Thursday September 21 2023 Forecast (7:20AM)

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DAYS 1-5 (SEPTEMBER 21-25)

High pressure hangs on through Friday with fair and pleasant September weather for the last 2 days of summer, but while this is going on, east-facing and south-facing shores will have high rip current risks due to distant Hurricane Nigel’s long-period swell, so keep that in mind if you have plans to be at the coast and in the water. Meanwhile, subtropical low pressure will develop and organize off the US Southeast Coast and drift north to northwest toward the coastline late this week. Its northern rain shield will make a run at southern New England, but I’m still of the meteorological opinion that guidance is over-forecasting the scope and aggressiveness of this rain shield, and while I’ve introduced a lot of cloudiness to the forecast for both weekend days, I don’t think the rain is going to blast into the region and wash out Saturday. I think some of it gets to the South Coast especially Cape Cod, but much of it runs into dry air in place and gets obliterated, and then peels off to the east, waiting for a weaker version of low pressure, which has interacted with the coastline now for many hours, to come drifting northward to bring some wet weather to the region on Sunday. After that, it will get shoved southeastward Monday by high pressure in Canada, though an upper level disturbance swinging through will result in lingering clouds and the chance of some lingering showers that day, if all goes as I expect it to. Reminder: Fall arrives with the autumnal equinox at 2:50 a.m. Saturday.

TODAY: Sunny. Highs 68-75, coolest coast. Wind NE up to 10 MPH.

TONIGHT: Mostly clear. Ground fog patches low elevations. Lows 47-54. Wind variable under 10 MPH.

FRIDAY: Mostly sunny. Highs 67-74, coolest coast. Wind variable up to 10 MPH with coastal sea breezes.

FRIDAY NIGHT: High clouds increase. Ground fog patches low elevations. Lows 48-55. Wind calm.

SATURDAY: High overcast, except thicker/lower overcast may bring some rain to South Coast / Cape Cod region. Highs 66-73. Wind E 5-15 MPH.

SATURDAY NIGHT: Mostly cloudy. Patchy fog. Lows 53-60. Wind E up to 10 MPH.

SUNDAY: Cloudy. Chance of rain, favoring the South Coast but possible anywhere. Highs 62-69. Wind E 5-15 MPH.

SUNDAY NIGHT: Mostly cloudy. Lingering showers and/or drizzle. Patchy fog. Lows 55-62. Wind E to N up to 10 MPH.

MONDAY: Lots of clouds. A possible shower. Highs 65-72. Wind N 5-15 MPH.

DAYS 6-10 (SEPTEMBER 26-30)

High pressure builds in from Canada with a stretch of generally fair weather during the middle of next week with near to below normal temperatures, then a moderating trend when a disturbance may swing into the region with some unsettled weather toward the end of the period, but less confident of that.

DAYS 11-15 (OCTOBER 1-5)

October’s early days show hints of weak westerly flow over our region, but a Rex block type set-up with high pressure dominating eastern Canada while low pressure hangs out to our south. This leaves the region vulnerable to battle zone unsettled weather, but for now my initial leaning is that high pressure to the north will be close enough / strong enough to keep us mainly fair. Long way to go to sort out the early October weather…

95 thoughts on “Thursday September 21 2023 Forecast (7:20AM)”

  7. https://www.star.nesdis.noaa.gov/GOES/sector_band.php?sat=G16&sector=can&band=09&length=24

    I don’t feel confident in this take, but looking at the eastern Canada 500 mb flow about 60 hrs from now and trying to back it up to present time, I think its those swirls northwest of Hudson Bay that eventually ride up and over Hudson Bay and then sharply drop southeastward into Eastern Canada.

    How that ultimately evolves might determine miss/swipe/deluge on rain.

  8. Thanks TK.

    The tv mets seem convinced of a weekend washout. Still time for forecasts to change at the last minute tomorrow I suppose.

  13. https://www.star.nesdis.noaa.gov/GOES/sector_band.php?sat=G16&sector=eus&band=GEOCOLOR&length=24

    https://www.star.nesdis.noaa.gov/GOES/sector_band.php?sat=G16&sector=se&band=GEOCOLOR&length=24

    Big view (US Atlantic coast)
    Smaller View (SE coast)

    Interesting swirl to the south of all the thunderstorms, which seems to have a bigger overall circulation.

    That very small swirl south of the thunderstorms, that couldn’t be the eventual sub 990mb subtropical system, could it ????????????

  16. Given the Patriots turnovers so far, I hope BB has the team practice with “wet” balls. Regardless of how far north that rain gets, it’s a sure bet the Meadowlands will be quite wet at game time on Sunday afternoon.

  18. It really is 2 systems for the east coast to deal with

    There is this low and it will have its own impacts close to it ……..

    ……….. and then to the north ……… more heavy rain caused by warm, humid air overrunning cool, dry air with wind caused by a pressure gradient.

    2. I heard a few things from my Dad as he was about 15 at the time and living in Canton. Blue Hill is only a few miles away and they had wind gust over 120 mph.

  27. After the 12z stuff, I feel like there’s not a lot of model concensus on either parts 1 or 2

    Some are bigger on 1 vs 2. For those who are more dominant in 1, there are differences in impact.

    A few are actually more impactful on 2 vs 1

    There’s intensity (pressure) disagreements.

    And its now Thursday for a weekend event, THURSDAY !!!!!!!!!

    1. What are the tropical models saying for this thing, now that it looks to have some tropical characteristics? Do the tropical models forecast rainfall?

  28. 12 z guidance review leads me to keep the exact same forecast I issued this morning…

    HINT: I’m not relying a lot on what the models are showing me. I’m taking into account things they’re not showing me. 😉

      1. South Coast is basically the coastline of CT, RI, and south-facing shores of MA stretching out to and including Cape Cod (and the islands). And you can kind of go inland about 5 to 10 miles basically – or generally “the coastal plain” to have the South Coast region that I speak of.

        Meanwhile the South Shore is the east-facing coast from the canal to Boston, similarly including the coastal plain.

        1. Thanks TK. So, Providence to Boston along I-95 is not considered the South Coast. I only point this out b/c that zone typically gets the same conditions and forecast as the “south coast.”

          1. They get similar conditions often, but not always. Of course it depends on the details of each situation.

            But on the broad scale, yes they are often very similar.

    1. Trust me I’ve battled with that “fear” while making mine.

      I’m wearing the proverbial bubble wrap suit – just in case my forecast crashes.

    1. Hah! Yes, never park under a steet light there .. or any beach really. 🙂

      As you know, Hampton is a second home to me. I got some great photos / videos on Saturday with the heavy surf from passing Lee.

  32. Not really in its “trustable” range yet, but the 18z 12km NAM is a little quicker to obliterate the rain area Saturday than the 12z run was.

  34. This week I have seen every possible forecast from TV mets for Saturday. The range goes from shunted south to “complete washout.”

    Poor humor: Forecasts for Saturday are all over the map.

    1. BA HA HA HA .. Well, it is a “guessing game” of sorts. Some of us lean one way, some of us another.

      Just talked to a colleague who is going with the Canadian model solution and thinks we’re in for quite the rain event, 3 days long.

      I disagree.

  35. Thanks, TK!

    I have done some reading on the Hurricane of 1938. I have a special photo book from my Mom who vaguely remembers that hurricane as a child.

    Two things that stand out to me:

    A rookie meteorologist in the NYC Weather Bureau allegedly correctly predicted the storm but was overruled by two senior forecasters.

    Also, the foreward speed of the cyclone. The Boston Bees (Braves) played an afternoon doubleheader that day and continued playing until the outfield fences collapsed and routine infield popups ended up in the grandstands behind home plate.

    A school bus carrying children home from school was swept out to sea by the surge along the coast (I cannot remember if it was MA, RI or CT) and all of the souls on board perished.

    1. RI PBS has always aired its award-winning film “Wake of ’38” on this day. If it’s on tonight, I will watch.

    2. Oh my. Thank you, Captain. I love that yiu have a scrapbook.

      I do know it wasn’t expected. My mom would have been 24. She and her mom took the trolley from Belmont to the Harvard square subway and then into Boston for the day. When they returned, the trolleys had stopped running out of Harvard square. They decided to walk home to Belmont. By the time they got opposite Mt auburn cemetery in Cambridge, trees, poles and wires were down all around them. A taxi driver from Morse Taxi, Cushing square, Belmont recognized them when he drove by and drove them home. Very possible he saved their lives

      That said, I wonder how folks at the braves game got home.

      I had not heard about the school bus. Heartbreaking.

  36. Speed at landfall: 47 mph (Landsea et al. 2013, National Hurricane Center; Hurricane Research Division Re-Analysis Project

    (Weather.gov > New York, NY > The Great New England Hurricane of 1938)

    I believe WxWatcher also mentioned the incredible forward speed of this storm in a recent post.

  37. Thanks, TK.

    For what it’s worth I’m building an ark. I don’t think there was a Joshua’s ark in the bible. But there was a Noah’s ark. Mine will be Trumpian: A big and beautiful ark, a perfect ark.

  38. Interesting they mentioned hurried in 1954. I was thinking of 1954 where we got stuck at Humarock. Mostly because even the. There was little to no warning

  39. Absolutely love the comment that underwarning will be measured in the cost of lives while overwarning will be measured in mere dollars and cents.

  40. With regard to TK’s colleague who is forecasting 3 days of rain:

    JR and Wankum have 2 1/2 days of rain (Saturday, Sunday and the first half of Monday).

    Murphy’s Law won’t apply since this is not an official holiday weekend. 😉

    Fwiw, that new (kinda cute) female met on Ch. 4 has rain just for Saturday and Sunday with clearing on Monday. She did use the word “washout” for this weekend.

      2. I think ch 4 also has a meterorologist on staff named Lexi (????) as well. Can’t remember her last name.

        Hire within the last year, but she has been off camera a while lately also.

  42. Appears the 00z model suite diminished the heavy rain threat Saturday to lighter rain, if I am interpreting correctly.

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