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Dan Rather: El Nino

Dan Rather, CBS Evening News anchor, put together this El Nino update exclusively for CBS.com.

El Ninos, which come roughly every three to five years, are strongest in the beginning and at the very end of the winter season.

And so it is with this exceptionally powerful El Nino, one of if not THE strongest El Nino on record.

The latest satellite photographs continue to show a very strong jet stream sweeping constantly across the Pacific. This is what is pushing the storms into California.

There are a number of storms , in effect, lined up out in the Pacific. They'll be coming into the West Coast, mostly into California, for a long while to come. There'll be breaks in between, perhaps even relatively long breaks. But these storms are out there, and WILL keep coming for awhile.

As the storms move into California and sometimes adjacent areas, the jet stream splits. The northern branch [the Polar Jet] takes storms up into the U.S. Northwest and Western Canada. This helps create an effect that holds the coldest arctic air in Canada. Thus, warmer weather than usual in the Upper Plains and Upper Midwest.

[Yes, there has been record snow in Louisville and Cincinnati, but temperatures in the Upper Plains and Midwest OVERALL are generally warmer than normal.]

The SOUTHERN wing of the split jet stream [the Sub-tropical Jet] sends an unusual amount of weather energy across the Southwest and South. That means more unusually heavy rain can be expected in Texas. [Along with occasional high winds, such as the up to 60-mile-an-hour ones expected in West Texas this day].

These storms brought by the Sub-tropical Jet from the far Pacific tap Gulf of Mexico moisture and, in turn, create severe weather across the South and on into Florida.

This is part of what has made Florida's winter so far unusually bad.

From Florida and surrounding areas, the Sub-tropical Jet tends [partially with the El Nino influence] to veer north, along the east coast. Sometimes these storms in the southern flow reach up close enough to inject moisture into the NORTHERN flow. This causes heavy INLAND snow in the Northeast, including New England.

The Northeast part of the country is the hardest to predict when it comes to El Nino's influence. Generally, a more unusual, less predictable winter is expected in the Northeast the remainder of winter and on into spring.

Overall, and for the country as a whole but especially for California, Texas and Florida, the amount of energy being injected into the jet flows is far more than in the usual winters. So the weather is more dramatic this year. "Energized by El Nino" is an accurate characterization.

Not everything that happens to the weather in North America this year can be traced to El Nino. But much, very much of it can be. And with satellite technology, IS.

This El Nino MAY have reached its peak. Most experts think it probably has. However, this one is so stong its effects figure to be felt for many weeks to come -- perhaps even well into summer.

Strong storms should continue to develop into Spring. This includes the potential for more than the usual number of tornadoes in the Southwest and South. [Texas has prime potential, for example].

Projections indicate a change to a La Nina development in the Pacific later in the year. When is the big, unanswerable for now question.

Outlook: El Nino, possibly melding into La Nina, for another 4-6 months at least.

Watch for Dan Rather weeknights on the CBS Evening News, and listen to "Dan Rather Reporting" on weekday afternoons and/or evenings on the CBS radio network.

CBS News weather consultant Bryan Norcross contributed to this report.

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