Sunday May 19 2024 Forecast (8:19AM)


Horrible forecast yesterday. No excuse, but the reason for me (and according to NWS discussion, others as well), extremely poor performance by short range guidance in picking up conditions that produce more widespread and persistent rainfall than they were indicating. A forecaster from NWS Boston noted that even the “best performing” piece of guidance was inadequate and far under-forecast the scope of the rainfall. Ouch. I gave a couple of forecasts to people for outdoor events that were less than accurate, to put it nicely, though the events worked out fairly well anyway. Still, not a good feeling when that happens! But, we move forward…

DAYS 1-5 (MAY 19-23)

Since the synoptic conditions haven’t changed all that much today from yesterday, today’s short term forecast is a little less optimistic than I indicated just 24 hours ago. No I don’t think we’re in for a repeat of the rainfall, but an overcast morning with drizzle patches and areas of fog may only improve very slightly, and I can’t rule out pop up showers at any time, as low pressure sits to the south and a fresh feed of Atlantic moisture remains in place. Finally, this begins its exit this evening as high pressure starts to shift in from the southwest and overtake our weather. While some lingering cloudiness is likely to be around Monday, expect a much nicer day overall with fair weather and it turning considerably warmer than the weekend was. This trend will continue for Tuesday and Wednesday as high pressure sits just to our south and puts us in a warm southwesterly air flow. This will give us a preview of summertime with many areas going over 80 for high temps. This, of course, will be a lot harder to achieve closer to the South Coast and over Cape Cod where a southwest wind is a direct ocean wind and the cooler water will have a significant modifying influence. Thursday, the temperature forecast will depend on the speed of an incoming cold front, which will bring the chance of showers and thunderstorms, along with associated cloudiness. Details TBD.

TODAY: Cloudy. Areas of drizzle/fog. Chance of a shower. Highs 56-63, coolest coast. Wind E to SE 5-15 MPH.

TONIGHT: Breaking clouds. Patchy fog. Lows 49-56. Wind SE to S up to 10 MPH.

MONDAY: Variably cloudy South Coast to MA South Shore / more sun elsewhere. Highs 62-69 South Coast to MA South Shore, 70-77 elsewhere. Wind S to SW 5-15 MPH.

MONDAY NIGHT: Partly cloudy. Lows 51-58. Wind S to SW up to 10 MPH.

TUESDAY: Sunny. Highs ranging from near 60 Cape Cod to 81-88 Merrimack Valley, interior MA, southern NH. Wind SW 5-15 MPH.

TUESDAY NIGHT: Clear. Lows 52-59. Wind SW 5-15 MPH.

WEDNESDAY: Sunny. Highs ranging from near 60 Cape Cod to 81-88 Merrimack Valley, east central to central MA, southern NH. Wind SW 10-20 MPH.

WEDNESDAY NIGHT: Partly cloudy. Lows 53-60. Wind SW 5-15 MPH.

THURSDAY: Variably cloudy. Chance of showers and thunderstorms. Highs 68-75, cooler South Coast. Wind SW 10-20 MPH.

DAYS 6-10 (MAY 24-28)

Models may not yet see what turns out to be a rain threat from passing low pressure on May 24, followed by fair weather to at least start and get into the Memorial Day Weekend, with the potential for the next shower threat around Memorial Day itself, unless a slower pattern holds it off til the end of the period. Will monitor the trends. Temps will be typically spring variable.

DAYS 11-15 (MAY 29 – JUNE 2)

Last few days of May look fair, early part of June maybe a shower threat. Progressive pattern – variable temperatures not straying too extremely.

32 thoughts on “Sunday May 19 2024 Forecast (8:19AM)”

  1. Thanks, TK.

    Predicting in any field is difficult. Meteorology especially so, due to the confounding factors. In the real world of climate and weather we can’t operate under (or even mimic at all) the conditions of a controlled experiment.

    And so, uncertainty is a feature inherent to any model. In econometrics there’s something called white noise or an error term which represents the portion of the dependent variable that the independent variables in the model do not explain. The larger the term the worse the model output and the less well it can predict.

    1. This is an excerpt from NWS discussion (some technical in here, but you get the idea easily):

      “Overnight guidance continued to perform horribly in identifying the
      presence of moderate to heavy showers along the I-95 corridor that
      seemed to be driven by a SW to NE oriented 925mb jet (~30kt in
      strength) and moisture convergence between 925mb-850mb. Even the
      NAMNest, that was one of the only pieces of guidance that diagnosed
      more widespread, impactful rain on Saturday, struggled to depict the
      nocturnal rain. Am very apprehensive to bite on guidance for today
      that suggests a completely dry day with only very modest changes in
      the synoptic setup; surface high and mid level ridging nudging in
      from the southwest with coastal low moving just ever so slightly
      eastward. So, while not anticipating that Sunday will be as much of
      a washout as we saw for portions of the area on Saturday, do expect
      shower activity will persist through at least the first half of the
      morning before PWATs fall below 1″ as low pressure finally draws far
      enough east. Given our tepidness to completely remove PoPs from the
      forecast today, heavily blended the Canadian into the forecast,
      which was the only model that accurately depicted the intensity and
      geographical spread of rain overnight with yesterday`s 12Z run. With
      NE flow, do expect shower activity to be remain most widespread east
      of the I-95 corridor, with lesser chances north and west.”

      (sorry for the poor formatting)

  2. Thank you TK. Yup, there was a lot more “weather” this weekend than I thought we would see. I even optimistically took a 6 mile shore walk early this AM and came home soaked through.

    As you know better than I, forecasting involves uncertainty and sometimes even a dose of chaos. Hence the metaphorical Butterfly Effect … a butterfly flapping its wings in South America can change the weather in Central Park. The problem is that most models cannot find all the butterflies all the time. I used to do business modeling and all I can say is that regardless of the field, we all seek perfect or near perfect outcomes using imperfect tools.

    I’ll still take your forecasts over anyone else’s any day of the week and I mean that very seriously!

  3. It’s interesting on model performance, global and short range …….

    Within the last 7-10 days, I remember one instance where I thought the models handled that so well !

    The short range simulated radars were spot

    So, something in the atmosphere really confounded the models.

    Perhaps since a piece of the event was from something offshore, perhaps there was less info put into the models since I’m guessing less balloon over the ocean to measure the atmosphere ?????

    Maybe a case study for a future weather conference.

    2 areas, central Mass and then overnight in eastern Mass. Both significantly underdone by the models.

  4. Thanks TK. Tough forecast, you always do your best.

    54 degrees on May 19th drives me crazy. I know it’s normal here but it’s the one of the biggest factors in people leaving the area.

  5. Good morning and thank you TK

    Was finally able to get out fishing this morning.
    I remained dry even though there was intermittent very light drizzle. Even so, I did NOT get wet at all. It was perfect fishing weather and I was rewarded.

    4 nice rainbow trout (12-14 inches)
    1 big Brook trout about 14 inches
    4 decent large mouth bass, all over a foot.
    And a crapload of blue gill, the price one pays to get at the good stuff. 🙂

  6. 12z GFS maintaining consistency on a very warm Wednesday.

    500 mb: heights of 579-582 dm

    850 mb: temps of 15-18C

    Nice southwest wind and decent 68 degree + sun angle.

    Taking a run at 90F west and northwest of Boston, away from an indirect south coast provided seabreeze.

    1. Although I like the nice weather, I am not ready for STINKEN 90s. Here’s hoping Boston stays in mid 80s with 50s dp. 🙂

      1. I think you’ll get both wishes Wednesday.

        Thursday might be the first “high humidity” day.

        Models seem to pool mid 60s dps ahead of the cool front that day.

  7. If the front on Thursday comes through during peak heating could be a few strong thunderstorms.

  8. Thanks TK.

    About 0.23″ of rain here yesterday and 2.10″ from the Wed night/Thursday storm. Never rained all that hard but it was constant light rain/drizzle all day. Enough to keep us from doing any yard work (which I will be going outside to do shortly). West of Hartford, not a drop of rain fell and the roads were dry. A localized event for sure.

    1. Not too many open in the lower 48.
      Arizona Snow Bowl in the Northern part of Flagstaff, AZ will be open weekends though the Memorial Day weekend.

      I think Pallisades Taho and Mamouth are still open iin CA and Mt. Hood? in ORE and
      Snow Bird? Utah and I am sure a couple of more.

  9. Boston has had the fewest 70 degree days at this point in the season in 2 decades.

    And they’re quite a few days behind the average first 80 degree day. But that’s going to be coming soon.

  10. PDS warned tornado on cell maybe an hour west of OKC.

    Looks extremely impressive on vertical velocity radar, couplet is easily scene.

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