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Uses of This Data
Twentieth century tracks were analyzed in this study (1901-2000). For a climatology of this magnitude, the effort so far simply represents a good first start. In all cases, the law of diminishing returns is at work with increasing effort required to mine older data. The user is cautioned that track information during the first half of the 20th century should be used with caution. Two events are generally considered to be significant in increasing the quality of the archived storm information. The first was the initiation of reconnaissance flights in 1944 (http://www.hurricanehunters.com/). The second was the introduction of weather satellites beginning with Tiros-1 launched April 1, 1960. As a result, a separate climatology for the period of 1951-2000 has been included.
There are other known deficiencies in the official archive as well. An Atlantic hurricane dataset is underway in the United States and will likely continue for many years to come. Accordingly, we will hold off updating the Canadian climatology until that reanalysis is complete. Meanwhile, the climatology of impacts is an ongoing work-in-progress as it employs proxy and anecdotal data sets and it will be updated as information becomes available.
The "Best Tracks" file, as it existed in April 2002, is used in this project. Accordingly, some aspects of this climatology are already outdated as a result of the ongoing nature of the reanalysis project. The 2002 and 2003 storms depicted in the land-falling hurricanes, as well as the track maps, were extracted from the spring 2004 release of HURDAT.
Track statistics were developed using the Mapinfo© desktop mapping package. In order to utilize Mapinfo©, the NHC "Best Tracks" database had to be ported to a compatible format. This was accomplished via a Visual Basic .NET© program written specifically for the purpose. The resulting Mapinfo© hurricane database uses multiple line segments to represent each storm track. The segments can be displayed geographically on a map background. Storm details (date, time, storm name, wind speed, etc.) are internally tied to each line segment. Thus, a line segment represents all the archived NHC data for a six-hour period during the event. See Figure 1.
An initial Mapinfo© geographic database query was conducted for each area of interest.
Example: all line segments that touched or entered a geographical area such as the East Scotian Slope marine forecast area were extracted. See Figure 2.
Structured Query Language commands were used to calculate storm frequencies from the initial selection of storms.
Frequently a given storm might have more than one line segment transiting the area (the storm took more than 6 hours to move through). The segment with the highest maximum sustained wind speed was used to calculate storm frequencies (first occurrence). In other words, data from only one line segment per storm was used in the wind summary statistics. For example, three different storms with Saffir-Simpson 2 strength (SS2) are found within the area.
Figure 2: Storms track segments passing through the Laurentian Fan marine area and within a 75 nautical mile radius of Fredericton, New Brunswick
Over the 50 or 100 year period, three unique storms reached SS2 intensity while crossing the area. Note that the exact positions of the storms is not contained in this study... the storms could have touched the boundary or passed directly through the middle of the area.
Storm Translation Speed
Storm translation speed is not directly contained in the NHC archive. This information was calculated within Mapinfo© by extracting the line length in nautical miles, then dividing by 6 (hours) to obtain the speed in knots.
Saffir-Simpson (SS) Scale
The Saffir-Simpson scale is not directly contained in the NHC archive. These numbers were calculated from the archived maximum wind speed. See the next section of the wind speed ranges associated with the scale levels.
The SS value was calculated regardless of the stage of development of the storm... it was applied to tropical storms and hurricanes as well as storms deemed to be extratropical or subtropical.
The following abbreviations are used in the summary statistics tables throughout this document.
|TD||Tropical Depression||< 34||< 63||< 39|
|SS1 (or S1)||Saffir-Simpson 1||64-82||119-153||74-95|
|SS2 (or S2)||Saffir-Simpson 2||83-95||154-177||96-110|
|SS3 (or S3)||Saffir-Simpson 3||96-113||178-209||111-130|
|SS4 (or S4)||Saffir-Simpson 4||114-135||210-251||131-155|
|SS5 (or S5)||Saffir-Simpson 5||>135||>251||>155|
|Less Than Hurricane||<64||<117||<74|
|ALL||Count of all tropical storms moving through the area, regardless of wind strength|
|Avg Sys Spd (kts)|
|The average system or translation speed of the storm in knots|
*1.0 knot= 1.1516 mph = 0.5148 m/s = 1.853 km/h
All times are in UTC (UniversalCoordinated Time) (previously called GMT(Greenwich Mean Time)). There is a 4-hour time difference between Atlantic Standard Time and UTC.
Example: 20:00 or 8:00 p.m.AST = 0000 UTC (the beginning of a new day).
Through much of the hurricane season, Atlantic Canada is operating on Daylight Savings Time, a 3-hour time difference is applicable in this case and the new UTC day begins at 21:00 or 9:00 p.m. ADT.
Interpretation of the Storm Frequency Tables
The numbers found in the frequency tables that follow are a count of each unique storm to cross a given area. For example, over the Canadian Hurricane Centre Response Zone the following 100 and 50 year statistics were generated:
Expanded Table Layout
All = 351: 351 unique storms touched or crossed the area during the 100 year period. The count is not based upon the storm intensity as it moved through the area… A tropical depression counts as one as does a force 3 hurricane.
S1 = 89: 89 distinct storms of Saffir-Simpson strength 1 transited the area during the 100 year study period. These 89 storms would be included in the 'All' value above.
Explanation of the Storm Table Listings
Detailed storm information is provided at the end of each section. The data is provided as a tabular listing and generally has the following columns:
|Gladys||Oct 21, 1968||8||65||SS1||25.0||975||E||Neutral|
Interpretation of the Frequency by Time Graphs
Numbers shown on some graphs may vary somewhat from the tabular storm listings. The storm details tables show the date on which the first occurrence of the highest wind was reported. A storm may have taken more than 6 hours to cross a given area. Thus it is possible to show more storms for say September 15 on the frequency by day table than are shown in the storm details table. (example: a storm reaches the area late on the September 14, with 50 knots maximum sustained wind--it is still over the area on September 15 but with 40 knot winds. It counts as both a September 14 and a September 15 storm on the frequency by day table but the storm details table will show on the 14th since that is the date of maximum wind.)
Frequently Used Terms and Names
- MapInfo: MapInfo© Corporation, One Global View, Troy, New York 12180
- Visual Basic: Visual Basic© Microsoft Corporation, 1 Microsoft Way, Redmond, WA 98052
- Translation Speed: Speed of the storm center with respect to the land or ocean... not to be confused with the storm's maximum sustained wind speed which is contained in the official archive.
- Saffir-Simpson Scale: The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale. (http://www.nhc.noaa.gov/aboutsshs.html)
- Extratropical: A term used in advisories and tropical summaries to indicate that a cyclone has lost its "tropical" characteristics. The term implies both poleward displacement of the cyclone and the conversion of the cyclone's primary energy source from the release of latent heat of condensation to baroclinic (the temperature contrast between warm and cold air masses) processes. It is important to note that cyclones can become extratropical and still retain winds of hurricane or tropical storm force. (http://www.nhc.noaa.gov/aboutgloss.html) Most storms of tropical origin are becoming extra tropical as they enter Canada's land or offshore areas. The storms are moving from very warm ocean areas to land or cold water and their energy source is being lost.
- Subtropical Cyclone: A non-frontal low pressure system that has characteristics of both tropical and extratropical cyclones. The most common type is an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center. In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center, and typically have a less symmetric wind field and distribution of convection. A second type of subtropical cyclone is a mesoscale low originating in or near a frontolyzing zone of horizontal wind shear, with radius of maximum sustained winds generally less than 30 miles. The entire circulation may initially have a diameter of less than 100 miles. These generally short-lived systems may be either cold core or warm core. (http://www.nhc.noaa.gov/aboutgloss.shtml)
- Tropical Cyclone: A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects). (http://www.nhc.noaa.gov/aboutgloss.shtml)
- Gale: Canadian marine warning definition for mid-latitude storms
- Storm: Canadian marine warning definition for mid-latitude storms
- System Translation Speeds: The average of the system translation speeds for all storms that crossed the area or grid cell. If a storm took more than 6 hours to transit the cell, then all of its 6 hour translation speeds were used in the average. The structure of the Mapinfo© database is such that the last report for a given storm will be represented geographically by a zero length line or point and the resulting translation speed will be reduced to zero. Inclusion of these false speeds would yield incorrect averages and they were excluded. Value is in knots.
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