Doug Simonian

El Nino Update: Not a matter of if, but how strong

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As the Spring season moves along, signs begin to become more clear regarding the development of an El Nino. Although there has been relatively high confidence in the development of an El Nino for quite some time, there was still a small bit of doubt, as some expressed skepticism. However, over the last month or so, the atmosphere has undergone changes which should remove any seeds of doubt regarding whether an El Nino will be developing this Spring and Summer. The only doubts that exist now is the final strength of the event (El Nino events usually peak in the Autumn): high-end moderate/low-end strong, a strong event, or a super strong event. For more information regarding the formation of El Ninos and what they mean for our weather pattern, check out the article we published last month. 

What has happened that makes us so confident? The easterly trade winds which usually keep warm water well to the west towards Indonesia have shifted to westerlies. 

This animation shows the progression of the strength and direction of wind currents. Note how they started off blowing from east to west, but have dramatically shifted in the opposite direction. This is a strong indicator that an El Nino is coming. Click to animate.

This animation shows the progression of the strength and direction of wind currents. Note how they started off blowing from east to west (easterlies, blue arrows), but have dramatically shifted in the opposite direction (westerlies, red arrows). This is a strong indicator that an El Nino is coming. Click to animate.

This means that the base state of the atmosphere which prevents El Nino events has completely changed to one that favors El Nino events. The typical climate pattern has easterly trade winds along the Equator, which blow warm water along the Equatorial Pacific to the west, towards Indonesia and Australia, leaving the rest of the Equatorial Pacific relatively chillier. Now that the surface currents have shifted to blowing from west to east, it becomes much easier for that same warm water from the west to move eastward throughout the rest of the Equatorial Pacific, leading to an El Nino.

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John Homenuk

Slow but persistent warmup the next several days

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As a warm front struggles to move north of the area today, temperatures have struggled as well — staying generally stuck in the mid 50’s for the majority of the day through the early afternoon. Although some warmer temperatures are anticipated by later this afternoon, the general theme will continue to feature east/northeasterly winds off the ocean waters and cooler than normal temperatures with clouds. A warm front has established itself to our south and west, and while that is providing much of the Mid-Atlantic with warmth, it is leaving us in a damp, marine airmass.

This front will struggle northward over the next few days, but the good news is that forecast models agree it will eventually make it. Friday looks to feature conditions more similar to Thursday than the past several days of this week — although there won’t be as many clouds, temperatures won’t reach much past the 60’s. This will be especially true near the coast, as east/northeasterly winds again bring in cooler marine air.

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Doug Simonian

Pleasant for now, showers later this week, warming trend this weekend

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Although an area of persistent troughing which has kept the area chilly this spring has remained in place, a high pressure system to our north led to downsloping westerly and northwesterly winds this afternoon. This warmed temperatures up to around 70 in most of the area, while keeping the atmosphere very dry, with dewpoints in the low 30s. The dry conditions in combination with the trough that is still in-place will allow temperatures to drop pretty quickly tonight, as areas in the interior could have temperatures falling into the upper 30s, and frost is possible. Elsewhere, low temperatures will probably fall in the 40s — still definitely chilly enough for the light jacket tonight.

Starting tomorrow, the weather pattern will begin to change. Warmth and moisture from the south and west will try to push towards our area, while the troughing will remain to our north and east. This will create a battleground, and a resulting warm front.

The above image shows the frontal boundary pretty clearly — the front is shown more clearly at the 850mb level, since surface temperatures are a bit more uniform due to continued downsloping flow. This will once again make surface temperatures a bit warmer for tomorrow than what they normally would be in our otherwise cooler airmass. This will allow high temperatures to approach 70 degrees again. Warm 850mb temperatures result in the potential for greater warmth given sunshine, but that potential is not always realized — and this is where the forecast becomes a bit more tricky for later in the week, which will be illustrated shortly.

Where the strong southwesterly flow at 850mb meets with the much lighter winds, is the general location of the frontal boundary, further illustrated by the strong temperature gradient. The continued northwest flow on the cold side of the boundary at 850mb will help keep things dry tomorrow, but once those southwest winds from 850mb approach in association with the front, our 850mb temperatures will rise, and the moisture in the atmosphere will increase significantly. This allows for the chance of showers and potentially even a thunderstorm on Wednesday night into Thursday morning. The warmer airmass will not allow temperatures to fall as much, as they will remain around 50.

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John Homenuk

Pleasant weather, warming trend expected this week

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The return of high latitude blocking (or above normal height anomalies over the higher latitudes from Greenland into Canada and the North Atlantic) has slowed the progress of spring, or at least the warmth which typically comes with it over much of the Northeast United States. While much of the Western, Southern and Central United States have already experienced widespread warmth with several days over 80 degrees, persistent troughiness and meandering upper level lows have meant cooler than normal temperatures and frequent cold fronts in the Northeast. A change is in order during this week, but will occur over the span of a few days as a warm front slowly pushes northward.

Initial conditions on Monday will be pleasant, but again dry and breezy. The National Weather Service warns of enhanced fire danger once again. The low humidity values and stiff breeze will allow for rapid spread of any fire after ignition. As recently as last week, Red Flag Warnings were issued throughout the area and several brush fires spread rapidly in parts of New Jersey. Other than the fire danger, Monday looks quite pleasant with high temperatures well into the 60’s and plenty of sun — with no chance of showers or thunderstorms during the afternoon as was the case this weekend.

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