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Seasonal Overview (top left)
The top left panel shows an overview of the year's tropical cyclone activity in
the North Atlantic to date, including any currently active storms. Also provided
are some general statistics for the "expected" number of tropical cyclones by the
end of an "average" season, as well as the expected number of tropical cyclones
by the current date in an average season. Abbreviations used are as follows:
- TS – Tropical storms
- HU – Hurricanes
- HU Minor – Hurricanes of Category 1-2 on the Saffir-Simpson Hurricane Wind Scale
- HU Major – Hurricanes of Category 3-5 on the Saffir-Simpson Hurricane Wind Scale
Also shown is the accumulated cyclone energy (ACE) index, another frequently-used
measure of seasonal activity. While ACE can be calculated for individual storms,
the ACE index provided in AIR's ClimateCast for the Atlantic represents the sum—across
all tropical cyclones during the season—of the energy used, taking into account
both the intensity and duration of each storm. Generally, an above-average season
can be defined as ACE >103, and a below-normal season as ACE < 66. Like the
tropical cyclone counts, ACE is provided for the current season to date, as well
as for the average season (i.e. climatology)—both overall and up to the current
date in an average season.
Sea-Surface Temperatures (top right)
The map in the top right panel shows current sea-surface temperatures (SST) anomalies.
These shaded areas indicate where SSTs are either warmer or cooler than the long
term average (climatology). Anomalously warm conditions can support activity over
and above levels expected based on long-term averages. The colored contours show
actual current SSTs. Areas of the ocean south of the dark blue contour (26.5°C)
represent a rough estimate of those regions that can support strong, deep convection
and thus tropical cyclone development. Note that current SSTs are also shown as
shaded areas in the Steering Currents map immediately below.
Wind Shear Conditions (bottom left)
The figure on the bottom left shows the current vertical wind shear between about
1km and 10km altitude. Elevated vertical wind shear conditions (10 m/s or greater)
can disrupt the overall structure of the hurricane. Strong wind shear can impede
cyclone formation or weaken an existing storm. Thus, in the figure, low shear (shaded
in reds) indicates regions where tropical storms could potentially exist or intensify,
and high shear (shaded in blues) indicates regions where environmental conditions
may inhibit further development.
Steering Currents (bottom right)
The bottom right figure shows, in contours, the 'stream function' at 500mb overlaid
on current SSTs. The stream function can be interpreted as the steering flow of
the atmosphere, thus indicating the direction in which a tropical cyclone is likely
to be headed. The steering flow is fastest where the contours are tightly packed
together and slowest where they are far apart. Red contours surround high pressure
centers, such as around the Bermuda High, a common summertime feature.
On each of these environmental condition maps is also shown the latest observed
and forecast tracks, including the cones of uncertainty, of any currently-active
tropical cyclones. Note that the cones of uncertainty indicate possible areas of
at least tropical storm-force winds over the next 3 and 5 days. Also note, the cone
of uncertainty indicates the region over which active storms may potentially track,
but the environmental conditions in place currently (SSTs, shear, steering) are
susceptible to change over the coming 1 to 5 days. In other words, the conditions
contained in the cone of uncertainty are current conditions, not conditions forecast
once the storm reaches a forecast location. The steering and wind shear conditions
are most likely to change in the coming 1 to 5 days, whereas the SSTs and SST anomalies
are more persistent—and indeed may persist for several days and even weeks to come.
The data used in the production of AIR's ClimateCast® Atlantic Real-Time Advisory
comes from the official government agencies charged with producing and distributing
real-time weather and emergency management services, including the National Hurricane
Center (NHC), the National Centers for Environmental Prediction (NCEP), and the
Climate Diagnostics Center (CDC)—all part of the National Oceanic and Atmospheric
Administration (NOAA).
Contact the ClimateCast® Team
AIR is actively engaged in climate research tied not only to real-time risk assessment,
but also to other often-discussed topics such as the impact of warming ocean temperatures,
climate change projections, and the implications of climate change for risk management.
This research will ultimately lead to further enhancements and refinements in the
ClimateCast suite of risk assessment tools. In the end, it is feedback from users
that guides the improvements that will make ClimateCast more directly applicable
to the catastrophe risk management process. We therefore encourage you to contact
AIR Worldwide at climatecast@air-worldwide.com with comments and suggestions,
and with thoughts about how the tools can be used to improve day-to-day decision
making.
If you have technical or business-related questions pertaining to this or other
ClimateCast® products, please contact your AIR representative. You can learn more
about AIR and its modeling and risk assessment products and services by visiting
our website at http://www.air-worldwide.com
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