations.
The picture was taken on orbital pass 131 a t 0326 GMT.
Dashed arrows show probable 200-mb. flow deduced from
upper-level trough existed aloft over the low-level center
of circulation. This structure, in all important aspects,
conforms to the model of a formative tropical cyclone as
described earlier [I].
3. TYPHOON JUDY, MAY 27-28, 1966
The tropical depression intensified rapidly and by 1800
GMT, May 26, 1966, it had attained typhoon status with
Robert W. Fett 607 October 1966
FIGURE 2.-An ESSA I1 view of typhoon Judy on May 27, 1966, pass 1109, 0028 GMT. Surface minds for 0000 GMT in the typhoon area
are plotted.
maximum sustained surface wind speeds est,imated at 70
kt. Figure 2 shows an ESSA I1 view of typhoon Judy at
0028 GMT on May 27, 1966. At this time the eye of the
storm was pinpointed by the JTWC at 16.5" N., 117.8' E.
Maximum wind speeds were estimated at 75 kt. The
position is in good agreement with general indications of
banding in the APT photograph and available surface
reports plotted in figure 2 . Note that the center is now
608 MONTHLY WEATHER REVIEW Vol. 94, No, 10
FIGURE 3.-An ESSA I1 view of typhoon Judy on May 28, 1966, pass 1121 a t 0105 GMT. Surface and 200-mb. winds for 0000 GMT in the
typhoon area are plotted.
embedded within the heavy overcast cloudiness. The
cloudiness stretching far to the east between latitudes 15"
and Z O O N. coincided with the trailing edge of the weak
polar front. Efr'ects of this frontal interaction diminished
on the following day when Judy was again viewed by
ESSA I1 (fig. 3). This picture, taken on May 28, 1966,
at 0105 GMT, shows typhoon Judy near its maximum
intensity. The JTWC reported its position at 0000 GMT,
May 28 as 18.5' N., 116.7' E., with maximum winds of
85 kt. The eye of the storm can be seen in the ESSA
October 1966 Robert W. Fett 609
FIGURE 4.-An ESSA I1 view of tropical storm Judy on May 31, 1966, pass 1160 at 0067 GMT. Surface and 200-mb. winds for 0000 GMT
in the storm area are plotted. Dashed arrows show probable 200-mb. flow deduced from the alignment of cirrus striations.
photograph near 18' N., 1 1 6 O E. This position, based on
a gridding accuracy for the photograph of plus or minus
30 n.mi., is in close agreement with the JTWC estimate.
As in the previous figure, the eye of the storm is well
within the confines of the major overcast cloudiness.
4. TROPICAL STORM JUDY, MAY 31, 1966
The final APT Photograph on May 31 at 0057 GMT
shows tropical storm Judy shortly after it traversed the
island of Taiwan (fig. 4). The effects of the high moun-
61 0 MONTHLY WEATHER REVIEW Vol. 94, No. 10
tain range on the east side of the island weakened the storm
appreciably as it moved off to sea to the northeast. The AET
picture, gridded to an accuracy of plus 01’ minus 30 n.mi.,
shows the center of circulation again on the edge of the major
overcast cloudiness near 25’ N., 123.5’ E. At 0600 GMT
the JTWC relocated the storm’s position, based on sur-
face reports, at 26.2’ N., 126.4’ E. Maximum winds
were estimated at 55 kt. Keliability of this fix was indi-
cated as poor and probably was in error, since the storm
center would have had to move toward the northeast at
a speed of 50 kt. in order to have attained this position
from the time of the APT fix, and this speed appears
excessive based on scanty wind reports available. The
surface wind reports at 0000 GMT, plotted in figure 4,
support the reliability of the APT fix.
A comparison of Judy at this final stage of development
with the initial view shown in figure 1 reveals the great
siniilarity of appearance that is characteristic of the two
stages. The centers of circulation are both on the edge
of the main overcast cloudiness which dominates pri-
marily the eastern semicircle of the storms. Anticyclonic
flow aloft over the convective areas is apparent in both
photos as revealed by the cirrus striations and plotted
200-mb. reports. The (‘Comma Configuration” is clearly
shown when one constructs a smooth curve southward
from the center of circulation tangent to the curved bands
leading into the vortex centers. Streamline analyses in
this configuration reveal a low-level asymptote of con-
vergence under the main overcast area.
5. CONCLUSIONS
The APT views of tropical cyclone Judy clearly reveal
a characteristic which appears to be inherent in the life
cycle of typhoon development and decay. The fact that
the center of circulation is found outside the areas of
major convection in the weaker stages fully supports
the contention made by Malkus [4] mho emphasized the
importance of the development of an eye before hurricane
intensity could be attained.1 It is a t this stage that the
zone of major convergence is transferred from outlying
--
1 More recent Endings indicate that in some rare storms, wind speeds of minimum
hurricane strength are occasionally found even with no wall cloud and with the center
of circulation near the edge of the major cloudiness. In these instances, marked banding
and small radius of curvature are noticeable in the satellite photos. Such configuration
has never typified the more intense storms and has been quite transitory in nature.
areas, and the eye-wall cloud complex becomes the dom-
inant and driving force of the storm. One can readily
appreciate that any vertical motion near the center of
circulation when it is on the edge of major cloudiness,
in a relatively dry environment, could result in only a
small release of latent heat. Hence only a minor reduc-
tion of pressure could occur and wind speeds would gen-
erally be light. Once the center is surrounded by con-
vective bands or a mall cloud, rising air in this moist
environment can release a maximum amount of heat
resulting in lower surface pressures and correspondingly
higher wind speeds. The reversion to the comma con-
figuration in the decaying stage signifies the dissipation
of the wall cloud and transference of major convergence
and vertical motion again to the convergence asymptotes.
A complete treatment of this phenomenon is beyond the
scope of this paper, but is certainly worthy of further
detailed consideration.
ACKNOWLEDGMENTS
This paper and the history of Judy were made possible by satellite
photos available to a remote field location-one of many now op-
erational throughout the world. This format is infinitely superior
to the coded NEPANS or schematic nephanalyses previously
available. The value of such real time data, particularly in the
Tropics, where conventional sources are limited, cannot be over-
emphasized. I n the realm of detecting, tracking, and monitoring
the intensity of tropical cyclones, application of such data is having
a truly revolutionary impact.
REFERENCES
1. R. W. Fett, “Some Characteristics of the Formative Stage of
Typhoon Development: A Satellite Study,” paper presented
a t National Conference on Physics and Dynamics of Clouds,
Chicago, Ill., Mar. 1964, 10 pp. plus figures. U.S. Weather
Bureau, Washington, D.C. (multilithed). See also, “The
Upper Level Structure of the Formative Tropical Cyclone,”
Monthly Weather Review, vol. 94, No. 1, Jan. 1966, pp. 9-18.
2. S. Fritz, L. F. Hubert, and A. Timchalk, “Some Inferences from
Satellite Pictures of Tropical Disturbances,” Monthly Weather
Review, vol. 94, No. 4, Apr. 1966, pp. 231-236.
3. R. W. Fett, “TIROS Photos and Mosaic Sequences of Tropical
Cyclones in the Western Pacific During 1962,” Meteorolcgical
Satellite Report No. 32, U. S. Weather Bureau, Washington,
D.C., Sept. 1964, 38 pp.
4. J. Malkus, “Tropical Weather Disturbances-Why So Few cf
Them Become Hurricanes,” Weather, vol. 13, No. 3, Mar.
1958, pp. 75-89.
[Received June 21 , 1966; revised August 8, 19661