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EuroboyDC 05-13-2013 10:54 AM

Weather Forecasts (Chesapeake in this case)
 
Good morning!

I am taking the boat out of Herrington Harbour North this afternoon and am a little bit perplexed by the forecast(s). I'm wondering if anyone could shed some light on this, as I always try to keep an eye on the weather.

- NWS says there is a small craft advisory in effect through late tonight from Sandy Point to North Beach. To my recollection, an SMA is triggered between 22-33 knot winds.

For this afternoon:

- Weather.com for Deale, MD, says 11-13 mph (9-11 knots) winds
- Windguru says 8-7 knots/gusting 11-13 knots (GFS), and 10-12 knots/gusting 13-14 knots (NAM). HRWe simply says 12-16 knots.
- Passageweather.com indicates 10 knots, dying off to 5 knots by 5pm.

As you can see, there is a good degree of contradiction here. Which model should I trust?

Also, given the circumstances, would you go out with a reef on a 30' O'Day 302 or just go full canvas?

Thanks for any insight!

Nico

rockDAWG 05-13-2013 11:05 AM

Re: Weather Forecasts (Chesapeake in this case)
 
For local sailing in the Bay, I always rely on NOAA and the weather channel on VHF.

Depending on your skills and the familiarity of the boat, to stay on the safe side, just reef. Besides, it is early in the season, just take it easy for a while.

Have fun !!!

PS: Welcome to Sailnet

jsaronson 05-13-2013 11:19 AM

Re: Weather Forecasts (Chesapeake in this case)
 
I start with the hourly forecast:
Hourly Weather Forecast for 38.97N 76.49W

I also check Thomas Point:
NDBC - Station TPLM2

It is usually easier to shake out a reef than put one in.

EuroboyDC 05-13-2013 12:01 PM

Re: Weather Forecasts (Chesapeake in this case)
 
Thank you for your feedback, gents.

I suppose I was mostly curious about the forecasts when seeing the SCA - it just doesn't make much sense to me, unless NWS is being overly conservative in issuing them.

But as you suggest, I'll probably start out with a reef as I can always shake it out if it's not needed.

Cheers!

Nico

DRFerron 05-13-2013 12:11 PM

Re: Weather Forecasts (Chesapeake in this case)
 
Nico,

Small craft advisory numbers are localized. So may be one thing outside of the Chesapeake, they may not be the same in the Chesapeake area. Each local NWS station around the country determines what they consider the wind speed/wave height combination should be for a SCA in their specific area.

At least, that's what was told to us at the weather seminar I took with a NWS forecaster.

jameswilson29 05-13-2013 12:12 PM

Re: Weather Forecasts (Chesapeake in this case)
 
Quote:

Originally Posted by EuroboyDC (Post 1029387)
- NWS says there is a small craft advisory in effect through late tonight from Sandy Point to North Beach. To my recollection, an SMA is triggered between 22-33 knot winds...
As you can see, there is a good degree of contradiction here. Which model should I trust?

There is no contradiction. The NOAA weather radio Small Craft Advisory is issued in advance of the SCA conditions and does not necessarily reflect current conditions. The weather synopsis portion of the forecast informs us that high pressure is steadily moving into this area through tonight. The wind speed range is predicted to increase another 5 knots this afternoon and evening from 10-15 knots to 15 to 20 knots - that is the basis for the SCA.

Quote:

Originally Posted by EuroboyDC (Post 1029387)
Also, given the circumstances, would you go out with a reef on a 30' O'Day 302 or just go full canvas?

I would not head out with a reef in the main in those conditions, but I would be more conservative in my jib choice with predicted increase in wind speed.

I head out plannng to use a full main, usually, then I judge the headsail by the conditions. You can always ease the main to reef once the jib is up. I usually rig everything in the marina for ease of possible use: jib sheets, whisker pole, spinnaker pole, spin sheets, turning blocks, unless I am only going for a short sail. On a number of occasions, it gets stowed without being used that day.

pdqaltair 05-13-2013 12:13 PM

Re: Weather Forecasts (Chesapeake in this case)
 
The definition of SCA depends on the area (google it). On the Chesapeake and Potomac it is :

Small Craft Advisory

Small Craft Advisories are issued for the Tidal Potomac River and the Chesapeake Bay when one or both of the following conditions is expected to begin within 36 hours:

1) sustained winds of 18 knots to 33 knots

OR

2) frequent gusts (duration of two or more hours) between 18 knots and 33 knots.

OR

3) waves of 4 feet or higher


Second, you really need to use NOAA wind speeds. Yes, this was a minimal SCA. Additionally, your feeling on the subject might be different at the mouth of the Potomac in a sailing dingy with a green crew. It is just an advisory. For cruising boats it mostly means clear the table, just in case.

jameswilson29 05-13-2013 12:24 PM

Re: Weather Forecasts (Chesapeake in this case)
 
Good point. Here are two very different examples of SCA, both near the mouth of the Potomac, one gusting and one with waves:

Gusting from the South (small waves near southern shore of Potomac):

Waves from a prolonged North wind, fairly stead wind in the teens:

chef2sail 05-13-2013 12:24 PM

Re: Weather Forecasts (Chesapeake in this case)
 
I have found that Lat-36.com to be most accurate for wind/ weather forcasting. Uses a variety of data


http://l-36.com/weather.php?lat=38.9...=ANZ500&v=0.50

EuroboyDC 05-13-2013 12:24 PM

Re: Weather Forecasts (Chesapeake in this case)
 
Thank you all for the additional feedback and info. As for the localized SCA parameters - I learned something new again. I do Google just about everything, but this didn't pop up.

Three hours to sailtime now, so we'll see how it goes. I do like the idea of putting up the full main and gauging the jib. Thankfully, I can just furl/unfurl the genny as needed. It'll help to have crew onboard this time, too. I took out a Catalina 27 on Cinco de Mayo, and that was a bit of a pain to single-hand that day.

For what it's worth, I'll post how it went afterwards - assuming I remember to do so, as the post-sail activities will involve watching the Caps in Game 7 at Calypso. (Sorry, Rangers fans)

Thanks again!

Nico


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