Friday, September 8, 2017

Our Forecast Keeps Looking Better

24 hours after saying we needed to brace for Irma the forecasts keep getting better for us up here in the Silicon Swamp of central Florida.  Unfortunately, the forecasts have gotten worse for the west coast of the state.  Let me show you a forecast that the local National Weather Service Offices have been offering.  You have to look for it, but on the forecast page for a given city (clicking on the map) it's on bottom of the right side bar.  It's a graphic called the Hourly Weather Forecast.  If you click offshore, it gives a forecast of wave heights, swell period, and a handful of other things.  If you click over land, you'll get something like the graphic forecast for my area.
Wind forecasts are in the second panel down and the bottom panel.  The bottom panel is winds at 20 ft above the ground, the second panel is surface winds and gusts.

In both cases, the peak wind is about 11 AM on Sunday, and correspond to a tropical storm.  The second panel says winds 60 mph, gusting up to 75.  Gusts are specifically excluded in the definition of hurricane, which uses 1 minute wind speed.  According to this, we're not getting a category 1 hurricane, and nowhere near the Category 4 storm that looks to be coming ashore somewhere in the keys and then coming making landfall in the southern end of the state.  
 
Of course, all of this is subject to change.  If the storm comes up farther to the east, we'll get worse conditions, and likewise if it stays off the west coast it will be worse for the Tampa Bay area.  Peninsular Florida isn't very wide - it's around 140 miles at the widest point.  In a path like Irma's, the difference in the uncertainty of the path covers the entire state.  A small difference in path can mean a big difference in the winds a place gets.  The reason that forecast cone gets wider is the historical accuracy of the forecasts: essentially about 100 miles wider per day.  

Meanwhile, there's something about this graphic that strikes me funny; I laughed out loud when I noticed it.  The green line, third panel down, is relative humidity.  You'll notice that our relative humidity actually goes down in the hurricane compared to the night before (shaded gray).  At 82%, it's lower than any value after 9 PM the night before, and the same as 3 AM tomorrow morning. 

I suggest a new state motto:  Florida, where our weather gets better during a hurricane!  Or another possibility, Florida: where the hurricanes are only slightly more humid than a typical night! 


14 comments:

  1. Not to worry, it will be absolutely miserable when we are cleaning up after.

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    1. Don't remind me.

      I took my antennas down today; cranked over the tower and pulled the beams, then lowered the vertical. This weekend is the Fall ARRL VHF contest, and I've been experimenting with FT8 lately. I'd really like to run the 6m station all weekend... but no... I have to take the tower down because of (spits) Irma!!

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    2. Oh come on now, be reasonable! You could always have let Irma take it down for you...
      }:-]

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  2. The forecast for me is for 79 gusting to 98. I will be on the 2 meter and 70cm band for the storm. Mostly monitoring SKYWARN and ARES frequencies in my area. I have a 2m antenna and a 20m antenna in the attic, so they can stay in place.

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  3. I can hit the local SARNET repeater with my hand held. http://www.sarnetfl.com
    HF vertical antenna down tomorrow. Will have two hamsticks used as a dipole on 40 m in the garage.

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  4. Good stuff. Thanks Divemedic and Terry.

    I've had the HTs and the monitor receivers on. That said, haven't heard much. I suspect it will get more active tomorrow.

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  5. You and Miguel have jinxed me. I'm just north of Tarpon Springs.

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  6. Glad to hear it, SiG.
    Good luck to you all, and be safe.

    Leigh
    Whitehall, NY

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  7. These storms are punishment to those who voted for Hillary in last November's election. Note that most of the damage in CONUS is occurring in BLUE areas...

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    1. While the BLUE voters are spending time flooding Twitter with hope that the storm kills Trump and all his supporters

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    2. Yo, Mark: how long was your power out after Matthew? It's looking to me like Irma should be less of a bother than Matthew, but we never know what poles or wires may get knocked down.

      Good luck with that!

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    3. I believe it was less than two days, but that was because FPL hauled a BUNCH of out-of-state crews in and turned them loose. And I don't think that much else of the state was hit too badly. With this storm trekking up the whole west coast after hitting Miami, I suspect they'll have other repair priorities. And even though my neighborhood is only one mile from their Indian River plant, and even though the high voltage (and very high voltage) lines that feed T'ville and points north go right past our subdivision, and even though we also feed from those same high voltage lines, we tend to be very low on their priority to restore power.

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    4. Well, at least it's not like Sandy in New York, when they ran off utility crews that weren't union workers.

      Good luck!

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    5. And good luck to y'all as well!

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