Weather Chat Thread

Here are the 1991-2020 normals for Bermuda. Koppenites/tropical wankers will be saddened to see that February no longer satisfies the arbitrary 18 C coldest month requirement.

An obscure AU weather date.... Cloncurry Shire still hasn't forgiven the BoM for removing this recording from the record books....hehe

An interesting video about extreme microclimates.

I compiled some stats for the absolute annual minimum temperatures (1991-2020) in fennoscandia.









Mean annual minimum:

Sweden: -40.9C

Norway: -41.0C

Finland: -40.2C





For the combined area:

indeed?

CMV: Sydney is Boston with a few 40C days thrown in

Excessive Heat in Australia: Understanding Causes and Impacts
( source: Weatherzone )

Excessive heat is not just a scorching summer’s day. It's a meteorological event characterised by temperatures that significantly exceed the average for a region. These heat conditions pose serious threats to both the environment and human health.
Excessive heat can be sorted into two categories: long-lasting heatwaves and short high-intensity heat. We can visualise both of these in action with the below case study: the min-max temperatures of Melbourne City in 2009.

There was an extreme heatwave from the 28th - 30th of January, while a week later on the 7th of February there was a single excessively hot day, infamously known as Black Saturday. Some of the standout weather observations on Black Saturday were:

46.4 degrees in Melbourne, the city's highest temperature on record

48.8 degrees at Hopetoun, Victoria's highest temperature on record

A wind gust of 120km/h at Mount Gellibrand, its highest on record for February

Relative humidity below 10 per cent in many locations

The Causes Behind Excessive Heat:

Excessive heat is formed via complex phenomena influenced by a variety of atmospheric, geographical and human factors:

Cold Fronts: A cold front can indirectly lead to excessive heat as it propels hot, dry winds ahead of it, elevating temperatures significantly before the cooler air mass arrives. For example, the events of the Black Saturday bushfires were significantly exacerbated by a strong cold front that triggered a surge of hot, dry and blustery northwesterly winds across Victoria. The blend of unprecedented high temperatures, low humidity and vigorous winds preceding the front led to exceptionally high fire danger ratings, contributing to the catastrophic conditions on Black Saturday.
High-Pressure Systems: Another significant meteorological cause of excessive heat is the presence of strong high-pressure systems. These systems act like a dome, trapping hot air in an area and preventing cooler air masses from moving in. The air within this dome warms up as it descends, leading to increased temperatures at the surface. High pressure systems can also become ‘blocked’ in place, allowing them to be nearly stationary for days or weeks at a time.
Clear Skies and Increased Solar Radiation: Clear skies result in an increased amount of solar radiation reaching the Earth's surface. Without clouds to reflect sunlight, more energy is absorbed by the ground, significantly raising temperatures.

Urban Heat Islands: In urban areas, the abundance of concrete, asphalt and other heat-absorbing materials leads to higher temperatures compared to surrounding rural areas. This effect is known as the urban heat island phenomenon. Buildings and roads absorb heat during the day and release it at night, leading to higher nighttime temperatures in cities.

Reduced Evapotranspiration: In areas with less vegetation, there is reduced evapotranspiration – the process by which plants release water into the atmosphere, creating a cooling effect. Deforestation and urbanisation can decrease this natural cooling, contributing to higher temperatures.

Seasonal Wind Patterns: Certain wind patterns can exacerbate heat conditions. The most impact of these is the Foehn Effect, where winds that blow over mountain ranges lose moisture on the windward side, and heat up as the air descends down the leewards side. This effect is significant for many of Australia’s capital cities, such as Sydney, Brisbane, Melbourne, Hobart, Adelaide, and Perth.

Ocean Currents and Sea Surface Temperatures: Changes in ocean currents and sea surface temperatures can influence weather patterns on land. For example, a warmer ocean can lead to increased air temperatures on adjacent land masses.

Low Soil Moisture: Dry soil conditions can also contribute to excessive heat. Moist soil typically absorbs more solar radiation, using this energy to evaporate water, which cools the air. Dry soil, on the other hand, reflects less solar radiation, allowing more heat to be absorbed by the atmosphere.

Impact on Wildlife and Ecosystems:

Excessive heat also has a profound impact on Australian wildlife and ecosystems. High temperatures can lead to habitat destruction, alter migration patterns and even cause heat stress and dehydration in animals. Aquatic ecosystems are not spared either, as increased temperatures can disrupt the oxygen levels in water bodies, affecting marine life. Additionally, excessive heat can lead to the increased prevalence of wildfires, which devastate habitats and cause a loss of biodiversity.

Role of Vegetation in Mitigating Heat:

Vegetation plays a critical role in mitigating heat, especially in urban environments. Trees and plants are natural coolants; they provide shade and release moisture into the air through a process called transpiration, effectively reducing ambient temperatures. In cities, where concrete and asphalt surfaces absorb and re-radiate heat, increasing green spaces can significantly counteract the urban heat island effect.

Shade and Cooling: Trees and large shrubs provide shade, which can lower surface and air temperatures.

Transpiration: Plants lose water during transpiration, which cools the air. This natural process is akin to a landscape-scale air conditioning system, which can make areas with abundant vegetation noticeably cooler.

Green Roofs and Walls: Implementing green roofs and living walls in urban architecture not only adds greenery but can also insulate buildings, reducing the need for artificial cooling.

Planning and Planting: For effective heat mitigation, urban planning may include strategic planting of trees and plants, considering factors like species selection, placement for maximum shade, and water efficiency.

Community Parks and Green Spaces: Large areas of green space, like community parks, can serve as urban oases, significantly lowering local temperatures and providing a refuge from heat for city residents.

The Economic Impact of Extreme Heat:

The economic ramifications of excessive heat are far-reaching. Labour productivity in industries such as construction and agriculture can drop significantly. There's also an increased demand for healthcare services due to heat-related illnesses. Furthermore, energy consumption spikes during extreme heat, leading to higher utility bills for individuals and increased operational costs for businesses.

The Black Saturday bushfires, caused by excessive heat, are regarded as one of the most devastating bushfire events ever recorded in the world. The bushfires claimed 173 lives, and destroyed 450,000 hectares of land, 2,000 homes and 1,500 buildings, leaving a lasting impact on the geography, population, and economic sectors.

Understanding the science behind excessive heat, its impact on our environment, urban areas and health and its economic implications, is crucial in developing effective strategies to mitigate these effects. While individual efforts like staying hydrated and cool are essential, broader solutions such as improving urban planning and investing in sustainable energy sources are vital for long-term resilience against excessive heat events.
Health and Safety Tips During Extreme Heat:
During extreme heat, it's crucial to take preventive measures to ensure health and safety. Staying hydrated, avoiding strenuous outdoor activities during peak heat hours and wearing light, loose-fitting clothing are key. It’s also important to recognize the signs of heat-related illnesses such as heat stroke and heat exhaustion, which include symptoms like dizziness, headache and nausea.

US Climate Prediction Center issues La Nina watch alongside El Nino advisory
( source: Weatherzone )

In the first week of January, we said that La Nina is more likely than either El Nino or neutral conditions by spring this year. This past Thursday February 8th, the US Climate Prediction Center maintained an El Nino advisory but also issued a La Nina watch. This is because El Nino is still active in the Pacific Ocean, but conditions are considered favourable by the US agency for a transition to La Nina within the next six months. In contrast, the BOM says it’s too soon to make such a forecast.

El Nino going down fighting

The current El Nino is going down fighting as the atmosphere links back up with the ocean. This recoupling of the atmosphere with the ocean will see more typical El Nino conditions briefly affect Australia before the Pacific Ocean shifts to neutral conditions during autumn. Recent large negative values of the Southern Oscillation Index show this recoupling (helped by a break period in the North Australian monsoon).

In the end of 2023 and through January 2024 the atmosphere became uncoupled from the oceanic component of El Nino. One of the factors leading to this was warmer-than-average sea surface temperatures in the western Pacific during December and especially during January which is extremely rare with an El Nino when those waters should be colder than average! The warming in the Coral Sea occurred rapidly and the southern part of the Coral Sea has remained warm into February. Oceanic models that were run several months prior did not predict that the Coral Sea would become so warm during this period, which had consequences for the seasonal forecasts made last year as well as the tropical cyclone activity (models did correctly predict the warmth of the Tasman Sea). The warm waters in the western Pacific will continue to have consequences for the seasons ahead.

Increasing chances of a transition to La Nina

Most oceanic models are predicting a La Nina to develop in the second half of 2024. Now, models can be wrong like when the pre-eminent model from the European Centre predicted neutral-to-El-Nino conditions in 2022 but a strong La Nina continued without weakening. But the same model did very well last year in predicting an El Nino.

But our prediction isn’t just taking models at face value. As we showed you last month, there is a recent historical precedent for a transition back to La Nina (2007 to 2011), and since 1998 La Nina has been the more common ENSO state due to the current state of a longer-term climate oscillation. Even more importantly, the observations below the surface of the equatorial Pacific show cold water making its way towards the surface. The following animation from December 2023 to February 2024 shows the observations of sub-surface temperature anomalies in the equatorial Pacific Ocean down to a depth of 450m below the surface.


This is crucial for the seasonal forecasts because when the cold water reaches the surface it will cool it, leading to an end to El Nino and then a transition to La Nina. It would be very difficult for an El Nino to redevelop after the cold water reaches the surface. These observations of what is really happening give confidence that the model predictions are going in the right direction. The US Climate Prediction Center predicts El Nino to end during the Southern Hemisphere autumn and then for a transition to La Nina potentially occurring during the Southern Hemisphere winter. The North American models predict the fastest transition occurring in our winter whereas the European model predicts a slower transition later in winter and early spring.

Here is the latest probabilistic forecast from the International Research Institute for Climate and Society:

Potential impacts if La Nina returns


The warm waters of the western Pacific that have worked at times to weaken the effects of El Nino this summer would actually work to strengthen the effects of a La Nina. The atmosphere would be more consistently linked with the oceanic component of a La Nina because the contrast between the warm waters in the western Pacific and the cold waters in the central and eastern Pacific would strengthen the trade winds and concentrate rising motion, low pressure and moisture to the north of Australia.

Looking at past years when a transition from El Nino to La Nina has occurred may give us some idea of the potential rainfall for this year. In those years, spring and summer have been the most impacted as this is when the La Nina had developed, with more precipitation than average in eastern and northern Australia. During autumn there was little difference from average, and during winter there was increased rainfall for southeast QLD and northeast NSW. And SA and WA (except for the north) saw the least differences from average throughout each season.

Weatherzone will keep you updated about the state of the Pacific Ocean and the associated weather for Australia throughout the year.

Concerns that media, social media are driving fear in coverage of El Niño weather event:
( Source: ABC AU )


In short: Australia's weather bureau says reports about its forecast are often sensationalised.
Australians who rely on the BOM's forecasts say reports about the El Niño created fear and anxiety.
What's next? A review of the Bureau's El Niño declaration concluded that communication on long-term forecasts could be clearer.
Sensationalist reporting and social media are being blamed for driving fear and anxiety about weather amid confusion about how to understand official forecasts.
The Bureau of Meteorology says reporting of its forecasts by mainstream and social media has focused on "more sensational elements" and its messaging is "crowd[ing] out fact-based forecasting".
"A lot of third-party reporting of El Niño and actually, just more broadly, the Bureau's observations, forecasts and warnings are often reported in their most sensational form by third parties ... that has been a challenge for us," the Bureau's chief customer officer Peter Stone said.
"We always need to work hard to make sure that our forecasts are received as accurately as we intend them to be."

Australians who rely on weather forecasts to make business decisions say the speculation and subsequent official declaration of an El Niño weather pattern, expected to bring warmer and drier conditions, created a sense of fear.

Exaggeration must stop:
Marc Greening, who farms at Book Book in the NSW Riverina, said reporting of the forecast had spooked many farmers who were still dealing with the trauma of recent drought.
"I remember watching a TV report with a map of Australia in mid-August with flames coming out of it, and it used the word catastrophic. The words super El Niño were used," Mr Greening said.

"You can see where the general public and people that make a living from weather forecasts got the sense that this was going to be bad.

"It's got to stop, this exaggerating, this jumping on anything to make people feel scared."

Despite the reporting, Mr Greening said it had been one of the best starts to summer that he could recall in more than 20 years at his property.
He wants changes to the way weather forecasts are reported in the media.

"You change your system if your customer doesn't understand it, and we are the customer," Mr Greening said.

"So I think [the Bureau] need to change their reporting, and really make a conscious effort to educate on what's going on."

NSW sheep producer Nigel Kerin said the forecast had spread rapidly.

"I think for me, the biggest, strongest thing that hit this and turned it was the mention of El Niño driven by social media," he said.

"It just put people into a state of fear and shock."

In Queensland's Lockyer Valley, where summer storms have caused havoc, hay and vegetable grower Chelsea Endicott-Davies said farmers had been confused by what she considered to be sensationalised reporting.

"One of the biggest problems is social media and media in general, trying to get that headline, putting out these big stories about cyclones and big weather events, chasing that down," she said.

"It's trying to get headlines but that is also creating fear in the general public, as well as for farmers trying to predict what they've got to try to do."

Benny Endicott-Davies said the reporting on social media about the weather in some cases was "fearmongering".

Bureau says El Niño was the right call
The Bureau of Meteorology has faced criticism in recent weeks after a wetter summer than many anticipated after the El Niño declaration in September.
Dr Stone says the Bureau made the right call.
"El Niño started just as we said it had, and it continues now and we actually expect El Niño itself to run through to autumn," he said.

"By and large, for the past five months our long-term forecasts have about a 65-per-cent accuracy for rainfall and 98-per-cent accuracy for temperature.

"And that's the best that you'll find anywhere in the world".

Some farmers have blamed coverage of the forecast for an influx of livestock in the market, pushing down prices, with sheep and cattle markets experiencing significant downturns.

Dr Stone said it was "drawing a long bow to link the Bureau's El Niño declaration to an impact on [livestock] prices".

Monash University atmospheric science researcher Kim Reid has reviewed the Bureau's El Niño declaration and summer forecast to see if the complaints stacked up.

"I looked back at the Bureau's long-range forecast, after all these complaints to see if they were fair," she said.

"And from September, the Bureau, were going for a drier-than-normal summer over most of Australia.

"But by October, they started to ease off on that forecast. And by November, they were only going for dry conditions in the west, and northern parts of Australia.

"And this is how a forecast typically behaves. It gets better as you get closer to the period that you're trying to predict," she said.

Dr Reid says it wasn't just an El Niño system driving Australia's weather this summer and that Australians need to understand that long-range outlooks are very different from day-to-day forecasts.

"The fact that a lot of people were confused by the summer outlook indicates that perhaps there is room for improvement in how the Bureau communicates their long-range forecast," she said.

"When they issue the one-month rainfall forecast, take it with a grain of salt and when there's a three-month forecast, take it with a cup of salt."