Alert Patches Rain Radar

The Weipa radar is situated at Weipa Airport, approximately 7.5km southeast of the township of Weipa at a height of 44m above mean sea level and 25m above ground level. The radar has good visibility in most directions and is able to detect precipitation from the Torres Strait in the north, the northeastern Gulf of Carpentaria, and to Pompuraaw in the south. Coverage to the east toward Lockhart River is somewhat reduced due to the intervening terrain, but tropical cyclones in the Coral Sea are still detectable. In optimal conditions coverage may extend as far as 250km from the radar, and possibly further out to sea for distant tropical cyclones. The radar is well sited to detect tropical cyclones over the northeastern Gulf of Carpentaria, and track thunderstorms approaching Weipa and the RAAF Base Scherger from inland parts. The Doppler capability provides enhanced detection of the potential for damaging winds from thunderstorms, and can also detect wind changes such as sea breezes. During windy conditions and rough seas, the Doppler radar output can be affected by 'sea clutter' (radar reflections from waves) as the sea surface reflects 'side lobes' (less powerful beams away from the main radar beam) of the radar beam, though echoes from actual precipitation are usually discernible in animated image loops. Large ships may also occasionally appear in radar images as moving arcs of reflectivity. Heavy rain over the radar site may on very rare occasions cause attenuation (reduced strength) of all signals. Path attenuation can also occur when the radar beam passes through an intense thunderstorm cell, reducing the returned signal from cells further along that path. When rain from cloud bands does not reach the ground (known as virga) there may be indications of rainfall that appears to dissipate as it approaches the radar. Apart from these limitations, the radar gives a generally good representation of rainfall intensity and highly reliable detection of severe weather threats. <a