Mainly tranquil conditions continue across the Atlantic Basin. We have no organized tropical cyclones, and it's unlikely that any form over the next week. The view from space shows little thunderstorm activity across the Atlantic tropics.
This loop of visible satellite imagery shows quiet weather across the Atlantic tropics.
Image Source: University of Wisconsin RealEarth
Four tropical waves are present:
- Along 76° west, over the western Caribbean Sea
- Along 55° west, just east of the Lesser Antilles
- Along 43° west, over the middle of the tropical Atlantic
- Along 25° west, over and south of Cabo Verde
None of them are producing any notable thunderstorm activity. The only one of the four that looks remotely interesting is the one over the middle of the tropical Atlantic because there is a broad turning motion with it. However, it is in an area where tropical cyclones rarely form in June, and it will meet strong vertical shear as it reaches the Caribbean Sea. That shear is evident in the satellite loop above; high clouds are moving eastward or northeastward, while patchy low clouds are drifting westward following the trade wind flow.
We likely see no developments in the Atlantic basin through the rest of June. The odds of development are slightly greater than zero over the western Caribbean and the Bay of Campeche. However, it's far more likely that tropical waves will slide right through the tropical Atlantic and Caribbean Sea without developing before crossing Central America. Thanks to this, the East Pacific, which has been quite active so far this season, will continue to pad its stats with the tropical waves developing over there. However, we'll see no effects from developments there as they all move westward or northwestward.
While things remain quiet in the Atlantic, it is a good time to prepare for the threats we will face once we get to the peak of the hurricane season. Please get ready for storms that could come our way later this year. If you need preparation advice, hurricane.sc is the go-to resource.
It wouldn't be summer in South Carolina without at least one heat wave, and we have one on the way next week. The cause will be an upper-level ridge that forms over the eastern part of our Fruited Plain starting this weekend. Upper-level ridges promote tranquil weather with above-average temperatures. It's something you don't mind seeing in January but would rather avoid in June or July.
Put simply, an upper-level ridge is a poleward bend in the upper-level winds. Below is an example of what it looks like on an upper air chart.
This upper air forecast map for the 500 millibar level from the ECMWF deterministic model (commonly called "The Euro") valid for Sunday night, showing a strong upper ridge over eastern North America. Jet stream winds flow in an arc around the ridge centered over West Virginia.
Image Source: WeatherBELL
Meteorologists use pressure (which you probably know falls as you go up in the atmosphere) as a measure of height because it makes the math we have to do easier (and meteorologists have to learn a LOT of math, at least four semesters of college calculus, including the magical concept of differential equations). So, our upper air charts show the height of a constant pressure level. That makes the chart much like a topographic map; you see the equivalent of mountains, ridges, and valleys (we call the valleys troughs). The upper ridge that is about to develop is akin to a tall mountain in the atmosphere, with a peak value of around 5,980 meters above sea level, or approximately 19,600 feet. Compare that to the lower heights over eastern Canada, which are around 5,330 meters, or approximately 17,500 feet.
The important part for us is that we're about to see a prolonged period of high heat, as this upper-level ridge will remain in place for about a week before breaking down. A cold front that moved through last night brings us slightly cooler and less humid air for today and Saturday. However, the heat will build starting Sunday and peak around the middle of next week. Temperatures will rise into the 95-100° range by Tuesday and remain there through Friday. Only our immediate coast and the higher spots northwest of I-85 will be somewhat cooler.
The figures above show actual temperatures, but the humidity will also increase. So, you can expect to see heat index readings peak over 100 over most of the state next week, with a peak in the 105-110 range over the hottest areas. In this case, the hottest air relative to average is north of us, so the Upstate and Catawba region will be almost as hot as the I-20 Corridor and inland Coastal Plain.
I'm sure you're thinking that an afternoon thunderstorm might cool things down for you later in the day or the evening, but don't count on it. Summertime upper ridges suppress afternoon thunderstorm formation. To get them to form will take a trigger of some sort, making them unlikely, except for the Inland Coastal Plain, where the sea breeze can be a trigger, and in the Upstate, as storms may form over the mountains due to uneven heating and drift that way. However, this activity will be spotty and possibly nonexistent until later next week, when the ridge begins to break down.
Hang in there; long-range computer models indicate that we'll see the heat ease to more typical midsummer levels starting next weekend and remain there through Independence Day. Keep cool, y'all!