Recent scrutiny has been directed at the Hong Kong Observatory (HKO) concerning the transparency and communication surrounding its tropical cyclone warning decisions. A watchdog has urged the meteorological body to improve how it explains the rationale behind issuing specific typhoon signals. This call for enhanced clarity comes as the city navigates its typhoon season, a period that typically runs from May to early November, bringing with it potential disruptions.
The core issue appears to be a perceived lack of detailed explanation for the elevation or maintenance of particular warning signals. While the HKO issues various signals—ranging from Signal No. 1 indicating a tropical cyclone within 800km to Signal No. 10 signifying gale or hurricane-force winds—the exact triggers and the Observatory's reasoning are not always explicitly articulated in a way that satisfies all observers. This opacity can lead to public confusion or questioning, particularly during significant weather events.
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Typhoon Signal Breakdown
Hong Kong employs a tiered system of tropical cyclone warning signals, each corresponding to a specific threat level:
Signal No. 1 (T1): Issued when a tropical cyclone is centered about 800 kilometers from Hong Kong and may affect the territory. This is the lowest warning level.
Signal No. 3: Indicates that a tropical cyclone is expected to affect Hong Kong within the next 12 hours. Local winds are noted to pick up progressively.
Increasing Gale or Storm Signal (No. 9): Signals that gale or hurricane-force winds are increasing or are expected to increase significantly.
Signal No. 8 (various directions): Warns of imminent threats from a typhoon with strong winds expected to affect Hong Kong. This signal implies gale or storm force winds blowing near sea level, with potential gusts exceeding 180 km/h.
Signal No. 10: The highest warning, signifying that winds with mean speeds of 118 km/h or more are expected.
Beyond typhoon signals, the HKO also issues other warnings, including the Strong Monsoon Signal (for winds at or exceeding 40km/h) and various rainstorm warnings (Amber, Red, and Black).
Context and Recent Events
The calls for better explanation emerge against a backdrop of past typhoon events. For instance, 'Tropical Storm Tapah' prompted the HKO to mention it may consider issuing higher signals, while also stating the Strong Wind Signal No. 3 would remain for most of the day, with forecasts of heavy squally showers on Monday and Tuesday. In another instance, 'Super Typhoon Ragasa' led to the issuance of a No. 10 warning, causing a city-wide standstill, before being downgraded. Similarly, 'Typhoon Wipha' saw the No. 10 signal in force for about seven hours, followed by a No. 9 signal and then a No. 3 alert.
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The HKO maintains extensive databases and educational materials detailing its warning system and historical cyclone data, accessible via its official website. These resources are intended to inform the public about tropical cyclones and the Observatory's operational procedures.
