Often, meteorologists pay close attention to the progression of the pattern very early in the Spring season. Although not backed by any statical research, it is often found that the patterns and trends in regards to frontal boundaries and airmass progression early in the Spring season can foreshadow how those very same boundaries will behave later in the season. This year has been no exception.
Early this Spring, warm fronts struggled to move northward from the Mid Atlantic, yielding instead to the cooler ocean waters and troughiness to our north and east. This very same thing occurred this past weekend, as warm front struggled northward from the Washington, DC area. Additionally, backdoor cold fronts have had plenty of push towards our area from New England — with marine air overtaking the pattern. This very same thing will occur on Tuesday, temporarily pushing out the warm airmass in place on Monday.
After some showers and thunderstorms impact the area Monday afternoon, the 80 degree temperatures will fall off and the main story will becoming a shifting surface wind direction. A trough to our north and east will help push a back door cold front southwestward from New England, and surface winds will shift from southwesterly (pumping in warm air on Monday) to east-northeasterly, bringing in cooler marine air. New England will fare even worse than we do – as temperatures there will be stuck in the 40’s with damp air and drizzle. For us, temperatures in the 60’s will be more common despite the presence of low clouds.
The good news is that, as a transient and unsettled patterns continues, the building ridge to our west-southwest will battle with the backdoor front and eventually win. Temperatures should rebound into the 70’s by Wednesday, and as the ridge continues to build and troughiness to northeast is kicked out, the backdoor front will weaken and dampen out. Rising mid level temperatures will bring temperatures back into the 70’s and 80’s by Thursday. Showers and thunderstorms will frequent the forecast, however, as a cold front finally approaches by Friday and Saturday.
Dew points, humidity, and why the air feels so darn thick: We hear it, and feel it all too often, especially living by the ocean waters. The warm summer days are characterized by heavy air and lots of sweat — with temperatures in the 80’s and 90’s but a very moist feel outside. Earlier today we received a question regarding the way all of this works — and to be fair, it is probably our error for not explaining it better in the first place.
First, it must be understood that the dew point is the temperature at which water vapor (with a constant barometric pressure) will condense into liquid. Humidity, accordingly, is the amount of water vapor in the air. Humidity can be measured in many different ways, but relative humidity is the most common. These are the percentages you’ll hear on the local news most often. Absolute humidity is the mass of water vapor divided by the mass of dry air in a volume of air at a given temperature. The hotter the air is, the more water it can contain.
So, as the National Weather Service puts it:
Relative humidity is the ratio of the current absolute humidity to the highest possible absolute humidity (which depends on the current air temperature). A reading of 100 percent relative humidity means that the air is totally saturated with water vapor and cannot hold any more, creating the possibility of rain. This doesn’t mean that the relative humidity must be 100 percent in order for it to rain — it must be 100 percent where the clouds are forming, but the relative humidity near the ground could be much less.
So, essentially, our area is often succumb by moist air masses (especially given our geographical location). When combined with summer-time heat, the rising dew points and relative humidity values leave us with soupy air and uncomfortable conditions.