Juliette had the distinction of being the strongest
eastern north Pacific
hurricane of 1995.
Its one-minute winds reached an estimated 130 knots.
a. Synoptic History
Juliette can be traced back to a
tropical wave
which exited west Africa on 31 August. This system trailed behind
Hurricane Luis,
which formed over the eastern Atlantic. The upper-level
outflow (and possibly subsidence) to the east of
Luis apparently
inhibited development of the wave as it propagated westward
across the Atlantic. Even though the cloud pattern associated
with this system was not well defined, continuity (using a
westward motion of 6° longitude per day) puts the wave axis near
Panama on 11 September.
The wave crossed central America on the 12th, and caused
increased thunderstorm activity in the vicinity of the Gulf of
Tehuantepec on the 13th, and near 100°W on the 14th. Late on the
15th (2330 UTC) when the system was near 103°W, the cloud pattern
became sufficiently organized so that an initial
Dvorak technique classification was performed.
The development trend continued, and based on intensity estimates by the
Tropical Analysis and Forecast Branch (TAFB) and the
Synoptic Analysis Branch
(SAB) of a T2.0 on the Dvorak scale, it is estimated that a
tropical depression,
Eleven-E, formed a little over 250 n mi to the south
of Manzanillo Mexico at 1800 UTC 16 September. The subsequent track is
shown in Figure 1 (41K GIF).
The developing tropical cyclone
was rather small in size, with a central area of deep convection only 50-100 n mi in
diameter. Based on Dvorak estimates from
TAFB and SAB,
tropical storm
intensity was reached at 1200 UTC 17 September. Further
strengthening, at a rather rapid rate, occurred, and Juliette is
inferred to have reached hurricane strength by 1200 UTC on the
18th, when satellite images revealed that an
eye was forming.
Continued rapid development took place on the 18th; by 1800 UTC Juliette's eye
was well-defined.
A narrow, weak, deep-tropospheric ridge lay to the north of
the strengthening hurricane, steering Juliette slowly in a
general west-northwestward direction. On the 19th, satellite
imagery suggested that the strengthening trend practically
ceased, and maximum winds levelled off near 105 knots. On that
day, it is possible that upper level outflow was being interfered
with by environmental northeasterly winds in the upper
troposphere. However on the 20th, as Juliette turned toward the
west, further intensification took place, with a fairly
symmetrical mass of very cold cloud tops seen around the eye on
satellite pictures. Juliette reached its peak intensity, with
estimated maximum winds of 130 knots, at 1200 UTC 20 September.
Later on the 20th, as a gradual weakening trend set in, the
hurricane turned back to the west-northwest, at a reduced forward
speed. This general motion continued for the next couple of
days. By 1200 UTC on the 22nd, maximum winds were down to 85
knots. Satellite images during the previous 24 hours or so
indicated the presence of concentric
eyewalls, and the inner
eyewall gave way to an outer wall, resulting in a large eye,
about 70 n mi in diameter. Around 0000 UTC on the 23rd, the eye
shrank to about half that size, and a minor restrengthening, back
to 90 knots, was noted. These intensity changes
are roughly consistent with an eyewall replacement cycle.
Steering currents around a mid-tropospheric low in the
vicinity of 27°N 130°W caused the hurricane to turn northward on
the 23rd. On the 24th, as the low opened up into an eastward-moving trough,
Juliette was steered north-northeastward with some
increase in forward speed. Shearing winds from the southwest and
cooler sea surface temperatures took their toll, and Juliette
weakened to a tropical storm late on the 24th. By 0000 UTC on
the 25th, the storm consisted of a swirl of lower-tropospheric
clouds, devoid of deep convection. With the influence of upper-level steering removed,
the dissipating cyclone's motion
became a south to southeastward drift. Juliette weakened to a depression
around 0000 UTC 26 September, and later on the 26th,
the then-meandering tropical cyclone dissipated.
b. Meteorological Statistics
The post-analysis best track
intensities for Juliette are listed in Table 1
and displayed in Figs. 2 (30K GIF)
and 3 (31K GIF),
which show the estimated minimum central pressure and maximum one-minute
wind speed, respectively, versus time. As is usual for eastern
north Pacific tropical cyclones, these intensity estimates were
derived mainly from analyses of satellite images, using the
Dvorak technique, performed by meteorologists at the SAB and
TAFB
(formerly the Tropical Satellite Analysis and Forecast unit,
TSAF, as in the figures) and at the
Air Force Global Weather Central
(AFGWC). The estimated peak intensity of Juliette, 130
knots at 1200 UTC 20 September, is consistent with a subjective
Dvorak T-number of 6.5 and a 3- to 6-hourly mean objective T-number
between 6.5 and 7.0 near that time. No ship reports of wind speeds
greater than 33 knots associated with Juliette have been received at the NHC.
c. Casualty and Damage Statistics
Juliette remained over water throughout its existence, and
no reports of casualties or damage have been received at the NHC.
d. Forecast and Warning Critique
The track forecasts for Juliette were, for the most part,
very good. The mean 12-, 24-, 36-, 48- and 72-hr position errors
were 35, 67, 78, 71, and 104 n mi, respectively. These are well
below the 1988-1994 averages. Overall, the intensity of Juliette
was underforecast. In particular, on the 17th and 18th of
September the NHC forecast/advisories and accompanying cyclone
discussions recognized that conditions were favorable for
strengthening, but they did not anticipate that Juliette would
intensify beyond 100 knots. This is typical, considering the
state of the art in tropical cyclone intensity prediction.
A tropical storm watch
was issued for a portion of Baja
California after Juliette had turned north-northeastward, and
some of the track forecast models predicted the cyclone to move
over that peninsula. It appeared likely that shearing and
weakening would nullify the effects of steering by the higher
level winds, and reduce the threat to Baja. However, since there
was a possibility that Juliette would maintain enough of its
intensity and reach land, the watch was issued as a precautionary
measure. When the hurricane weakened rapidly and its forward
motion slowed, it became obvious that the watch was unnecessary.
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