Wednesday Forecast

67 Comments

7:26AM

DAYS 1-5 (AUGUST 28-SEPTEMBER 1)
Get ready for a PRE. What’s a PRE? The letters stand for predecessor rain event, and the short explanation is that it’s a significant area of rain (usually in the form of numerous to widespread showers/thunderstorms) that extends out from a tropical system (depression, storm, hurricane). It does not always connect to the precipitation shield of the storm itself, although it can. In this case, it will be a rapidly developing area of showers and embedded thunderstorms just south of to over southern New England, starting this afternoon, peaking tonight, and exiting west to east in the early hours of Thursday. It is the result of Tropical Storm Erin as it tracks north northeastward off the Mid Atlantic and New England coast, and a cold front moving into and across New England from west to east. Behind this will come drier weather for the balance of Thursday, continuing through Friday and well into the Labor Day weekend through Sunday, which is the first day of September. High pressure initially centered from the Ohio Valley to near southern New England will deliver fairly warm air Thursday-Friday, and as the high center shifts more to the north and east so that it is situated in the St. Lawrence Valley by later Saturday and Sunday, we will see more of a northeasterly to easterly air flow and a cooling trend, somewhat like last weekend.
Forecast details…
TODAY: Partly sunny morning. Mostly cloudy with scattered to numerous showers arriving from south to north during the afternoon. Increasingly humid. Highs 76-83, coolest along the coast. Wind SE 5-15 MPH.
TONIGHT: Cloudy. Numerous to widespread showers and a chance of thunderstorms, diminishing west to east toward dawn. Areas of fog. Very humid. Lows 64-71. Wind light variable.
THURSDAY: Cloudy with showers Cape Cod very early, otherwise clearing and becoming mostly sunny. Moderately humid. Highs 77-84. Wind W 5-15 MPH, higher gusts.
THURSDAY NIGHT: Clear. Lows 60-67. Wind W 5-10 MPH.
FRIDAY: Sunny. Highs 78-85. Wind W 5-15 MPH.
FRIDAY NIGHT: Clear. Lows 58-65 Wind NW 5-10 MPH.
SATURDAY: Sunny. Highs 75-82. Wind N 5-15 MPH.
SATURDAY NIGHT: Mostly clear. Lows 57-64. Wind NE 5-10 MPH.
SUNDAY: Mostly sunny. Highs 70-77, coolest coast. Wind NE 5-15 MPH.

DAYS 6-10 (SEPTEMBER 2-6)
High pressure should hold in place to the north of the region with an easterly flow for Labor Day Monday September 2 with dry weather but will have to watch for some ocean cloudiness in eastern coastal areas. There may also be some pop-up showers Monday but not looking for a widespread wet weather event. High pressure should shift southward with increasing warmth and humidity September 3-4 and as a front approaches from the northwest September 5 we increase the chance of showers and will have to watch to see if moisture from Dorian becomes involved. It’s far too early to know what, if any impact, that moisture will have, as the track of that system is not known for certain yet. High pressure from Canada should end the period with cooler/drier weather.

DAYS 11-15 (SEPTEMBER 7-11)
The overall pattern should feature a westerly flow with a couple disturbances bringing shower risks around September 7 and 10. Temperatures near to above normal.

67 thoughts on “Wednesday Forecast”

  4. It will be interesting to see if this event over-achieves.

    Water temps running 1-2 C above average to our south.

    I recall the Salem/Beverly 5-6 inch rain plume from a recent summer, as well as 2 Cape Cod summer rain events in the past 5 to 8 years that all over achieved. In these 2 events, you may recall the image of the sand dunes up around wellfleet that gave way, and in one of the instances, took a car with it down the dune.

      1. Thanks JpDave.

        So, with this as a general anticipated forecast, I wonder if these amounts get overachieved ??

  5. Thank you, TK. Sutton kiddos are off to school today. Sigh. The summer vacation goes by way too fast. Always did for me.

    1. This summer really seemed to fly by for me also Vicki. The kids were out earlier than the last few years but it still seemed to be gone in the blink of an eye. Thankful they aren’t dealing with extreme heat and humidity though.

      1. You’re right that they were even out earlier. I think it is just so nice to have them home that the time flies by. And sure is nice not to have the heat and humidity

  6. Good morning and thank you TK.

    To PRE or not to PRE, that is the question.

    So, will this be a genuine PRE, psuedo-pre, min-pre, frontal passag infused with
    tropical moisture or just an ordinary frontal passage.

    From what I have researched, to be officially classified as a PRE, there is a requirement
    for 4 inches of rain within a 24 hour period. Some models show that, while others
    are not even close. I got that from the WPC.

    Here is a link that will download a power point NWS training presentation
    on Predecessor Rain events. It is really good and well worth a read in light
    of what may happen later today.

    http://www.wpc.ncep.noaa.gov/hmt/seminar_files/PRE_NWS_Teletraining.ppt

  7. Thanks TK
    Looks like eastern parts of SNE will be where the highest rainfall totals will be.

    Tweet from Meteorologist John Homenuk on Dorian
    Dorian has tracked to the north of all NHC and model forecasts from just 48 hours ago. Much of this can be attributed to a northward reorganization of its circulation, but the change in anticipated track is very significant. Both the GFS and Euro were still too far south at 00z.

    This tweet from Andy Hazelton an assistant scientist from the University of Miami
    Latest pass through #Dorian finds the storm has strengthened a little more, with flight-level winds over 70 kt (80 mph) and surface winds of at least 55 kt (65 mph).

  8. Thanks TK!
    Thanks Jp Dave for posting the power point regarding a pre event, very interesting. If this does set up over sne it will be interesting to see where the axis of heaviest rain sets up, and if training occurs there could be some impressive totals in isolated locals. Like a winter storm it will be a radar watching day.

  9. Thanks TK!

    Recent dryness should help mitigate the overall threat of flooding for SNE through tonight. However, some of the guidance including the last couple of HRRR runs are ominous for southeast New England, particularly urban centers like New Bedford and Cranston which flood easily in heavy rain. Amounts will likely vary widely, with many areas likely seeing under an inch of rain but a stripe of 2-5+” possible. The landmark study that JP Dave posted restricted what it considered a PRE to only events producing observed amounts of 4″ or greater. While I suspect we will get that somewhere anyways, it’s very apparent now, more so than yesterday, that this is a classic PRE setup.

    Like clockwork this time of year, it’s all about the tropics right now. Dorian increasingly looks like a serious threat to the CONUS.

      1. Ha !

        We’re arriving at Myles Standish Forest today to camp. Probably will have 2-3 ft of standing water under our camper by morning. We’ve stayed in the site we are in many times and it definitely pools water in heavy rain events. Should be fun.

  10. Looking at that HRRR total precip you posted JpDave the big difference in projected rainfall totals. Hardly any rain where I am while areas in eastern New England the projected rainfall totals ramp up in a big way.

    1. Yeah.

      We’ve had those systems a million miles offshore that have a lengthy moisture
      connection. One many march’s ago, with a foot of snow comes to mind.

      Also. I don’t know if it equates, but there is the front end thump.

    2. Yes and no. An inverted trough is similar. But inverted troughs are not exclusive to snow events either.

  14. Had a cool lightning show here on St. Thomas this morning, I kept on missing the lightning. Storm looks to travel over St. Croix Ie southwest of me, also saying hurricane conditions are now possible due to the shift in tract. I’m halfway up the hill

    2. I’m sure, with your background, you have already done this.

      Being on a hill, how does the terrain look around you? Are you susceptible to mud slides or fresh water flooding coming down the hill in your location ?

  15. Tweet from Meteorologist Ryan Hanrahan on Dorian
    Not a great update from the NHC. Dorian forecast to strengthen to a category 3 as it approaches Florida this weekend.

  16. At this point for us here in SNE at direct impact looks unlikely from Dorian. I would say anyone from the Carolinas Georgia and Florida need to pay attention to Dorian.

    1. Thanks Jimmy. Of course if the Carolinas are affected then I would have to be concerned about my relatives in NC and VA.

    1. Will be a MAJOR hurricane when it reaches Florida. Hard to believe just a few days ago, maybe a brief cat 1, then POOF over the mountains.

  19. Tons of model divergence re: rainfall totals from the PRE.
    Regular NAM most impressive. HRRR has been waffling all over the place.
    Looking at radar, nothing solid as of yet, although there is one good batch
    well to the SW of us.

    2. Example:

      16Z HRRR has 0.85 inch for Boston
      17Z HRRR has 3.32 inches for Boston

      One hell of a difference for a run one hour later.

  20. Tropical Tidbits site is useless at the moment.
    Buffering,buffering,buffering and buffering some more!)(@&#*!&#(*!&@#*&!

  22. 12z EURO has Dorian making landfall twice in Florida. Southern Florida north of Miami and then the Florida panhandle. Looking at the position of the second landfall it is not far from the location Hurricane Michael made landfall last year. Thankfully many days away and things will change.

  24. Absolutely getting hammered with rain here. Picked up .87” in about 25 minutes!! 1.08 since it started so far!!

  25. Glad they knocked Erin back down to a TD. It was probably never a TS anyway, but it’s moot now. Just a stats pad. 😉 Even Petey B. said it was a depression when they had it as a storm. It had extremely poor structure and didn’t look like a TS at all to me. So now a TD soon to be post-tropical and out of the picture, just having given some moisture to our event today/tonight. All gone by morning! We have some nice weather ahead (as indicated in the forecast above). But we’ll be watching Dorian for sure! This is a good example of how a forecast can change. The center doesn’t go over the mountains. It comes out the other side of the islands in much better shape than it would have otherwise and it’s a totally different ballgame. But that’s tropical weather for you!

    1. I’m sure you’re a great Dad, Coastal. In the coming months there will be plenty of opportunities to run around in the rain, and a few months down the road … snow.

      1. I love the sound of snow but am now looking for a hard freeze or two so I can just go outside at night. I truly miss being able to do so

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