Donning my fleece at 5:30 this morning I was thinking how amazing the weather has turned this month and what a contrast it is to what we had the first half of summer. Many of us know that the period between August and September can be some of the best weather of the year with warm days and dry conditions. I’ll be updating the details of the weather on Twitter at @growingwisdom Please follow me there. Feel free to comment or ask questions too.
The meteorological pattern we are in the midst of will provide virtually flawless conditions for the next week to 10 days. One of the things that can happen in the atmosphere this time of year is something we call persistence. This idea is that once a pattern becomes established it tends to feed on it itself. The science behind this is the warm dry conditions will build further warm dry conditions which then get stuck in place for a while. As the air dries, it becomes harder for it to rain and high pressure systems become stronger.
Eventually the atmosphere will push something into the status quo that will break down the high and it will rain, but the dry spell can last a long time. In our case this year, we can sustain a week of dry weather because we have had so much rain this summer. However, the top soil will dry out quickly so keep the watering can handy for newly planted material, annuals and those ripening veggies.
Last summer, the Midwestern part of the country saw this type of pattern establish itself early in spring and last well into fall. This is why the drought was so devastating to that region of the country.
Persistence forecasting is something the models and those of reading the models also take into account. It doesn’t matter the time of year either. In winter, persistence forecasting might keep it cold and dry or snowy or even mild. A meteorologist would be reluctant to forecast a snowstorm in the midst of a snow drought using persistence.
The weather map below shows where the center of the big high pressure system will be for the next week or so. This high means that the jet stream will be up in Canada and prevent the cool fall-like air from penetrating the country.
While we have had some cool days and nights the past week, overall it’s starting to look like the second part of August and into September will average warmer than normal. In spite of this prediction there is good news for those of you who don’t like the heat.
Temperatures overall are going to cool this time of year, a warm September won’t be as hot a warm July and the chances of hitting 90F rapidly decrease once we hit Labor Day.
This time of year a typical day would see afternoon temperatures in the 77 to 83 degree range. You can shave 10 degrees off this range by the time we get to the final days of September.
Lastly, I want to address the tropics which have been very quiet this year. So far very dry air has been inhibiting the formation of any significant tropical systems. Over the next 7 to 10 days some changes in the tropical pattern will bring more conducive conditions to tropical formation to the Atlantic basin and in turn an increase in tropical activity is likely.
Gardening this week
Tomato and corn season is upon us here in New England and the produce is wonderful. My own tomatoes are now coming to maturity and the video below is an update to one tomato plant I rescued last fall from a sidewalk at Framingham State. The plant was growing in the crack of the concrete and I kept it alive all winter.
I’ll be updating the details of the weather on Twitter at @growingwisdom Please follow me there. Feel free to comment or ask questions too.