The Hwy. 92 gap and the pressure gradient to Redding

Meet the nemesis of Coyote and 3rd. Ave. winds.PG2ReddingSWflow

by Mike Godsey

This blog is a work in progress but it is so relevant today that I thought I would at least post the graphics.

Sometimes you read in the forecast that the pressure gradient is strongest to Redding. And you  probably wonder how an areas so far from the Bay Area could impact our wind.

Basically the most common summer wind over the ocean is the North Pacific High’s surface  WNW to NW to NNW winds.

When those ocean winds are more WNW to NW the Peninsula receives decent wind if there is a good pressure gradient towards Sacramento or Bakersfield.

However anytime the North Pacific High’s surface winds go NNW there is a good chance that the Central Valley thermal low will center in the northern Central Valley towards Redding.

This means there will be a SOUITH to NORTH pressure gradient from the Bay Area to Redding.

So as the wind of the North Pacific High curves towards the coast and into the Bay it turns from NNW to W to WSW to SSW. and follows the topography towards Redding.

This curving process starts just outside the Golden Gate and continues in the central Bay and over San Pablo Bay.ZZ5A01FC57

This means strong wind from the north tower of the Golden Gate to Pt. Isabel into San Pablo Bay. And if the S. to N. pressure gradient is too strong the wind bypasses Sherman Island and heads into Napa until mid morning or later.

But it you look at a relief of the Peninsula closely you will notice that there is a SW facing gap in the coast range from Half Moon Bay to the Peninsula waters. And with a SW push of marine layer wind this means that Coyote and 3rd. Ave. are likely to have unfavorable weak winds near shore. Which stops any
WNW from getting to the launch sites.

You can see this happening in this satellite animation.

Paradoxically the wind out at the channel marker may be N. during a SW push and Palo Alto is likely to see useful NW wind. To get the story behind this Palo Alto eddy go to blog.weatherflow.com/meet-palo-alto-eddy/

.Hwy92gapSW

Posted in San Francisco

Sometimes when models bicker…

Forecasters cringe.ZZ71828F5B

by Mike Godsey

As you read my forecast for 7 AM this morning you are also probably cringing both at its length and all the weasel words.  Well here is my excuse:

Different models have different  resolution, different parameters and approach the physics of the atmosphere from different perspectives. So when it comes to sometime as ephemeral as wind they often bicker about the forecast winds.

But almost always you can look at all the real time empirical variables like satellite imagery, sensors, weather balloon data, radar, cams etc. and infer which model is more accurate on  a given day.

But some days, like today the models are extremely divergent about the wind strength and distribution in the afternoon yet they are all forecasting the same AM wind pattern.

That is the case today in the Bay Area. Two of the most useful high rez. models, the HRRR and the WRAMS are forecasting clouds and SW flow in the morning with strong NW winds at the ocean buoys and a eddy like circulation around the Golden Gate creating SW flow.

But for this afternoon they have radically different forecasts.

Looking at the anemic upper image for 5 PM you can see that the HRRR model has almost no wind forecast for the Peninsula and Waddell with the upper teens to 20 wind outside at Crissy and barely making Berkeley. And the coast stays cloudy and windless.

Now look at the bloody lower image showing the 5 PM WRAMS forecast. This model is forecasting upper teens to mid 20’s wind in the Bodega to near Treasure Island to 3rd. triangle with Waddell also seeing at least upper teens to 20 wind.

These are both great models but they can’t both be right.

So I was up at 4AM this morning looking at every bit of empirical data to see which model is supported by the data. All the sensor data from our sensors and the ridge top sensors were showing SW flow and smothered the Bay Area and extended to the Sierra. All of which supports the limp wrist HRRR and NWS forecast.

However subtle details of the satellite imagery led me to go with a stronger wind  forecast more in line with the WRAMS.

So here I am at 9:45 AM still pouring over the data to see which way the wind is blowing for my 11:30 AM forecast.

Special Update Issued at: 5/23 10:06 AM Lots of weasel words in the forecast today. This blog tells the back story: When models bicker!
Now at 10AM I am sticking my neck out and staying with the current forecast. Why? 1. An eddy has formed from Berkeley to Larkspur which is a sign of NW wind over the Marin coast range. 2. the Golden Gate eddy seems to be shrinking. 3. The fog offshore is being shredded by NW winds. 4. I am seeing a faint hint of Año Nuevo clearing. 5. Half Moon Bay and Waddell have turned NW. There are all signs of increasing NW flow. But be aware that all the other sensors are still showing SW flow even on all the hilltops. Last call for bets!

Posted in San Francisco

Troughing versus Ridging-a tale of two opposites

In the blog just prior, we are talking about surface pressures and the effects on winds as we experience them in the short term. This post is dealing with more long term patterns and how they may relate to our everyday forecast. Sometimes the difference takes place high above, in the upper atmosphere……

This last winter on the West Coast we experienced a much drier and warmer season, while over on the East Coast, just the opposite occurred. The atmospheric explanation for this was a persistent upper level ridge, camped out the entire region, driving wetter and colder weather up and over the Northwest. These ridges are like mountains in the atmosphere, composed of high pressure domes, up into the steering winds that drive weather here on Earth. The upper level section is generally at about 300-500 mb, or 18,000 to 30,000 ft. up. The flows here are like a river, that guides smaller disturbances and storm cells to their next destination. The ridging drove the cold snowy weather far away from the West Coast many times….

Conus.ridge

Lately we have been experiencing just the opposite. An upper level trough pattern has been in charge, grabbing low pressure systems and directing them over the Northwest and California, one after another. The trough originates near the Gulf of Alaska, and this cool river of air makes a great breeding ground for thunderstorms, as warm air on the surface, rises in the spring sunshine, encounters the cold air above, and condenses out the water into clouds-sometimes very large and powerful ones.

streamlines5.18.24hr

upper low trough

upper low trough

 

Another notable is the way air rotates around a low pressure, counterclockwise.If you look at the right edge of that circle in Nevada, you will see that this rotation would drive up southeast and up into eastern Oregon….

This opposite flow pattern is often referred to as wrap around flow, for the way it navigates the edge of the low pressure center and returns upslope into a region like Eastern WA or OR.

 

 

Hence the recent pattern of afternoon thunderstorms that build as clouds move in from the south……..

Upper low Influenced Thunderstorms

Upper low Influenced Thunderstorms

Makes for the weak easterly winds you see here at Arlington, while the windy spot, Jones Beach, is feeling the push from surface high pressure offshore. It has also kept stronger winds from filling in over the NearEast in the afternoons……

The thunderstorms gather most readily around the mountains where air encounters most lift.

Posted in Columbia River Gorge

Gorge Goes Great!

Combo of massive NPH and unusual venting thermal low in Basin promise strong wind!

by Mike Godsey

Most models and forecasts promise strong wind this Friday and through the weekend.

You all know the mantra: high pressure over the ocean extending towards Portland and low pressure towards the Columbia mean good wind. But exactly what do these high pressure low pressure critters look like.

Looking at the top image find the NPH centered about 700 miles west of the Oregon coast.

You can think of the North Pacific High as huge area where air from the tropics descends from aloft. As this air descends GorgeIsobarsclose to the surface it compresses creating a high pressure zone. All this descending air creates a dome of high pressure which we call the NPH. The isobar lines show areas of equal pressure. The closer the lines are together on the dome of high pressure the stronger the pressure gradient. Think of the elevation lines you see on a topographic map and you got the picture.  You might expect this wind to flow straight out from the surface of the NPH however since the earth rotates the wind actually spirals out from the center in a clockwise fashion.GorgeNPHLowpressure

When the NPH is near the Oregon coast it brings northerly winds to the coast. When it is closer to Hawaii it brings NE trade winds.

Now look at the same image and find the thermal low pressure in the Columbia Basin. Basically as the summer sun, or in this weird year the spring sun, heats the land of the Columbia Basin the surrounding air is warmed. As this warm air expands it creates a low pressure area. The greater the heating the lower the pressure.

So now you have high pressure to the west and low pressure to the east. And the isobars are closest together near the Gorge. (See note below.)

Now look at the animation and check out the clockwise winds of the NPH. Now zoom your mind into the area just west of
the Oregon coast. Notice how some of the NW wind from the NPH peels off and heads towards the Gorge as if feels the pressure gradient induced by all those tightly stacked isobars over the Gorge.

 Now really zoom your mind into the upper right corner of the animation to the Columbia Basin. And then look at the cos up below. This is where the thermal CBasinCCWwindslow pressure lives. What is unusual about this coming blow is that the Basin is really not that hot but the low pressure is quite strong. Why? Look carefully and you will notice that there is a counter-clockwise circulation around  the low pressure. This is being induced by a spinning low pressure just aloft. And this sucks up the rising air in the Basin which makes the low pressure stronger and the wind  in the Gorge stronger. So let’s wait and see if this big blow develops as modeled. Remember when looking at the animations that the current models do not “see” the walls of the Gorge and the resulting venturi effect on the wind velocity.

Note: Unfortunately even the highest resolution model that covers the Gorge, the HRRR model at 3 km resolution, does not resolve the walls of the Gorge. So the models often show the isobars and the strongest pressure gradient in the wrong  place. (When I did the forecasting for the America’s Cup preliminaries we ran the WRAMS model at an incredible 250 meters resolution which would resolve the Gorge pretty well. If only windsurfers and kiters had the deep pockets  like the AC people) That is one reason Gorge going is so difficult.

Posted in Columbia River Gorge

Time for an Audit of the Spring Time Sea Breeze in SC.

5-12-15 0700am

By WeatherFlow meteorologist Shea Gibson.

As we get into the latter part of the spring, we start to see hotter air masses continuing to surge into the SE Region. This prompts a higher rate of instability and thunder-storming along the Sea Breeze fronts just inland of the coast.  With water temps continuing to warm up, the surface decoupling issues start to slowly dissipate and convective outflow is able to help enhance the Sea Breeze circulations.  BUT….we still have to watch for marine layering with these significantly hotter air masses until water temps warm to a mixing point. We also have to watch for cloud contamination as these thunderstorms flare up and are steered by the mid and upper level winds across and over the convergence zone(s). Breaching of the coast line and overunning of areas that exhaust the thermal lift zones ultimately kills the winds along the beach.

So we start by looking at what are a few ingredients of a consistent or perfect “thermally enhanced Sea Breeze” for the SC coast – which can include the following:

1. The night before…a modest W or NW downsloping land breeze in association with radiational cooling at night (can include a healthy inversion with a distant cold front to show moderate values for a period). Northeast Gulf High pressure can help supplement the overnight land breeze on its downsloping – and to keep its place and/or provide mid and upper level Westerly steering of lee-side/inland/piedmont troughing that spark areas of storming (hence outflows head west out towards the ocean to be cooled, condensed and circulated). These High’s can contain a “drifting” displaced lobe of mid or upper level high pressure to reach the Southern Appalachians. Too far north up the mountain chain and cloud contamination could occur with a more Northerly steering and/or sheering of cloud tops.

2. Into the day…robust Atlantic / Bermuda High pressure steering in a synoptic Southerly flow (8-12kts optimal for the starting point) and heating things up with dry air along the immediate coastline. This helps nudge the Sea Breeze front ashore in the morning hours.

3. Sea Surface Temps/ Water Surface Temps stay at least within 5-10 degrees of high air temps for surface mixing optimization. A 15-20 degree difference, by observations, tends to create decoupling issues/marine layering of some level or thickness.  Recent obs pin the full coupling with hotter air masses reaching into the 90’s to SST 75°-76+ in temps observed May 19/20th as SST’s reached those marks. (There are some dynamic properties here in play…definitely up for discussion for hydrological points of view as to why there seems to be a threshold where the decoupling issues end).

4.  Convective potential (CAPE) is extremely helpful for atmospheric mixing for increased height of vertical stacking. Healthy thunderstorm builds inland and across the piedmont to provide a streamlined ceiling of outflow.

Ok first up is the Sea Surface Temps in succession from 4/30/15 – 5/20-15…temps were right around  71 °-72 ° on May 11 and a more solid 72° on May 12 after a hot day.

SST 4-30-15 to 5-20-15Ok let’s dive right in to 5-11-15 and take a peek at the overall setup for the day…notice remnants of Ana still spinning along southeast NC – with leftover moisture/troughing to the southwest.

5-11-15

Here is the Rawindsonde Observation (RAOB) Skew T sounding for 5/11/15 at 12UTC (7am EST). We see a very slight inversion to start the morning out and the air drying very quickly as we ascend. The convection inhibition (CIN) covers the area between the ground and the level of free convection – or basically where the warm stable air layer is situated that is keeping the thin cooler layer below it from rising (preventing updrafting). Then as we go higher we see where that skews over towards the area where mixing can occur somewhere just above 850mb. That is where the Convective Available Potential Energy (CAPE) values begin and we see much higher potentials for instability/storm building properties proceed up to just above 200mb’s where equilibrium is met. That is the level where vertical cloud stacking would end. Notice the CIN where the thermal cap is a solid SW 20kt flow.  Instability can only be achieved if that thermal cap is broken ..which this day was not a problem.

5-11-15 Skew T 7am

Surface CAPE is at a positive 1260 J/kg…mixed layer at 870 J/kg and forecast surface to be 2010 J/kg – or “large” for our area.

CAPE values in Joules per kilogram…

CAPE TABLE

Here is an additional development of mid level High drifting up into the Southern Appalachians to show the divergent mid to upper level NW’erlies.

5-11-15 gulf high

Quick double check of the 300mb jet stream to make sure we aren’t missing anything – checks out just fine. Frontal boundary lies just along the dip in the midwest with no mid or upper level factors.  Nice little polar jet streak up the Mississippi River states with the subtropical jet barely feeding into it over Texas, but otherwise remaining weaker to the south.

15051112_jetstream_anal

Ok so let’s take a look at the forecast for the day…

5-11-15 fx5-11-15 fx tables

Graph for the day at Isle of Palms – I’d call this a win for us with winds peaking out just a bit early..but there is a good reason for this.

5-11-15 IOP GRAPHGraph for the Charleston Harbor – a bit above values – but again for a good reason:

5-11-15 CHAS HARBOR GRAPHThis day’s air temps were predicted to be in the lower 80’s (along areas near the water)…but what happened was a record high air temp of 90° inland (perhaps a couple of degrees extra at other locales) as recorded by the US National Weather Service Charleston.

FB_IMG_1431388037027Look at the difference it made when marine layering showed up and created a wider spread of air temps. See below graphs with info for a snapshot of the difference.

23

NOW…with this surge of hot air, we had a rather large line of thunderstorms develop inland along the Sea Breeze front. Here is WeatherFlow meteorologist Tim Kent’s SPC Mesoscale Analysis update to the team showing the unstable air masses and areas of convection.

Screen Shot 2015-05-11 at 2.02.14 PMScreen Shot 2015-05-11 at 2.04.15 PM

Here are the radar loops for the day – notice the flare up of storms that get pushed from SW to NE with slow movement (Northerly sheer). This was a very lengthy line of storms spanning the entire SC coast.

5-11-15a

Incredible outflow boundary setup for the evening.

5-11-15b

Bottom line for May 11 for winds: Rapid heating with inland convection and Sea Breeze circulations were able to show a decent overall Sea Breeze setup.  Ultimately, cloud contamination got the better of the coast, but marine layering was already showing its teeth to cap speeds in the low teens along beaches. I physically observed a thin haze and almost a fog bank forming along outer beaches. This also contributed to storms fizzling out over this stable air.

Here is the PM skew T as a follow up just to show how saturated the atmosphere was inland:

5-11-15 Skew T 7pm

 ON TO May 12…

First let’s a take a look at the Skew T for the 7am sounding.  The thing to gather here is less CAPE values for the day and dryer overall air higher (still a muggy air mass up until around 600mb’s) up as far the the Sea Breeze is concerned; however, that will change later as the cold front makes its way eastwards. The other thing to consider here is the mid level Westerlies lingering around 10kts for the sounding…not much but just enough of a spread to keep an easterly drive of clouding aloft for outflow to help enhance circulations just a bit.  The inversion was much less pronounced to start the day and the thermal cap broke early – got some visual on earlier cumulus cloud building that morning to the west and north. The heavier upper sheer doesn’t have much effect until almost at the equilibrium level.

5-12-15 0700am

Double check of the jet stream analysis to make sure we still aren’t seeing any extra feed into the upper levels…fairly quiet there until later in the afternoon, where speeds do pick up.

15051212_jetstream_analLooking at the northeastern Gulf of Mexico, however, we do see the High right in place at 5:00AM (perhaps just a tad northwest of the inner curve). This is also helping with that mid level Westerly flow into SC. You can clearly see the synoptic Southerly flow up the SC coast already getting under way with tighter gradients residing out over the Gulf Stream.  Frontal boundary forming convective areas along MS/AL/GA.

5-12-15 0500 SPCHere it is at 11:00AM  – just wanted to show its migration pattern as it meanders around the inner Gulf curve of FL. Ridge axis to the east and frontal boundary becoming a bit more diagonal are likely culprits of a slightly stronger mid level Westerly flow over SC = sort of a zonal flow [squeezing] up into the state.

5-12-15SPC HIGH 1100AM

Forecast for the day by WeatherFlow meteorologist Dr. Tom Allen – good mentions of muggy air mass and talk about Sea Breeze storm potentials:

5-12-15 fx5-12-15 fx tables

Graph from IOP Pier – another win for our mets team! Notice the bump up in speeds in the evening as the cold front closed in and inland thunderstorms sparked several extra knots.

5-12-15 IOP GRAPH

Graph from the Charleston Harbor (Fort Sumter Front Range Light) – higher values as low level jetting, circulations and escape from mild marine layering helped the build. Always gotta watch that harbor – very tricky spot as heated land masses to the SW provide hotter dryer air and aid greatly in the surface mix.

5-12-15 CHAS HARBPR GRAPH

Charleston International Airport for inland comparison – notice the air temp differences again with a bit less effect and a jump in wind speeds during approaching convective activity in the evening around 6:30-7pm for the beaches:

Charleston Intl stats:

CHS INTL 5-12-15

IOP air temps:

IOP air temps 5-12-15

CHS Intl Airport air temps- gives you somewhat of an idea of the urban heating effects in the industrial/heavy industrial zone of North Charleston:

CHS INTL air temps 5-12-15

Here are the radar loops from the day where you can see more of a west to east progression -and an afternoon flare up of storming just west of Charleston:

5-12-15a

(Notice the outflow boundary collision in the evening as the front closed in on the coast)

5-12-15b

And last but not least…the Skew T for the 7pm sounding. The mid and upper level Westerly flow aloft is pushing 25-30kts at this point.

5-12-15 7pm Skew T

More on the outflow boundary collision here – and this is pretty neat!

http://blog.weatherflow.com/battle-of-the-outflow-boundaries/

Here are a couple more schematics of the Sea Breeze front and what is occurring at the leading edge:

sb_front.free

sea_breeze_schematic

THEORY: Based on the thermal cap inversions so very common here in the mornings, it seems there is a sub-circulation going on underneath these caps in the morning hours as the Sea Breeze front drifts ashore and slowly makes it its way inland.  The thinner the layer, the weaker the flow. As the cap lifts the flow widens and increases. This explains the jumps in the mid-morning hours we see at times just at the edge of the front (lifting winds) that calm down upon its passage and slowly build back up upon cool air advecting back down from the outflows.  Eventually land heats to a point where the cap breaks – lifting and mixing occur with additional outflow fueling the Sea Breeze – which makes the full wheel of building winds.  A tighter gradient over the coast from inland troughing and rapid heating helps to get this outflow going much earlier in the day.

More to come on the SC/GA/SENC Sea Breezes as we get into the hotter months.

Cheers,

WeatherFlow Meteorologist Team.

 

Sources:

Skew T’s provided by: NOAA http://www.spc.noaa.gov/exper/soundings/

Radar loops provided by: National Center for Atmospheric Research – http://weather.rap.ucar.edu/

CAPE table provided by: Meteorologist Jeff Haby http://www.theweatherprediction.com/habyhints/305/

Jet Stream archives provided by: http://squall.sfsu.edu/crws/archive/jetstream_archive.html

SPC Mesoscale Analysis pages for editing: http://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=17

Surface map pages for editing provided by WSI via Intellicast.com

Posted in Coastal South Carolina

Battle of the Outflow Boundaries

By WeatherFlow meteorologist Shea Gibson.

On May 12, the US National Weather Service in Charleston, SC made a Facebook post to see what would happen when outflow boundaries collide.

An “outflow boundary” is also known as a “gust front” and is generated from the outflow of air in the downdraft of a thunderstorm that crashes to the surface, where the air spreads rapidly in the direction the low level winds are going. It is considered a type of cold front and is a rapid evaporational cooling mechanism at the mid levels of the atmosphere; however, significant cooling can be felt at ground level as well by 10 to sometimes a 20 degree drop here in SC. The edge of the outflow boundary is detected by (Doppler) radar as it captures the convergence along the leading edge.  The edge is thickened and visible as cool air dives along down-drafting into warm air. Don’t be fooled, because it’s not just a release of energy – it can trigger a fast moving line of intense storms so keep an eye to the sky when you think thunderstorms are over in the distance. It may not be over just yet.

In this case…there were two outflow boundaries – one was generated from earlier thunderstorming that fizzled out along the Sea Breeze line…and the other generated ahead of a cold front thunderstorm line sweeping eastwards from the upstate.

https://www.facebook.com/NWSCharlestonSC/videos/947152191973909/

1

outflow1

https://www.facebook.com/NWSCharlestonSC/videos/947502228605572/

Here are the results…where you can see the flare up of convection associated with the collision.

2

outflow2

Here is a great vid from National Weather Service out of Wilmington, Ohio that breaks down a massive collision on May 28, 2014. You can see the explosive interaction… impressive!

Although this occurs more commonly than you would think, it’s not very often you get the chance to see them while in progress since they happen so quick. The next time there are storms in the area and you are thinking about it, check the local radar and see if you can spot one.

What does this mean for winds along the coast? Stay tuned…we have a juicy Sea Breeze article coming soon that relates to this day.

Cheers!

WeatherFlow Meteorologist Team

Posted in Coastal South Carolina

Exiting upper trough stirs up NW wind at the surface.

NW winds from the NPH…NOT!

by Mike Godsey, mike@iwindsurf.com

Yes, the wind felt like normal NW wind curving into Southern California and the bay today May 15. However the North Pacific High’s surface NW winds are nowhere to be found in the upper troughDeparting NWwindpacific near California.

Southern California

The tiny surface low associated with the upper trough in the image pushed through the Southern California bight and exited south of San Diego today. Strong NW winds at the surface stirred up by the upper trough caused the NW winds to crank up LATE in the afternoon from Leo to San Diego. But there was just too much NW wind the wind to hit the coast further north.

Bay Area

Rather strong NW wind  aloft stirred up the surface wind while hefty pressure gradients to all parts of the Central Valley sucked those winds into most sties on the coast and inside the bay.

Posted in Los Angeles, San Diego, San Francisco

Upper trough at ≈ 18,000 ft.

Shoves the North Pacific High over 1000 miles west of California

by Mike Godsey, mike@iwindsurf.com

Upper troughBAY

Posted in Los Angeles, San Diego, San Francisco

Warm cap inversion in the Peach State. Is this why their peaches are so sweet?

11210507_10205022347256510_141336241685117781_n

By WeatherFlow meteorologist Shea Gibson.

A friend of mine, Mike Maguire, sent me some fascinating pictures of what was believed to be a frontal boundary. He is a pilot and was up at FL380  – or Flight Level 38,000ft at 8:37AM Friday, May 8, 2015.

The following 5 photos taken by Mike Maguire.

11066550_10205022347416514_5982692348199292856_n

 

11210507_10205022347256510_141336241685117781_n

 

11255500_10205022347096506_443586912899188604_n

 

10929137_10205022347816524_917280332399192856_n

 

11011903_10205022347656520_6202780625442976454_n

Noticing the stratocumulus texture, my first thought was a fog bank or moisture curtain of some sort over a land feature such as a river or high hills range where elevation was a lifting factor. I asked Mike, “Was that over the Chattahoochie River maybe?” He responded, “I don’t think so Shea. We were past Colliers Navaid (IRQ) by about 5-10 minutes on the way to Atlanta”.  At that point  realized that this was simply suspended above the ground and was peeling back due to sunlight and dryer air filling in behind it.

Here is the weather balloon ROAB Skew T to the closest spot at FFC (Peachtree City, GA) from Colliers, SC that would be inline with that observation and guess what? A very pronounced warm cap inversion.

atl inversion

Fairly moist air up until about 600mb (~14,000 feet) where we see the dewpoint shift drastically to cooler temps and air dries out aloft for the most part (which also allowed for this clear shot).

Either way, riddle solved. That would be an upstate significant warm air inversion for sure. Very neat to see it on a Skew T vertical profile from a weather balloon where available, but even better to have a pilot snap a few shots to share!!

Thanks to Mike Maguire for the shout out. Keep up the safe flying – and please don’t stop sharing with us- we truly appreciate it!

And we wonder- with this repetitive cool moist air dammed up along the southern Appalachians creeping down into the piedmont and foothills valleys- does this keep that morning dew trapped underneath and make those peaches the sweetest in the country? Hmmm we might conclude and be happy with that idea.

Cheers,

WeatherFlow meteorologist team

Posted in Coastal Georgia

Eddies in the Bight and Big Winds for Isabella and San Diego

by Kerry Anderson & Mike Godsey

Anyone who says the weather is boring in Southern California isn’t trying to forecast the winds this afternoon. The WindAlert Plus model below shows the strong winds we forecast for the NW coastline and also for Isabella today.  We expected that but were a surprised at how much the winds increased this afternoon for San Diego beaches. What is driving all this wind.

May12,2012

We have a strong onshore flow due to high pressure gradients to the Great Basin.  This afternoon’s surface pressure map (below) shows the center of the low in Northeastern Nevada.  Note the spacing of the isobars between that Low and the coast.  This results in the strong NW winds that have been driving down the coastline.

ZZ28FC0111

When we get a strong Northerly flow move toward the coastline the air is forced to flow over the Santa Ynez Range which is a mountain range that parallels the northern coastline of the Southern California Bight.  As the air is forced over the range and then descends into the Bight eddies form.   We’ve been watching a couple of eddies that have been churning in the Bight.  A Gaviota eddy has kept winds above 20 mph along the Santa Barbara County shoreline for the last 24 hours and another larger eddy developed overnight and has been centered just north of Catalina Island. IsabellaBigday

As the larger eddy formed the winds on the south east side of the Bight turned more southerly and the winds were funneled around the eddy and up through San Diego.  Winds have started to decrease for the San Diego beaches as the eddy fades.  Lake Isabella though is benefiting from a continuing strong pressure gradient.

Silver Strand and Lake Isabella

Posted in Los Angeles, San Diego