UPDATE 6/19/19 WEDNESDAY 7:30pm 2019 Summer Sailstice Overnight Ocean Race Forecast:
The forecast is looking a bit clearer now that we are within 2 days time for the race, with a pressing (meandering) front trying to press south overehad and then retreating north. There is more agreement in the model outputs that we are more likely to see a moderate morning Westerly flow lasting into the early afternoon before tapering off towards modest values at the start of the race. This will depend on the gradient in place, so expect a slightly higher value yield than what models show for now - we've seen this before with the West flow in the harbor. The front could press close just to our north, but looks to lift by late afternoon and through the night as Atlantic High pressure nudges it northwards.
I am breaking it down into time increments from the riday afternoon start and into Saturday morning:
Race Start Time 3:30PM:
W/WNW flow ~260-300° 9-13kts with potential for a residual gradient of 11-15kts before fading to the lower values over an hour or two period. There is a chance for SW flow to enter with a small boost to low teens starting around 4PM if Sea Breezes decide to kick in.
6PM - 9PM:
With the mention above about the SW Sea Breezes, we'll keep that as a possibility. By dusk and into the twighlight hours, that SW flow should fade to a modest or light 7-11kt WSW flow between 235° and 260°.
9PM - 12AM:
WSW flow continues 7-11kts with some fading to perhaps 5-9kts by the midnight hour.
Continued WSW flow 6-10kts with a bit of West backing at times due to land breezing.
Westerly land breezes 5-9kts with an element of WSW blending in at times. May see a tendency to turn more WSW or SW as the sun starts to come up.
WSW flow to start 5-9kts-->possible SW turn as mild Sea Breezes brings speeds up to 7-11kts.
Waves directions + heights look to hold from the South at around 1-2ft overall...but with any bump in Sea Breezes late afternoon Friday, could see a bit of 3ft chop in the evening, calming back down around 2ft.
Godspeed and I'll see some of you at the Skippers Meeting tomorrow night where we'll do a final analysis.
~Meteorologist Shea Gibson
2019 Summer Sailstice Overnight Ocean Race Preliminary Forecast given Monday 6/17/19 at 9:30PM:
The forecast starts out pretty tricky being ~5 days out, so things are apt to chanage a bit over the next couple of days. We'll see if the forecast holds or needs some tweaking by the time we get to Wednesday night and at the Skipper's Meeting on Thursday. For now here is the General Synopsis:
Thursday night into Friday morning...A strong area of Low pressure wobbles to the north over the New England states, which produces a backdoor cold front below it that swings down through the SE Region. The result is a moderate to strong W-->WNW/NW wind field that slowly fades through the day on Friday. Now comes the tricky part with some current model disagreement:
Scenario 1: Either the front pushes through to southeast SC and a modest to moderate NE/ENE flow fills in behind it through the night and possibly into the early morning hours. (18z GFS is currently hinting at this one)
Scenario 2: The front stalls and then backs north, with dual Atlantic High pressure / FL High pressure lobes filling in a moderate SW/WSW flow up from underneath the boundary. (12z EURO is currently pointing to this one)
Now I am not just looking at the GFS / Euro and the CMC (Canadian GEM) is back-and-forth a bit - pretty inconsistent as always but still worth a small darn. The NAM 12km and other higher rez models will come into play next few days for further guidance. My current evaluation after looking at all the data tells me that in these types of setups, it takes a good punch of NE winds to make it through, and that continental High behind the front does not look strong enough to force it overhead for a stall and to the south. With that said, I am more inclined to go with the SW/WSW flow from underneath to swing up and across our area as the parent Low (that is leading the front) pulls boundary away to the NE out to sea.
In total..my preliminary forecast is for a zonal Westery flow at the start of the race between 255° and 300° with speeds on the fall. May start out moderate with strong impulses in the 15-19kt ranges (gusts low 20's) and fade more W/WSW near dusk to 11-15kts. Then, nocturnal jetting may cause winds to back more SW between 225°-240° for a period through 9pm to midnight. As the front pulls further away to the north, winds veer slightly more WSW 240° - 255° through early morning hours with 13-17kts and higher gusts further offshore. This continues until sunrise and backs SW into the mid to late morning hours as the Sea Breeze commences.
Waves....primary swell direction will be from the S/SSE with an initial forecast of 1.5-2.5ft at the start. SW/WSW primary directions could create some chop along that into the night, but the overall heights look to fall to 1-2ft by 6AM.
Stay tuned as we continue to interrogate the data over the next few days. Eventually we hope it will do as it is told for us.
Next Update: Wednesday 6/19/19. See you at the Skippers Meeting Thursday!
~ Meteorologist Shea Gibson