Martell: ENSO-Neutral Weather Persists, But Movement Toward La Nina

January 22, 2013 05:50 AM

The following content was provided by meteorologist Gail Martell of 

ENSO-Neutral Weather Persisting

A weak La Nina signal seems to be emerging in late January. For a full fledged La Nina to occur the sea surface temperature anomaly must fall below the -0.50 C threshold. Presently, conditions are considered ENSO-neutral with sea surface temperature anomalies near -0.40 C.

With ENSO-neutral conditions, showers are possible in the Southern Great Plains. The five-day forecast calls for light to moderate moisture in the Southern Great Plains. The southern jet stream would carve out a deep trough over the southwest United States, spinning out waves of showers into the southern Great Plains. Precipitation from .10 to .40 inch is predicted in hard red winter wheat in the updated outlook.

Stable High Pressure Stressing Brazil and Argentina Crops

A large stable ridge of high pressure is having a detrimental effect on crops in southern south America blocking rainfall and sharply reducing humidity. Subsiding air in key farm states is drying out the atmosphere, while also reducing chances for showers.

High Pressure Dominant southern So America

Hot days and cool nights have occurred frequently this month, due to the ultra-dry atmosphere. For example, Sao Luiz Gonzagas, a weather station in northern Grande do Sul, is expected to top out at 93 F today, the projected maximum temperature. Rapid cooling is predicted overnight with a low of 65 F. A very large daily range in temperatures 28 degrees F indicates a super-dry air mass. Soil moisture is rapidly declining at the same time that crop moisture needs are increasing. Corn is believed to be pollinating or filling kernels in Parana, Brazil's leading corn state. Soybeans may be getting set to bloom or set pods. Parana is Brazil's second top soybean state, after Mato Grosso, and Rio Grande do Sul the fifth leading producer.

24 hour rainfall So America

On the positive side, Mato Grosso crop potential is improving with increased rainfall in January. December had been abnormally dry in Brazil's leading soybean state where over 30% of soybeans are grown.

Shallow Rooted Crops in Jeopardy

Argentina crop conditions also have deteriorated from unseasonable dryness in January. Indeed, the moisture stress may be worse than southern Brazil, due to delayed planting dates and shallow rooting in corn and soybeans.

South Brazil Dry Forecast

Relentless rains caused sharp delays in planting, a significant portion of corn and soybeans getting planted in December and January. These later planted crops are rapidly succumbing to moisture stress as the top soil layer has dried out in January. Rains have been modest, or non-existent, this month in Buenos Aires, Cordoba and Santa Fe, the top 3 farm provinces.

The weather forecast for South Brazil and Argentina remains drier than normal this week with a continued influence from high pressure offshore.


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