Thought it might be an to idea keep these in one thread for a calendar year. Currently threatening the NE Australian coast is Cyclone Debbie (13P). One minute wind speeds of 105 kts. Gusts to 130. Due to reach land in the next few hours.
Hope all everyone including the Irish will be OK.
Not sure how accurate that JTWC advisory is now, as the Australian Bureau of Meteorology are indicating a maximum 10 minute wind speed of 95 kts with gusts to 130. Pretty strong. Daylight now in eastern Australia. The eye has yet to come onshore.
Local radar image. Distinct eye feature can be seen.
10-minute mean speeds will always be lower than 1-minute. That's why pound for pound, a 100-knot typhoon is stronger than a 100-knot hurricane because the typhoon's 100 knots are measured over 10 minutes whereas the NHS use 1-minute mean speeds.
YBHM 272248Z AUTO 12093G118KT 0150 // OVC008 32/32 Q0974= (SPECI)
YBHM 272246Z AUTO 12092G118KT 0150 // OVC008 31/31 Q0972= (SPECI)
YBHM 272233Z AUTO 12093G105KT 0250 // BKN008 OVC012 31/31 Q0973= (SPECI)
YBHM 272230Z AUTO 12079G116KT 0300 // BKN008 OVC012 30/30 Q////= (SPECI)
YBHM 272227Z AUTO 12081G116KT 0300 // BKN008 OVC012 31/31 Q0975= (SPECI)
YBHM 272215Z AUTO 12097G120KT 0250 // SCT006 OVC012 29/29 Q0975= (SPECI)
YBHM 272212Z AUTO 12086G120KT 0300 // SCT006 OVC012 26/26 Q0974= (SPECI)
YBHM 272200Z AUTO 13086G104KT 0200 // SCT005 SCT008 OVC012 26/26
It may have formed in open water, well away from any human habitation, but Sub-Tropical Depression One has already made a name for itself.
It shows on satellite imagery as a swirling mass of thunderstorms, located about 1,170km to the westsouthwest of The Azores. It has sustained winds of 55 kilometres per hour (km/h) and it is heading towards the north at 22km/h.
Such low pressure systems are usually confined to the hurricane season, which runs from June 1 to November 30. This depression seems to have beaten the odds, becoming only the fourth such depression recorded in the Atlantic, according to NOAA's Historical Hurricane Track website.
The formation of these tropical or sub-tropical lows usually requires sea surface temperatures (SSTs) of at least 26.5C. Currently, SSTs in the region are only 20C, and the disruptive effects of wind shear (the change of wind speed and direction with height) are quite high.
This depression seems to have sustained itself because of the very cold air extending through the atmosphere, which has supplied the atmospheric instability for thunderstorm formation, required for One's classification.
Only one of the previous April depressions - Tropical Storm Ana in 2003 - went on to become a named storm.
It is possible for systems to develop into full-blown storms outside the hurricane season. This happened in 2016, with Hurricane Alex in January and Tropical Storm Bonnie in May.
There are many state and private organisations that issue predictions of the coming hurricane season. The general consensus seems to be that activity will be slightly below average, with a total of 11 to 12 named storms, four to six hurricanes, and between zero and three major hurricanes.
It is unlikely that Sub-Tropical Depression One is going to cause any revision of the forecasts. If SSTs had been well above average, then that might have been a different matter. But seasonal hurricane forecasting is still in its relative infancy, so forecasters will be closely monitoring the situation in the Atlantic in the weeks ahead.
Source: Al Jazeera and news agencies