March 2023 Outlook SA
March 2023 outlook SA
Forecast prepared between March 7th-9th 2023
Review:
G’Day one and all, sorry for the delay to this outlook, I’ve been away on a long-awaited trip! The March outlook rainfall wise won’t truly reflect as a forecast given a week has already lapsed but this will at least encompass what is left. Only scattered showers have occurred so far this month with a couple of troughs but some mid-level based thunderstorms did pass through the agricultural areas during the late afternoon and evening of the 5th, but rainfall totals were light. A quick look back at February, usually a hot month and generally un-inspiring over SA and parts of VIC and this one was no exception. No significant tropical infeed which resulted in mostly stable conditions. A cold start blended with a hot finish saw temperatures come in close to average however a majority of the state was slightly above average, but the Lower SE remained slightly below.
Rainfall wise most of the state once again came in below average and this can be reflected in the following images below.
Figure 2: February rainfall percentages – source BoM http://www.bom.gov.au/climate/
We can clearly see most of the state was below average looking at the deciles and especially the percentages with only the Lower SE coming in above average and a little portion of the NE corner of the state. The anomalies in Figure 3 below also tell a similar story but show that the usual tropical influences over the far NW corner of the state in particular were non-existent.
Figure 3: February rainfall anomalies – source BoM http://www.bom.gov.au/climate/
Reflecting on the February outlook here is what we had for that:
“So my overall outlook for February is average to below average for the Lower and Upper North, the Eyre Peninsula and West Coast and potentially into the NW Pastoral as well. The Mallee and Riverland will also be similar though possibly closer to average. Average to potentially slightly above average rain falls as possible about the far Lower SE and the Southern coasts and ranges as well as the far northern border areas. Most other areas will be average or slightly below however one decent rain event can really blow things to much above average over the drier areas. The greatest chance of strong infeed of moisture is the NE corner followed by the far western border form decayed TC activity.”
The net result on that is fairly good, we saw the wetter spots in both the Lower SE and far NE corner and with a broad average to below average trend for much of the remainder of the agricultural areas. The northern border areas however did not receive that infeed for rainfall, only the far NE. The Southern coasts and ranges had a tiny, localised slither of slightly above average rainfall.
Meteorological Discussion:
Now given the first week of the month has lapsed I won’t spend long with the March discussion. Currently we have seen a couple of cold fronts move through bringing scattered showers primarily to the southern agricultural areas but also parts of the northern as well. Orographic influences have seen some handy totals in the Mt Lofty Ranges with Uraidla and Crafers West receiving 41mm and 40mm respectively. Most other totals have been in the order of 5-15mm across the agricultural areas.
The current pattern sees a little more Southern Ocean influence over the southern part of the country with the main tropical focus still remaining in that convergence I have mentioned many updates prior over inland QLD and up to Cape York Peninsula. Very heavy rainfall with flooding will occur and some of this will trickle down into Lake Eyre over the coming months. A fair bit more rain will drag SE along the jetstream across Central inland QLD out of the monsoonal low and give good rainfall to much of SE QLD.
For the remainder, conditions will largely be dry though weak systems in a mobile pattern will continue to cause temperatures to jump around a bit – a more fluid pattern than we are used to in March, and this can be largely attributed to the very active sunspots we have at the moment which often cause wild jetstream fluctuations. There is no heavy moisture setup to our NW to grab however so unless a Tropical Cyclone tracks and re-curves in our window, we won’t see a large infeed out of the NW.
A weak front will mostly impact the Lower SE around the 11th-12th bringing a band of showers, before a large high ridges in behind. A weak trough will attempt to deepen across the interior in response to some cold air aloft but apart from tightening the SE/E gradient below it, it shouldn’t do a great deal. Another front will be due around the15th-16th and again on 18th as the mobile pattern keeps up. There should be at least some swell generated for those that are keen in that area! It will be hot ahead of the 15th system with freshening NW winds and elevated fire dangers.
Climate Drivers
The Pacific has not changed a great deal from the last update as we still see the warm sub-surface encroaching from the west at about 150m (see Figure 4). Trade winds still remain average to slightly above in strength with an uptick now in Monsoonal Low formation in the Western Pacific and Coral Sea likely through March with a number of these going on to become Tropical Cyclones – and March is the peak month for these warm-cored beasts. I tend to find a good balance between SE trade winds and NW Monsoonal flow yield the best results as overly strong monsoon flow tends to flatten out the lows and in turn steer them too quickly, halting their intensification. The current monsoonal flow does have some strong bursts, but the breadth and length of the flow is short with many segments. These segments are the interruptions caused by the cyclogenesis within the monsoonal trough itself. I envisage multiple monsoon bursts (short-lived) with Tropical Cyclones through March with potential for Severe ones in the Coral Sea and adjacent Western Pacific waters. Overall though, the La Nina is on the way out now.
The Indian remains completely irrelevant at this point in time with a blend of cooler and warmer anomalies across the basin. There is some warming off the NW shelf and off Indonesia which in spring would be fantastic but for now I don’t expect much of an impact other than to provide a little more fuel to any Tropical Cyclones that do move or form over that area. Long term we are looking at a neutral to weakly positive IOD through winter and spring.
The MJO is moderately strong in phase 7 and is nowhere near affecting the mainland at the point in time. A large downwelling area (see Figure 6) is moving over the continent which is mostly responsible for such a dearth of activity off the NW coast. The stronger burst into phase 7 has caused the weakening of the La Nina ever so slightly but will need multiple Westerly Wind Bursts (WWB) to really knock it out completely which should happen through autumn and winter. Finally the SAM is neutral with a negative bias and the fluid westerly belt combined with the onshore flows at times, we should see a neutral to negative trend continue for the meantime. This is not uncommon when the MJO is moderate to strong in phases 6 and 7. I expect a return to more positive values later in the month.
Districts:
Eyre Peninsula
Remaining mostly fine for the period although some isolated light coastal showers are possible as a weak front clips the SE corner of the state on the 11th-12th. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th before heat builds to the NW ahead of a faster moving cold front with temperatures rising to the high 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly a light coastal shower. Rainfall for the period less than 1mm.
Upper North
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th with downslope winds in the evening especially likely to be gusty at times. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the mid to high 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly a light coastal shower near the gulf but not much in it at all. Rainfall for the period less than 0.4mm.
Lower North
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th with downslope winds in the evening especially likely to be gusty at times. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the mid 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly light coastal showers near the gulf and higher peaks but not much in it at all. Rainfall for the period less than 0.8mm.
Yorke Peninsula
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th, especially about the foot and exposed coasts. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the mid 30’s, mostly in the north with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly light coastal showers but not much in it at all. Rainfall for the period less than 1mm.
Kangaroo Island
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th, especially about exposed coasts. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the low 30’s, with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly light showers but not much in it at all. Rainfall for the period less than 2mm.
Adelaide Plains
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th with downslope winds in the evening especially likely to be gusty at times. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the mid 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly light coastal shower near the gulf/southern suburbs but not much in it at all. Rainfall for the period less than 0.6mm.
Mt.Lofty Ranges
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing windy conditions out of the east, chiefly again on 11th-12th with downslope winds in the evening especially likely to be gusty at times. Weak front clipping coast early 12th with isolated light showers. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the low to mid 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with light coastal showers near the southern coasts and ranges but not much in it at all. Rainfall for the period less than 2-3mm.
Riverland/Mallee
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing slightly windy conditions out of the SE, chiefly again on 11th-12th. Heat building to the NW ahead of a faster moving cold front with temperatures rising to the mid to high 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly a light coastal shower near the gulf but not much in it at all. Rainfall for the period less than 0.4mm.
Upper SE
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing slightly windy conditions out of the SE, chiefly again on 11th-12th. Light showers developing about the coast with a weak front on 12th.Heat building to the NW ahead of a faster moving cold front with temperatures rising to the mid 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with possibly a light coastal shower but not much in it at all. Rainfall for the period less than 1mm.
Lower SE
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing slightly windy conditions out of the SE chiefly again on 11th-12th. A band of showers developing with a weak front on 12th.Heat building to the NW ahead of a faster moving cold front with temperatures rising to the low to mid 30’s with elevated fire dangers and freshening NW winds on about the 15th. Much cooler as a new ridge establishes from about the 16th with light coastal showers but not much in it at all. Rainfall for the period less than 3-5mm.
Western VIC
Remaining mostly fine for the period. New ridge pushing across after with trough deepening inland tightening gradient between the two causing slightly windy conditions out of the SE chiefly again on 11th-12th. A band of showers developing with a weak front on 12th.Heat building to the NW ahead of a faster moving cold front with temperatures rising to the low to mid 30’s with elevated fire dangers and freshening NW winds on about the 15th to 16th. Much cooler as a new ridge establishes from about the 16-17th with light coastal showers but not much in it at all. Rainfall for the period less than 3-5mm about the SW District grading to less than 0.4mm for the Mallee.
Final Notes:
- La Nina will break down and dissolve into a warm neutral state through winter with a push to weak El Nino for spring. If we only go warm neutral then it is far more likely to see a decent El Nino for 2024.
- Weak positive IOD or at least a neutral state looks likely in the Indian.
- Lake Eyre and associated feeding creeks/tributaries should see good flows for a number of months
- Tropical Cyclone activity to continue in Pacific but also fire up late March in Indian again
- Tropical Cyclone Freddy that began off WA (currently over Mozambique Channel) now on track for a world record for longest ever TC and also most accumulated energy
- Below average period from April to August broadly looks likely however more frontal action through winter with more zonal wind and less cut off lows looks the pattern at this stage.
- Frost risk is increased compared to 2022 with a few moderate to heavy ones likely through winter
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.
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