a. Synoptic history
An extratropical low pressure system formed just east of the Turks and
Caicos Islands near 0000 UTC 25 October in response to an upper level
cyclone interacting with a frontal system. The low initially moved
northwestward, and in combination with a strong surface high to the north
developed into a gale center six hours later. By 1800 UTC that day it had
developed sufficient organized convection to be classified using the
Herbert-Poteat subtropical cyclone classification system, and the best track
of the subtropical storm begins at this time
(Table 1 and Figure 1).
Upon becoming a subtropical storm, the cyclone turned northward. This
motion continued for 24 h while the system slowly intensified. The storm
jogged north-northwestward late on 26 October, followed by a
north-northeastward turn and acceleration on the 27th. During
this time, satellite imagery indicated intermittent bursts of central
convection while Air Force Reserve Hurricane Hunter aircraft indicated a
large (75-100 n mi) radius of maximum winds. This evolution was in contrast
to that of Hurricane Michael a week-and-a-half before. Although of similar
origin to the subtropical storm, Michael developed persistent central
convection and completed a transition to a warm-core hurricane.
After reaching a 50 kt intensity early on 27 October, little change in
strength occurred during the next 24 h. The storm turned northeastward and
accelerated further on the 28th in response to a large and cold
upper-level cyclone moving southward over southeastern Canada. A last burst
of organized convection late on the 28th allowed the storm to reach
a peak intensity of 55 kt. A strong cold front moving southward off the New
England coast then intruded into the system, and the storm became
extratropical near Sable Island, Nova Scotia, around 0600 UTC 29 October.
The extratropical center weakened rapidly and lost its identity near eastern
Nova Scotia later that day. It should be noted that the large cyclonic
circulation that absorbed the subtropical storm was responsible for heavy
early-season snowfalls over portions of the New England states and
b. Meteorological statistics
Table 1 shows the best track positions and intensities
for the subtropical storm, with the track plotted in
Figure 1. Figure 2
and Figure 3 depict the curves of minimum central
sea-level pressure and maximum sustained one-minute average "surface" (10 m
above ground level) winds, respectively, as a function of time. These
figures also contain the data on which the curves are based: satellite-based
Hebert-Poteat and experimental extratropical transition intensity (Miller
and Lander, 1997) estimates from the Tropical Analysis and Forecast Branch
(TAFB), the Satellite Analysis Branch (SAB) of the National Environmental
Satellite Data and Information Service (NESDIS), and the Air Force Weather
Agency (AFWA), as well as data from aircraft, ships, buoys and land stations.
The Air Force Reserve Hurricane Hunters flew two mission into the storm with
a total of four center fixes. Central pressures on both flights were in the
997-1000 mb range, and the maximum flight level (1500 ft) winds were 60 kt
on the first flight and 61 kt on the second. A weak temperature gradient
was observed in the system on the first flight, suggesting that the cyclone
still had some baroclinic characteristics. The second flight showed a
uniform airmass within 100 n mi the center with temperatures of about
The storm had a large envelope, and many ships reported 34 kt or higher
winds. Table 2 summaries these observations.
There were few observations near the central core. Canadian buoy 44137
reported winds 160/39 kt with a pressure of 979.1 mb at 0200 UTC 29 October,
which is the basis for the lowest pressure. Other reports from this buoy
indicate that the winds increased in the last hour before the center passed,
suggesting that some kind of inner wind maximum was present even as the
storm was becoming extratropical. Earlier, a drifting buoy about 35 n mi
southeast of the center reported a pressure of 996.6 mb at 2051 UTC 27
October, which showed that the storm had begun to deepen.
Sable Island, Nova Scotia, reported a pressure of 980.6 mb as the center
passed over at 0600 UTC on the 29th. Maximum sustained winds were
35 kt after the center passage at 0700 and 0800 UTC. Several other stations
in eastern Nova Scotia and southwestern Newfoundland reported sustained
35-50 kt winds around 1200 UTC on the 29th.
The maximum intensity of this system is uncertain. Satellite intensity
estimates late on the 28th and early on the 29th along
with a 35-40 kt forward motion indicate the possibility of 65-75 kt
sustained winds. However, this is not supported by surface observations
near the center early on the 29th. The maximum intensity is
estimated to have been 55 kt.
c. Casualty and damage statistics
No reports of casualties or damage have been received at the National
Hurricane Center (NHC).
d. Forecast and warning critique
No advisories were written on this storm, as a decision was made
operationally to handle it in marine forecasts as an extratropical storm.
Post-analysis of satellite imagery and of 27 October aircraft data are the
basis for classifying the system now as subtropical. Due to the operational
handling, there are no formal NHC forecasts to verify. Large-scale
numerical models generally performed well in forecasting the genesis and
motion of this cyclone. The models did mostly underestimate the
intensification that occurred north of the Gulf Stream. However, this
strengthening was fairly well forecast by the GFDL model.
No tropical cyclone watches or warnings were issued for this storm. Marine
gale and storm warnings were issued in high seas and offshore forecasts from
Marine Prediction Center and the TAFB of the TPC. Gale warnings were also
issued for portions of the North Carolina coastal waters by local National
Weather Service offices.
Miller, D. W and M. A. Lander, 1997: Intensity estimation of tropical
cyclones during extratropical transition. JTWC/SATOPSTN-97/002, Joint
Typhoon Warning Center/Satellite Operations, Nimitz Hill, Guam, 9 pp.
Best track, Subtropical Storm, 25-29 October 2000.
|Lat. (°N)||Lon. (°W)
|25 / 0000||21.5|| 69.5||1009|| 30|| extratropical low|
|25 / 0600||22.5|| 70.0||1007|| 35||extratropical gale|
|25 / 1200||23.5|| 70.9||1006|| 35||"|
|25 / 1800||24.5|| 71.7||1005|| 35||subtropical storm|
|26 / 0000||25.7|| 71.7||1004|| 35||"|
|26 / 0600||26.6|| 71.7|| 1003|| 35||"|
|26 / 1200||27.4|| 71.8|| 1002|| 40||"|
|26 / 1800||28.3|| 72.1|| 1000|| 45||"|
|27 / 0000||29.2|| 72.5|| 997|| 50||"|
|27 / 0600||30.0|| 72.6|| 997||50||"|
|27 / 1200||30.9|| 72.5|| 997||50||"|
|27 / 1800||32.6|| 71.6|| 996||50||"|
|28 / 0000||34.2|| 70.7|| 994||50||"|
|28 / 0600||35.7|| 69.9|| 992||50||"|
|28 / 1200||36.5|| 68.1|| 990|| 50||"|
|28 / 1800||38.0|| 65.5|| 984|| 55||"|
|29 / 0000||40.5|| 62.6|| 978|| 55||"|
|29 / 0600||44.0|| 60.0|| 980|| 50||extratropical|
|29 / 1200||46.0|| 59.5|| 992|| 45||"|
|29 / 1800|| ||absorbed into larger extratropical low|
|29 / 0200||41.7||61.6||976||55||minimum pressure|
Selected ship and buoy observations of subtropical storm or greater winds
associated with the subtropical storm, 25-29 October 2000.
|Dock Express 20||25/1200||27.0||68.9||050/45||1009.0|
|Splendour of the Seas||25/1800||28.6||65.2||070/40||1015.0|
a 8 minute average wind
b 10 minute average wind
Best track for the subtropical storm, 25-29 October 2000.
Best track minimum central pressure curve for the subtropical storm, 25-29
Best track maximum sustained 1-minute 10 meter wind speed curve for the
subtropical storm, 25-29 October 2000. Vertical black bars denote wind
ranges in subtropical and extratropical satellite intensity estimates.