2006 Central Pacific cyclone

The 2006 Central Pacific cyclone, also called 91C.INVEST or Storm 91C, was a strange weather event in 2006. Forming on October 30 from a mid-latitude cyclone in the north Pacific mid-latitudes, it moved over waters warmer-than-normal. It got some characteristics more normal for subtropical or even tropical cyclones. However, as it came closer to western North America, it fell apart. Moisture from its remains then caused a lot of rainfall in British Columbia.

Storm history
A cut-off extratropical cyclone over the central north Pacific moved into a place with sea surface temperatures as high as 2 °C above normal for two days.  By October 31 the system had gotton convection, a warmer-than-normal core, and an eye-like characteristic.  During this time it had moved east, then northeast, and then northwest.

On November 1, the system had estimated winds of 100 km/h (60 mph) and its most developed convection. After that, it slowly weakened, moved counter-clockwise, and headed east towards the west coast of North America. On November 2, wind shear started affecting the storm, and all convection was gone by the next day, when it was located roughly 520 mi (840 km) off the coast of Oregon.

This system's center of circulation passed south of observation buoy 46637 on November 1. The buoy's lowest pressure reading was 989 mb/hPa. Other buoys indicated that a rather large area of low pressure was associated with the system. Buoy 46637 was not at the system's center of circulation, so it is possible that this system had a lower minimum pressure than was actually measured.

Impact, preparation, and records
As a result, to the weather system, the American National Weather Service gave out wind watches for the Oregon Coast.  The system brought heavy rain to parts of Vancouver Island.

If Storm 91C is really a tropical or subtropical cyclone, it has several records. Since right now it is not officially either, its holding these records is also unofficial. Because the storm formed at 36°N, this system is the northernmost formation in the eastern north Pacific basin. The previous record-holder was Tropical Storm Wene, which formed at 32°N before crossing the dateline.  In addition, this system's track data shows that it crossed from the central to the east Pacific because it formed at longitude 149°W and dissipated at 135°W.  Only two other known tropical cyclones had done that before.

Nature of the system

This system has been thought to be a tropical, subtropical, or extratropical cyclone.

Mark Guishard, a meteorologist with Bermuda Weather Service, had the opinion that the system had finished tropical cyclogenesis and was a tropical cyclone. Meteorologist Mark Lander thought that cloud tops were similar to several Atlantic hurricanes, Hurricane Vince in example. James Franklin, a meteorologist at the National Hurricane Center, thought that:

The system was of frontal origin... the frontal structure was eventually lost.... The convective structure resembled a tropical, rather than subtropical cyclone, and the radius of maximum winds (based on QuikSCAT) was very close to the center, also more typical of tropical cyclones... on balance, it was more tropical than subtropical.

Clark Evans of Florida State University reported that forecasting tools showed that the system's structure was same with that of a subtropical or barely tropical cyclone. NASA, which is not a meteorological agency, thought that the system was a subtropical cyclone.

In its review of the 2006 Atlantic hurricane season, the Canadian Hurricane Centre said that the storm was to be an extratropical cyclone.  Since this system had one-minute sustained winds of 100 km/h (60 mi/h), which are above the 60 km/h (39 mi/h) boundary between a depression and a storm, it would be able to be a named storm if it was a tropical or subtropical cyclone. However, neither of the official Regional Specialized Meteorological Centers for the eastern north Pacific, the National Hurricane Center and the Central Pacific Hurricane Centre, include this system in their yearly archives, nor is it included in the official "best track" file.  So this system is not an official tropical or subtropical cyclone of the 2006 Pacific hurricane season.

References

Other websites

 Unofficial track data

2006 in weather
Tropical cyclones in North America
Hurricanes in the United States
2006 in North America