Sailing Weather Service Forecast
Sponsored by North Sails & Southern Spars
2013 Sperry Top-Sider Chicago NOOD Regatta
Issued 0645 LT 07 JUNE 2013
WARNINGS AND ADVISORIES: There are no active warnings or advisories posted for the sailing area. However, conditions can change quickly. Monitor NOAA All Hazards Radio on your VHF for the latest official warnings and advisories from The National Weather Service.
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SYNOPSIS: An great start to this weekend’s regatta is expected with high pressure across the northern Great Lakes to Central Plains controlling conditions today. A frontal system and Tropical Storm Andrea over the east coast. The pressure gradient between the high pressure and frontal system supports a moderate N/NNE flow over the racing area that will hold for much of the day.
The High pressure is pushing unseasonably cool air south across the Great Lakes. An upper level trough over WI is maintaining clouds across the area this morning. These two things are expected to limit thermal effects such that minimal lake breeze influence is anticipated today. The wind will be controlled mainly by modest fluctuations in the gradient wind strength and direction through the day.
CURRENT CONDITIONS: Winds are fairly steady NNW/N across the sailing area 9-14 knots. There has been a trend toward easing wind and veering wind overnight.
Satellite indicated widespread low cloud across WI, northern IL, and Lake Michigan, with little movement under the upper trough supporting it. The radar shower a few very light echoes which may be some minor rain showers within the cloud deck. Any showers are not expected to amount to anything significant.
FORECAST DISCUSSION: NNW/N winds along the immediate coast this morning 10-14 kts. Generally building mid-/late-morning and veering N/NNE 12-17 kts. N/NNE breeze may back to N through the afternoon, and ease 9-13 kts in the latter half of the afternoon.
WEATHER: Mostly to partly cloudy this morning as stratocumulus holds across Lake Michigan, WI, and northern IL. There is a very small risk of a few isolated and very light rain showers under this cloud deck, mainly this morning. Some breaks in the clouds developing from time to time and it may attempt to clear out over the lake this afternoon. But on balance, you should generally expect more clouds than sun and unseasonably cool temperatures.
TEMPERATURE: Cool low-50sF this morning warming only to near to the 60F afternoon.
SEAS: 2-4 ft.
Detailed Wind Forecast:
Time Wind Speed Wind Direction (MAG)
(LT) Mean Range Mean Range
0900 12 09-15 005 350-020
1000 13 11-16 010 355-025
1100 14 12-16 015 360-030
1200 15 13-17 015 360-030
1300 14 12-16 010 360-025
1400 13 11-16 010 360-025
1500 12 10-15 010 360-020 …possibly more right if trending lighter
1600 11 09-14 005 355-020
1700 11 08-13 005 355-020
1800 10 08-13 005 350-020
HEDGE: FORECAST CONFIDENCE: ABOVE AVERAGE
1) The models are in very good agreement today. Models and observations agree reasonably well at the moment. Therefore, I have no reason to significantly deviate from the model predictions in the forecast table. There is some modest uncertainty with regard to the slight easing trend in the latter half of the afternoon. Winds may stay more or less moderate through the later afternoon, with little change in the wind direction.
2) Today’s wind is expected to be relatively steady and gradient dominated. Oscillating shifts and pressure lines will be most important strategic race factor, rather than looking for any persistent shifting trend.
3) Note that rapid changes in the cloud cover will have an impact on the wind field across the course area. If there is cloud onshore and active clearing offshore, then watch for an easing, right trending breeze. Alternatively, cloud advancing from the N may bring wind it stronger, left-shifted breeze.
4) Sometimes in this wind direction, a line of convergence cloud can develop parallel to the north shore. This is a friction effect, where slightly more left-shifted breeze off the shore convergence with slightly more right-shifted breeze over the lake. If this develops near or over the course area then you should be aware of the possible wind shift across the cloud line. Also, wind would tend to be stronger on the right side of the line looking upwind.
5) This morning, emphasis for the breeze will be away from the shore. Late morning, stronger breeze may fill right into the shore make for more even pressure on the course. In the afternoon, watch for a possible easing trends will offshore, especially if the wind is more right-shifted than expected.
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OUTLOOK FOR SATURDAY (08 JUNE 2013)
High pressure shifted east over northern Lake Michigan tomorrow while the remains of Tropical Storm Andrea along the east coast move off Cape Cod. As the high shifts more overhead, winds the gradient and resulting winds will ease. Clearing skies are expected along with slightly warmer temperatures.
Backed NW/NNW winds in the morning will veer N again late morning. Strongest winds are forecast in the morning, with weak drainage and the remaining gradient working together. As the day progresses, veering and easing gradient arrive as the high pressure moves closer. Minor thermal effects may cause the wind to veer more aggressively toward the NE or even ENE, but likely at very light speed.
Detailed Wind Forecast:
Time Wind Speed Wind Direction (MAG)
(LT) Mean Range Mean Range
0800 07 04-09 340 325-360
1000 10 07-12 350 335-010
1200 09 07-11 360 350-020
1400 07 05-10 020 010-035
1600 07 05-09 030 015-045
1800 05 03-08 045 030-060
SEAS: Decreasing to 1 ft or less.
WEATHER: Some scattered clouds otherwise mainly sunny. Cumulus will likely develop over the IL shore late morning through afternoon.
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OUTLOOK FOR SUNDAY (09 JUNE 2013)
Deteriorating weather conditions are expected as a low pressure approaches Chicago from the west. This will bring improving winds, mainly on a building SE gradient. However the risk of showers and thunderstorms increase.
WIND: SE 6-12 kts in the morning, tending SSE and building 12-18 kts. Chance of winds tending S/SSW through the afternoon and increasing to 16-22 kts.
WEATHER: Increasing clouds with a chance of showers in the morning and thunderstorms in the afternoon.
Forecast prepared by Sailing Weather Service, LLC
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