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stormy weather

Discussion in 'Ask All Sailors' started by jon hansen, Apr 16, 2018. Add this thread to a FAQ

  1. jon hansen

    jon hansen

    Joined May 25, 2012
    731 posts, 277 likes
    john alden caravelle 42
    us sturgeon bay, wis
    the great lakes got April showers this last weekend. 28" of 'wet, mashed potatoes' at my summer house on sturgeon bay, wis. over 2" of rain here in toledo.
    the good news is this is how we keep the great lakes full. for twenty years the lakes had been dropping. now they are filling. i prefer deep keels on sailing vessels. my houses sit on high ground. i'm a happy camper.

    there is a storm in the north atlantic right now with a double eye, that is 28.1 " at it's center. WOW! is that a hurricane? it is HUGE!

    Ireland is taking it on the chin today
    https://www.windy.com/?42.618,-62.446,4,i:pressure,m:e7radAL
     


  2. Spooled Again

    Spooled Again

    Joined Dec 27, 2012
    364 posts, 31 likes
    Precision 22 (Sold), O 240 (Sold), Precision 28
    US Somers Point
    Where getting blasted with rain and wind at this moment here in N.J. Between the storm surge and rain off my dock lines are tighter then guitar strings.
     


  3. rgranger

    rgranger

    Joined Jan 19, 2010
    4,540 posts, 652 likes
    Hunter 26
    US Smith Mountain Lake
    Is the 28.1 in mmHg (bars) ?
     


  4. justsomeguy

    justsomeguy

    Joined Feb 20, 2011
    6,095 posts, 711 likes
    Island Packet 35
    US Tucson, AZ/San Carlos, MX
    I'm betting inches of mercury.
     


  5. rgranger

    rgranger

    Joined Jan 19, 2010
    4,540 posts, 652 likes
    Hunter 26
    US Smith Mountain Lake
    Yeah maybe. 28.1 inches would be 0.94 atmospheres. I don't really have a lot of perspective. Is a 6% drop in air pressure a big drop? Intuitively that does not seem like a huge gradient to me but I really don't have a basis to gauge with. 30 inches Hg is about one atmosphere.
     


  6. jon hansen

    jon hansen

    Joined May 25, 2012
    731 posts, 277 likes
    john alden caravelle 42
    us sturgeon bay, wis
  7. kappykaplan

    kappykaplan

    Joined May 1, 2011
    717 posts, 92 likes
    Pearson 37
    US Lusby MD
    28.1 inHG = 951.6 millibars, so it's a pretty intense low!
     


  8. jon hansen

    jon hansen

    Joined May 25, 2012
    731 posts, 277 likes
    john alden caravelle 42
    us sturgeon bay, wis
    28.1" is really, really, really. low. as in hurricane low.

    we share interests in wind toys. there is only two types of wind. gradient and thermal. understanding gradients is a huge concept for operating these wind toys. i was taught inches here in the states. it's what i know. mid west public schools. back in the fifties and sixties.
     


  9. justsomeguy

    justsomeguy

    Joined Feb 20, 2011
    6,095 posts, 711 likes
    Island Packet 35
    US Tucson, AZ/San Carlos, MX
    Superstorm Sandy was 27.76 inches.
     


  10. rgranger

    rgranger

    Joined Jan 19, 2010
    4,540 posts, 652 likes
    Hunter 26
    US Smith Mountain Lake
    Thanks ... that helps.
     


  11. dlochner

    dlochner

    Joined Jan 11, 2014
    1,769 posts, 582 likes
    Sabre 362
    US Fair Haven, NY
    Jon, I'm glad the upper Great Lakes have water in them. However, would you please keep the water in the upper lakes, we have more than enough water down here. Last year you didn't and this is what happened to my marina. :poke:

    IMG_0400.jpg Version 2.jpg
     


  12. Pirate Dave

    Pirate Dave

    Joined Dec 23, 2016
    39 posts, 21 likes
    Catalina 27
    us Clinton CT
    Shoot, I thought Stormy Weather was going to be about Stormy Daniels and te Donald !!!! I feel cheated !!!!
     


    LeslieTroyer likes this.
  13. Justin_NSA

    Justin_NSA

    Joined Jul 7, 2004
    4,402 posts, 620 likes
    Hunter 30T
    US Cheney, KS
    We're heading in to tornado and hail season. Yippee! :(
     


  14. Allowishish

    Allowishish

    Joined Oct 30, 2017
    79 posts, 47 likes
    Catalina c 27
    Long Monday US Lake Pueblo
    we are having winds in the low 30's with gust to the 50's out here today.

    There are a few bout on my dock that do not use a spring line... with todays wind direction that is really going to suck for them.
     


  15. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,390 posts, 568 likes
    Hunter 430
    US Waveland, MS
    Katrina landfall 27.4 inHg
    Camille land fall 27 inHg
    1935 labor day Hurricane 26.3 inHg
    I have a video of my rolled vinyl kitchen flooring "ballooning" as Katrina eye passed.
    My ears popped too.
    Jim...
     


    rgranger likes this.
  16. Roland5048

    Roland5048

    Joined May 12, 2004
    971 posts, 264 likes
    Hunter Cherubini 30
    US New Port Richey
    How about posting it? I bet that would look interesting, if not downright eerie.
     


  17. rgranger

    rgranger

    Joined Jan 19, 2010
    4,540 posts, 652 likes
    Hunter 26
    US Smith Mountain Lake
    Thanks @JamesG161

    And everyone else. This post has been a real education. I've always measured pressure in units of atmospheres so looking at inches of Hg does not give me an intuitive feel.
    In order to calibrate my head.. I did some conversions. For the rest of you who do not think in inches of Hg here are some conversions that I made for myself.

    Normal Air Pressure
    1 Atm = 29.92" Hg = 1013.25 millibar
    1935 Labor Day = a 12% pressure gradient
    0.88 Atm = 26.3" Hg = 892 millibar
    Camille land fall = 9.8% pressure gradient
    0.902 = 27" Hg = 914 millibar
    A 10% Gradient
    0.9 Atm = 26.93" Hg = 912 millibar
    Katrina land fall = 8.4% pressure gradient
    0.916 Atm = 27.4" Hg = 928 millibar
    It seems like most weather maps use millibar. As I was reading up on this I ran across the following rule
    1. Isobar lines may only pass through pressures of 1000 + or - 4. In other words, allowable lines are 992, 996, 1000, 1004, 1008, and so on.
    Some questions that remain in my mind are.. how close do two lines need to be in order to create a approximate 10 mph breeze? or a 20 mph breeze? etc. I think if I had that info in my head, I could look at a weather map and make much better predictions about wind speed in an area.

    anybody here know this info?
     


  18. rgranger

    rgranger

    Joined Jan 19, 2010
    4,540 posts, 652 likes
    Hunter 26
    US Smith Mountain Lake


    Last edited: Apr 17, 2018
    JamesG161 likes this.
  19. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,390 posts, 568 likes
    Hunter 430
    US Waveland, MS
    I will look for it.
    When my Katrina adjuster was here for my really Minor home Katrina damage <$20K, I showed him the video and he nearly freaked out.
    I lost my office entirely , just a clean slab and bent building structural steel warehouse.
    Here is a picture of my office 2 days after Katrina. Yes that was a iMac from my office too.
    KatrinaOffice.jpg
    Before, I couldn't not see the Water Tower. See the 2x4 on the floor, that is where my desk was.

    Notice NO MUD... almost like it was pressure washed.
    Zero leaves in the trees.
    Waveland MS was the real ground zero.
    Jim...
     


  20. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,390 posts, 568 likes
    Hunter 430
    US Waveland, MS
    For the weather buffs, 1000 milliBars = 1 standard Atmosphere at sea level, is used for all hurricane and storm forecasting.
    They search out 800 millibars and 500 millibars for the Hurricane Hunter's fly throughs. Then they zig zag at that pressure, not altitude.

    The real key is the diameter of the LOW pressure. That gives a big Area of pressure reduction.
    Three things for all ship's watches.
    1) Time
    2) Celestial position
    3)BAROMETRIC pressure CHANGES...

    Fast falling... LOOK out
    Slow Rising... clear sailing.
    Jim...

    PS: I was Sandy's diameter and the lack of Hurricane standard building codes that caused the major damage.
     



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