NH Summer/SH Winter 2023 Discussion Thread

Mean temp for the first 3 days of June was 8.7C. That's early May means. Turku has seen similar temps in early June in 2017, 2012, 1991, 1975, 1972 and 1962. Early June 1975 was the absolute worst with a 7.0C mean.

Nice and cool yesterday, only got to 66 (19 c). Had steady, light rain for several hours until the early afternoon, which is very unusual for June. No thunder either. Similar start to today with a rainy morning.

We got 0.65" here on Thursday, but of course I missed it, being in a room at work without windows. Nothing since then, and nothing worth getting excited about in the forecast either.

The AQI here currently is 131: "unhealthy for sensitive groups". It looks kind of hazy, but I thought it would more so given that kind of number.

Truly deplorable Iceland crummer day today, with a hideously cold 67.8°F (19.9°C) high as well as subarctic overcast rot the entire day to boot. On the bright side however, Wednesday has been upgraded for the warmer, due to weather model consensus slowing down the cold front's progression that day.

Very wet today, raining all day until the late afternoon with 1.98” (50 mm) being recorded. This makes it the wettest June day since 1992! Wettest day overall since 18, 2017.

Also quite cool with a high of just 63 (17 c) and most of the day was in the 50s. Once the rain stopped it was really pleasant to be out in.

With today’s rain, June has already exceeded the monthly average with 2.63” (67 mm) so far.

Lows in NC last night...you can really see the PURE 100% COLD. Das ist polar

Australia Officially On El Nino Alert:
( source: Weatherzone )

El Niño and the typically drier-than-usual weather it brings across much of Australia is now officially one step closer after the BoM issued an El Niño Alert this Tuesday, June 6.

"The Bureau's *ENSO [El Niño Southern Oscillation] Outlook has been shifted to El Niño ALERT, indicating a 70% chance of El Niño forming this year," The BoM said on Tuesday afternoon. "This equates to roughly three times the normal chance of an El Niño forming."

While an official Alert does not definitely mean El Niño will be declared in 2023, it indicates a significantly elevated likelihood, and it's an upgrade from the previous state of "El Nino Watch" which simply meant an increased risk of an El Niño occurring compared to most years.

What is El Niño again?

In short, it's a shift in water temperatures and winds in the central and eastern tropical Pacific Ocean that affects weather in numerous ways both in Australia and elsewhere.

Both El Niño and La Niña are examples of climate drivers – broad-scale climatic patterns which influence our day-to-day weather.

El Niño is associated with a sustained period of warming in the central and eastern tropical Pacific Ocean, while La Niña is associated with a cooling of waters in that region. Both events are associated with shifts in broad-scale wind patterns, which in turn affect our weather.

El Niño causes a weakening or reversal of the direction of the trade winds in the tropical Pacific. This atmospheric shift decreases the development of cloud that leads to heavy rainfall to the north of Australia. This then affects Australia's weather more broadly.

You might also hear the term "ENSO" this week. It simply means the "El Niño-Southern Oscillation" and it's a term that describes the wavering between El Niño and La Niña states in the Pacific region.

How does El Niño typically affect Australia?

El Niño typically causes below-average rain over large areas of Australia

It also typically causes above-average daytime temperatures

While days are usually warmer, clearer nights often cause an increased risk of frost during winter and spring

El Niño often means reduced winter snow depths in our southern alpine region

El Niño can also increase fire danger in parts of the county

It often means a late onset of the monsoon (which feeds our tropical wet season) and can also reduce tropical cyclone activity in the Australian region

How do we know that El Niño is probably on its way?

As Weatherzone meteorologist Ben Domensino explained recently, the BoM uses both observations and forecasts from several oceanic and atmospheric indicators to monitor whether El Niño, La Niña or neutral conditions are present in the Pacific Ocean.

We'd urge you to read his story in full, but the super quick version is that the BoM looks at sea surface temps, winds, climate models and the Southern Oscillation Index (SOI).

The (SOI) at present is particularly relevant. See the massive dip on the graph below?

For the record, the SOI measures the atmospheric pressure difference between Tahiti and Darwin. But what you really need to know is that it dropped below -7 on May 16 and continues to plummet.

Why is a plummeting SOI significant?

Because a SOI level of -7 El is the Niño threshold, and May 16 was the first time the 30-day SOI index had reached the threshold of -7 since mid-2020.

Due to the variable nature of the SOI signal, negative values of -7 or lower need to be sustained for around three months before the Bureau officially declares El Niño. We're not there yet. But we're getting a lot closer, and today's El Niño alert was issued after the SOI index had been at -7 or lower for two months.

Netweather members have been excitedly posting charts showing the UK's first 30°C. I can see why - what a stonking chart this is! Very convincing heat, widespread over the nation.

I wonder how Renmark is doing outta this ?