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Tropical Cyclone Diagrams - new TCs

Tropical storm strike probability charts.

Charts are available to show the potential tropical cyclone activity at different time ranges throughout the forecast.  They encompass both tropical cyclones that are present at analysis time and those that come into existence during the forecast.  These are an experimental product in which TC assignation, for cyclonic features, is based on identifying a warm core. 

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See Tropical Cyclone Products for existing TCs for more detailed products for officially observed (by a Regional Specialized Meteorological Center (RSMC)) tropical cyclones.

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Fig8.1.16.2-1: To view tropical cyclone activity:

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• all tropical cyclones (wind speeds >8m/s),
• tropical storms (wind speeds >17 m/s),
• hurricanes/typhoons (wind speeds > 32m/s). 

Web charts

Tropical storms are identified by the existence of a warm core isobaric depression.  The charts show the probability of the passage of storms identified in this way (some possibly not yet developed) within a 300km radius of a given location. 

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 Fig8.1.16.2-2  Tropical storm strike probability chart from ensemble data time 12UTC 28 February 2017.  This indicates the probability of the passage of storms (some possibly not yet developed) within a 300km radius, between 9 and 11 days ahead (during the 48hr period between 12UTC 8 March and 12UTC 10 March 2017).   The western storm passed across Madagascar as intense tropical depression ENAWO before weakening by the time of the chart.  The central storm became a tropical depression 07S passing just east of Madagascar.   The north-eastern storm developed a wind circulation near 90E but didn't reach tropical storm status.   These developments are reflected in the probabilities shown on the chart, though of course this will not always be the case.  Probabilities given by colours in the scale.

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Fig8.1.16.2-3: Examples of spurious indication of tropical storm strike probability in NE Atlantic.  The technique has incorrectly identified a high-latitude well-occluded frontal depression as being a tropical cyclone.

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Strike probability charts for a sequence of forecast lead-times clearly indicates the forecast probabilities of development of a tropical cyclone, storm or hurricane.  The example below (Fig8.1.16.2-4) shows the probability of a tropical system near northeast Australia.  Selection of tropical storms, tropical cyclones or hurricanes from the tab at the top of the display allows investigation of the evolution and forecast intensity of the tropical system.

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Fig8.1.16.2-4: Web charts tropical storm strike probability charts from ensemble probability charts data time 12UTC 03 January 2018 verifying at  T+144 (12UTC 09 January 2018) and T+192 (verifying 12UTC on 11 January 2018).   Forecast from ensemble, data time 00UTC 8 January 2018.    The charts show probabilities associated with tropical storm force winds indicated to increase from a weaker pre-existing tropical cyclone near the northwest coast of Australia.

ecCharts

Tropical cyclone, tropical storm, and hurricane strike probability charts are also available on ecCharts.  These are an experimental product based upon identification of the warm-core circulation during the forecast period.  They are useful during and after extra-tropical transition of these features as they move into mid-latitudes.  ecCharts have the advantage that boundary layer (or any other) winds can be superimposed.

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Fig8.1.16.2-5: ecChart tropical storm strike probability chart from ensemble with 100m winds (m/s) from HRES for T+96 verifying at 00UTC 12 January 2018.  Forecast from ensemble, data time 00UTC 8 January 2018.  With effect from Cy49r1, HRES

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