Doug Simonian

From Strong El Nino to Strong La Nina?

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Over the past few months, we have had an El Nino. In fact, it has been one of the strongest El Ninos on record, and is one of the reasons why this past winter was generally quite warm, and why the Pacific Jet stream was so fast and active. It also helped to trigger the historic blizzard we had on January 22nd-23rd. Currently, while we still have an El Nino at the surface, conditions are rapidly flipping towards La Nina when one takes a deeper look at the oceans, as well as the trends in the climate models.

Under “normal” conditions, where there is no El Nino nor a La Nina, the trade winds are persistent in the Equatorial Pacific, which generally blow from east to west. This “pushes” the warmest Equatorial waters further west towards Australia and Indonesia, leaving cooler waters in their wake with more upwelling of subsurface cool water as well. Over the past year or so, these trade winds rapidly weakened and even reversed in some areas, allowing warm water to flow back eastward (instead of getting forced westward) towards the entire Equatorial Pacific, spreading eastward towards Peru. As warmer water builds, Oceanic Kelvin waves, which move from west to east — but also move up (upwelling) and down (downwelling) to transport warm or cool water vertically — are able to push warm water to strong depths and generate “pools” of warm water. This allows an El Nino to sustain itself, as even when a brief period of trade wind acceleration takes place and more upwelling happens, the water upwelled is still warm. It can take months to fully reserve a new El Nino equilibrium.

But finally, the proverbial rubber band is snapping.

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Miguel Pierre

Monday Musings: Warm, Dry Today…Backdoor Cold Front & Possible T-Storms Tomorrow

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High pressure off the Mid-Atlantic coast will be control of weather. A couple passing upper-level disturbances will bring cause clouds to mix with sunshine today. But light southwesterly winds will help temperatures to rise into upper 60s to lower 70s, away from the south-facing shores. Tonight will be partly cloudy with low temperatures upper 40s to lower 50s. A warm front lifting north the region may cause some scattered showers and isolated thunderstorms late tonight or early tomorrow morning.

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Miguel Pierre

Very Warm with Showers & T-storms Later Today… Pleasant Weekend Coming Up

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Very warm weather conditions are expected with more clouds will mixing with sunshine today and light southwest winds. High temperatures will reach the upper 70s to perhaps lower 80s this afternoon, despite more clouds. Near the shore, the southerly flow and sea-breezes this afternoon keep temperatures much cooler in the upper 60s to lower 70s.

A cold front approaching region will likely cause some scattered showers and a few thunderstorms around region, later this afternoon and this evening. Instability will be minimal due more clouds and lower surface dewpoints. Any thunderstorms could contain heavy downpours and lightning. But severe thunderstorms are not anticipated. Also Yankees fans, please check out our SportsCast page for forecast updates today for a possible rain delay for the Yankees game tonight.

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Miguel Pierre

(Premium) Will High-Latitude Blocking Bring Chilly Temperatures and More Rain Next Week?

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Since the breakdown of stratospheric polar vortex more high-latitude blocking has become common the last few weeks.  Model and ensemble guidance are again showing blocking returning again for next week. But will it give pattern change featuring just below average temperatures? Or will a parade of systems coming out the Pacific, cause the Southeast ridge to build more?

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