la nina Archives - Reduce Flooding

It’s always nice to start the new year by looking at the big picture. And big pictures don’t get much bigger than this. The image below comes from NOAA’s Global Data Explorer. It shows sea surface temperature anomalies in the Pacific and Atlantic. Reds show areas with warmer than normal temperatures. Blues are cooler.

*Sea surface temperature anomalies from 12/20/21 to 12/26/21. Source: NOAA.*

Degrees of Variation

The dark red areas are a whopping 4-5 degrees Celsius above normal. The dark blues are 3-4 degrees Celsius below normal. It takes 1.8 degrees Fahrenheit to equal 1 degree Celsius. So in terms of the temperature scale that most people in the US use, that’s up to 9 degrees warmer and 7.2 degrees cooler – a 16.2 degree spread.

This helps to explain the record warm December we just had. Houston is in that band of red that stretches across the northern hemisphere. Also notice how red the Gulf of Mexico is.

According to the EPA, an increase in sea surface temperatures can lead to an increase in the amount of atmospheric water vapor over the oceans. “This water vapor feeds weather systems that produce precipitation, increasing the risk of heavy rain and snow.” And we just had extreme snowfalls from the Sierras to the Rockies.

Role of Ocean Currents

Ocean currents help distribute this moisture around the world. According to NOAA, “almost all rain that falls on land starts off in the ocean.”

*The world’s major ocean currents distribute heat and moisture across the globe. Source: NOAA.*

“Ocean currents act much like a conveyor belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics,” says NOAA. “Thus, ocean currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth’s surface. Without currents in the ocean, regional temperatures would be more extreme—super hot at the equator and frigid toward the poles—and much less of Earth’s land would be habitable.”

Cyclical Variation

Sea surface temperatures vary in cyclical, but irregular patterns (roughly every 3-6 years). Right now, we are under the influence of a La Niña pattern, that recurs every few years and can last as long as two years. This page on NOAA’s site explains what causes the changes. They often start with ocean currents veering off course for a period of time or stronger than normal trade winds.

The World Meteorological Association gives this La Niña an 80% chance of lasting through this spring before returning to normal (neutral) conditions.

Posted by Bob Rehak on 1/1/22

1586 Days since Hurricane Harvey

Jeff, Lindner, Harris County’s meteorologist, predicts strong to severe storms Saturday that could bring heavy rains. He says most locations will receive .50 to 1.5 inches of rain. But some isolated areas could see 2- 3 inches.

*File photo: storms build when warm, moist air collides with cooler air. Rapid cooling turns the moisture into precipitation.* *And we could see a 40 degree drop tonight.*

Near Record Warmth Again with Moist, Onshore Flow

According to Lindner, record and near record warmth will continue for one more day across the area before a cold front arrives on Saturday bringing temperatures back to near normal.

The combination of moist onshore flow and a warm start to today should elevate temperatures into the low 80s this afternoon. That will be at or near record highs again.

“Records have fallen at local climate sites nearly each day this week as the incredibly warm December continues,” says Lindner.

Colliding Cold Front from North

As a cold front from north Texas moves south tonight and into Saturday, widespread showers and thunderstorms will develop along and ahead of it. The very moist air ahead of the front will cause instability when it arrives. A few of the storms on Saturday could become strong to severe.

Heavy rainfall will be possible with the stronger storms. It currently appears that most locations will receive anywhere from .50-1.5 inches with some isolated totals of 2-3 inches.
Jeff Lindner, Harris County Meteorologist

The front should move out into the Gulf by Saturday evening and temperatures will fall into the 40s, says Lindner.

Second Disturbance Arriving Sunday from Mexico

Yet another disturbance moving northeastward out of Mexico on Sunday will increase cloud cover and bring more light rains. But Lindner thinks most of the heavy rains will remain offshore. He predicts drizzle for much of the region on Sunday and Monday with temperatures holding in the forties and fifties. After that temperatures should increase again.

The current forecast for Christmas looks warm.

La Niña Likely Affecting Current Weather

Daily temperature records continue to fall at several climate sites both for highs and “warm” lows. This December is among the top five warmest Decembers at all local climate monitoring stations. And this is THE warmest December ever at Galveston.

Many records also fell on Wednesday across the central plains and Midwest. Wisconsin had the warmest December temperature ever recorded in modern times at 72.

The powerful storms that swept across the plains on Wednesday also brought the first ever recorded tornadoes in the month of December to Minnesota and Wisconsin.

The cyclical La Niña weather pattern that we are now in likely contributes to the record temperatures. La Niñas are typically warmer than El Niño patterns. The two alternate in the Pacific and influence patterns of the jet stream. NOAA and the National Weather service predict the current La Niña will continue through spring next year.

Posted by Bob Rehak on December 17, 2021, based on a report by Harris County Meteorologist Jeff Lindner

1672 Days since Hurricane Harvey

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