Colder Biased 2017 Brazil Winter Raises Frost Threat
By Drew Lerner
Kansas City, May 22 (World Weather Inc.) – Brazil winter temperatures will be colder biased this year and that will raise the potential threats of frost and freezes from southern grain areas into coffee and sugarcane country. It is too soon to predict the 
severity of the winter, but a repeating cycle in the upper atmosphere is expected to present weather patterns similar to those in both 1981 and 1963 and in both cases significant frost and freeze conditions impacted several important crop areas including coffee, citrus and sugarcane production areas.
Three important weather trends will be playing into this year’s cold bias for Brazil. The first and most important is the return of the weather trends seen last in 1999 and more importantly in 1981 and 1963. The repeating trend should bring multiple opportunities for a south to north air flow pattern aloft over South America bringing Antarctic air into the region during short periods of time. The pattern will be tested by the tendency for global warming in recent years and many scientists will be anxious to see how significantly anomalous the cool biased pattern can get. It is very interesting to note that Northern Hemisphere weather patterns in recent 
weeks have started looking much like that of 1963 which was a cooler biased decade. World Weather, Inc. is not suggesting that the temperature bias in the atmosphere has returned to that of 1963, but the upper air wind flow pattern is going to be similar and that promoted some impressive cold surges during the South America winter of 1963. The pattern was seen again 1981and both winters were cold enough to generate some frost and freeze conditions. When the pattern reappeared in 1999 it occurred under the strong influence of La Nina which likely diminished some of the impact of the repeating weather pattern.
As we have pointed out many times in the past there is a strong correlation with Brazil coffee, sugarcane and citrus freezes occurring near the sunspot minimum. This well documented study has proven false only two times since the start of the 20th century. The correlation says that frost and freeze events in Brazil coffee areas tend to occur within two or three years of the sunspot minimum and 
occur most often when neutral ENSO conditions are prevalent. Solar or sunspot minimums occur every 10-12 years and the only two solar minimums that were not bothered by frost or freeze conditions (within 2 or 3 years of the minimum) was in association with the 2008 minimum and the minimum that occurred in the early 1920s. There have been at least light freeze and frost events in association with all other solar minimums since the start of the 20th century.
Picking the year that is most likely to experience frost and freeze conditions can be a real challenge, but the repeating weather cycle noted above can play a significant role of influence for the frost and freeze year. The solar minimum is predicted sometime in the 
period from 2018-2020. That puts 2017 in a statistically more favored period for a cold air event of significance, but that does not guarantee the event.
Studies have also been made in recent decades trying correlate ENSO events with frost and freezes in Brazil. These studies have been a little inconclusive even though it has been proven that significant frost and freeze events tend to occur in neutral ENSO years. The problem with the association is that there are far more neutral ENSO years than El Nino or La Nina years so the odds are much higher that frost and freezes would occur in the neutral years. There have been significant freezes in El Nino and La Nina events, but they are much less common and some scientists suggest that freezes are less likely during one of these events. However, World Weather, Inc. believes the statistics are skewed because neutral ENSO conditions are far more 
common than El Nino La Nina events. We cannot make the assumption that neutral ENSO events actually increase the potential for freezes because there is no reason why one phase of ENSO would have more influence on cold air than another phase. If we assume for the moment that there is an actual statistically more favored association between significant freeze events in Brazil and neutral ENSO events then that gives 2017 a little more potential for such an event because ENSO is neutral and will likely stay that way through the Southern Hemisphere winter season.
In addition to the repeating weather cycle, the approaching sunspot minimum and neutral ENSO conditions there is one more important feature that may be evolving and that is cooler than usual sea surface temperatures off the lower east coast of Brazil. Recent studies have shown that there is a tendency for cooler than usual ocean water to be present off the lower Atlantic coast of Brazil during frost and freeze events. To a certain degree, that association makes since. Cooler ocean water would support a stronger surface high pressure system in the region. Having the ocean cooler than usual when cold air comes to southern Brazil should help reduce airmass modification because cooler ocean water generates less water vapor and tends to keep air temperatures above the surface of the ocean a little cooler biased. The lack of warm and humid conditions above a cool ocean should reduce airmass modification and help to reinforce the cold air a little better when strong surges of cold come into southern Brazil and eastern Argentina, Uruguay and southern Paraguay.
The cold ocean water scenario needs further study, however. There is some suspicion that the cooler ocean water results from frequent cold air masses moving through the region instead of cool ocean water helping to generate stronger cold air masses that can produce damaging freezes. World Weather, Inc. believes whole-heartedly that in the case of strong south to north cold surges moving into eastern Argentina and southern Brazil the cooler ocean surface temperatures are, the less moderation of the airmass will take place. Therefore, having cool water off the lower Atlantic Coast of Brazil in a year dominated by south to north cold surges near a sunspot minimum and in a neutral ENSO year could support a better potential for crop damaging cold.
Ocean temperature changes in this most recent week have started to warm off the lower Brazil Atlantic Coast after cooling in previous week. It is unclear whether this warming trend is long term or just a temporary adjustment after recent cooling. For now, this signal is not very clear, but World Weather, Inc. will continue monitor conditions off the coast of Brazil in the next few weeks.
In conclusion, World Weather, Inc. feels it has been many years since each of these cold weather signals for Brazil have occurred simultaneously and that is enough reason to wave a big caution flag that some threatening cold may come to into eastern Argentina, Uruguay, Paraguay and southern Brazil this winter. The damaging cold events that occurred in 1963 and 1981 occurred in mid- to late-June and late July respectively.
The cold surge that occurred a little more than three weeks ago in southern Brazil was an impressive and notably earlier than usual event. Frost and light freezes occurred at that time from northeastern Rio Grande do Sul into the southern grain areas of Parana. The cold was quite early relative to the start of the cold season and the ease in which temperatures plummeted across the region certainly makes the potential for more cold air later this winter a viable possibility and the situation will need to be closely monitored.
In addition to the higher risk of cold surges in Brazil coffee, sugarcane and citrus areas this winter, there will be additional bouts of greater than usual rainfall from Mato Grosso do Sul to Minas Gerais and neighboring areas each time a cold surge comes along. The winter is likely to be wetter biased in these areas, but keep in mind that each rain surge will be followed by cooler and drier air leaving some crop areas in a wetter and cooler biased pattern for 2017.
World Weather, Inc. forecasts and comments pertaining to present, past and future weather conditions included in this report constitute the corporation’s judgment as of the date of this report and are subject to change without notice. Comments regarding damage or the impact of weather on agricultural and energy as well as comments made regarding the impact of weather on the commodity and financial markets are the explicit opinions of World Weather, Inc. World Weather, Inc. cannot be held responsible for decisions made by users of the Corporation’s information in any business, trade or investment decision.
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