Late season Hurricane Nicole was a tenacious
tropical cyclone that persisted for several days over the northeast
Atlantic.
a. Synoptic History
Nicole developed from a nearly stationary and strong frontal low which persisted for several days over the
northeast Atlantic, centered a few hundred miles south of the Canary Islands. Satellite imagery suggested that the frontal
low acquired tropical characteristics when a tightly-wrapped convective band developed around the
center of circulation. It is estimated that the system reached
tropical storm status at 0600 UTC 24 November. Later on, a ship with call sign PFSJ
confirmed that the system had acquired tropical characteristics when reported 36 knots at
1200 UTC 24 November just to the north of the center of the tropical storm. The tropical cyclone was then located in the
central portion of a larger upper-level low where the vertical wind shear was relatively weak. This is typical for these
late-season developments in the subtropics. Nicole continued to become organized while an intermittent eye-feature was
observed on satellite images. Maximum winds increased to 60 knots as indicated by
reports from the same ship.
Nicole moved toward the west-southwest for the next few days while located south of a strong mid-level
high pressure ridge. An upper-level trough moved rapidly eastward over the system, producing a strong wind shear. The
shear removed most of the convection associated with the tropical cyclone which weakened to
tropical depression status on
26 November. If fact, the system became so weak that advisories were discontinued. However, the ridge which followed
the upper-level trough became superimposed over the system, decreasing the shear. Deep convection regenerated and
unexpectedly, the system reacquired tropical storm strength by the 27th.
Nicole then began to move on a west-northwest track. Thereafter, it turned toward the northeast ahead of
another strong approaching cold front. Nicole intensified further and reached hurricane status with peak winds of
75 knots and a minimum pressure of 979 mb at 0000 UTC 1 December. These estimates were
based on satellite images which revealed the formation of an eye,
resulting in objective T-numbers oscillating around 4.5 on the Dvorak scale.
In addition, data from the Defense Military Satellite Program
(DMSP) 85 GHz sensor showed an almost complete eyewall. During that period,
Nicole was moving over a region of anomalously warm sea surface temperatures of the order of 2 or 3 degrees. This
anomalous feature was probably partially responsible for the intensification of the system. Nicole moved rapidly northward
and north-northwestward around the periphery of a large deep-layer cyclonic circulation and became
extratropical by 1800 UTC 1 December.
Nicole's track is shown in Fig. 1. (26K GIF)
Table 1 is a listing, at six-hourly intervals, of the best-track
position, estimated minimum central pressure and maximum 1-minute surface wind speed.
b. Meteorological Statistics
The best track pressure and wind curves as a function of time are shown in
Figs. 2 (9K GIF) and 3 (9K GIF)
and are primarily based on data from satellite intensity estimates from the
Tropical Analysis and Forecast Branch (TAFB),
the Satellite Analysis Branch (SAB)
and the Air Force Weather Agency, (AFGWC in figures). Observations from
the ship PSFJ were crucial to determine the structure and the intensity of Nicole. In fact, the storm's intensity was
operationally increased to 60 knots based on a 58-knot
wind report from that vessel at 1800 UTC 24 November.
c. Casualty and Damage Statistics
There are no reports of casualty and damage from Nicole.
d. Forecast and Warning Critique
The NHC average official track errors in n mi for Nicole (excluding the tropical depression and
extratropical stages were 51 (23 cases), 117 (21 cases), 183 (18 cases), 252 (15 cases) and 377 (14 cases), respectively, for
the 12-, 24-, 36-, 48-, and 72-hour forecast periods. These numbers are larger than the 1988-1997 average errors of 47, 88,
127, 166 and 248 n mi for the same time periods. The errors produced by the track models were also large, primarily
beyond the 48-hour period.
Nicole was forecast to dissipate after being hit by strong shear. Instead, Nicole regenerated and reached
hurricane status. This reflects once again the uncertainties in intensity forecasting, particularly at higher latitudes whose
development is associated with extratropical sources.
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