La Nina...

Posted By: SP Daily

La Nina... - 07/07/10 07:16 PM

Atached is an ENSO Update release yesterday by WMO. A weak La Nina phase of ENSO is evolving in the Pacific and is forecast to last through most of the current Hurricane Season, with possible return to neutral conditions towards the end of the year.... No El Nino is foreseen to evolve in the foreseeable
Kindly note this Hurricane Mitch excerpt from the preliminary NEMO database...
General Information
13th named Storm, 1998 Season Hurricane Mitch Cat V / 155 mph winds. Max wind attained 180 mph. Devastated the Honduran island of Guanaja then move onshore over northern Honduras after 33 hours as a Cat V. Central pressure was down to
905 mb (26.73 in). Produced storm surge of around 44 feet, according to one model. October 26, 1998 No death in Belize. Over 11,000 death in Central America: about 6,500 in Honduras alone; 4,600 - 11,000 missing in Honduras.
Areas mostly impacted were: Honduras, El Salvador, Belize, Guatemala, Nicaragua, Mexico. Cost in damages was estimated at over US $5 Billion in Central America; US $10 Million in Belize. Research conducted over recent decades has shed
considerable light on the important role played by interactions between the atmosphere and ocean in the tropical belt of the Pacific Ocean in altering global weather and climate patterns. During El Niño events, for example, sea
temperatures at the surface in the central and eastern tropical Pacific Ocean become substantially higher than normal. In contrast, during La Niña events, the sea surface temperatures in these regions become lower than normal. These
temperature changes are strongly linked to major climate fluctuations around the globe and, once initiated, such events can last for 12 months or more. The strong El Niño event of 1997-1998 was followed by a prolonged La Niña phase that
extended from mid-1998 to early 2001. El Niño/La Niña events change the likelihood of particular climate patterns around the globe, but the outcomes of each event are never exactly the same. Furthermore, while there is generally a
relationship between the global impacts of an El Niño/La Niña event and its intensity, there is always potential for an event to generate serious impacts in some regions irrespective of its intensity.
Three significant tropical cyclones impacted Belize during this period, namely: Mitch in October 1998; Keith on October 1, 2000; and Iris on October 8, 2001.
Posted By: SP Daily

Re: La Nina... - 07/09/10 01:29 AM

La Nina developing, could mean more hurricanes

By RANDOLPH E. SCHMID (AP) – 8 hours ago

WASHINGTON — The climate phenomenon known as La Nina appears to be developing, threatening more bad news in the efforts to clean up the oil spill in the Gulf of Mexico.

When a La Nina occurs there tend to be more hurricanes than normal in the Atlantic and Caribbean regions, which include the Gulf of Mexico.

The federal Climate Prediction Center said Thursday that La Nina conditions are likely to develop in July and August.

La Nina is marked by an unusual cooling of the sea surface in the tropical Pacific Ocean. Water temperatures in that area can affect air pressure and winds, resulting in changes in the weather in many parts of the world.

In a La Nina, wind shear is increased over the Pacific and reduced over the Atlantic. Wind shear is the difference in strength of winds at low levels compared to higher level winds.

A strong wind shear reduces hurricanes by breaking up their ability to rise into the air, while less shear means they can climb and strengthen.

Thus, the Climate Prediction Center notes, "there tend to be more Atlantic hurricanes during La Nina because of this expanded area of low vertical wind shear."

In addition, during a La Nina "more hurricanes form in the deep tropics from African easterly waves. These systems have a much greater likelihood of becoming major hurricanes, and of eventually threatening the U.S. and Caribbean islands," according to the center, a part of the National Oceanic and Atmospheric Administration.

The climate center's current hurricane forecast for this season is for 14 to 23 named storms of which 8 to 14 are expected to be hurricanes and 3 to 7 major hurricanes.

The center noted that during June, sea surface temperature continued to decrease across the equatorial Pacific Ocean, with cool areas expanding across the central and eastern Pacific. In addition, increased rainfall persisted over Indonesia, while the area of reduced rain expanded westward over the western and central equatorial Pacific.

Combined with changes in the winds over the Pacific "these oceanic and atmospheric anomalies reflect developing La Nina conditions" which are likely to continue through early 2011, CPC said.

The last La Nina occurred from the fall of 2007 to the spring of 2008. The opposite mode, El Nino, with warm Pacific conditions, has been in place since the spring of 2009.
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