Seasonal Climate Outlook, Dec – Feb 2012/13.

Seasonal Climate Outlook, Dec – Mar 2012/13.

Issued January 1, 2013, by Anthony Violi

Current Overview :

Currently, the climate is beginning to respond to the inevitable push of the season change into a summer pattern. There has been a large displacement of moisture, pressure systems and rainfall patterns during the Spring, due to the positive Indian Ocean Dipole.. This has forced the patterns to be slow to transition into late Spring like conditions. In the last few weeks the IOD has broken down and gone into neutral conditions, meaning rainfall will increase from now on as moisture begins to increase from the NW corner of the country and moves South.

The top end is now transitioning from build up, into monsoon. As per my previous forecasts, cyclone activity and an earlier monsoon are tracking well. There still remains a large likelihood of a lot more cyclone and monsoonal activity. Given that SST are now very warm on the western coasts, and starting to warm for the Eastern coasts, all that stands in between us copping a deluge and a drier than normal summer is the Souther Annular Mode (SAM) keeping all the moisture and troughs to our north. its my thought that the monsoon will overcome the resistance and become dominant with an extraordinary amount of warmth off the NW coast.

Here is the current month rainfall for Australia, which is a big improvement, and signals the pattern is beginning to build as the wet season approaches.

dec 2102

Now let’s have a look at the climatic indicators.

As I have pointed out previously, the forecast El Nino has failed to gain any semblance in the Pacific. The forecast of cool neutral appears well on track. Significant cooling is now reaffirming in the tropical equatorial Pacific Ocean.

Here is the current drivers for the Pacific Ocean region that I am seeing as influencing the climatic pattern.

Trades are still Easterly, consistent with a La Nada. Very little westerly winds are evident in this diagram, so its neutral all the way with consistent SE trade winds across the equator.

sst_wind_anom_5day_ps32

Southern Oscillation Index was flying along until a tropical Low went through Tahiti and caused a big drop in the figures. Its now at -7.0 for the 30 day average, which will recover soon once we get rid of mid Decembers readings.

soi30

CFS, and the BOM, and all the other climate models, finally agree with my forecast from months ago that an El Nino will not occur. It will be a neutral year, which is a good result for us after 2 record La Nina years. Here is the Nino 3.4 area, the centre of the Equatorial Pacific.

nino34Mon

You can see form the above forecast, the climate models show cooling in the central Pacific until April, then rebounding warmer than normal again for another warming phase of either neutral or weak El nino. This is no surprise because the models always forecast this every year, then react accordingly. Its still my forecast for a La Nina for 2013, but much water  (no pun intended) needs to flow under the bridge.

Here is Nino 1 and 2, close to the South American coast. This is where the cooling of the oceans start as a result of upwelling of cold water.

nino12Mon

Again, a cooling off until April and then a rebound, we will keep a close on this into the New Year and see what eventuates.

Sea Surface temperatures are very interesting, very messy and all over the place, in line with a climate that is all over the shop. Here is the sea surface temperature anomalies on the 21st Nov.

So, now i can explain the crayon drawings! First off, in red, the cold waters have returned in the Bering sea near Alaska. These feed down the American coast and into the Equatorial basin. At the current time they are nowhere near as cold as a few months ago, however its starting to cool again with the onset of winter in the NH, so expect any warming to be short-lived in the Pacific.

So now, lets look at the comparison! I kept last months outlook in there for a good reason, and thats because its happened exactly as planned. The warmth has now moved towards the QLD coast, thanks to the strengthening of the trade winds, the cooling has accelerated in the Pacific, and the Indian is extraordinarily warmer than normal.

The green circle indicates warm water NW of the country has returned, as the IOD has now returned to neutral. This is why December’s rainfall has increased.  This will continue all summer and maybe into the autumn. Remembering that the IOD always warms up late October, its April to October period that needs to be warmer than normal for good Winter and Spring rains.

Will definitely be a neutral, even though there is cooling and warming simultaneously it looks like a break even neutral, with neither side favoured. What is important is that the trade winds should bring enough moisture for good rainfall to the country. How much is the million dollar question?

As noted in previous forecasts, notice the warmth in the Central Indian Ocean, providing fuel for fronts and low pressure systems over the next few months with a great moisture source. Once both areas are warm in tandem, which is now beginning to occur, I think it lines us up for an enormous summer rainfall problem again for most of the country.

Also of note is the heat due to the build up of cloudless days over the desert in the winter months. This heat cannot be ignored, and will move South in the summer months. There should be enough moisture by then to ensure we don’t break records, and also enough cold air lurking to keep it at bay so any heat that does eventuate will not be long lasting events.

Forecast for Summer : January 2013 to April 2013.

Northern Territory : Temperatures will be average through the forecast period, especially February through April.  Rainfall will be above average through the Northern Territory areas for all of the forecast period, and will become especially so for all areas through the monsoon season. There is also a risk of severe cyclone occurrence within the forecast area in this late forecast period. Monsoonal rain will be above average again, particularly areas exposed to western coastal regions.

Queensland: Temperatures will  be slightly warmer than average through the forecast period for all of Queensland except the far north. Rainfall will be above average throughout the period January through to April. Also, the risk of heavy rains remains as I expect the SST of the Qld coast to warm as the warmth in the Pacific sloshes east. An impact from a cyclone, or maybe a couple of cyclones is a good possibility as well. The likelihood increases through February – April .

New South Wales : Temperatures will be slightly above average for the forecast in NSW, and well above average in January for the two inland western districts. Temperatures will be about average, to slightly below average for all districts after the end of January. Rainfall will be below average in the NW initially in early January, then average for the remainder. The remainder of NSW will have average to above average rainfall this forecast period.

Victoria : Temperatures in Victoria will also be average to slightly above average for all of the forecast period, for Northern and NW districts.  Southern areas will see average to slightly below average temperatures during the forecast period. Rainfall will also remain average for all Southern areas, and average for the northern areas after mid January. Rainfall will increase in the early February for all districts.

Tasmania : A continuation of the trend for Tasmania with average temperatures for the entire period and state. Rainfall will be variable, average in western areas and below average slightly in Eastern areas.

South Australia : South Australia will see average conditions throughout for the temperature outlook. Initially temperatures in January will be slightly above average in the Northern districts, then will even out to average  to slightly below average after the middle of January. Rainfall will be average to slightly below average in the coastal regions, and average to slightly above average in the northern districts.

Western Australia : Temperatures will be slightly above average in the forecast period, particularly through the Southern and inland areas.  After that the rest of the forecast period will see temperatures average out to normal. Rainfall will be average for the entire state through December, except Southern areas which will be above average. However I expect rainfall to increase markedly through the forecast period for most areas not coastal, and will become above average to very much above average through the Northern half with the onset of a very active monsoon.

Notes:  Humidity is now beginning to increase across the country as the top end build up season has now transitioned into a monsoonal onset. It has been a great build up so far and has surpassed last years build up considerably.  Also, the Indian Ocean has rapidly warm as previously suggested, this warming trend will stick around for the next 6 to 9 months and should ensure above average rainfall across much of the Northern half of Australia, and the SE states.

Also the risk now of serious flooding is still significant. In fact the Northern half of the country is quite likely to see significant monsoonal rainfall. Dewpoints are very high through the North, and now we starting to see the spill of moisture from the NW part of the country to the southern parts.

The position of the Long Wave Trough also puts us at significant risk, however its actually been doing the opposite by sitting in no mans land rather than drop away or stay very high. This has caused upper ridging and blocking for the southern half of the country, hot weather and little rainfall.  We are looking for a relaxing of the westerlies to allow the blocking and ridging to subside, and the troughs to become more active from the North. This should begin with monsoonal onset in early January.

Summary :

Warmer than normal temps will continue for another month in the North of Australia, average elsewhere. Then a cooling trend will emerge, and average to slightly below average temperatures will be fairly common for the remainder of the outlook. The general trend for the forecast period is for humidity to increase, along with rainfall for the entire country, except the Sw corner of the country, where the trend will be in reverse.

On a verification note, the pattern has moved much slower than in my previous forecast, my forecast is still unchanged. Late spring did not deliver the rains to the southern states, it did however deliver good rains to the northern states. The monsoon has seen a much better build up season, and the monsoon is much earlier than previous year.

Advertisements

Seasonal Climate Outlook; November 2012 – February 2013.

Seasonal Climate Outlook;  November 2012 – February 2013.

Issued by Anthony Violi, on 22rd October 2012

Current Overview :

Currently, there are a lot of bizarre goings on with respect to climatic activity. There is currently a large displacement of moisture, pressure systems and rainfall patterns. This has forced the patterns to be slow to transition into late Spring like conditions. There is also a large seperation of airmasses that has been apparent for sometime now, with the Northern half of the country extremely warm, and the Southern half extremely cold. Usually by now, even in a neutral year, the pattern should have transitioned into Spring and we would see much more heat and inland troughs moving South. There are a few reasons for this.

The biggest factor is the Positive IOD, which is colder than normal water sitting off the NW coast of the country. Coupled with this, the air that was quite moist in the westerly wind flow has become dry in recent months, in conjuction with the record levels of Sea Ice in Antarctica. Its my belief both of these phenomenon have coupled together to prevent a breakdown of the positive IOD. In short, cold and drier air has moved up from the relentless barrage from the Southern Ocean, and been swept up through the inland and then NW out into the Indian Ocean. The effect is little moisture over the interior for at least 6 months, with little rainfall, and well above average temps.

This is because of the positioning of the high pressure systems, which have stayed well North. Something a lot like this for example, i have drawn the line of where the cold air comes up from and gets dragged across the Top End and out over the Indian Ocean.

Now, this pattern is a normal climate response after 2 years of record rainfall. Its dragging up cold air, and drying everything out. Usually, this happens most winters. However, this year, its taken it to new levels, the pattern is trying to break from what you see here but is struggling. By now we should have seen the high pressure system further South, allowing moisture to move South from the tropics and given most of the country some rain. The heat troughs over WA and QLD are moisture starved at the moment and are struggling to get moving, so its like a vicious circle. This has caused my forecast of a fairly wet October for some parts to not eventuate, and my belief is that the Antarctic Sea Ice at record levels has had an effect.

In any case, lets look forward to what is coming up. My outlook is almost unchanged.

As i have pointed out previously, the forecast El nino has failed to gain any semblance in the Pacific. The forecast of cool neutral appears well on track. All other indicators are well de-coupled from the oceans, in fact the oceans are starting to couple with the atmosphere at present.

Here is the current drivers for the Pacific Ocean region that i am seeing as influencing the climatic pattern.

Trades are still Easterly, consistent with a La Nada.

Note also though that the trades have weakend somewhat, so a stalemate is in progress. In short, it wont have an effect, it will be neutral year, it will only determine how much heat is released from the oceans, and how big next years La Nina will be.

Southern Oscillation Index is 2.2 for the 30 day reading, and -1.80 for the 90 day reading. By the end of November it should be at zero for the 90 day average as we lose the negative figures from August which was a -6 month. Again, a neutral tendency.

Here is the graph: The positives are La Nina tendencies, and the negatives are El Nino tendencies. The SOI is calculated as the difference in Sea Level Air Pressure between Darwin and Tahiti.

CFS, and the BOM, and all the other climate models, finally agree with my forecast from months ago that an El nino will not occur. It will be a neutral year, which is a good result for us after 2 record la Nina years. Here is the Nino 3.4 area, the centre of the Equatorial Pacific

Here is Nino 1 and 2, close to the South American coast. This is where the cooling of the oceans start as a result of upwelling of cold water.

Sea Surface temperatures continue to lose heat, here is the anomaly chart. I have drawn some indicators on here, and i wil leave up the sst chart from last month to see the difference.

So, the cold upwelling has now got stronger, in the red circle. This is colder than normal water being dragged up due to the strong SE trade winds near South America. In a neutral, or normal pattern, this occurs. The blue then spreads towards Australia as it sloshes westwards on these winds. In the black circle is the slightly warmer than normal water, at the moment there are no westerlies to push this water towards South America. It should move towards Australia with the Easterly trades, which will increase the moisture levels for the monsoon season, and provide more rainfall for much of the eastern half of Australia.

The biggest change is in the orange circle, which is the IOD region I mentioned earlier. Finally the pattern is starting to slacken and it has now warmed quickly at the surface. Note also that it warms every year in November, and stays warm until April. The IOD is only important from April – October, as was seen this year. In any case its warmed nicely now so we will start to see the effects of this warm water in the coming weeks and months.

Here is the last months Sea Surface Temperatures to see the changes.

Will definitely be a neutral, even though there is cooling and warming simultaneously it looks like a break even neutral, with neither side favoured. What is important is that the trade winds should bring enough moisture for good rainfall to the country. How much is the million dollar question?

As noted in previous forecasts, notice the warmth in the Central Indian Ocean, providing fuel for fronts and low pressure systems over the next few months with a great moisture source. Once both areas are warm in tandem, which is now occurring, I think it lines us up for an enormous summer rainfall problem again for most of the country.

Also of note is the heat due to the build up of cloudless days over the desert in the winter months. This heat cannot be ignored, and will move South in the summer months. There should be enough moisture by then to ensure we dont break records, and also enough cold air lurking to keep it at bay so any heat that does eventuate will not be long lasting events. Nevertheless, its possible that we could get some very hot weather, by the next update in November, I will have a much clearer picture on the heat and its effects for Southern areas.

Forecast for Spring: November 2012 to February 2013.

Northern Territory : Temperatures will be slightly above average through the forecast period, tending less so in January and February.  Rainfall will be average through the Northern Territory areas for all of the forecast period, and will become above average for all areas through the monsoon season. There is also a risk of severe cyclone occurrence within the forecast area in this late forecast period. monsoonal rain will be above average again, particularly areas exposed to western coastal regions.

Queensland: Temperatures will  be slightly warmer than average through the forecast period for all of Queensland except the far north. Rainfall in November will be average to slightly below average through all of Queensland, except the inland which will be below average. However during December through February rainfall will increase substantially for all areas of Queensland. Also, risk of cyclone activity cannot be ruled out this forecast period, though i will have a closer look at this in the update for Qld, in late November

New South Wales : Temperatures will be slightly above average for the forecast in NSW, and well above average in November and December for the two inland western districts. Temepratures will be about average for all districts after the Xmas period. Rainfall will be below average in the NW initially in November, then average for the remainder. The remainder of NSW will have average to above average rainfall this forecast period.

Victoria : Temperatures in Victoria will also be average to slightly above average for all of the forecast period, for Northern and NW districts.  Southern areas will see average to slightly below average temperatures during the forecast period. Rainfall will also remain above average for all Southern areas, and below average for the Northern areas in November.  However rainfall will increase through late November through Northern areas and be about average for the forecast period.

Tasmania : A continuation of the trend for Tasmania with average temperatures for the entire period and state. Rainfall will be variable, average in western areas and below average slightly in Eastern areas.

South Australia : Southern areas will be slightly above average for temperatures for the entire forecast period. Northern areas will see early above average temperatures through November, averaging out by December. Rainfall will also be highly variable, southern areas will see average rainfall tending wetter through the latter part of the period, Northern areas of SA will see below average rainfall until late November when rain will increase markedly.

Western Australia : Temperatures will be slightly above average in the forecast period, particularly through the Southern and inland areas. Early season records did occur as forecast, and may continue for another 4 weeks until mid to late November. After that the rest of the forecast period will see temperatures average out to normal. Rainfall will be average for the entire state through November, except Southern areas which will be slightly above average. However i expect rainfall to increase markedly through late November through February for most areas not coastal.

Notes: We did see early Spring warmth for most of the inland areas, moving South, as previously forecast. Humidity will increase from early November onwards, deep Easterly trades should ensure lots of moisture will be advected over the country. Also, the Indian Ocean has rapidly warm as previously suggested, this warming trend will stick around for the next 6 to 9 months and should ensure above average rainfall across much of the Northern half of Australia, and the SE states. I am also forecasting a much earlier build up season, and then earlier monsoon arrival than last summer. Probably mid December, as per my previous outlook.

Also the risk now of serious flooding is still significant. I cannot rule that out until a later period, in the next update I will have a close look at this as it is the question I get asked most. However, in another months time we can have a good look at the set up and the build up will be well and truly on. We will need a significant increase in the surface Dewpoints, and by then I will know one way or the other.

The position of the Long Wave Trough also puts us at significant risk this summer yet again for another deluge, this is another ace in the pack that didnt quite line up in the last 2 years despite record rainfall. This is the key element of the forecast, if the pattern of colder air does not retreat South in the next few weeks then it can have profound effects on rainfall and temperatures across the entire country.

As mentioned last month it could also be the ace in the pack that interacts with the moisture and delivers massive rainfall to southern states.

Summary :

Warmer than normal temps will continue for another month in the North of Australia, average elsewhere. Then average temperatures will be fairly common for the remainder of the outlook. The general trend for the forecast period is for humidity to increase, along with rainfall for the entire country, except the Sw corner of the country, where the trend will be in reverse.

Next Update by November 20th 2012.