Following two years of cold water in the equatorial Pacific ocean, the next year is almost always a warm, El Niño event. Not this time. A weak surge of warm water along the west coast of the Americas this fall relieved the build up of warm water in the western Pacific then the incipient El Niño failed. Strong tropical atmospheric convection in the Indonesian region, driven by exceptionally high sea surface temperatures there, kept the incipient El Niño from intensifying. Tropical air that rises up in monsoonal rains over Indonesia sinks in the subtropics over the eastern Pacific ocean. This convection cell is one of the processes that creates the east Pacific high, the high pressure area that keeps California dry in the summer. Over the past six months, extraordinarily warm water in the Indian ocean kept the monsoonal convection from moving towards the central Pacific ocean, preventing the development of El Niño. The east Pacific high did not break down despite the brief surge of warm water along the equator. Now the water is cooling and the east Pacific high is reintensifying, strengthening the grip of drought across the southwest and southern plains. The consequences are disastrous.
The U.S. hard red winter wheat crop, which is in the worst condition since the USDA began reporting conditions, was declared a disaster on January 9. And new long range forecasts by the Climate Prediction Center predict the drought to get worse in the southern plains and the southwest. Heavy rains in the Ohio valley have improved conditions there and raised the Mississippi River south of Cairo, but the upper Mississippi River continues to drop towards record low levels which would make the river impassible to commerce.
Wheat growers in the Southern Plains have known the effects of a drought for about 120 consecutive weeks, and now their neighbors to the north have been added to the drought disaster list. Nearly 600 US counties—20% of them—have been declared disaster areas in the first such USDA designation in 2013. Drought and heat, an environment unsatisfactory for the development of the hard red winter wheat crop, have seriously threatened the vitality of the crop.
No significant precipitation is expected in the U.S. Great Plains in the next 10 days, forecaster DTN said in a report yesterday. Northern and eastern areas of the region may be very cold, and temperatures in wheat-growing areas in the northern Midwest may near zero degrees Fahrenheit (minus 18 degrees Celsius), according to the report. The U.S. winter-wheat crop was in the worst condition since 1985 as of the end of November after dry weather, Department of Agriculture data show.2013 is the third year of drought in the grain belt.
“Nearly all of the Northern Plains was enveloped in drought by October, which is a record in the 13-year US Drought Monitor history. Drought coverage also rapidly increased in the Midwest, peaking at about 73.7 percent in July, which is also a USDM record. In early 2012, the Southern Plains was recovering from the 2011 drought. The percent area in moderate to exceptional drought decreased to a low of about 32.3 percent in May 2012 before expanding again to peak at about 73.7 percent in July.”And newly released forecasts by the Climate Prediction Center predict worsening drought in the west and the plains. The east Pacific high, the subtropical high pressure area offshore of California is strengthening. Cooling waters in the east equatorial Pacific ocean support continued strengthening of the high over the next 90 days. The high will push the storm track north towards the Pacific northwest and southern Alaska, producing dry conditions in the southwest and the plains.
During the upcoming three months, a much drier pattern is expected across the southern third of the Nation (from central California to the eastern Gulf Coast).This limits the prospects for further drought improvements during the latter end of the wet season in California, Nevada, and western Arizona, and in fact increases the probabilities for drought development and deterioration in the tri-State area. This also marks a change from recent wet conditions in the southern Plains and western Gulf Coast as drought development and persistence is forecast for Texas by the end of April. Similarly, drought development and persistence is possible in the eastern Gulf Coast States, but less likely further north. In contrast, enhanced probabilities of surplus precipitation and subnormal temperatures across the northern U.S. (from the northern Rockies eastward to the upper Midwest and into the western Corn Belt) increase the odds for drought improvement. Some improvement is possible across the middle Mississippi Valley and the Piedmont, the latter area from wetness forecast for the rest of the month.
Weekly sea surface temperatures:
The surface of the tropical Pacific continued to cool during the past fortnight. Cool anomalies are now evident along the equator in the eastern half of the Pacific, (see the SST anomaly map for the week ending 13 January below). Warm anomalies remain in the western tropical Pacific between the Date Line and about 150°E and surrounding Australia from the South Australian–Victorian border to the Western Australian–Northern Territory border. Anomalies in most of these areas are on the order of 1 °C cooler/warmer than average.
Heavy rains in the midwest have raised water levels on the Ohio River and the Mississippi River south of Cairo, Illinois, but worsening drought in the west and the plains may cause the upper Mississippi River to become impassible near St. Louis, Missouri. Large quantities of grain are transported by barge on this part of the river. Rising water below Cairo is good news for shipping, but agricultural products from Iowa and the northern plains may not be able to make it to Cairo by February 1. The Army Corps of Engineers is blasting rock formations at Thebes, adding 2 feet to the channel. This has postponed the closure of this part of the river to barge traffic. However, that may be a temporary victory because little rain is in sight. Water levels are forecast to drop for the next 2 weeks to levels that may be too low for barge traffic.
Intensification of the Walker Circulation is one of the predicted effects of global heating.
The Walker Cell: The Walker circulation is the result of a difference in surface pressure and temperature over the western and eastern tropical Pacific Ocean. A pressure gradient from east to west and causes surface air to from high pressure in the eastern Pacific to low pressure in the western Pacific. Higher up in the atmosphere, west-to-east winds complete the circulation. The Walker circulation affects precipitation patterns in many locations, including the Southwest, and influences the easterly trade winds, oceanic upwelling, and ocean biological productivity. It also provides the background against which El Niño-Southern Oscillation (ENSO) events take place.The cooling of the eastern Pacific, caused by the intensifying Walker circulation, combined with the warming north Atlantic is recreating the atmospheric conditions that led to the dust bowl and to megadroughts that devastated the Anasazi (e.g. Mesa Verde).
This could be the beginning of a megadrought.
This video explains El Niño, La Niña & how they affected the weather in 2010 & 2011.