Monday Forecast

114 Comments

6:59AM

DAYS 1-5 (SEPTEMBER 2-6)
A quick warm front / cold front combination will cross the region for this Labor Day and we will lose our dry weather to showers and a few thunderstorms. The day will not be washed out, but any time after mid morning is open to passing periods of wet weather, lasting through evening before drier air arrives overnight. High pressure brings a nice day Tuesday, warming up with a feel of summer coming back as many more people head back to school / college / work. A bit of a cruel joke from mother nature there, and that summer feel will last well into Wednesday as well, in fact for some, a run at 90 is possible as a southwesterly air flow grabs some heat to the south and pulls it our way. Another cold front will put an end to that by Thursday but ahead of it may come some Wednesday evening showers and thunderstorms. As we get to the end of the week, that front will settle just south of the region Thursday with somewhat cooler/drier air moving in, although sun that starts that day will probably be gone by the end of it as a larger shield of cloudiness associated with Dorian starts to move in. Now don’t go thinking that we’re going to be hit with Hurricane Dorian head on. So far, all indications continue to be that the hurricane, after the center barely staying offshore of FL/GA/SC and possibly scraping NC, will track northeastward and its center, in the process of becoming non-tropical (a transition that we often see at that spot) will pass well to the southeast of New England. But when these storms go through that transition they usually expand quite a bit in size and this expansion certainly will put southeastern New England under its cloud shield. The question is whether or not any of the rainfall gets up into the region and if so, how much would make it. We’ll answer that going forward, but for now, going to go with a period of wet weather arriving during Friday, favoring southeastern locations. Of more certainty are the large ocean swells and rough surf impacting the coastline later in the week.
Forecast details…
TODAY (LABOR DAY): Variably cloudy. Afternoon showers possible favoring central MA and southwestern NH. Highs 70-70. Wind SE up to 10 MPH.
TONIGHT: Mostly cloudy with showers likely evening. Partly cloudy with patchy fog overnight. Humid. Lows 60-67. Wind S up to 10 MPH.
TUESDAY: Mostly sunny. Highs 78-85 except cooler South Coast / Cape Cod. Wind W 5-15 MPH.
TUESDAY NIGHT: Partly cloudy. More humid. Lows 62-69. Wind SW 5-15 MPH.
WEDNESDAY: Partly cloudy. Humid. A late-day shower or thunderstorm possible mainly north and west of Boston. Highs 83-90 except cooler South Coast / Cape Cod. Wind SW 10-20 MPH.
WEDNESDAY NIGHT: Variably cloudy with showers and thunderstorms possible evening. Partly cloudy with patchy fog overnight. Humid. Lows 60-67. Wind SW 5-15 MPH with higher gusts shifting to W.
THURSDAY: Partly sunny morning. Mostly cloudy afternoon. Less humid. Highs 70-77. Wind N 5-15 MPH.
THURSDAY NIGHT: Cloudy. Lows 56-63. Wind NE 5-15 MPH.
FRIDAY: Cloudy. Chance of rain, favoring southeastern parts of the region. Highs 66-73. Wind NE 10-20 MPH except 15-25 MPH with higher gusts toward Cape Cod.

DAYS 6-10 (SEPTEMBER 7-11)
Based on current thoughts, any impact from Dorian on September 7 should be early rain possible South Coast / Cape Cod, pulling away quickly, but lingering large swells and rough surf along the coast, with dry weather and on the cooler side with a gusty north breeze. Again at day 6 this is not a super high confidence forecast so details will be added as the outcome of the situation is more well known. Either way, the back half of the September 7-8 weekend will be pleasant, cool to mild and dry. September 9-11 we should see high pressure centered to the north and northeast of New England, like a couple other recent episodes, and a northeast to east air flow to start the period, then turning more southeast to south as the high slips off to the southeast. This would bring generally fair weather, starting out drier/cooler then transitioning to a bit more humidity and warmth later by the very end of the period.

DAYS 11-15 (SEPTEMBER 12-16)
The first few days of the period look warmer than average with mostly fair weather as high pressure takes up residence to the south of the region and sends in a westerly air flow while the jet stream lifts to the north over a flat ridge of high pressure. A trough coming along from Canada later in the period could cause some showers then a transition to cooler weather.

114 thoughts on “Monday Forecast”

    1. Figured that. It maxed out yesterday. Still had people (off the blog) telling me no way was it done strengthening. Each situation is slightly different but there is a limit to how strong one can get before it can’t strengthen anymore. Atmosphere knows how to keep itself in check. This time it was a combination of storm-created upwelling as it blows its warm water source away from its center which is then replaced with cooler water from underneath, as well as some limited land interaction with those islands – just enough to have an impact. Soon it will be starting to feel the first effects of shear to the north but that won’t happen much until tomorrow.

      Still holding with the forecast track SAK and I were talking about late Thursday. Wildcard is still if the center makes it to the Outer Banks and exactly how significant the coastal impact is from northern FL up to NC. I suspect significant to some degree, but far from severe.

    1. This is a case it applies perfectly. That, for this region, was written with the idea that most weather moves west to east. We have a frontal system moving in from the west, and its advancing clouds were turned red by the rising sun.

  5. Anchor on WBZ at 6AM said: “It’s cloudy in Boston”. Actually, it was mostly clear there at the time (given I was up and looking in that direction from 10 miles away). It was just that the sun hadn’t come up yet. 😉 There will be some partial sun today, though clouds will dominate overall. 🙂

  8. He’s literally crawling at 1mph. I think we were splitting hairs with a stall. I cannot imagine the devastation on those islands.

  10. Ryan Hanrahan was mentioning in a tweet last night an isolated tornado was possible today. Waiting to see the latest SREF. It has been consistent in showing a low tornado risk on Wed for parts of interior SNE and higher values in VT and NH.

  12. NWS Boston take on Wednesday

    A few things we have going for us that would support some strong to severe storms: the moisture mentioned before (PWATs also approach 1.75″), good instability (CAPE values 1000-1500 J/kg, mid and upper level lapse rates >6.5 c/km), good forcing (convergence ahead of the cold front, divergence aloft under the RRQ of an H3 jet, and a 35-40 kt LLJ), and enough bulk effective shear to support updrafts in storms that form (35-45kts). Additionally, good 0-1 km shear (15-25 kts) and 0-1km SRH (~125ms) would indicate some potential for a few rotating storms. Given the forcing and amount of moisture we`ll also have to watch for some heavy downpours and urban flooding potential. One thing that could hold us back as far as the severe threat would be the lack of moisture in the mid/upper levels. Compared to Monday`s event, for instance, moisture is negligible above 850mb

    1. they also mentioned mid level dry air could limit some updrafts potential. but if a storm develops it might be quite strong

  14. Looking at those 7 day forecasts Dr. Stupid posted you don’t need to be a meteorologist to know when the cold front passes SNE.

  15. Thanks TK.

    A comment on the NHC: Like TK, I have disagreed with multiple classification decisions by the agency this season. I do not believe this is a result of trying to inflate numbers (any scientist and even most of the public can see through the notion that more storms automatically makes a season “active”), rather I think it’s a case of us as scientists trying to over-complicate things, which we do with unfortunate frequency. We try to make black and white a subject matter that is very gray.

    However, the NHC deserves utmost praise for their performance so far on Dorian. When all is said and done, I can almost guarantee that the NHC average forecast error will outperform just about every piece of guidance we have. The NHC is often called slow to adjust. I’d argue another way to say “slow to adjust” is “good forecasting”. They do not play the windshield wiper game, and most of the time, including with Dorian, that will pay off. Great mets like them and like TK, SAK, etc. have this figured out. Go back and look through the track forecasts for Dorian over the past few days. They’ve been just about perfect.

    1. A final note, notice I said track forecasts. Intensity forecast errors may end up rather large, though it’s harder to say where NHC will rank among guidance. We continue to possess little to no skill in forecasting the intensity of tropical cyclones.

      However, it wasn’t all that long ago that the NHC was forecasting a newly minted Dorian to become a category 1 hurricane when most of the guidance showed the storm dissipating or never forming at all. So even there, the NHC deserves credit.

    2. They sucked in terms of it being a hurricane and making landfall over. ST. Thomas not towards Puerto Rico and asa tropical storm. It making landfall in st. Thomas was not forecasted

      1. The forecast errors in that area were almost entirely caused by a center reformation, which is near impossible to predict. None of the guidance forecasted that either. At that point most of the guidance was still struggling to realize Dorian even existed.

  16. Latest SREF for Wed has a low tornado risk up for most of SNE. There is an elevated risk Springfield area west eastern VT NH and western ME.

  18. Latest outlook from NHC has 30% chance tropical storm force winds for Cape and Islands, a 10% chance for tropical storm force winds eastern SNE and 5% chance for tropical storm force winds rest of SNE. I look at these percentages as what type of winds we would get in a Nor’easter.

  19. Lesson learned by me……don’t assume someone misinterpreted a report. Stall it did. I feel sick thinking about what the folks have to be going through on those islands.

  20. Answer to yesterday’s quiz. (Sorry for being a day late. Smoke alarm went off in house last evening. No fire. Ugh!)

    1) Hurricane names are reused every 6 years. “Arlene” has been the most repeated name. How many times has it been used?

    A. 7
    B. 9
    C. 11
    D. 15

    The correct answer is C.

  21. Thank you WxW!

    Just to clarify I’ve actually used the term “slow to adjust” regarding their forecast track. What I mean by that is they won’t jump from model run to model run. They are cautious and careful and tend to work with trends versus big jumps.

    While I have not agreed with everything they have done this season I think overall they still do an exceptional job.

      1. It is? Good news. I’ll have to look again. I thought it was still stalled. I’d sure like to see it turn and get out of there.

        2. the movement should be very slow for about twenty-four more hours while the turn takes place and then a very slow acceleration will begin.

          1. I didn’t know that when a hurricane starts to turn in another direction it loses a bit of strength, relatively speaking.

            1. It doesn’t necessarily.

              It’s already weakening anyway. And the turn is slowly in progress now. However the two are not necessarily related and usually not related.

  23. Interesting to see the euro at 120 hrs, an extra tropical Dorian receiving energy from the northern trof that captures it. Pressure that was 960 mb near the Outer Banks drops to 947 mb east southeast of New England. Poor far eastern Nova Scotia and Cape Breton are going to get quite a wind event.

    1. Those are your spiral bands. These will give the peninsula occasional squalls of rain (some with thunder), but they will gladly take these over that central core and eye wall.

      1. Absolutely !

        I can’t imagine what those Bahama Islands experienced being in that central core and eye wall for so many hours.

      1. Sure thing.

        I search US water vapor loop and of all the ones that come up, I believe this is from Penn State.

    2. They are very helpful to understand what’s going on, and today they are verifying what some were suspecting and cautiously forecasting, hoping at least FL could be spared a fate like that the northern Bahamas suffered. Nothing could be done about that.

      If you think about it, having a CAT 5 over any land mass for any length of time is rare. Not that many strike land. When they do, they weaken rapidly. Islands are generally small. Even ones in the tropics are rarely directly struck by intense cyclones. This was a worst-case scenario for those 2 islands. We may never see that again in our lives. However, because weather is what it is, and doesn’t follow hard statistical rules that we set in place, it could happen again soon just as easily. Let’s hope not.

      1. It is simply horrific.

        Depending on how close he is if he runs the coast, the damage may span at least four states. Flooding after Florence devastated the Carolina coasts plus some. I mentioned on here yesterday that daughter who just drove through that area said damage was still quite obvious.

        1. Yes Vicki, I was wondering if the rainfall will be significant along the coast of SC and NC since they will be just northwest of the track.

          1. They should see some of everything, flooding from rain, coastal flooding, and wind damage. The good news is all the while Dorian will be weakening. But it’s weakening from such an intense place that it will still pack a punch.

            So there are silver linings, but the cloud is still quite dark.

      2. For sure.

        That was incredible seeing that eye slowly cross that one island, at that speed and intensity.

        I’m guessing most if not all that island was submerged. I think at the time, the tide surge was 18 to 23 ft and I’m guessing most, if not all that land is below that elevation.

  30. Torrential downpour at the moment here. No lightning but extremely heavy rain. Picked up .82 “ in 25 min!!

  31. By the time Dorian becomes “extratropical” up here, it could still have heavy rain and fairly strong winds, correct?

  32. Today’s activity, timing-wise and lack-of-thunder-wise (just embedded in some areas) is about as expected.

    Will watch that 2nd line to see what it does this evening… Eh is my current feeling.

    Wednesday, probably a bit too warm upstairs for anything really to get cranking. Will re-evaluate of course. The front lags a bit and may arrive well after max heating. The pre-frontal trough will probably be weak, and the best energy is going to travel down the St. Lawrence Valley and miss this area by a great distance.

    Thursday, much cooler, and I may have to lower my temps on my forecast especially for the coast. We also probably start sunny but end the day with a thick overcast and a threatening look to the sky. However, I don’t think we see the Dorian rain shield get into the area until Friday afternoon and favoring the southeastern areas. Gone by dawn Saturday. Weekend looks spectacular to me at the moment. Only ointment fly would be a trough swinging down from the northwest sometime Saturday that could trigger a shower if there’s enough cold air above. Sunday looks like a great day for apple picking and maybe getting some cider donuts! Pats play a night game to open the season. 🙂

            1. There has been only one CG strike in Sutton. And it was very close to you. All the rest have been to the east.

              1. 0.25 is generous. As crow flies, it would be less. And yes. I was not aware lightning tracker reports anything but cloud to ground. I didn’t have to see this one on map to know it hit close by though. I think this part of town shook

                1. Yes, just CGs, but I bet there were a host of in-cloud or cloud-to-cloud discharges as well. Looks like that kind of set-up to me.

                2. Could well be. It was intense enough.

                  Up to 1.36 now with a bit of a pickup. For the record I hate my screens. The water sticks to them like a sheet and i can’t see out

  36. Decent storm going on here now as well. Heavy rain. Occasional good rumbles of thunder from activity mostly to my south.

        1. It’s about the heaviest I can recall it raining in Marshfield in a while.

          We missed a lot of those thunderstorms the past many weeks. Our lawn is burnt and hardly growing.

  44. This is a photo taken looking west from my back stairway on Woods Hill through the downpour (raindrops are the black fuzzy dots in the photo) at the sun breaking out at the end of my t-storm: https://scontent.fbed1-2.fna.fbcdn.net/v/t1.0-9/69359147_10157582421297265_8973281047600955392_o.jpg?_nc_cat=111&_nc_oc=AQnmfk8gi0lKtGD_0zqaDAfAh7iBko2f4uCVBumgqLBJeIitVmzq-1LNZekLyXjPRdg&_nc_ht=scontent.fbed1-2.fna&oh=1a21e0cfdc4954bde25350f651308cdb&oe=5E028DC3

    This is a photo taken down the street from Woods Hill, at Woburn High School, of the full single & partial double rainbow at the end of the storm: https://scontent.fbed1-1.fna.fbcdn.net/v/t1.0-9/69453108_10157582434817265_3858918864372891648_o.jpg?_nc_cat=105&_nc_oc=AQlL0PsNfmK-AfCH56w_HyHz-29OOn-H0M4S9psc4E3zLr-efp7esH1nCyHegXITePM&_nc_ht=scontent.fbed1-1.fna&oh=fbd678512832f636217198a231dbd01a&oe=5DFDEF6E

    Sorry for the long links, just grabbed them from FB.

  45. Wow Vicki you beat me in the rain department today. I ended up with .98 a good soaking none the less. You tallied quickly. Just imagine siting in one of those bands for hours on end adding in 150+mph winds, hard to comprehend. I wish the best for the folks down there. I hope people heed and have heeded the advice of the experts. Structures can always be rebuilt!!

    1. You sure are right. One met said it is like sitting in the middle of a tornado for hours on end.

      Our grand total was 1.55. It seemed to blow up on top of us

      1. And that depth of 80F water temp is impressive. How many times in New England is the near beach water warm, say 73F, and you swim out a bit and the water gets colder ……

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