Tuesday Forecast

65 Comments

7:30AM

DAYS 1-5 (JULY 19-23)…
High pressure moves in today and hangs around through Thursday with fabulous mid summer weather. Heat and humidity returns Friday along with a few isolated showers and thunderstorms as a disturbance approaches from the northwest. Heat hangs on Saturday as well with a west northwest flow and a high pressure ridge centered west of New England.
TODAY: Mostly sunny. Highs 78-86, coolest Cape Cod. Wind NW 5-15 MPH.
TONIGHT: Mostly clear. Lows 58-66, coolest interior Valleys. Wind NW under 10 MPH.
WEDNESDAY: Mostly sunny. Highs 77-85, coolest coastal areas. Wind light variable with coastal sea breezes.
THURSDAY: Mostly sunny. Lows 58-66. Highs 77-85 coast, 85-90 interior.
FRIDAY: Partly cloudy. Risk of PM t-storms. Lows 60-68. Highs 80-88 coast, 88-95 interior.
SATURDAY: Mostly sunny. Lows 62-70. Highs 85-95, coolest Cape Cod.

DAYS 6-10 (JULY 24-28)…
Warm to hot and humid with a risk of showers/thunderstorms July 24-25 and again by the end of the period.

DAYS 11-15 (JULY 29-AUGUST 2)…
Similar pattern, above normal temperatures, limited but not absent shower/thunderstorm chances.

65 thoughts on “Tuesday Forecast”

  5. Good morning and thank you TK.

    Noticeably drier this morning. DP 56 at Logan and destined to drop some more
    during the day, I think.

  6. Logan got really skunked with only 0.1″. I suspect most Boston neighborhoods including mine got much more rainfall, relatively speaking of course.

    Thanks TK!

  7. The 12Z Euro SWEAT Index is at 325 or greater for Boston on Friday.
    Some of the higher Euro Severe parameters I have seen since I have been monitoring
    this kind of data.

    http://imgur.com/vShZGXu

    SWEAT
    Severe Weather ThrEAT index; a stability index developed by the Air Force which incorporates instability, wind shear, and wind speeds as follows:

    SWEAT=(12 Td 850 ) + (20 [TT-49]) +( 2 f 850) + f 500 + (125 [s+0.2]) where
    Td 850 is the dew point temperature at 850 mb,
    TT is the total-totals index,
    f 850 is the 850-mb wind speed (in knots),
    f 500 is the 500-mb wind speed (in knots), and
    s is the sine of the angle between the wind directions at 500 mb and 850 mb (thus representing the directional shear in this layer).

    SWEAT values of about 250-300 or more indicate a greater potential for severe weather, but as with all stability indices, there are no magic numbers.

    The SWEAT index has the advantage (and disadvantage) of using only mandatory-level data (i.e., 500 mb and 850 mb), but has fallen into relative disuse with the advent of more detailed upper air sounding analysis programs.

    GFS still looks pretty robust for Friday with plenty of shear and veering of the winds
    with height. Something to monitor.

  8. Thanks for clearing that SWEAT. When I read your first sentence, I thought that the NWS came up with a new heat index or something. Lol. 😀

    1. I may need to read this 9 times and even then ……. 🙂 🙂 🙂 🙂

    2. WOW! That was a mouthful. Very interesting.
      BUT will there really be an improvement? That is the question.

      One would assume so, based on reading that material. 😀

  10. I guess my interest in today’s weather is ……

    The battle of some cool air advection vs the drought, lowering dewpoints and NW surface flow.

    Seems the TV concensus is 82F to 83F at Logan, but I notice TK’s range goes to 86F. I agree with that 86F.

  11. Yesterday’s rain had a sharp cutoff for some. Nothing at my house but right down the road not even 1/2 a mile it must have poured.

  12. Yesterday, rain in my neighborhood of Boston (Back Bay) was pretty pathetic. Perhaps 0.2 inch, which dried up almost immediately. Not even a heavy rain shower. I was surprised given how threatening it seemed for a while (dark sky, rain clouds). Just not a summer with much rain at the coast, I guess. I did have some wind, but nothing major. I do realize that other neighborhoods in Boston got more wind and perhaps more rain, although I see that Logan checked in at 0.1 inch, which sounds about right given the meager amount I got.

    1. J0shua, we got nailed in JP. I had previously estimated 1/4 inch.
      I am revising that upwards to about 1/2 inch, perhaps a bit more.

  14. Thanks TK
    I saw some of the pictures from up there with the trees knocked down from those storms. Those were some feisty storms to say the least. All I got was some brief rain.
    Looks like Friday is our next watcher for thunderstorms as EURO and GFS showing more than enough instability for strong severe storms.

  15. Tweet from meteorologist Ryan Hanrahan for Friday
    Some computers hinting at the potential for big storms on Friday. By no means a guarantee but worth watching.

    1. Agreed. Worth watching for sure. We’ll know more as we get closer.
      What concerns me about Friday, should it materialize, is the shear
      in the atmosphere. We “could” get some more rotators, even more than
      yesterday. Will have to monitor those conditions as Friday nears.

      Of course timing is key. Right now, timing for Eastern sections may not
      be quite optimal, but within the window. We shall see.

  16. 12z NAM also hinting at a good amount of instability for Friday.
    Want to see 12z EURO. Those were impressive severe parameters on the 0z run from a model that is conservative with those types of parameters.

      1. Is it showing good CAPE for eastern mass as well? Or is the threat more towards western mass as usual

  17. EURO GFS NAM all show enough instability for strong to severe storms. Now we wait on the 12z runs of EURO and GFS.
    This doesn’t mean something will happen. We have seen this in the winter when the models show accumulating snow and we don’t get any. This is something worth watching.

    1. I’ve been outside since 8:30 so a brief shower will be ok. It’ll be GREAT if thunder is attached. This is my favorite type of beach day.

  20. Quick peak at 12z GFS enough CAPE for thunderstorm development but nothing impressive. CAPE greater than 1,000 Friday for a large portion of SNE with the exception of southeastern, MA.

  21. The Boston harbor buoy’s wind has come around to 040, much different than Logan’s fairly steady NW wind ……..

  22. Thanks, TK.

    Here in Sudbury yesterday we got caught between the storms. Some thunder and a few drops of rain. Sky didn’t even get that dark. But my sister in Framingham got quite the storm – never got that dark but lots of thunder, lightning and windswept rain and even some hail. I heard a tree went down in Framingham – not sure what part of Framingham.

    Today is refreshing albeit somewhat breezy; HHH supposedly returns for late in wk. That’s ok – it is summer. Just wish we could get 1 or 2 days of light to moderate rain to soak the ground so there won’t be any runoff then a couple days of heavy, steady rain. Oh, well. Guess that’s not coming anytime soon.

    1. Agreed, Rainshine. Sharp cutoffs were evident yesterday. Even across the city of Boston there were significant differences in terms of rainfall and even wind. Where I live we most definitely need rain.

  24. A very brief period of quite warm temps in Northern Europe, and across the British Isles. 80s and low 90s for a 2-day stretch! The exclamation point is sarcastic, I admit. For them that’s reason to panic. Well, I lived there. I know they do panic when it’s hot and when it snows. The article below points to differences in the way we define heatwave (which I believe is more accurate and sensible) and the way the British Meteorological Office defines it. To me the British definition is nonsensical, for it could indicate a heatwave in January:

    “According to the Met Office definition, a heatwave is when the daily maximum temperature exceeds the average by 5°C for more than 5 consecutive days.”

    This one really leaves me scratching my head. See article below. Some nice pictures, and you’ll get a sense of how the Brits handle (they don’t) heat.

    http://www.telegraph.co.uk/news/2016/07/19/british-weather-set-to-reach-temperatures-of-35c-in-a-brief-heat1/

  26. 12Z Euro is out through Monday.

    It “appears” to have backed off some on severe for Friday, although still some
    decent parameters. Actually has a better chance of Severe on Sunday.

    We’ll wait and see how it all shakes out.

    Also, once again, EURO has NO HEAT WAVE! for about the 5th run in a row.
    Has 90s Thursday, then 80s Fri,Sat, Sun and Mon.

    1. GFS has 90+ Thu,Fri,Sat,Sun,Mon AND Tue with a scorcher on both Sun and Mon with temps in the upper 90s!!

      YIKES! Go Euro, Go Euro, Go Euro!!!!

  27. 12z GFS also backed off for Friday but still enough instability for thunderstorm development.

    1. Next chance from the GFS is Monday, not Sunday like the Euro.

      Just too far out for the models to handle. They can’t even figure out Friday yet.

  28. FWIW, the latest HRRR shows some showers all over Eastern sections from the coast of Maine to South of Boston.

    1. The HRRR often thinks that cumulus clouds will be showers. There may be a few isolated ones, and mostly sprinkles otherwise, but 95% of the area will see nothing.

      1. Yes, you have explained this before.

        Reading your link on the upgrade, it looks like they will at
        least partially address this, if not fully. let’s hope so anyway.

        These clouds sure look like they want to drop some rain.

        Probably not, but they look nice.

        Did you see the photo I posted?

  29. Models will go back and forth for Friday. One thing to take away from the 12z runs of NAM EURO GFS there is still enough instability there for thunderstorm development. Will see what future model runs show.

  30. Some signs point to Friday being similar to yesterday in many aspects. Details to be worked out obviously.

    Sunday may not be so clear cut either. We will likely end up on the north side of a boundary, something one of my professors called a “baroclinic zone”. It acts like a cold front / warm front even though there is not much of an air mass change across it. Sometimes its more of a dew point front than anything. If we get into the air on the north side it may act more like a warm front coming back with more cloudiness for a time on Sunday before higher dew point air returned. It’s too far away to figure out anything resembling accurate timing and placement of said boundary.

    I do favor the warmer forecast of the GFS versus the less warm ECMWF.

  31. Hazardous Weather Outlook up for the region for Friday thunderstorm potential.
    THERE IS THE POTENTIAL FOR SCATTERED SEVERE THUNDERSTORMS FRIDAY
    AFTERNOON AND EVENING, BUT A LOT OF UNCERTAINTY REMAINS. IF ANY
    SEVERE THUNDERSTORMS ARE ABLE TO DEVELOP, THE MAIN RISKS WOULD BE
    DAMAGING STRAIGHT LINE WIND GUSTS AND LARGE HAIL.

  32. From NWS out of Taunton discussion for Friday
    A remnant EML and west northwest flow aloft can
    result in high end severe weather in the northeast, but that comes
    down to timing. For example, if the shortwave arrives too early or
    late we can be spared much in the way of severe weather.
    Nonetheless, this certainly has potential and will need to be
    watched closely.

    1. Thank you JJ.

      I have posted a link on this before, but for those who do not know what
      and EML or understand it, have a look at this.

      http://bangladeshtornadoes.org/EML/emlpage.html

      The bottom line here is, The Worst NE tornadoes often occur when there
      is an EML.

      This is not to be alarming, but rather for education and understanding.

      It’s a few days away.

  33. A lot change in just a few days. This will come down to timing as always.
    The 12z run models are hinting at enough instability in place for storms so we have some agreement here. Will see what the 0z runs say and future model runs.

  34. Looking at the SREF probabilities on CAPE for Friday for SNE on cod.edu site
    Greater than 500 CAPE 95 – 100 percent
    Greater than 1,000 CAPE 85 – 90 percent although 95 percent Springfield area west
    Greater than 2,000 40 -50 % range

    1. CAPE
      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/sbcape.conus.png

      LI

      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/sbli.conus.png

      0-3km HELICITY

      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/srh03.conus.png

      0-3km EHI

      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/ehi03.conus.png

      0-1KM is less.

      SuperCell Composit

      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/scp.conus.png

      Significant tornado parameter

      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/stp.conus.png

      Cross over chart, winds at surface, 850 mb and 500 mb

      http://maps1.pivotalweather.com/maps/models/nam/2016071918/078/crossover.conus.png

      1. Significant tornado parameter

        Significant Tornado Parameter (STP)

        A multiple component index that is meant to highlight the co-existence of ingredients favoring right-moving supercells capable of producing F2-F5 tornadoes. The STP is formulated as follows:

        Sig Tor (CIN) = (mlCAPE / 1500 J/kg) * (ESRH / 150 m2/s2) * (EBWD / 12 m/s) * ((2000 – mlLCL) / 1000) * ((mlCINH + 200) / 150)

        where “ml” denotes the lowest 100 mb mean parcel, ESRH = the effective storm-relative helicity, EBWD = the effective bulk wind difference over the lower half of the storm depth (effective inflow base to EL height). The EBWD term is capped at a value of 1.5 as in the Supercell Composite Parameter, though the minumum value is raised to 12 m/s. The mlLCL term is set to 1 for mlLCL heights -50 J/kg.

        The “Sig Tor (fixed)” is similar to the “sig Tor (CIN)”, except that mlCAPE is replace with sbCAPE (surface parcel), ESRH is replaced with 0-1 km SRH, the EBWD is replaced with 0-6 km bulk wind difference, and the CINH term is dropped.

        For additional information, see Thompson et al. (2004).

        another

        Significant Tornado Parameter (fixed layer)

        A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), and surface parcel LCL height (sbLCL). This version of STP mimics the original formulation presented by Thompson et al. (2003) by using fixed-layer calculations of vertical shear, and substitutes the surface lifted parcels as an alternative to the ML parcels in the “effective layer” version of STP.

        The index is formulated as follows:

        STP = (sbCAPE/1500 J kg-1) * ((2000-sbLCL)/1000 m) * (SRH1/150 m2 s-2) * (6BWD/20 m s-1)

        The sbLCL term is set to 1.0 when sbLCL 2000 m; the 6BWD term is capped at a value of 1.5 for 6BWD > 30 m s-1, and set to 0.0 when 6BWD < 12.5 m s-1.

        A majority of significant tornadoes (F2 or greater damage) have been associated with STP values greater than 1, while most non-tornadic supercells have been associated with values less than 1 in a large sample of RAP analysis proximity soundings.

        Additional information can be found here and (Please open this link in another browser window.)

        And this link is to a really fine explanation:

        http://www.quincyvagell.com/2013/07/03/stp/

  36. SREF did a good job yesterday highlighting the areas where tornado would be possible. In fact there was a tornado touchdown in northern Maine yesterday.

    1. got rid of a sea breeze? yup

      19 Jul 4:54 pm 80 48 32 NNW 11G25 10.00 FEW060,SCT075,SCT250 1016.5 30.02 30.007
      19 Jul 4:47 pm 82 50 33 WNW 13G28 10.00 SCT060,BKN075,BKN250 30.02 30.007
      19 Jul 4:45 pm 82 50 33 WNW 17 10.00 SCT060,BKN075 30.02 30.007
      19 Jul 4:35 pm 82 52 35 NNW 16G22 10.00 SCT060,BKN075 30.02 30.007
      19 Jul 4:25 pm 75 61 61 W 7 10.00 SCT060,BKN075 30.02 30.007
      19 Jul 4:15 pm 75 63 65 S 6 10.00 SCT060,BKN075 30.02 30.007
      19 Jul 4:05 pm 75 63 65 E

  38. Heavy clouds just about passed with blue sky behind. Do those have to do with sea breeze convergence boundary ?

    2. Once the clouds were done being formed and the boundary collapsed, the leftover clouds were just pushed southeastward by the prevailing flow, which was from the northwest.

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