Tropical Cyclone Report
22 - 26 October 2002
James L. Franklin
National Hurricane Center
26 December 2002
After reaching a peak intensity of 145 kt, Hurricane Kenna made
landfall near the fishing village of San Blas, Mexico, as a
category 4 hurricane (on the Saffir-Simpson Hurricane Scale) with
120 kt winds. Only an unnamed hurricane in 1959 and Madeline in
1976 are known to have been stronger at the time of landfall than
Kenna. Kenna was responsible for four deaths.
a. Synoptic History
Kenna developed from a disturbance that moved westward across
Central America and entered the eastern North Pacific basin on 19
October. Using satellite Hovmoeller diagrams, it is possible to
track the disturbance back to about 70 west longitude on 16
October, and the disturbance may have been associated with a
tropical wave that passed Barbados late on 14 October. After
crossing Central America, the disturbance gradually became better
organized, and Dvorak classifications began late on 20 October. The
system continued to develop, and became a tropical depression at
0000 UTC 22 October about 325 n mi south of Acapulco, Mexico.
The "best track" chart of the tropical cyclone's path is given
in Figure 1, with the wind and pressure histories shown in
Figure 2 and Figure 3,
respectively. The best track positions and intensities are
listed in Table 1. The depression moved westward and quickly
reached tropical storm strength at 0600 UTC 22 October. Kenna,
moving around the periphery of mid-level high pressure over Mexico,
turned to the west-northwest with little change in strength for the
next 18 hours. During this time, much of Kenna's deep convection
was associated with rainbands well removed from the circulation
center, but on 23 October, Kenna strengthened when these bands
began to dissipate and convection became concentrated closer to the
center. Kenna became a hurricane about 400 n mi south of Cabo
Corrientes, Mexico, between 1200 and 1800 UTC 23 October. Kenna
continued to strengthen on 24 October, while its heading turned to
the northwest and then north late in the day as its forward speed
slowed to about 9 kt. At 1800 UTC 24 October, roughly 24 hours
after reaching hurricane strength, reports from a reconnaissance
aircraft indicated that Kenna's winds had reached 140 kt and its
minimum pressure had fallen to 917 mb.
The flow ahead of a large mid- to upper-level trough west of
Baja California turned Kenna to the northeast beginning late on 24
October. As Kenna began to accelerate toward the coast of Mexico,
satellite imagery suggests that Kenna intensified slightly and
reached its peak intensity of 145 kt with a minimum pressure of 913
mb near 0000 UTC 25 October. At this time Kenna was about 125 n mi
west-southwest of Cabo Corrientes. Kenna continued to accelerate,
and although the hurricane was still over warm waters, it began to
weaken under increasing shear associated with the upper trough. By
1200 UTC that day, a second reconnaissance aircraft reported that
the minimum pressure had risen to near 940 mb. Despite the sharp
increase in pressure, Kenna's convective activity increased in the
hours just prior to landfall, and cloud top temperatures dropped to
near -90°C. The reconnaissance aircraft reported extremely severe
turbulence that was among the most intense ever experienced by the
flight crew. Data from the aircraft indicated that the hurricane's
maximum winds were only slowly decreasing, and Kenna made landfall
near San Blas, Mexico, at 1630 UTC, with winds estimated to be near
120 kt. Kenna continued moving northeastward and weakened very
rapidly inland over the mountains of Mexico; by 0000 UTC 26 October
it was a minimal tropical storm, and the circulation dissipated by
0600 UTC. The remnants of Kenna moved into the northwestern Gulf of
Mexico later that day, and enhanced rainfall in the southeastern
b. Meteorological Statistics
Observations in Kenna
(Figure 2 and Figure 3) include satellite-based
Dvorak technique intensity estimates from the Tropical Analysis and
Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and the
U. S. Air Force Weather Agency (AFWA), as well as flight-level and
dropwindsonde observations from flights of the 53rd
Weather Reconnaissance Squadron of the U. S. Air Force Reserve
On several occasions, the reconnaissance aircraft reported 700
mb flight-level winds of about 145 kt, corresponding to a surface
wind of about 130 kt. A dropsonde at 1857 UTC 24 October reported
average winds of 180 kt over the layer from 75-225 m (the lowest
150 m of wind data available). Adjustment of this observation to
the surface using the mean eyewall wind profile yields a surface
estimate of 140 kt, and this was the basis for the assigned best
track maximum wind near the time of the reconnaissance mission. The
peak intensity of 145 kt is based on an increase in both subjective
and objective Dvorak T-numbers in the hours after the aircraft
mission concluded. While the Dvorak classifications were highest at
0600 UTC 25 October, a sequence of microwave passes shows that the
eyewall began to decay after 0111 UTC. As a result, the peak
intensity of Kenna has been assigned to 0000 UTC on the
The lowest observed pressure in Kenna was 918 mb at 1859 UTC 24
October. However, the dropsondes released in the eye of Kenna
tended to miss the pressure center, as the surface winds on these
drops were near 30 kt. Therefore, minimum pressures in the best
track are slightly lower than the raw values reported in aircraft
vortex messages and plotted in Figure 3.
Kenna's minimum pressure is
estimated to be 913 mb, based again on an increase in Dvorak
classification numbers after the time of the aircraft mission.
The reconnaissance mission on 25 October provided some
interesting observations. The highest satellite-based intensity
estimates occurred at 0600 UTC, when the minimum pressure is
estimated to have been 915 mb. After 0600 UTC, the eye rapidly
disappeared. At 1335 UTC, the aircraft reported a minimum pressure
of 945 mb, 27 mb higher than what had been observed 17 hours
previously, yet the peak 700 mb flight-level winds (147 kt) were
virtually unchanged. As noted earlier, there was a burst of very
deep convection in the early morning hours just prior to landfall,
with cloud top temperatures near -89°C. The conflicting signals
from the pressure and wind data make it difficult to assign a
landfall intensity. The best track landfall intensity of 120 kt is
a compromise of the various observations, including a rapid
deterioration in the overall satellite presentation despite the
deep cold convection, and reflects a concern that the aircraft wind
report may not have been completely representative of surface
conditions. One could easily argue for a landfall intensity either
10 kt higher or lower than the value given here.
Surface observations from land stations are given in Table 2.
There were very few observations from the landfall of Kenna. At
Tepic, Nayarit (located about 15 n mi inland) the peak measured
wind (10 min mean) was 76 kt, with a storm total rainfall of 3.35
in (85 mm). At Islas Marias, about 40 n mi to the left of the track
of Kenna, 1.38 in (35 mm) of rain was recorded. The maximum rain
totals reported from the states of Colima and Nayarit were 9.84 in
(250 mm) and 4.72 in (120 mm), respectively.
The Meteorological Service of Mexico estimates that the storm
surge in San Blas was as high as 16 ft (5 m). Storm surge also
affected Puerto Vallarta, but no measurements are available. There
were reports of 10 ft waves rushing inland from the bay.
There were no ship reports of winds of tropical storm force
associated with Kenna.
c. Casualty and Damage Statistics
Mexican authorities report four deaths from Kenna. In San Blas,
an elderly woman died when the wall of her house collapsed. One
person in Santiago Escuintla was killed by flying debris. There
were two deaths due to drowning. An elderly man drowned in Santiago
Escuintla, and another elderly man fell into the river Florido.
Both of these are believed to have occurred during the storm as the
victims fled their homes. All but roughly 200 or so of the 9000
residents of San Blas evacuated the village, likely accounting for
the relatively low number of casualties. There are media reports of
over 100 injuries in San Blas and Puerto Vallarta from flying glass
and other debris.
In Puerto Vallarta, storm surge was primarily responsible for
the estimated $5 million (U.S. currency) of damage, largely to
hotels. There are no estimates of damage in San Blas, however,
media reports indicate that 80% to 90% of the homes were damaged or
destroyed. Large commercial shrimp boats were dragged up to 300
yards from their docks.
d. Forecast and Warning Critique
Average official track errors (with the number of cases in
parentheses) for Kenna were 27 (14), 41 (12), 70 (10), 93 (8), and
175 (4) n mi for the 12, 24, 36, 48, and 72 h forecasts,
respectively (OFCL, Table 3). These errors are significantly lower
than the average official track errors for the 10-yr period
1992-2001 (36, 67, 97, 125, and 182 n mi, respectively). The
landfall location, in particular, was extremely well forecast
The official forecast errors were also smaller than nearly all
of the objective track model errors including, most notably, those
from the Global Forecast System (AVNI). The Global Forecast System
consistently forecast Kenna's landfall too far to the north, and
often seemed to initialize the vortex poorly. Outperforming OFCL
was the deep layer BAM (BAMD), and at 72 h, the GFDI, UKMI, and the
consensus models GUNS and GUNA. That the BAMD was a good performing
model and the AVNI was not is interesting, as it indicates that the
Global Forecast System did well in forecasting the environmental
steering flow inputs to the BAMD, but did not handle the hurricane
itself very well.
Although the OFCL track errors were relatively low, they did
contain a significant slow bias. For example, the 48 h bias vector
was 198/71 n mi, or 76% of the mean absolute error. The first
forecasts to indicate a landfall within the 72 h forecast period
were slow by about 10-14 hours. This bias decreased to about 7
hours one day prior to landfall.
Kenna intensified from 40 to 140 kt in 42 hours. The
strengthening of such tropical cyclones is rarely anticipated, and
Kenna was no exception (Figure 5).
Average official intensity errors
were 15, 27, 41, 52, and 49 kt for the 12, 24, 36, 48, and 72 h
forecasts, respectively. These are much larger than the average
official intensity errors over the 10-yr period 1992-2001 (7, 12,
16, 18, and 21 kt, respectively). There was a 75 kt under-forecast
at 48 h, four under-forecasts of at least 50 kt at 36 h, and even a
30 kt under-forecast at 12 h. The official forecast errors were
comparable to those from the SHIPS and GFDI models, which also had
large under-forecast biases.
Table 4 lists the watches and warnings associated with Kenna.
The hurricane warning was issued roughly 25 hours prior to
Table 1: Best track for Hurricane Kenna, 22-26 October 2002.
|22 / 0000||11.4||99.4||1006||30||tropical depression
|22 / 0600||11.5||100.4||1004||35||tropical storm
|22 / 1200||11.7||101.4||1003||35||"
|22 / 1800||12.1||102.5||1003||35||"
|23 / 0000||12.6||103.6||1002||40||"
|23 / 0600||13.1||104.6||997||50||"
|23 / 1200||13.6||105.7||990||60||"
|23 / 1800||14.2||106.9||980||75||hurricane
|24 / 0000||14.9||108.0||970||90||"
|24 / 0600||15.5||108.5||955||105||"
|24 / 1200||16.4||108.8||935||125||"
|24 / 1800||17.3||108.8||917||140||"
|25 / 0000||18.3||108.3||913||145||"
|25 / 0600||19.3||107.5||915||145||"
|25 / 1200||20.4||106.5||939||130||"
|25 / 1800||22.1||105.1||960||100||"
|26 / 0000||23.7||103.5||1000||35||tropical storm
|26 / 0600||dissipated
|25 / 0000||18.3||108.3||913||145||minimum pressure
|25 / 1630||21.7||105.4||950||120||landfall near San Blas, Mexico
Table 2: Selected surface observations
for Hurricane Kenna, 22-26 October 2002.
|Maximum Surface Wind Speed|
|Tepic|| || ||? ||76 || || || ||3.35
|Puerto Vallarta||25/1350 ||997.6 ||25/1415 ||30 ||40 || || ||
|San Blas|| || || || || ||16 || ||
|Islas Marias|| ||1007 ||? ||81d || || || ||1.38
|Colima, site unknown|| || || || || || || ||9.84
|Nayarit, site unknown|| || || || || || || ||4.72
aDate/time is for sustained wind when
both sustained and gust are listed.
bExcept as noted, sustained wind
averaging periods are 10 min.
cStorm surge estimated, reference height
Table 3: Preliminary forecast evaluation (heterogeneous sample)
for Hurricane Kenna, 22-26 October 2002. Forecast errors for
tropical storm and hurricane stages (n mi) are followed by the
number of forecasts in parentheses. Errors smaller than the NHC
official forecast are shown in bold-face type. Asterisks indicate
models not available at forecast time.
|Forecast Technique||Period (hours)
|CLP5||56 (14)||149 (12)||253 (10)||348 ( 8)||488 ( 4)
|GFDI||40 (13)||68 (11)||121 ( 9)||136 ( 7)||156 ( 4)
|GFDL*||36 (13)||48 (11)||78 ( 9)||125 ( 7)||131 ( 4)
|LBAR||27 (14)||50 (12)||88 (10)||125 ( 8)||291 ( 4)
|AVNI||37 (12)||75 (12)||107 (10)||139 ( 8)||210 ( 4)
|AVNO*||53 (14)||76 (12)||112 (10)||144 ( 8)||226 ( 4)
|AEMI||35 ( 9)||89 ( 9)||122 ( 7)||157 ( 6)||241 ( 3)
|BAMD||28 (14)||49 (12)||61 (10)||66 ( 8)||133 ( 4)
|BAMM||34 (14)||58 (12)||83 (10)||112 ( 8)||249 ( 4)
|BAMS||44 (14)||84 (12)||140 (10)||194 ( 8)||362 ( 4)
|NGPI||40 (14)||103 (12)||157 (10)||181 ( 8)||227 ( 4)
|NGPS||46 (14)||72 (12)||128 (10)||182 ( 8)||225 ( 4)
|UKMI||50 (13)||83 (11)||92 ( 9)||108 ( 7)||160 ( 4)
|UKM*||47 ( 7)||76 ( 6)||94 ( 5)||114 ( 4)||205 ( 2)
|GUNS||27 (13)||56 (11)||89 ( 9)||115 ( 7)||135 ( 4)
|GUNA||19 (11)||47 (11)||79 ( 9)||101 ( 7)||133 ( 4)
|OFCL||27 (14)||41 (12)||70 (10)||93 ( 8)||175 ( 4)
(1992-2001 mean)||36 (2203)||67 (1947)||97 (1700)||125 (1472)||182 (1091)
|*Output from these models was unavailable at time of forecast issuance.
Table 4: Watch and warning summary for Hurricane Kenna, 22-26
|24 / 0900||Hurricane Watch issued||Mazatlan to Cabo Corrientes
|24 / 0900||Tropical Storm Watch issued||South of Cabo Corrientes to Manzanillo
|24 / 1500||Watches upgraded to Hurricane Warning||Mazatlan to La Fortuna
|24 / 1500||Watch upgraded to T.S. Warning||South of La Fortuna to Manzanillo
|25 / 2100||All Warnings discontinued||-
Best track positions for Hurricane Kenna, 22-26 October 2002.
Selected wind observations and best track
maximum sustained surface wind speed curve for Hurricane Kenna,
22-26 October 2002. Aircraft observations have been adjusted for
elevation using a 90% reduction factor for observations from 700
mb. Dropwindsonde observations include actual 10 m winds (sfc), as
well as surface estimates derived from the mean wind over the
lowest 150 m of the wind sounding (LLM), and from the sounding
boundary layer mean (MBL). Objective Dvorak estimates are 3-h
linear averages. Landfall is indicated by the solid vertical
Selected pressure observations and best
track minimum central pressure curve for Hurricane Kenna, 22-26
October 2002. Objective Dvorak estimates are 3-h linear averages.
Landfall is indicated by the solid vertical line.
Official track forecasts (dashed lines,
with 0, 12, 24, 36 ,48, and 72 h positions indicated) for Hurricane
Kenna, 22-26 October 2002. The best track is given by the thick
solid line with positions given at 6 h intervals.
Official intensity forecasts (dashed lines)
for Hurricane Kenna, 22-26 October 2002. The best track intensity
is given by the thick solid line.