ITHACA, N.Y. — Weatherwise, September is about as perfect as weather gets around these parts. Temperatures are still on the warm side, but there are fewer intrusions of hot, humid air as we see in the summer months, so we end up with fairly comfortable conditions with modest amounts of precipitation.

With that in mind, this week will be a meteorological textbook example. Apart from a hot, humid Wednesday and subsequent cold front, it will be fairly dry and temperatures will mostly stick to the 70s for highs during the week ahead. More interestingly, the models are sniffing out a substantial heat wave late month, and we’ll have to see if that ends up being comfortable warmth, or humid heat.

Graphic courtesy of the Northeast Regional Climate Center.

Weather Recap

With August in the books, it looks like the month will go down in the records as one of the cooler and wetter Augusts in the history of Tompkins County. The average temperature of 66.0 °F was 1.4 °F below normal – in fact, the highest temperature for the month was only 85 °F at the Northeast Regional Climate Center’s Game Farm Road weather station, recorded on August 6th (the NRCC lists the high on the 7th, but each new day of recording starts at 6 AM, so the high temperature on the 7th is actually the high temperature from the previous afternoon). In terms of seasonal ranking, 2019 is the 27th coldest August in 127 years of records – so pretty chilly, but not extreme.

Graphic courtesy of the Northeast Regional Climate Center.

On the precipitation side, the Game Farm Road weather station recorded 5.41″ of the wet stuff, well above the 3.63″ the station typically sees in the month of August. That’s pretty darn wet – in the seasonal rankings, it’s a tie for 12th wettest in the 127 years of August records. Granted, it’s all relative – an August wet and cold is generally less noticeable than a January wet and cold, which likely means Arctic blasts and snowstorms – but it’s definitely notable.

Looking across the meteorological summer statistics (meteorological summer being all of June, July and August), it ended up being a hair on the cool side, with an average temperature of 66.8 °F, 0.7 °F below normal and 46th coldest in the 127 summers on record, and with 14.60″ of rain during those three months, it was the 18th wettest on record. The average is 10.86″, so we basically got the equivalent of an extra month of rain.

Quick final note on the records, it wasn’t as if every place in the Northeast was uniformly cooler and wetter than normal. In fact, according to the NRCC, the cool summer was mostly just an upstate New York phenomenon. New York, Boston, Philadelphia, even Albany were all substantially above normal temperature-wise (in fact, Albany had its 12th warmest summer in almost 150 years of records). Precipitation-wise, most of the Northeast was on the dry side or near normal – Game Farm Road just happens to be a very localized anomaly. So that cool, wet summer is very much a Tompkins County phenomenon rather than a state or regional event.

Looking into the meteorological fall (September, October and November), the Climate Prediction Center is calling for a strong chance of a warm fall and near normal precipitation, and at least the precip part will hold true for this week, though temperatures should be near normal for the week as a whole.

Precipitation, mean sea level pressure and 1000-500 mb thickness (temperature proxy) for 2 PM Tuesday afternoon. Warmer, more humid air will flow into the region as a result of southerly flow on the back side of the high pressure system, and ahead of the low over the upper Great Lakes. GFS Model output courtesy tropicaltidbits.com.

Your Weekly Weather

We’re ending the weekend on a meteorological high note with partly cloudy skies interspersed with doses of sunshine, the nearest precipitation being a few disintegrating showers up north over St. Lawrence County.  This is the result of a high pressure system currently centered over Lake Superior, keeping the air overhead relatively stable, and on the cool side thanks to northwesterly flow within the clockwise circulation of the high. This high should retain control during the overnight and through the day Monday, so expect comfortable, dry conditions to continue for the start of the work week.

For Sunday night, it will be quiet, with decreasing cloud cover and no rain expected, and the light north wind will die down. However, if you’ll be out and about, you’ll want a jacket or sweater, as lows in Ithaca will bottom out in the upper 40s, and in the mid 40s in our more rural and higher elevation areas.

Monday will be a pleasant day to be outdoors with the high just to our north. Except partly cloudy skies, calm winds, and temperatures topping out in the low 70s. Monday night will see a weak southeast wind as the high continues to shift eastward, and temperatures will be a little warmer, with an overnight low in the low 50s in Ithaca and its inner suburbs, with partly cloudy skies.

The next storm system begins to approach from the Upper Midwest Tuesday, and southerly flow ahead of the low will combine with southerly flow behind the high to produce warmer and more humid conditions. Tuesday should remain dry during the daytime hours, but it will be a tad on the humid side with dewpoints in the mid 60s, and an air temperature topping out in the upper 70s. Scattered showers will begin to move into the Southern Tier after sunset, with numerous showers across the greater Ithaca/Tompkins County area after midnight as the warm front approaches. The warm front is the leading edge of the warm sector of the low; in the Northern Hemisphere, you can think of that as being roughly between 3 o’clock and 6 o’clock relative to the center of the low. With the cloudiness, high dewpoint and southerly breeze, temperatures will stay on the warm side Tuesday night, with mid 60s and periods of light to moderate rain, especially after midnight.

The bulk of the rain looks like it will pass to the north Wednesday, but it will be a muggy, unsettled day. Dewpoints will be in the low-to-mid 70s and a high temperature in the mid 80s, that will feel more like 90 or low 90s with that very high humidity in place. It will be partly cloudy, but with unstable air, numerous showers and some thunderstorms will be firing off across the region, so you’ll want to have an umbrella handy. It doesn’t look like a washout by any means, but the high water content of the air will allow for some downpours that could trigger flash warning advisories, so you’ll want to keep an eye out if you live in a low-lying area or next to creeks or other areas prone to flooding.

In addition to that, the atmospheric dynamics (shear) and atmospheric energy available to developing storm cells could fire off some strong thunderstorms, but it’s a bit too early to be sure; just keep an eye on the forecast if you’ll be outdoors Wednesday afternoon. Most of the thunderstorms will wind down Wednesday night with the passage of the cold front and the loss of energy from daytime heating, but showers will continue to play a role in Wednesday night’s weather, with partly cloudy skies between cells, and a low in the low 60s.

On Thursday, Canadian high pressure will move into our region once again, and just like now, its location to our northwest will drive a stabilizing, cooling northwest breeze into Tompkins County. A few showers with some lingering instability to our south should dissipate by lunch, leaving mostly cloudy skies and a high in the mid 70s. Thursday night will be quiet and cooler, with partly cloudy skies and a low in the mid 50s.

High pressure will shift eastward on Friday but otherwise bring one more nice day of weather, with partly sunny skies turning cloudier later on, and a high in the mid 70s. That comes to an end with the next storm system, this low centered over Canada but having a fairly extended cold front sweeping all the way into the lower Mississippi Valley. Friday night will be mostly cloudy and dry ahead of the front with showers forming late, and a low in the low 60s.

Saturday will see the front pass through with a building ridge of warmer air pushing it to the north as time progresses, effectively riding over the top of the ridge as it pushes northward. There will be scattered showers, but the cold front won’t make much of a punch – in fact, with that growing ridge, it’ll actually be warmer Saturday, with a high in the upper 70s. The rain will steadily shift northeastward and away from Tompkins County Saturday night, with dry conditions after midnight and a low in the upper 50s. Sunday is looking warm and dry, with partly cloudy skies and a high in the upper 70s.

Graphic courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Well, this is interesting. the medium-range models have latched onto the idea that the mid-latitude ridge over the Eastern United States will be rather substantial and persistent, sustaining a dome of warmer air over our region for the second half of September, in what my meteorological textbooks would describe, if they could, as a “big ol’ ridge of hot air”. With the jet stream displaced northward (and compensating for that with a dip in the Pacific Northwest), it’s looking like some unseasonable warm is in store for mid-month onward through late September, with near-normal precipitation mid-month, and perhaps drier than normal for the last third of the month. That would portend a warm start to astronomical fall, and perhaps a few more days of tee shirts and BBQs still on tap.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.