A combo spinning low pressure near Sherman Island and powerful NW ocean winds and winds aloft arrives in the afternoon.
by Mike Godsey
It is the prefect storm if you like powerful, gusty, shifty winds. A beefy unseasonal North Pacific High slams strong NW wind at the surface. While at ≈ 18,000 ft. 105 knot winds from a 500 mile wind upper low pressure stacks counter-clockwise spinning winds via surface low pressures all the way to the surface with the focus being in the Sherman Island to Napa area. This means big NW wind near the coast from the hilltops all the way up to over 3 miles above us. This wind aloft will tend to transfer momentum to the surface which you will experience as powerful gusts, lulls and shifts.
If they arrive as I expect it means that you may experience strong NW wind at the surface with a chance of random blasts from the SW that could descend near the surface. This would be a recipe for an accident.
The 7AM weather balloon today detected 30 knot winds at about 10,000 ft above Oakland. Those winds are modeled to descend this afternoon and shift from NNW to SW.
Below is a sampling to the crazy winds we saw at many sites in the Bay Area today. Notice the abrupt shifts, gusts and lulls. The Bodega Profiler imagery is the most interesting. You can see how the winds aloft which were faint in the morning built rapidly in the AM to 40 knots and descended to the surface.
The National Hurricane Center has kept Joaquin at a Category 4 Hurricane with 130mph winds (slightly down 5mph from 5AM). It has very recently started the northerly turn and is heading North at 3mph. Pressure at 939mb’s. The slight weakening phase is likely due to cold water up-welling to the surface to limit further strengthening for now. Could gain strength as it lifts north over warmer waters again. The forecast path shows a majority of models (UKMET, GFS and EURO ECMWF) pulling it away from the coast and off to the NE while weakening over time. However, there are still a few models that pull it more westerly into the coast around coastal Low/upper Low pressure…so we cannot fully rule anything out until this storm picks up forward momentum and speed. Then, the forecast path becomes much clearer and solidified with forward progress. Storms this large, once they get going fast on one direction, tend to stay along their forecast tracks. In the meantime, the Bahamas are continuing to get battered with very strong winds and rains – so keep them in your thoughts for their prolonged experience down there.
—>The bigger picture for us here in Charleston (and all of SC for that matter) is the rain event unfolding. Yesterday was just a start to the lengthy stream of rains forecast for our area. Low pressures developing along the coastal frontal boundary and to the south along an upper trough will back into the coast while Joaquin starts to head north.
This sets up an atmospheric river along the coast with additional upstream from Joaquin to the south. The latest WPC rainfall estimates are at 5-6 inches over the next 24hrs and 12-15inches collectively over the next 5 days (pics below). Keep up with all Watches, Warnings and Coastal Advisories here: http://www.weather.gov/chs/
***–>The important thing to remember with this is that the winds and rain we are currently seeing today along the SC coast are NOT associated with Hurricane Joaquin. They are associated with and upper Low to the southwest and a coastal surface Low to our south (and any other secondary/tertiary Lows that develop along the boundary offshore). We may see a few coastal impacts from Joaquin this weekend with outwards increases in winds, additional tidal surging from driving winds and additional rains.
—>Waves this weekend expected to reach 4-7 feet along Sullivan’s Island/Isle of Palms, SC with 5-8 feet possible along Folly Beach, SC as Joaquin jogs north and east. Swell period looks to be anywhere from 9-14 seconds. Driving stronger East winds Saturday could make it a blow-out, but possible cleanup sesh on Sunday as winds lighten. Swell expected to peak Sunday morning. http://polar.ncep.noaa.gov/waves/viewer.shtml?-multi_1-latest-hs-US_eastcoast-
—>Winds will be very tricky as these Low pressures continue to wobble around along the coast. High pressure continuing to wedge down from the north + outwards pulsing gradient from Joaquin creates a stronger wind field (tightened pressure gradient to be exact) Saturday to show upper teens to mid 20’s E/ENE’rlies with heavy rains and possible T-storms. Lots of UP’s and DOWN’s expected. Sunday, we see the wind field diminish as the gradient relaxes and system activity pulls away from the coast. At least ….we’re hoping Joaquin will help pull all of the activity away with it. Attached to this post is the Pro Forecast from us at WeatherFlow (available in our WindAlert, SailFlow, FishWeather, iKitesurf and iWindsurf apps and products)
Beautiful cumulonimbus clouds thrust over the far East Bay.
by Mike Godsey
The San Francisco Bay Area is one of the most beautiful urban areas in the USA. Weather wise its juicy marine layer clouds are unparalleled as they flow over the coast range in the summer. But one thing the Bay usually lacks weather wise is massive thunder heads.
Yesterday there was not much thunder but there was one enormous thunderhead over the East Bay as you can see in these photos and the satellite video.
Looking at the video notice how moisture from the tiny low pressure system to the west condenses and forms masses of clouds as it rises up the coast range.
Especially notice in the satellite view the huge cloud mass that abruptly forms over the far East Bay due east of the Golden Gate.
That same convective cloud mass is clearly visible in the photos below.
For many days a weak surface low pressure has been blocking the North Pacific High’s surface NW winds from reaching the Bay Area. Finally yesterday the upper trough at ≈ 18,000 ft. brought some scattered showers to the Bay Area. Nothing unusual about all of this. But what is unusual is the NW clearing winds we see tomorrow. Typically this time of year the North Pacific High is small and well offshore. But overnight the tiny NPH you see at the start of this animation expands hugely so it spans the pacific waters from Baja to the Gulf of Alaska.
Notice the small North Pacific High off Southern California today. This is a good position to give Southern California some upper teens wind today but it does nothing for the wind starved Bay Area.
At the start of the animation find the counter-clockwise spinning winds of the tiny low pressure that has been keeping the Bay Area winds weak. Watch carefully since this feature gets blasted apart fast in the next 12 hours.
Next watch as a huge but elongated North Pacific High forms. You can recognize it by the clockwise winds that spiral out of the high pressure.
Now watch as the North Pacific High’s surface NW winds build near the Northern California coast.
But there are some issues with NW clearing winds this time of year. The Central Valley and the Great Basin are beginning to cool. This means the pressure gradients will be mild. This is a similar scenario as we see in early spring when there is strong NW wind at the ocean buoys but coaxing the wind through the gaps in the Bay Area coast range is problematic since there is a weak pressure gradient.
You can see this issue in the first half of the 2nd animation.
The light orange color you see about 10-20 miles west of the Bay Area is the North Pacific High’s surface NW winds. Notice how they fade away near the coast. By themselves these surface winds would only bring upper teens wind to sites near at or near the coast.
The second half of the animation shows the winds at about 1000 feet. Notice that they are much stronger than the surface winds. My forecast for GUSTY upper teens to weak low 20’s tomorrow hinges on these winds at 1000 feet hitting the coast range and creating NW moving turbulence that stirs up GUSTS at the surface. Time will tell if I am right.
Joaquin is now a hurricane and could very well become a major hurricane in the next day or so. As of 8am this morning on September 30, 2015, winds are up to 75mph and pressure down to 970mb’s. Movement SW at 6mph towards the Bahamas. Models currently still trend westwards for a US landfall somewhere near OBX to south VA, but this trend could change with any shifting of the atmosphere around this “weakly” guided storm. As far as computer models…The EURO is currently taking it out to sea, but it hasn’t been very consistent. GFS last few runs keep it into the coast with a sharp westerly turn near northern OBX. The HWRF model seems to be rather consistent as of right now, so we’ll keep watch on it. For now and the immediate future, Hurricane warnings are up in the the Bahamas. Not much movement expected over the next day or two. Look for further strengthening today as we continue to monitor.
Watch Joaquin here during its lifetime in our Datascope StormTrack links with ALL weather stations activated for free for everyone’s efforts and interests.
And now we have something unique just popping up on the visible satellite. Looks like old Invest 99L from the Gulf has made it into the Atlantic and has some surface spin. Seems to be heading to the SE towards Joaquin for now. Certainly thickens the plot!
We’ll keep an eye on this system as things continue to develop….
Mixed bag of …..man what a mess. Joaquin expected to meander a couple or 3 days then make a move while slowly strengthening. NHC still betting on the West over to North turn. Could slide SW and strengthen near the Bahamas for a good tan and a fresh Mojito…then get pulled away to the NE by the approaching front…or get sucked into the NJ/NY coast late this weekend. Just not sure yet. Son of Sandy? An Outer Banks experience? Or a flexing Fish Storm bomb? You be the judge on “The Battle of the Bad Hair Day Models”.
All jokes aside, we hope that there is a safe overall outcome of whatever happens. Keep a good eye on the this area of the world for the next few days as we see what unfolds. I’m sure it will be a good learning experience on many levels no matter what.
Yesterday the forecast offered a massive North Pacific High
and NW wind and today….
by Mike Godsey
Just yesterday the Bay Area forecast was touting the appearance of a massive North Pacific High stretching from California to the Gulf of Alaska to Hawaii. And mild but useful NW flow curved into many sites as upper teens to weak low 20’s wind. So what is with the weak mostly southerly winds forecast just 24 hours later?
And then over your morning coffee you read this gibberish forecast as words fail to capture what happened overnight.
Sometimes only words can really capture reality so let’s use these graphics tell the story.
In this next image you are seeing the modeled winds at the 500mb level at ≈ 18,000 ft. Notice how the southward extending loop of wind is looking like it might pinch off from the main flow of wind.
If this happens we will have a Cut-Off Low off the California coast. Already this circulation has produced a counter-clockwise spinning surface SW of Northern California.
Remember the winds you see in this image are NOT the winds that fill your sail or kite. But they do steer and impact the surface winds.
The last image shows the surface winds over the pacific early this morning. Note how huge the North Pacific High has become.
Also note the strong NW winds that were at the Bay Area ocean buoys yesterday are far from shore today.
This is due to two things.
1. Notice how the tiny surface low pressure to our SW is sucking up the winds of the North Pacific High and pulling them away from the coast.
2. Also note how the mountain of air we call the North Pacific High has extended a ridge toward the Pacific Northwest and Canada. When this happens the winds along the Bay Area coast turn N to NNW so it is harder for them to reach our shoreline.
This NNW flow also conducive to the formation of a tiny eddy west of the Golden Gate which creates southerly flow in the AM.
At the same time the upper trough brings cooler air into the Central Valley weakening the pressure gradient. All of this spells a major weakening of the NW winds and produces light southerly winds for many sites today.
This time of year the North Pacific High is suppose to be shrinking not bulging… why?
by Mike Godsey
You know the routine. The twin Bay Area winds machines, the North Pacific High’s surface NW winds and the thermal winds to the Central Valley that propelled your kite or sail all summer are both suppose to be fading in late September. So why are the Bay Area ocean buoys AND Sherman Island gusting into the low 20’s this morning?
The NW winds have ramped up because the “old” small, weak autumn type North Pacific High has died while a new steroidal NPH has suddenly blossomed over much of the eastern Pacific. You can see this in the animation that covers the time from yesterday morning to late this afternoon.
First find the clockwise spiraling winds of the old North Pacific High. This has provided the weak NW wind for the Bay Area winds in recent days.
2. Now notice how fast the new North Pacific High formed last night.
3. Now check out how the North Pacific High’s clockwise spiraling winds are delivering NW wind to the Bay Area coast even at dawn and those winds should ramp up to the low 20’s or stronger this afternoon.
Why is the North Pacific High so huge this late in the season? For the answer check back later today but for now think about hurricanes and El Nino.
Well, it has been a weird season and a marine surge is possible.
by Mike Godsey
Wow! Take a look at the difference in the surface winds today and tomorrow. I have been issuing a Marine surge ALERT! in the forecasts for several days now. This is still an iffy forecast for a simple reason: Marine surges are summer critters.
Although there can be several different causes but the result is a sudden increase in the depth of the marine layer clouds that thrust though the Golden Gate and the Hwy. 92 gap and southerly winds that sweep all the way to Sherman Island. If you are new to the Bay Area and marine surge take a look at this time lapse video which shows a marine surge in action.
But this is late Sept. and typically the Sherman Island season is over by now. Even as I have been issuing a Marine surge ALERT! in my forecasts for Tuesday, Sept. 22 I have been half expecting that the variables would change and I would be back pedaling but now 24 hours before I expect the marine surge to begin its ramp up all signs are GO!
This is not only a unseasonal marine surge it also has an atypical cause. The marine surge tomorrow morning starts typically as the Central Valley thermal low finally retracts from the coast so the nagging heat wave begins a fade.
Looking at the model animation to the left the low pressure areas are in light blue.
Notice that today the Central Valley thermal low is is all the way over the coast in the morning and early afternoon. This means there is no pressure gradient to suck the ocean winds into the bay.
Then watch as the low pressure pulls back to near the East Bay which allows modest wind this afternoon.
Tomorrow the heat wave begins to subside. As this happens the retreating low pressure leaves a lobe of low pressure over the North Bay creating a mild southerly pressure gradient and Sherman Island, which has been dead for days, should se some mid to upper teens winds tomorrow morning. Normally this time of year all Sherman would see would be a fizzled marine surge.
But keep watching the animation and you can see that in the afternoon a deep low pressure develops over Redding which enhances to marine surge. Then the low pressure suddenly balloons and spans the area from the N. Central Valley all the way into the Great Basin .
Winnemucca, Nevada may not be high on your must visit list but it and the other Great Basin sites show a dramatic pressure change tomorrow afternoon.
This pressure change causes the northerly wind of the North Pacific High to make a major curve over the Bay Area so we have southerly wind that focuses in north tower of the Golden Gate past Point Blunt and over the northern East Bay all the way to Sherman Island.
Meanwhile as you can see in the last animation the winds aloft further support the notion of a marine surge. Especially note the sharp kink the 850 mb winds that will transfer some wind to the hilltops. When this happens Sherman Island, which has no topography to the SW for a long ways usually has enhanced winds.
Obviously this is complex scenario and I could be proved wrong since it is always safer to forecast for typical expectations but if I am right Sherman Island will se low to mild mid 20’s tomorrow afternoon.
On Saturday, September 12, 2015, a friend of ours at iKitesurf named David Saunders had a kiteboarding accident on Kentucky Lake and was willing to share the story with us for educational purposes – very admirable I might add.
Here is where we are talking about as we zoom into the region.
There is a sliver of beach there along the tree line shadowed out in this frame, but enough to launch a kite in with shallow waters along the side.
Here is David’s account of what happened:
“Yesterday afternoon I had a very serious kite lofting accident. We were flying 17m kites and the wind was low enough that we were having trouble staying upwind. As I went to shore to recover the kite I was hit buy a huge gust that instantly pulled me over 30ft in the air straight up. I kept flying the kite and was able to redirect out to the water. Unfortunately I hit in about 2ft of water, crashing feet, ass, head. Knocked goofy, I tried to release my CL, but immediately got lofted again. This time with no hands on the bar. I bashed through the trees and somehow ended up on the ground at the edge of the water. (Friends) Steve Flankey and Jaredan Braal were there to help me and call 911. From there, boated to an ambulance and Life Flighted to Vanderbilt. Broken left shoulder blade, 3, or 4 ribs. Fractured fibula, ankle, toe and a bone in my foot. The good news is nothing seems to be too messed up and should heal fine. Tomorrow morning they will decide whether or not to operate on my shoulder blade. (I’m hoping not). Bottom line, just a very bad time and location to be strapped to a big kite. Thanks so much to Jaredan and Steve as well as all the EMS that saved me. Sorry for the crazy news, but I will be fine.”
David also adds: “I was wearing an impact vest (which surely saved some injury). Also, I was not wearing a helmet and actually had one in my kite bag. I usually didn’t wear a helmet in light wind, but had started wearing one for jumping. I was very lucky only to have only 4 staples in my head with a small cut. I will wear my helmet all the time now.”
And good news as of a September 18th update – he will NOT need surgery after all. On to the road to recovery!
Now…let’s take a look at why this happened – and it’s not what you would think. After doing some research, I put together this video for that area on that day.
Here is an illustration of a gust front:
An animated version of an outflow boundary/gust front:
These gust fronts can and do travel hundreds of miles at times as they feed off of and overtake the lower cooler stable air with warmer air rising up ahead of them – or in this case – an area of cooler water for acceleration. Makes it that much harder to predict.
Here is the closest sensor from the exact spot. Stilly Hollow sensor ~12-14 kilometers to the NE
RECAP on the video: The sensor showed a spike in winds at 20kts just around 4:26PM. This sensor is up in the hills and land shadowed, so we can assume that the readings were lower than what occurred over the water. By description of events, we may have been looking at 10-15kts higher than that with winds surging to 30-35kts, which on a 17 meter kite is highly overpowered and highly unmanageable.
And take a look at that 10 degree air temperature drop behind the gust front!
Here is a picture of the exact bank where it happened. I made edits according to the information available and how winds work along the elevated topography with a tree line. In this scenario, there were likely 2 eddies. The first one extending out over the water from the over-vertical hill tree line creating a vortex, then the second one from near the tops of the trees where the normal flow has nowhere else to go but up before transitioning back to inland. Even there…the air is still going up as inflow to the gust front.
(Friend of David’s named Jaredan Braal in this photo below for perspective)…
Here is a great .gif of what winds do when they approach mechanical transition..or an up-slope/ridge lift in topography. You can see where the lines squeeze together. That represents a “tightened gradient” where winds are accelerating as they lift. Add a vertical resistor such as a tree line with over-vertical branching…and you would get an eddy, or vortex, with further lifting ahead of it. Even though trees are porous and have open gaps, a large strong volume of air rushing in all at once can offset the absorption of the flow and stack up quickly.
There was so much force from his kite and body weight, it snapped a few stronger limbs off a tree.
Friend and witness Steve Flankey took notes and talks about it:
“What was so surprising was the speed at which Dave was lofted. He was sitting in the water and the kite was at the zenith too. He had no chance to release the chicken loop after the first landing (which he did an amazing job of keeping the kite under control). The kite lifted him back off the water at lighting speed. One last thing, Dave is being modest when he says he was at 30′. The first lift was approximately a full line length off the water. NO JOKE. Those are 27 meter lines too, I think. So glad Dave is such a skilled kiter.”
David furthers this in saying, “Even though I understand the obvious upflow created by the steep shoreline, I had not previously experienced it. Most of the time when we got too close to shore, we experienced turbulent, but lower wind as it seemed like the trees kind of absorbed it. Often times, the kite would simply drop when too close to shore, and occasionally experience a bit of a ‘swirly’.”
The story made also it into the local news at the Paris, TN “Post-Intelligencer” – article by Glenn Tanner:
WHAT TO LOOK FOR: This happens more frequently than you would think all around the country – and world for that matter. It’s knowing what to look for before heading out on the water or open area. irst thing is to check with the local US National Weather Service for any advisories, watches or warnings they may have put out for your area: http://www.weather.gov/ . Always check your regional area on radar to see if there are storms in the vicinity or on the way. Also…check the local winds and check winds elsewhere ahead of storming. There are some visuals you can see with gust fronts, such as “roll clouds” or “shelf clouds”, but those may not present themselves every time.
Here is a pic of a Roll Cloud.
Other visuals or auditory/sensory forewarnings may include:
Thunderheads or stormline well in the distance – lightning ( or audible thunder in the distance).
A thin line of clouds appearing out of nowhere that are traveling across the area at a visible speed.
Water surface becomes very choppy at a distance with no clouds at all.
Air tempertaure drops several degrees (becomes rapidly cooler all of a sudden).
Wind speeds pick up significantly at a nearby weather station.
Not every weather station is trust worthy, so know your area well enough to decide what is good information and bad information. You don’t have to be a meteorologist to know the details of inclement or dangerous weather when it is on the way, but knowing about storms and their associated outflow boundaries/gust fronts (as in this article) is very important in the world of wind sports.
We at WeatherFlow have a great set of tools available for wind/water sports enthusiasts and anyone else to use to help view the real time winds/radar and satellite imagery out there…along with many other features. You can actually setup any weather station in our entire network to “alert” you when winds come up to higher levels at your custom settings for directions and speeds.
Going forward, we at WeatherFlow certainly hope that David heals fast and heals well. Although he is experienced as many are, there is always a chance that something out of the ordinary and unexpected occurs. He is not the first one to have this happen – and held himself together pretty well considering the first loft that would have sent most into panic mode.
As for the Kiteboarders of Kentucky Lake (and Tennessee) – if you are ever in that area and would like to check with the local first before riding, we highly recommend contacting them first before going out at “Tennessee and Kentucky Kiteboarders”: https://www.facebook.com/groups/173153366119985/