The reports here summarise weather events and climate news, including a round-up of their media coverage. They are archived in the relevant day's Daily Weather Summary to help make it a more complete record of the day's events. Timeliness of the reports is entirely at the mercy of my available time so, for the most up-to-date information, make good use of my media links here.
Near stationary Dorian continues to lash Grand Bahama island
Tue 3 Sep 2019
Hurricane Dorian will be remembered for the long period it has remained nearly stationary over the northern Bahaman island of Grand Bahama. It made landfall at Elbow Cay, 170km east of the city of Freeport, the island's largest settlement, at 02.40 AEST 2 September and at 21.40 AEST this evening, 43 hours later, it had moved only 160km to lie 40km NNE of Freeport. For much of this time it remained stationary over central Grand Bahama with one-minute sustained winds initially 270km/h gradually dropping to 200km/h and central pressure rising to 950hPa as the hurricane diminished from Category 5 to Category 3. Today's SMH gave a good explainer of why the hurricane has come to a virtual halt‡ - in short, because steering currents in its vicinity are non-existent.
The Tribune in the Bahamas published this extraordinary video taken from a well-prepared house at Pine Bay in central Grand Bahama. It gives a feel for what it is like to live through what at that stage was a Category 4 hurricane in a house built up on 4.5m stilts with the storm surge lapping the floor boards. Taken about the same time, this video shows the Freeport International Airport, barely distinguishable from the surrounding ocean below a 7m storm surge with waves on top of that. Much of Grand Bahama Island is less than 10m above sea level.
Bahaman police have confirmed that five people have died so far, but with the hurricane still raging it will be some days before all areas have been accounted for. The same applies to an initial estimate by the International Red Cross of 13,000 homes destroyed or badly damaged across the Abacos and Grand Bahama islands. Power, water and roads have been cut and airports in the northern Bahamas closed.
In its 19.00 AEST Forecast Discussion, the National Hurricane Center noted that Dorian's eyewall was becoming less defined, the deep thunderclouds surrounding it were beginning to fragment and upper-level outflow in the western half of the hurricane was becoming more restricted. They expected it to maintain intensity for about 36 hours before gradually weakening as it accelerates northwards, parallel to the US coast. The NHC retain their warning that users of the track forecast "are reminded not to forecast on the exact forecast track. A relatively small deviation to the left of this track could bring the core of the hurricane near or over the coastline."
Category 5 Hurricane Dorian pounds northern Bahamas, threatens east coast of USA
Mon 2 Sep 2019 2019
| Category 5 Hurricane Dorian runs west along the island of Grand Bahama at 23.22 AEST today. Look carefully into the eye and you can see a whitish (warmer, so lower level) inner eye and circulations. The eye is slightly deformed due to Dorian's interaction with the island. While the hurricane's track has been difficult to predict because of a very stagnant upper air situation, the National Hurricane Center believes it will curve to the NW before skirting the US coast all the way from Florida to the Carolinas. NOAA via Tropical Tidbits.
This is Hurricane Dorian at 23.22 EST (09.22 local time) which had almost come to a halt over central Grand Bahama island, just NE of the city of Freeport. It is a truly monstrous storm. It developed in the central Atlantic on 24 August, reached hurricane strength on the 28th and reached Category 5 intensity yesterday 1 September. As it made landfall at Elbow Cay, just east of Great Abaco Island to the east of Grand Bahama, it bottomed at a pressure of 910hPa with sustained 1-minute winds of 295km/h.
Hurricane Dorian has tied with Hurricanes Wilma (2005), Gilbert (1988) and the "Labor Day" Hurricane of 1935 as having the second strongest 1-minute sustained winds in the Atlantic in the modern record. Hurricane Allen in 1980 had the strongest at 305km/h. Dorian ties with the "Cuba" Hurricane of 1924 as having the fifth-lowest Atlantic hurricane central pressure at landfall; the "Labor Day" Hurricane has the record for that with 892hPa while Wilma holds the record for the lowest pressure over the open Atlantic of 882hPa.
As the satellite image shows, Dorian has an extremely well-defined eye nearly 40km in diameter. The eye is slightly deformed as it has encountered friction over the island, and an inner eyewall has formed somewhat lowering sustained winds to 270km/h with gusts to 320km/h. Storm surges of 5.5 to 7m are expected and have occurred if this video from Bahama's The Tribune can be independently verified. The video was carried in this NBC news story giving what was then known about the northern Bahamas and shows a house-high storm surge on Great Abaco. The Tribune* is running live updates on the hurricane, though the devastation will mean that it will be days before a detailed picture of damage and people's survival emerges.
The National Hurricane Center (NHC), in its 05.00 local time (19.00 AEST) Forecast Discussion said that the currents steering the hurricane have weakened to the point where it is almost at a standstill over the eastern Grand Bahama Island, moving westward at best at 2km/h. The forecast upper situation is most likely to slowly steer Dorian to the NW then N before accelerating to the NE, a track which would cause it to move parallel to the east coast of the United States. The NHC adds "Although the official forecast [track] does not show Dorian making landfall along the Florida east coast, it is still possible for the hurricane to deviate from this forecast, and move very near or over the coast. Users are reminded not to focus on the exact forecast track."
Coastal evacuations are taking place in Florida and Georgia, and the Carolinas are next in line. The Guardian is running live updates* which is a good place to keep abreast of general developments and impacts, while the National Hurricane Center page* has the latest forecasts for Dorian down below the map. The Forecast Discussion is best if you can cope with a little technical information. For forecast tracks, model forecasts and satellite images updated every 5 minutes* go to Tropical Tidbits who also give a good detailed commentary* updated regularly.
NSW: Heavy rain, storms hit Central Coast
Sat 31 Aug 2019
On Friday 29 August an upper cold pool moved from inland NSW across the Hunter Valley and Mid North Coast. This created an offshore trough that swung moist southeasterlies and rain onto the Illawarra and Central Coasts. On the coastal side of the trough, convergence lines formed where winds from slightly different directions meet and, having nowhere else to go, have to rise producing rain. The instability caused by the cold upper temperatures made sure this rain was heavy.
With the system virtually stationary, some of these convergence lines sat over the same places for hours and, in the case of the Central Coast, for over a day before moving very slowly northwards. The Gosford area saw the heaviest falls. In the 2 days ended 09.00 today, Gosford AWS recorded 198mm, Kangy Angy to its north 200, and East Gosford 193, Ettalong 192 and Kincumber 181. The southern Newcastle suburb of Blacksmiths recorded 181 while Wyoming on the Lower Hawkesbury River had 184mm and Mangrove Mountain 168. Most gauges from the Hawkesbury to southern Lake Macquarie had over 150mm. Some areas had their heaviest two-day falls in over three years.
In Sydney, rain graded from heavy on the coast and North Shore to light in the west. Falls were generally between 50 and 80mm in the east and 20 to 50mm in the west. Highest falls in the 2 days to 09.00 today were 127mm at Wahroonga and Forestville and 117 at Hornsby and Mosman (Spit Bridge), much of it from one convergence line that lodged diagonally across the area. The Wollongong Coast saw falls mostly between 20 and 40mm, but the exposed Bellambi Point managed 77mm.
The upper cold pool caused a massive dump of hail in the Coffs Harbour area as it passed on Friday night. The storm was faithfully captured for Facebook in this video by Coffs Harbour Fishermans Co-op staff, picked up in this article by ABC News. Coffs Harbour gauges picked up 20 to 25mm while Sawtell, 8km to the south, recorded 37mm all in the space of less than an hour before 6pm.
Late start to NT and QLD wet season likely. Fri 30 Aug 2019 If you live in the northern half of Australia, one of the hottest topics of conversation is when will the wet season start. The last of the Bureau of Meteorology's Northern Rainfall Onset Outlooks for the 2019-2020 season was issued yesterday indicating a 70% likelihood that the wet season will have a later start than normal across the Top End and central parts of the NT, Cape York Peninsula and eastern Queensland, and the far north Kimberley in WA. Most of the rest of northern WA is more likely to see an early start, while inland areas of the NT and QLD are more likely to have a slightly later start.
The wet season is defined as starting when 50mm has fallen since 1 September, about the amount needed to stimulate plant growth. The "normal" dates on which the wet season starts are shown on this map, while you can get the detailed Northern Rainfall Onset Outlook here. There's also lots of useful information on this tab.
Rural Bank's Weather Update to end. Fri 30 Aug 2019 For years, popular weather presenter and meteorologist Jane Bunn in association with the Rural Bank has presented a monthly Weather Update on the Bank's website. Specially tailored for farmers, it featured a good summary of the past month's weather along with the BoM's 3-month climate outlook. What set it apart was that separate videos were available for each state.
The last of the Updates has just been published. This is the NSW link, but other states are in the menu at right. In an email, the Bank says "After a very successful partnership providing monthly weather video summaries for farmers, we are looking at other ways to provide relevant weather information." They will have to be good to beat the quality of the Updates.
The BoM's Climate Outlook presentation has improved, but the forecast hasn't
Thu 29 Aug 2019
The Bureau of Meteorology's first upgraded Climate Outlook was released this afternoon with all the improvements mentioned in this earlier blog. You'll find them when you dig into the detailed rainfall and temperature outlooks. The breakdown into weeks for the first month is a major step forward, while the twice-weekly limited updates needed to keep the weekly forecasts current will be very welcome.
As for today's Outlook which covers the whole of spring, the news is less cheery. A positive Indian Ocean Dipole, cool waters in the Indian Ocean NW of Australia and a neutral El Niño-Southern Oscillation pattern mean that the three-month outlook remains strongly tilted to continuing drier and warmer than normal conditions.
The latest Climate Outlook is always here and you can find archives of them here all the way back to 2000. When I clicked the link to the Outlook video, which always contains additional, useful bits of information, I was directed to the BoM's full Youtube channel containing hundreds of videos. The video is here*, but a direct link would have been much better.
Major dry-season conflagrations drive further loss of Amazon rainforest
Wed 28 Aug 2019
| Satellite imagery from all sources of all fires burning during the six hours to 04.00 EST today. Since the start of 2019, NASA's AQUA satellite has identified 179,471 fires across South America, with the most affected countries being Brazil 83,329, Venezuela 26,569, Bolivia 19,111, Colombia 14,336, Argentina 14,280, Paraguay 10,723 and Peru 6,400. The majority of these fires are in the Amazon basin. INPE
The Amazon dry season from August to November has long been the time when spent crops or freshly felled clearances have been burnt off. This year's burning has seen a major increase in numbers of fires compared with recent years, especially in the Amazonas and Rodonia States in W and SW Brazil and in Bolivia. Parts of the Amazon rainforest in Venezuela, Colombia and Peru are also affected.
Brazil's National Institute for Space Research (INPE) data shows more than 75,000 active fires in the country, 84% up on the 2018 figures for the same period according to the BBC. NASA reported that fire detections by its Aqua satellite were the highest since 2010 to this time of year with indications 2019 may be a record for Amazon fires [space.com].
2010 was a year of El Niño-induced severe drought in Brazil, and IPNE figures*† (scroll down to Country Annual Comparative Table and select the Every Year tab) show that in 2010 127,147 fires had been detected in the year to 27 August compared with 83,329 for the same period this year. Drought conditions are not a factor this year which has seen a very mild start to the dry season.
In the era of satellite fire detection since 1998, the only other years of greater fire numbers, again for the 1 January to 27 August period, were 2002 to 2007 when massive deforestation took place. Since then many factors have reduced deforestation including the creation of public lands [Wikipedia]. However, scientists in Brazil are arguing that deforestation is again increasing due to the pro-development policies of the government of Brazilian President Jair Bolsonaro [ScienceMag]. There is certainly no doubt that this highly visible spike in wildfires has focussed the wrath of Western media and politics in particular and gained world-wide condemnation from environmental groups.
Escalating deforestation of the Amazon basin from logging, burning and clearing has been an issue of international concern for many years, since the Amazon rainforest is both a major source of oxygen production and a carbon sink as well as home to indigenous communities. In his weekly address last Sunday 25th, Pope Frances told thousands in St Peter's Square "We are all worried about the vast fires that have developed in the Amazon. Let us pray so that with the commitment of all, they can be put out soon. That lung of forests is vital for our planet” [Reuters]. That would have resonated in Brazil, the world's largest Catholic country.
BoM announces improvements to long-range forecasts and radar service
Fri 23 Aug 2019
From 29 August, there will be major changes to the Bureau of Meteorology's climate outlooks, currently issued twice monthly for the month and three month periods ahead.
The rainfall and temperature outlooks will include additional weekly and fortnightly periods as well as the current monthly and three-monthly periods. The temperature outlooks will also include difference from average maps. The one and two-week outlooks will be updated on Mondays and Thursdays, while the one and three month forecasts will be updated weekly on Thursdays.
From 24 August, all radars will be available to view full-time. Up to now, some radars have split their duties between being available to public view and being used by the BoM to track weather balloons to measure upper atmosphere conditions up to four times a day. The last of these wind-finding radars, including those at Hobart and Perth Airports, Wagga Wagga, Alice Springs, Gove, Broome, Esperance and Norfolk Island, have been upgraded so that they are now available for full-time public weather-watch duties.
Climate indicators stay unchanged on warm and dry into spring
Thu 22 Aug 2019
The Bureau of Meteorology's fortnightly ENSO Wrap-Up, issued on Tuesday, remains stuck on warm, dry conditions to continue for most central and southern areas of the country. With the El Niño-Southern Oscillation (ENSO) still neutral, the mostly positive Indian Ocean Dipole (IOD) is the dominant climatic driver.
The BoM says "All climate models surveyed by the Bureau forecast positive IOD conditions to continue for the southern hemisphere spring. Typically, a positive IOD brings below average winter–spring rainfall to southern and central Australia, above average daytime temperatures for the southern two-thirds of Australia, and increased fire risk in the southeast."
In the north of the country, the Madden-Julian Oscillation (MJO) has been weak and is not expected to produce rain or storms in the next week or two. Waters around northern Australia are cooler than average, which also increase the likelihood longer term of drier than normal conditions.
The current ENSO Wrap-Up is here and the Weekly Tropical Climate Note is here.
NSW, VIC, TAS: Gales and a final front bring high seas, snow and fires to the Southeast
Thu 22 Aug 2019
Updated Fri 23 Aug 2019 23.30 AEST, new information in para 3
The focus of gale to storm-force winds and high seas moved north overnight as the last in a series of cold fronts moved up the NSW coast today. Diabolical conditions continued through Bass Strait and along the VIC and NSW coasts while winds were strong enough in places inland to cause damage.
The main weather stations in and around Bass Strait showed it was not the place to be sailing today. Top gusts reported included Wilsons Promontory 143km/h and Gabo Island 135 on the VIC coast, while out in the Strait, Kingfish B oil-drilling platform 80km off the coast from Lakes Entrance reported 130 and Hogan Island 139km/h. 6329km of air has blown past the anemometer on Hogan Island in the three days to 09.00 today for a three-day average speed of 88km/h.
The Manly Hydraulics Lab waverider buoy, in 90m of water off the Sydney Northern Beaches suburb of North Curl Curl, reported a maximum wave of 13.32m this afternoon, with the highest significant waves (the average of the highest third of waves) reported as 6.28m. Land-based reports indicated 4 to 5m waves on some Sydney beaches in the surf zone. At 10.30, the NSW SES reported it had received 131 call-outs, mainly in the South Coast, Illawarra and Southern Highlands for downed trees, branches and fences but also some buildings unroofed. One of these was Bunnings in Goulburn which lost roofing iron during the evening. More call-outs were expected once the stronger winds with the front hit Sydney. High inland wind gusts included Mallacoota 96km/h and Eildon Fire Tower and Yarram 89 in VIC, and Mt Boyce and High Range 98, Albion Park (Wollongong Airport) and Bombala 93, and Bega 91 in NSW. Full wind details are here and here in the Daily Weather Summary.
Bushfires flared in the strong winds, with the NSW Rural Fire Service reporting 70 fires going at 22.00 today. Only one of these, near Belmont SW of Newcastle, was at Watch and Act status and was affecting traffic on the Pacific Highway. Another fire to its northwest closed the M1 motorway for a period this morning. The rash of fires vindicate the decision by the RFS to declare an early start to the Bushfire Danger Period in 20 Local Government Areas from 1 August.
Wind eased in TAS during the day. Snow was expected to fall as low as 400m overnight into today in southern and highland areas and the northeastern high country with snow easing and levels rising during the day. ABC posted this scene this morning at Mount Field, west of Hobart.
Related media: SMH‡
NSW, VIC, TAS: Strong winds, high seas batter southeastern states
Wed 21 Aug 2019
Gale force winds hit the three southeastern states on Tuesday and Wednesday, with winds over storm force reported at coastal locations. In offshore waters, winds of 70 to 100km/h were forecast to bring 5 to 8m swells onto the NSW coast.
The SW winds are being squeezed between a strong 1035hPa high pressure system over the Bight and a deep 975hPa low SE of Tasmania (see map). This satellite animation from Andrew Miskelly shows the rush of cold air between the two systems like cake mix between the beaters in a Mixmaster, and the long fetch which developed such a large swell. Fronts and troughs in the stream are making for even stronger winds for a few hours as each one passes.
Maatsuyker Island, off Tasmania's South Coast, reported top wind gusts of 146km/h yesterday and 148km/h today with an average speed over the whole 24 hours to 09.00 today of 98km/h. Many coastal locations in TAS, VIC and the islands in Bass Strait saw winds almost as strong. Damaging wind gusts also made their way inland across all three states, with Hobart City recording 120km/h yesterday and Goulburn Airport 100 today. Full lists are in the Daily Weather Summaries for yesterday and today.
While Tasmania's West and mountain areas are renowned for their constant wet weather, they have really turned it on over the past three days. Darwin Dam east of Queenstown has recorded 233mm in the 3 days to 09.00 this morning, 111mm falling in 24 hours to 09.00 yesterday. This ABC video of flooded campgrounds at Mount Field National Park also shows the well-known Russell Falls in robust full spate.
- * Asterisked links are to real-time material that was correct at time of posting, but may expire or be replaced by newer material.
- † Requires translation to English
- ‡ Linked site has partial paywall
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