Tropical Cyclone Report
Tropical Storm Cristina
9 - 16 July 2002
Cristina was a tropical storm that moved generally toward the
west-northwest across the eastern Pacific basin with wind speeds
briefly reaching 55 kt.
a. Synoptic History
Cristina originated from an area of disturbed weather that was
first identified near Panama on July 6th. This weather
moved westward as a tropical wave-like feature, but there was no
prior continuity with a tropical wave across the Atlantic basin.
The first signs of a low-level circulation appeared on the
8th, centered about 300 n mi south of Puerto Angel,
Mexico. The system was upgraded to Tropical Depression Four-E on
the morning of July 9th, when convection was well-enough
organized to warrant a tropical cyclone classification. The
depression was then located about 300 n mi south of Acapulco. The
"best track" begins on the 9th. A map 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 just north of due westward at 10 to 15 kt
for the next three days, under the steering of a mid-level ridge to
its north. During this period, a hostile environment of strong
vertical shear frequently affected the deep convection, causing the
partial exposure of the low-level circulation center. Also, the
low-level circulation often appeared elongated or perhaps
non-existent, as observed from satellite imagery, while the deep
convection was often poorly organized or shapeless.
Early on the 12th, the depression became Tropical
Storm Cristina when deep convection developed near the center along
with some banding features. An upper cut-off low over Baja
California began digging southward. This weakened the steering
ridge, allowing Cristina to slow its forward speed and to begin a
turn toward the north-northwest. Cristina very gradually
strengthened, reaching 55 kt on the 14th with tight
banding features. Shortly thereafter, Cristina quickly weakened,
the low-level center became fully exposed, and a west-northwestward
motion was resumed under lower-level steering. By the
16th, Cristina was reduced to a swirl of low clouds
moving westward over colder water about 750 n mi west-southwest of
the southern tip of Baja California.
b. Meteorological Statistics
Observations (Figure 2 and Figure 3)
used to construct the best track
wind speeds and pressures are mainly 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). These were supplemented by
occasional QuikSCAT passes, one of which showed several 40-kt wind
speeds early on the 14th, uncontaminated by rainfall.
Center position estimates based on geostationary satellite images
were supplemented by SSMI and TRMM microwave images.
c. Casualty and Damage Statistics
Cristina did not affect land and there are no reports of deaths
d. Forecast and Warning Critique
Average official track errors (with the number of cases in
parentheses) were 37 (11), 52 (9), 66 (7), 86 (5), and 66 (1) n mi
for the 12-, 24-, 36-, 48-, and 72-h forecasts, respectively.
Except for the 12-h average error, these errors are considerably
smaller than the average official track errors for the 10-yr period
1992-2001 (36, 67,97, 125, and 182 n mi, respectively). However the
numbers of cases (only 1 at 72 h) are small at the longer forecast
periods. It is noted that the GFDL, UKMET and GFS dynamical track
models did not do as well as the official forecast at 36 through 72
Average official intensity errors were 8, 10, 11, 11, and 15 kt
for the 12-, 24--, 36-, 48-, and 72-h forecasts, respectively. For
comparison, the average official intensity errors over the 10-yr
period 1992-2001 were 7, 12, 16, 18, and 21 kt, respectively.
Again, all but the 12-h average error are smaller than the previous
Table 1: Best track for Tropical Storm Cristina, 9-16 July
|09 / 1200||11.5||100.3||1008||30||tropical depression
|09 / 1800||12.0||101.7||1008||30||"
|10 / 0000||12.4||103.3||1007||25||"
|10 / 0600||12.8||104.7||1007||25||"
|10 / 1200||13.0||106.0||1007||25||"
|10 / 1800||13.3||107.3||1007||25||"
|11 / 0000||14.0||108.6||1007||25||"
|11 / 0600||14.2||109.6||1007||25||"
|11 / 1200||14.3||110.5||1006||30||"
|11 / 1800||14.3||111.5||1006||30||"
|12 / 0000||14.2||112.5||1005||30||"
|12 / 0600||14.2||113.6||1004||35||tropical storm
|12 / 1200||14.2||114.6||1004||35||"
|12 / 1800||14.1||115.2||1003||40||"
|13 / 0000||14.1||115.7||1003||40||"
|13 / 0600||14.3||116.1||1003||40||"
|13 / 1200||14.6||116.6||1000||45||"
|13 / 1800||15.0||117.1||1000||45||"
|14 / 0000||15.7||117.5||1000||45||"
|14 / 0600||16.2||117.8||997||50||"
|14 / 1200||16.6||117.8||994||55||"
|14 / 1800||17.1||117.9||995||50||"
|15 / 0000||17.5||118.0||1000||45||"
|15 / 0600||17.9||118.5||1005||35||"
|15 / 1200||18.5||119.4||1009||30||tropical depression
|15 / 1800||19.1||119.8||1009||30||"
|16 / 0000||19.4||120.4||1009||30||"
|16 / 0600||19.7||121.1||1009||25||"
|16 / 1200||19.8||121.9||1009||25||"
|16 / 1800||20.0||122.7||1010||25||"
|17 / 0000||dissipated
|14 / 1200||16.6||117.8||994||55||minimum pressure
Best track positions for Tropical Storm Cristina, 9-16
Selected wind observations and best track maximum
sustained surface wind speed curve for Tropical Storm Cristina,
9-16 July 2002.
Selected pressure observations and best track minimum
central pressure curve for Tropical Storm Cristina, 9-16 July