December 2022 update SA
December 2022 update SA
*Forecast prepared between Dec 16th-19th 2022
Review:
G’Day everyone, the final update for 2022 is here and what a year it has been, I think we have had the lot this year, perhaps only missing extreme heat though a little taste of that will come to finish out the year.
The first half of December has seen for the most part relatively cool to mild conditions with only a couple of hot days with some extreme fire danger thrown in. Stream showers in an onshore flow associated with a SW flow between the 11th-14th which did result in some annoying totals across the agricultural areas with Laura receiving 14mm, Crystal Brook 12mm, Georgetown 9mm, Kadina 8mm and numerous other 5-8mm totals over the period of those 4 days. Further south across the Lower SE, totals were higher owing to a greater depth of cold air closer to the head of the cold pool that slung below the state with Mt.Gambier Airport receiving 22mm, Nangwarry 21mm, Coonawarra and Naracoorte with 13mm and Robe with 12mm.
After this till the current time we have seen fairly settled conditions with good weather for reaping crops however freshening SE-E winds at times will have elevated the fire danger a little as the strong high moves east and a low-pressure trough deepens from the west which I will now cover more in the next section.
Meteorological Discussion:
As we enter the final couple of weeks for 2022, we finally start to look at a pattern that is more typical of this time of the year without the enormous cut off lows and cold pools of October and November. But there is one last surprise or two in store to round out the year with a couple of thundery troughs to move through.
Firstly, though we are currently in the broad reset trend as we build-up to a Monsoon Onset across the top of the country. A large high is slow moving and now anchored south of Tasmania and this feature will continue to move eastwards in the coming days. Now the key feature of this is that is has remained slow moving which has given tropical moisture a chance to advect inland from the tropics into a deepening trough of low pressure over inland NT and SA. This trough will bring an increase in showers and thunderstorms across the NE & NW Pastoral and Western Coast Districts on the 19th before combining with an upper trough moving in from the Bight. Severe thunderstorms are likely during the afternoon of the 19th over the NE Pastoral and N Flinders. Together these two systems will cause showers and thunderstorms to slowly creep eastwards on the 20th and 21st before the features weaken and move out of the state by the 22nd. A new bubble high will replace the trough causing mild to warm conditions in the leadup to Christmas.
The slow-moving nature of this trough will make for a complex 20th and 21st period where showers and thunderstorms will mostly be focused over the Eyre Peninsula, Pastoral areas and Northern ag areas. The main focus will be during the afternoon over Eyre Peninsula, chiefly the northern portions up into the Pastorals where Severe thunderstorms are likely, with the slow-moving nature and tropical moisture combining to provide a flash flooding threat as well as wet microbursts for damaging wind so please take heed. Large hail is less likely than the big systems from October and November but in the strongest storms this is still a reasonable chance. Also, a focus will be across the Upper and Lower North and perhaps far N Yorke Peninsula during the afternoon and evening of the 20th as the activity moves eastwards. Further south and east the instability drops off a little which will see more mid-level showers possibly tending to patchy rain areas, but overall humid conditions will prevail.
On the 21st the trough with humid conditions moves eastwards and weakens but sees a greater potential east of the Mt.Lofty Ranges, in particular over the Riverland, Mallee and Upper SE as heating causes showers and thunderstorms to re-develop. Severe thunderstorms are again likely, perhaps not quite to the level of the day before, but flash flooding will be a threat and potentially damaging winds if wet microbursts do occur. Wind shear may also be just enough for a large hail threat in stronger storms.
Now for the all-important Christmas Day it looks about as good as you could wish for, perhaps a little warm for some but for the most part in the high 20’s to low to mid 30’s across most districts, perhaps the mid 20’s about the coast and more southern portions of the Lower SE and KI. No rain whatsoever so it will be a perfect day out for a BBQ and any outdoor activities!
Beyond this however the upper ridging builds and anchors down to the east for a short period, the first proper effort of the entire season and as a result we are likely to see temperatures in that 36-40C bracket around the 26th to 27th before a stronger system displaces the upper ridge granted that it is the first effort, the pushback from the south shouldn’t be too difficult. This system potentially could link up with better jetstream support and utilise some tropical moisture for a thundery change of showers and thunderstorms around the 28th but a special update will occur should it be sufficient in strength to warrant.
The pattern then continues to quickly transition to a summer pattern with the heat I have expected to quickly make itself known in January. Inland WA will dominate with the heat engine turning over and over and as time wears on, we will see more regular intrusions of this heat into the agricultural areas of SA so be ready for high 30’s to low 40’s into January, potentially as early as the first week.
But with the heat comes the southward push of the Monsoonal lows and I’d expect one or two Tropical Cyclones to be born out of this first monsoonal push, most likely curving SW off WA but the soupy hot Coral Sea could show its hand here as well. Inland NT and QLD will finish 2022 quite wet and start 2023 in similar fashion with flooding rains becoming a feature. The Lake Eyre basin as mentioned in the past will eventually cop this rainfall before the northern Murray Darling Basin also sees heavy rainfall into January so renewed flooding in previously flooded areas is likely...it is not done yet at all.
One final note about the Murray/Darling flooding in that the peak is still expected to be within the vicinity of 1931 but a bit higher overall, maybe by 30-40cm going by the Loxton tree that I showed many months ago. This of course varies from location to location with the Murray being narrower around Blanchetown to Mannum with less floodplain as the cliffs constrict the horizontal distance and thus as a result the water can only go upwards. There will be a high river for much of the summer and this is before renewed rainfall upstream, especially over the Darling so it is likely for multiple peaks (less than the current) over the remaining 2-3months of the monsoonal season before it all quietens down and levels drop right away.
Climate Drivers:
The Pacific has seen little change over the past fortnight with only perhaps a subtle warming around the Australian tropical coastline which bodes well for fuel for the approaching monsoon. That is most likely due after Christmas and into the New Year at this stage which for the most part is a standard time of arrival. In the Sub-Surface however, there is a significant amount of warmth building and encroaching towards the east at a depth of approximately 125-225m (see Figure 1). This warm water push will likely spell the end of the La Nina but at this point in time, it faces a battle to do so... so the La Nina should remain into the New Year for a while.
Figure 1: Sub-Surface temperature anomalies in ENSO region showing warm water at depth of 125-225m – source BoM http://www.bom.gov.au/climate/enso/
The Indian is now irrelevant as mentioned in the December outlook with the IOD returning to neutral values now. There is however some warmer water (slightly) off the NW WA coastline which will give the Monsoon an ever so slight boost as it develops later this month and provide some welcome rainfall for a fairly parched inland WA in the coming weeks.
Moving on to the MJO and currently this has been gathering in strength which we can see in Figure 2 below. It is currently in phase 2 and moving eastwards to impact the mainland later this month and early in the New Year with a monsoon onset (albeit a patchy one still) and general increase in tropical shower and thunderstorm activity, extending further inland across the Pastorals/Interior regions in the coming weeks.
The SAM has had its brief dip into negative territory which was expected but short-lived. We certainly have seen a lot of cooler weather about the southern coastline form this with a lot of SW-SE winds and fresh afternoon seabreezes and even stream showers as covered from the review. This will decrease as the SAM swings back positive and stays there in anticipation of the Monsoon Onset so more SE-NE winds across the mainland instead and less potent onshore flows and seabreezes.
Districts:
Eyre Peninsula
Deepening trough moving slowly across the district from 19th with mid-level showers and isolated thunderstorms, chiefly in the north during the afternoon and evening. Upper trough and humid conditions moving in after increasing activity to general showers and thunderstorms on 20th with severe thunderstorms likely during the afternoon causing local heavy falls & flash flooding as well as potentially damaging winds chiefly about northern and Eastern Eyre Peninsula. Showers and thunderstorms contracting eastwards and clearing early on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or areas of rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 15-25mm across Western and Lower Eyre Peninsula increasing to 25-35mm further north. More significant but isolated totals with stronger thunderstorms may deliver 40-60mm falls, some in rapid time with even potential for 80mm should the 28th system also be significant.
Upper North
Deepening trough moving slowly across the district from 19th with mid-level showers and isolated thunderstorms, chiefly over the Flinders with potentially severe afternoon thunderstorms there. Strong downslope gully winds in the morning. Upper trough and humid conditions moving in after increasing activity to general showers and thunderstorms on 20th with severe thunderstorms likely during the afternoon causing local heavy falls & flash flooding as well as potentially damaging winds, more likely in the north and west of the district. Showers and thunderstorms re-developing early on 21st with severe thunderstorms in the afternoon in the far east possible before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or areas of rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 10-20mm across the district. More significant but isolated totals with stronger thunderstorms may deliver 30-50mm falls, some in rapid time with even potential for 50-60mm should the 28th system also be significant.
Lower North
Deepening trough moving slowly across the district from 19th with mid-level showers developing later, chiefly in the north. Strong downslope gully winds in the morning. Upper trough and humid conditions moving in after increasing activity to general showers and thunderstorms on 20th with severe thunderstorms possible during the afternoon causing local heavy falls & possible flash flooding, more likely in the north and west of the district. Showers and thunderstorms re-developing early on 21st with severe thunderstorms in the afternoon in the far east possible before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 10-20mm across the district. More significant but isolated totals with stronger thunderstorms may deliver 30-50mm falls, some in rapid time with even potential for 50-60mm should the 28th system also be significant.
Yorke Peninsula
Deepening trough moving slowly across the district from 19th with possible late mid-level showers developing in the far north. Upper trough and humid conditions moving in after increasing activity to general showers and thunderstorms on 20th with severe thunderstorms possible during the afternoon causing local heavy falls & possible flash flooding in the far north of district. Showers and thunderstorms becoming much more isolated and less significant towards the foot of the Peninsula. Showers and isolated thunderstorms re-developing early on 21st before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system.
Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year, especially in the north. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 10-20mm across the district. More significant but isolated totals with stronger thunderstorms may deliver 20-40mm falls, some in rapid time with even potential for 50-60mm in the north should the 28th system also be significant.
Kangaroo Island
Deepening trough moving slowly across the district from 19th though remaining dry initially. Upper trough and humid conditions moving in after with showers and possible isolated thunderstorms on 20th. Showers and isolated thunderstorms re-developing early on 21st before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with warm to hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 10-20mm across the district. More significant but isolated totals with possible thunderstorms may deliver 20-25mm falls, some in rapid time if stronger cores do form.
Adelaide Plains
Deepening trough moving slowly across the district from 19th though remaining hot and dry. Strong downslope gully winds in the morning. Upper trough and humid conditions moving in after increasing activity to general showers and isolated thunderstorms on 20th although less likely towards the southern suburbs. Showers and isolated thunderstorms re-developing early on 21st before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year, especially about the Outer Plains. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 15-25mm across the district. More significant but isolated totals with stronger thunderstorms may deliver 20-40mm falls, some in rapid time if stronger cores do form.
Mt.Lofty Ranges
Deepening trough moving slowly across the district from 19th though remaining hot and dry. Strong downslope gully winds in the morning over the western slopes. Upper trough and humid conditions moving in after increasing activity to general showers and isolated thunderstorms on 20th although less likely towards the southern ranges. Showers and isolated thunderstorms re-developing early on 21st with possible local heavy falls about the northern ranges before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Lingering onshore light showers about southern coasts and windward ranges on 22nd in a cooler southerly flow. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year, especially towards the Northern ranges. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 15-25mm across the district. More significant but isolated totals with stronger thunderstorms may deliver 30-45mm falls further north, some in rapid time if stronger cores do form.
Riverland/Mallee
Deepening trough moving slowly across the district from 20th though remaining hot and dry at first. Upper trough and humid conditions moving in after with showers and isolated thunderstorms developing on 20th chiefly about the Riverland late in the day. Showers and thunderstorms re-developing early on 21st with severe thunderstorms causing local heavy falls, possible flash flooding and damaging winds before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or areas of rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 15-25mm across the district. More significant but isolated totals with stronger thunderstorms over the Riverland mainly may deliver 30-45mm falls, some in rapid time with even potential for 50-60mm should the 28th system also be significant.
Upper SE
Deepening trough moving slowly across the district from 20th though remaining hot and dry at first. Upper trough and humid conditions moving in after with isolated showers and thunderstorms developing later on 20th and chiefly in the north. Showers and isolated thunderstorms re-developing early on 21st before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Slight chance of a severe thunderstorm in the far north or east of the district later on 21st. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or areas of rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 10-20mm across the district. More significant but isolated totals with stronger thunderstorms in the far N and E may deliver 20-30mm falls, some in rapid time.
Lower SE
Deepening trough moving slowly across the district from 20th though remaining hot and dry at first. Upper trough and humid conditions moving in after with isolated mid-level showers developing later in the evening on 20th and chiefly in the north. Showers and isolated thunderstorms increasing early on 21st before contracting further eastwards and clearing later on 21st as a new ridge moves in from the Bight. Lingering onshore showers on the 22nd in a cooler southerly flow. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due either later 28th or 29th at this stage potentially with more showers or areas of rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 8-15mm across the district. More significant but isolated totals with stronger thunderstorms in the far N and E may deliver 20-30mm falls, some in rapid time.
Western VIC
Deepening trough moving slowly across the district from 20th though remaining hot and dry at first. Upper trough and humid conditions moving in after with showers and isolated thunderstorms increasing early on 21st before contracting further eastwards and clearing during the early hours of the 22nd as a new ridge moves in from the Bight. One or two thunderstorms may well be severe about the Mallee and Wimmera on the afternoon and evening of the 21st with flash flooding and damaging wind the greatest threats. Lingering onshore showers about the SW District coastline on the 22nd in a cooler southerly flow. Temperatures rising through the Christmas period with very hot conditions around 26th to 28th ahead of a moderate cold front and upper trough due on the 29th at this stage potentially with more showers or areas of rain and isolated thunderstorms with a tight thermal gradient. Fresh to strong and hot to very hot N to NW winds with elevated fire danger may present ahead of this system. Cooler onshore flow behind this change before temperatures rise once more with hot conditions once again by the New Year. Rainfall for the period highly variable depending on thunderstorm activity but for the most part 8-15mm across the district. More significant but isolated totals with stronger thunderstorms in the far N and E may deliver 20-30mm falls, some in rapid time.
Finals Notes:
- Thundery trough with upper support 20th-21st with severe thunderstorms likely north of a rough line from Elliston to Maitland to Gawler to Bordertown
- Potential follow up system on 28th though strength is uncertain at this stage
- Devastating flooding along the Murray will continue well into January with a peak a little above the 1931 level making it the third worst in recorded history behind 1870 and 1956
- Monsoon onset with significant tropical intrusion likely into NT with heavy falls and flooding inland in coming weeks
- Heat lows and upper ridging (but with tropical moisture infeeds) will begin to dominate the mainland as we move into January and February
- Autumn 2023 still looking like a drying trend as time progresses
Link to temporary blog website: https://farmweathersa.blogspot.com/
Happy Farming and Cheers from The Weatherman
*Note – For interest only, all thoughts are of The Weatherman and may not be reproduced without my consent.
Comments
Post a Comment