“When in Drought, Leave it Out”

“When in Drought, Leave it Out”

We don’t know who first coined that phrase, but like most meteorological rules of thumb, it tends to hold true most of the time. Here in New England, especially Southern New England, we are definitely in a drought.

20160719_northeast_trd
Latest update from the U.S. Drought Monitor.

A persistent pattern has led to warm and dry conditions across the Northeast for the past several months.While scattered showers and thunderstorms have produced locally heavy rainfall in some areas recently, widespread rainfall has been lacking. Many cold fronts have come across the region with little rainfall and coastal storms are rare in the summer to begin with. Even waves of low pressure passing south of New England along stalled out cold fronts have been too far south to produce much rain across our area.

m3ppct_northeast_jun16
Rainfall since the start of April has been well below normal across the region, especially in the Merrimack Valley. Image provided by the Northeast Regional Climate Center.

 

The dryness has been most noticeable since the beginning of June. Since June 1, Boston’s Logan Airport has recorded just 1.99″ of rain. This is the driest June/July on record in the city. The current record is 2.03″ from 1949. If Boston does not receive more than 0.04″ before Sunday night, a new record will be set (more on that later). In Worcester, the 3.18″ during the same timeframe is the 4th lowest total on record. In Lowell, 3.12″ of rain has been reported since June 1. This is the 8th lowest total on record.

So, is there any relief on the way? Maybe, though we wouldn’t count on it. A cold front will move across the region late Thursday and early Friday, then stall out south of New England. A wave of low pressure will ride along the wave, passing south of us on Friday. This wave will produce locally heavy rain and thunderstorms across the Ohio and Tennessee Valleys on Thursday, before it heads for the Mid-Atlantic states Thursday night. The question then is, how far north does the low and its associated rain shield get? This is the same situation we often see in the winter when trying to determine if a storm will miss us completely, bury us with heavy snow, or come too close and give us rain instead of snow. Thankfully, we don’t have to worry about snow for another 3-4 months at least.

Right now, there are several different solutions among the models, which have a rather large impact on the forecast.

gfs_tprecip_boston_15
GFS model forecast for total rainfall through Saturday night. Image provided by WeatherBell.
cmc_total_precip_boston_15
GEM (Canadian) model forecast for total rainfall through Saturday night. Image provided by WeatherBell.
nam_total_precip_boston_29
NAM model forecast for total rainfall through Saturday night. Image provided by WeatherBell.

For the past few months, as we’ve mentioned previously, most of these storms have passed too far south to have much of an impact on us. For this reason, we’re inclined to lean that way with the forecast for Friday as well. That means we’re going with the GFS model above. Is there a possibility that one of the other models is right and we do get heavy rain? Sure, they could very well be right, but we’re not betting on it.

Droughts feed on themselves, which is how the expression at the top of the page came into existence. When the ground is dry, there is even less moisture available for approaching systems. When there’s less moisture available, less rain falls. When less rain falls, the drought gets worse. So how do we break the drought? When we have one in the summer, usually, the answer is with a tropical system. Either a tropical storm/hurricane comes up the coast and slams into New England dumping copious amounts of rain on us, or one hits farther down the coast (North Carolina or the Gulf) and weakens inland and the remains of it move this way with heavy rainfall. The Summer of 1955 was hot and dry like this one has been. Then, in the span of a week in August, two Tropical Storms (Connie and Diane) brought record rainfall to the region, with widespread flooding. Of course, that’s not the scenario we prefer. A more gradual transition to a wetter pattern is the best case scenario, but that isn’t how is usually works.

So, right now, you’re probably asking “is there a tropical system heading our way?” No, there isn’t, not yet. Since our record-setting June, there hasn’t been any activity at all in the Atlantic in July, but that could be changing. A tropical wave moved off the coast of Africa on Tuesday, producing plenty of shower and thunderstorm activity. Although some of that activity diminished today, conditions are still favorable for some development over the next few days. The odds of the system becoming a tropical depression are still fairly low, and the odds of it impacting any land, let alone New England, are still fairly remote.

al962016
Model forecasts for the track of a tropical disturbance in the Eastern Atlantic. Image provided by the University of Wisconsin.
al962016_inten
Model forecasts for the intensity of a tropical disturbance in the Eastern Atlantic. Image provided by the University of Wisconsin.

Now that we’re approaching the beginning of August, these waves should start to move off the coast of Africa every few days. At least a few of these will eventually become tropical systems as we approach the peak of hurricane season, which is late August into late September. Another area to watch is down near the Bahamas. Sometimes tropical systems form in this region, and they can quickly strengthen and head up the coast within a couple of days, which is exactly what Hurricane Bob did in August of 1991.

For now, do your rain dance and pray for rain to save your garden or lawn. It doesn’t look like any beneficial rain is coming anytime soon (unless the NAM is right on Friday).

2 thoughts on ““When in Drought, Leave it Out”

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