Category: Southeast & Gulf

Mystery Fog Bank Drifts Into the SC Coast on 3/27/20.

By WeatherFlow meteorologist Shea Gibson written on 3/29/20.

Lots of folks on the water (and meteorologists alike) saw a fog bank encroach the coastline late Friday afternoon and into the evening. It was rather peculiar because we generally would see a marine layer (fog) build along the coast as ambient air temps surpass the water temps by a substantial amount through the day, or leftover from nighttime into the morning.  This fog bank; however, was one that crept up on us in the afternoon and we can definitely can understand how legendary nostalgic maritime vessel and pirate stories would have started.

The setup at the coast was a classic warm pattern for the SE Region with Atlantic High pressure bringing somewhat moderate SW/SSW Sea Breezes into the coast. As with all successful Sea Breeze circulations, humidity was very low at the beaches and just inland. Sea surface temps (SST’s) were in the mid to upper 60’s and ambient air temps topped out around ~86°, making a difference of around 14-16 degrees. This is not very much of a difference to create a marine layering along the coast, but rather would be a very shallow surface layer if anything.

Here is a snapshot is what the cooler shelf waters were on that day. You can see the Gulf Stream offshore as the warmer body of water in the low 80’s.

At some point in the afternoon, a cool and stable pool of air managed to develop over the shelf waters. It was curved around the Atlantic High pressure and was nudged into the coast along the Sea Breezes. Here is what I caught off the GOES16 visible imagery:

To many on the water and beaches that day, it came as quite a surprise. Not only did it make air temps drop several degrees, it also eventually killed off the winds by several knots as this pool of stable air was injected into the Sea Breeze circulation.

Here are a few pics of the area from the locals:
This one from Daniel Cubberly Goldston at Kiawah Island just south of Charleston.

This one from Andy Lassiter at Folly Beach:

And this one from Eric Angermeier at the back marshes of Folly:

The NWS Charleston even issued a Dense Fog Advisory to cover the time for the effects: https://www.facebook.com/NWSCharlestonSC/photos/a.252200621469073/2999798246709283/
With the Sea Breeze being so moderate before the fag bank moved in, it was pushed into the coast where warmer, unstable air existed and dispersed by 7:00PM.

You can see the air temp drop starting just after 4PM inside the Charleston harbor at our Fort Sumter Front Range Light.

And here are the winds dropping after the cool air injected itself into the Sea Breeze circulations. It was not immediate, but rather gradual. This data was pulled from our weather stations at both the Isle of Palms pier and the Folly Beach pier.

So we already know that marine layering can hamper speeds and cause Sea Breeze decoupling where onshore flow is occurring off the cooler waters, but what about that magic number where this complication does not happen anymore? After watching SST’s and Sea Breezes for several years, I have pinned it right around 76°+ for the Charleston area when waters actually start feeding the instability factor (instability = more wind). For an additional reference point, in tropical system development we generally see 80°+ as being the fuel from the ocean surface.

As always, we are life-long students to this science and always watching, researching and sharing what we learn. Stay safe and cheers from us at WeatherFlow!

Shea Gibson
SE/East Coast Wind Forecasting
New Station Project/ Outreach
Twitter: @WeatherFlowCHAS
Facebook: Shea Gibson – Meteorologist

Sources: Our own WeatherFlow Datascope product. Nasa Sport SST: https://weather.msfc.nasa.gov/sport/sst/ ; College of DuPage Nexlab https://weather.cod.edu

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CAD Burn Down Event

By WeatherFlow meteorologist Shea Gibson 3/26/2020

Ever heard of CAD? It is a term in meteorology known as “cold air damming”, where cool dense air settles under an area of High pressure under a blanket of thick stratiform clouds (mid to low level clouds). Along the East Coast, we see that this cool body of air sometimes becomes lodged between the coast and the Appalachian mountain range and can sit for hours or days at a time depending on the atmospheric setup. They can be hard to predict and keep air temps several degrees cooler until it wears off. For the East Coast, including the SE Region, the main way to get rid of CAD is to inject warm air from the east, southeast, south and southwest…which you will see below. Keep reading.

Today, Thursday March 26, 2020, we saw a rather large but disorganized pool of cold air settling down across the SE region and backing up against the mountains. A moderate area of High pressure was bottled up over the Appalachians and was pulling cool Northerly flow down around it with a thick cloud bank.

Here is the satellite imagery around 10:11AM (14:11UTC) showing a rather large cold pool extending from parts of the coast all the way to the mountains…mostly focused along the steeper up-slope of the mountains along the western foothills.

As winds started nudging in from the ocean and over the warmer land mass that was exposed earlier, we saw the curtain of stratus clouds begin to evaporate from east to west and south to north. If you look closely, you can see how the clouds were “sloshed” up-slope and overlapped the existing cloud deck due – and winds aloft nudged this overlapping . This puddling effect came out quite well in our Goes-16 satellite imagery. Just click play for some animation.

You can see that as the day progresses, the CAD is broken up by warm Southerly winds from the south and southwest from Georgia into SC….and East winds cutting across NC. Eventually just about all of it dissipates. And guess what? It allows the Sea Breezes to circulate at the coast for added bonus to the wind sports communities!

We call these warmer air masses “CAD killers” when we see this kind of dissipation/evaporation. It may seem just like a cloudy morning then a sunny afternoon to some, but if you look closer in some of the visible tools available to us now, you can find some really cool atmospheric dynamics. The sky acts like an ocean at times. Great to see it in real time. 🙂

Stay safe and cheers from us at WeatherFlow!

Shea Gibson
SE/East Coast Wind Forecasting
New Station Project/ Outreach
Twitter: @WeatherFlowCHAS
Facebook: Shea Gibson – WeatherFlow

Sources: Tropical Tidbits https://www.tropicaltidbits.com/ ; College of DuPage Nexlab https://weather.cod.edu/ 

 

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West Coast Wind Blog: We owe it all to a Cut-Off Low as Baja winds ramp up.

by Mike Godsey, mikeATiwindsurf.com

With a bit of luck and a Cut-Off Low that behaves according to the models we see a 3-5 day El Norte blow for La Ventana and Los Barriles, Baja Sur.

This graphic for Saturday Nov. 30, 2019, shows the setup.

1. First, notice the huge storm over the mid-USA. This low-pressure system, that brought crazy winds, rain and snow to much of the west coast a few days ago is now tracking eastward.

2. Now note the second large storm out in the Pacific just off the west coast of the USA. Normally this storm would bring a day or two of stormy weather to the west coast and then move into the Great Basin displacing the El Norte wind creating high pressure located there. But far above this surface storm at ≈ 18,000 ft. is a near Cut-Off Low that is mostly disconnected from the upper winds that steer weather systems from west to east. This means this surface storm is likely to just loiter off the west coast for a few days.

3. Check out the small high pressure area in the Great Basin. This high pressure should cause El Norte winds today that augment the La Ventana local sea breezes today.

4. Notice the isobars extending from that high pressure. The closer those isobars are to each other the stronger the pressure gradient making for stronger winds.

4. This is creating the El Norte winds indicated in green in the Sea of Cortez. If that Cut-Off Low above storm#1 holds station while storm #2 departs eastward then the high pressure#3 can stay over the Great Basin and we see days of El Norte winds.

 

 

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8/29/10 Thursday Night 9:15PM ET Discussion on Hurricane Dorian

By WeatherFlow Meteorologist Shea Gibson

Discussion viewable on Facebook Live:

 

Stay safe and cheers from us at WeatherFlow!

Shea Gibson
SE/East Coast Wind Forecasting
New Station Project/ Outreach
Twitter: @WeatherFlowCHAS
Facebook: Shea Gibson – WeatherFlow

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West Coast Wind Blog: Where to go for Baja winter winds.

Where to go for Baja winter winds:

by Mike Godsey, mikeATiwindsurf.com

First, don’t confuse the April-Oct. down-the-line wave riding at Punta San Carlos and the other spots on the Baja Pacific coast with Sea of Cortez kiting and windsurfing. Different season, different crowd, and scant wave riding except when there is exceptionally big swell that breaks on sandbars or reefs and provides backside wave riding like you see in my photo from Cabo Pulmo to the right.

It is always tricky to make hard and fast wind rules but after having spent a total of 60 months living in Baja over 35 years I’ll stick my neck out.

Most years the Sea of Cortez winds are the strongest and most reliable from December to mid-February so this is the best time to visit if you are a windsurfer. If you are kiting add a month or two earlier and later. If you are a foiler you don’t even need to be reading this. If California is having an early winter then strong Baja winds can start in early November. If it is an extraordinarily mild winter in California then you better hope that the fishing is good in Baja. (this relates it being a El Nino or La Nino or Neutral winter which is a topic for another blog) The best pattern is when there are well-spaced storms coming over the west coast with clear spells between each storm. For example, in Nov. 2001 an unending series of storms hit the west coast and there was little wind in Baja.

When El Norte blows, all the sites from Punta Chivato to Cabo Pulmo have wind. Don’t switch sites if it is dead at your site… all the sites are probably dead. The only exceptions to this rule are Cabo Pulmo and La Ventana. Sometimes Pulmo just does not get wind. While La Ventana can have a very light sailable wind when the other sites are dead.
Most reliable winds (from most consistent to least consistent):

1. La Ventana
2. Los Barilles
3. Punta Chivato
4. L.A. Bay
5. Punta Arena
6. Cabo Pulmo

Strongest winds and most radical conditions (locations with typically the strongest winds and the most radical locations are mentioned higher on the list):
1. Cabo Pulmo (shown in photo)
2. Los Barilles
3. La Ventana
4. L.A. Bay
5. Punta Chivato
6. Punta Arena

Dangers

Baja has few of the sharks that worry sailors on the west coast and Hawaii. The only dangers here are needle fish. These sea-going daggers have been known to leap out of the water causing puncture wounds. If you see long narrow fish 1 to 2 feet long jumping out of the waves in front of you, dump into the water and water start going the opposite direction. Hitting one of these daggers when it is moving at 20 mph and you are moving at 30 mph can send its point jaw into some unpleasant places. At all of the sailing spots, longtime sailors can recount last seasons fish stories. For example, if you are at La Ventana, drop by Ventana Windsurf and ask Steve to see the X-rays of his butt. And when at Las Barilles, stop by Vela and ask Bill about his knee. The danger is small but the stories large. At times, there are man-of-war jellyfish but they are small compared to the ones in Maui. All in all Baja sailing is very mellow.

 

More Details:

Los Barriles

This used to be most popular Baja windsurfing destination. If you are coming down for a short trip and like at least a hint of resort life and the proximity to the Los Cabos nightlife and shopping, this is the best place to consider.

There is a wide variety of accommodations ranging from windsurfing resorts to the camping of North Beach. Please see our “Resorts and B&Bs” page for further information. The social life is hot (by Baja standards) and there are lots of stores and places to eat. Telephones, banks, RV park, gas stations await you. There are superb resort and windsurfing rental facilities. For your none windsurfing partner Los Cabos an hour to the south may beckon. There amaze of resorts, golf courses and tennis courts and shopping malls stand ready to devour money and time.

The wind is strong and side shore with very big swell close to shore. On most days, this a rugged place for complete beginners. There is often a good size shore break but once you are a few feet from shore it is no problem. Sometimes there are boats anchored in the inshore waters that you have to watch out for. If you sail southward you will find several points with breaking surf and fun backside wave sailing on larger days.

The winds are a bit stronger here than at La Vantana but when El Norte dies there can be periods of no wind. The large sweeping beach way downwind acts to catch wayward sailors but if you are more than a mile offshore you will have a long drift.

The wind alternatives range from ATVs, to world-class fishing, to exercise classes, sea kayaking, and mountain biking. From shore you can see the windline as it moves towards the land. Typically the wind picks up at a civilized hour in the late morning. In town are all the supplies you need and there are good restaurants. There is usually a satellite network so you can get the weather channel and track those Highs and Lows. There is also internet access. On a typical year the winds blow 4 or 5 days out of seven here. The wind here is fairly consistent and the swells can get very large.

This is the easiest sailing place to find. From the border, head south for several days. The highway goes right on the outskirts of town. Head into town to your destination.

Los Barriles caters more to travelers staying at windsurfing resorts and RV parks, but also offers beach camping. In addition, this area has the most complete infrastructure including supermarkets and medical care.

Baja Adventures offers a full-service Bed & Breakfast in Buena Vista — just south of Las Barilles. This nice B&B offers rates from single bunk rooms to double accommodations.

Vela Windsurf Resorts is located in front of the main launch in Las Barilles — on the beach at Bahia de Palmas, 1/2 mile east of Highway 1, on the north side of town. Vela has a reputation for having some of the best windsurf equipment, accommodations, and instructors in Baja.

If your budget or lifestyle prefer beach camping, then you may be able to camp at North Beach in the arroyo on the north of town. The status of this camping area is always in flux.

Martin Verdugo’s is on the beach at Bahia de Palmas, next to Vela. It is partially shaded area with 69 level RV sites and 25 tent sites. There are full hook-ups, flush toilets, showers, laundry, and a restaurant & Bar. The RV camping here is crowded and you are parked with almost overlapping mirrors. This is definitely not a pristine Baja experience but the sailing is great!

The Playa de Oro RV resort has 54 RV sites and 2 tent sites. It has full hook-ups, flush toilets, showers, boat ramp, laundry, and ice. You can make reservations by calling (818) 336-7494.

 

La Ventana
The northernmost of the fabled East Cape sites. South of La Paz this site was relatively unknown until the 93/94 season. 15 years ago we sailed here for a week and never saw another sailor.

The water and air are warm and the campsites are fairly protected from the wind. If your are driving down for a week or two and sailing is your only goal, this is a good place to spend your trip. The sideshore winds at La Ventana are a combination of two wind patterns. The hot, broad San Juan de los Planes valley downwind creates a local thermal wind that accelerates a mild 18 knot El Norte into fun 20-25 knot breeze. When El Norte cranks this thermal assist gives La Ventana serious winds.

 

The wind at La Ventana is further accelerated by the venturi effect created by Isla Cerralvo located offshore. The swells are a bit smaller than sites to the south (still they dwarf the Gorge on a 4.0 day) but they line up cleaner than Los Barriles. There is backside wave sailing at the small break at the shallow sandbar about 300 feet off the camping beach. There is another good wave sailing place at the turn of the beach to the south. None of these offer real down the line surf sailing but they are fun!

 

There is more interesting back side wave sailing 200 yards upwind with glassy breaking waves. There is also some wave action to the south at the bend in the beach. At all of these sites, a surfer can use a long board in the early morning before the wind kicks in. There is world class surfing 90 minutes away at Todo Santos on the pacific side but don’t expect any wind.

The sandbar in front of the camping area absorbs the shorebreak making this Baja’s best place for complete beginners. There are lots of very sharp sea urchins in the cobblestones towards the pier just downwind. Unless you are able to return exactly to one of the cleared pathways through the cobbles you should wear booties.

If you climb the small hill across the road in the morning you can see the windline and watch as it approaches the shore. A huge beach sweeps downwind acts as a parachute for drifting sailors. Even if you break down 6 miles outside you will land on the beach after drifting only about 1-2 miles. On a typical year the winds blow 4 to 6 days a week.

Be forewarned this is not a place for those looking for nightlife. There is a nice campground with water, trash pickup, showers, and somewhat funky restrooms. It can be very crowded at times. The town has no bar, no paved roads, no gas station, and unreliable phones. There are several tiny but good restaurants. There are 3 small windsurfing and kiting B&Bs. See our “Resorts and B&Bs” page for a full listing. If you are camping the prices for provisions are currently cheaper than at other Baja sites.

The reason La Ventana was so late being discovered is its isolation from Mex. 1. To get there if you are driving south, watch for the airport on the right as you near La Paz. If you are flying into La Paz leave the airport heading east and turn right when you reach Mex. 1. Once past the airport, head towards La Paz. When you get to the whaletail monument turn right and you will be on Boulevard Las Garzas (also called Agustin Olachea). Follow it to the first stoplight where you will turn right on Boulevard Luis D. Colosio. Continue out of La Paz and it turns into Hwy 286 to SJ de Los Planes.

You will know you are on the right road when you pass the Pepsi and Coca Cola bottling plants. Then the road heads to a mountain ridge. Then it drops down an endless hill into the Los Planos valley, where you will have your first view of La Ventana and the huge island offshore. If it is blowing you will see flashes of mylar sails.

As the road levels out, look for a paved road on the left going to El Sargento. Go about 7 KM to the tiny village of La Ventana. Just past the garish pink house on the left you will see Baja Joe’s, then Ventana Windsurf. A bit down the road is the campground. Captain Kirk’s is on the right about a half mile further.

 

Punta Chivato

Located between Santa Rosalia and Mulege at the end of a 15 mile dirt road, Chivato offers scenic high wind camping. El Norte is somewhat accelerated here by the thermal warm basin of spectacular Conception Bay to the south. There is big swell and flat water speed sailing here in strong winds. Produce and water are sometimes available and there is a resort nearby. The rumors of the camping area on the beach being closed have so far not been realized and improvements to the camping area are being made. The camping is on a firm sand beach. The launch is sandy with none of the rocks found at most of sailing sites. There is OK diving right near shore on windless days but fish are scanty near shore. The wind and water are very cool compared to the sites way to the south. The fishing is good from a kayak but nothing like the East Cape sites at this time of the year. Blowing sand can bury equipment and slow moving sailors. Typically the winds blow 2 to 3 days per week.

Chavato is easy to find. There is a sign “Palo Verde” at the entrance to the road to Punta Chivato. Once on this 15 mile dirt road follow the sign
“New Road” at the fork in the road. The road is usually it is in pretty good condition unless it has rained recently.They have reopened the hotel restaurant and are building a second restaurant near the airstrip.

 

Secret Spot

Located south of Santa Rosalia there is a place with some nice waves. You need a boat to get there easily. Breaking swell with good rides.

 

Cabo Pulmo

Cabo Plumo has spectacular scenery, Baja’s only coral reef, great fishing, whale watching, kayaking, hiking, biking, diving, huge swells, and very high winds. The only element missing many years is reliable wind. There are only about 20 wind-protected camping sites and they are usually taken by long-term campers. Camping on the exposed beach in 25 to 40 knot side offshore winds is not fun and it is not uncommon for sailing gear and small dogs to be blown out to sea.

Like Jay Valentine once said, “this is a site waiting for an accident to happen.” Be forewarned Pulmo is for advanced sailors only. The winds are side-offshore and the shore break fattens up on broken masts. If you break down far outside you risk being washed up in Central America.

On the upper reef, the breaking swells are far larger and more vertical than other sites and the white water can sweep your equipment away. 500 feet downwind, the razor sharp lower coral reef has fangs that stick above the surface at all but the highest tides. Do not sail in near the lower reef since the water ranges from 4 feet to 4 inches in depth.

Killer whales are occasional visitors to the edge of the reef. On a typical year, the wind blows 2 to 3 days per week but there can be long spells with no wind and conversely, long spells with continuous wind if you’re really lucky.

Unlike the rest of Baja, the winds typically blow all night and sleeping can be a challenge. It is not uncommon for the wind to fade by mid-morning. If you sleep in a tent, ear plugs are necessary. The nearest potable water is 16 miles away. When the wind has blown in the 3.0 to 4.6 range for several days, well-organized 6 to 9 foot swells break as they hit the shallow reef beyond the point. Its like backside sailing without an impact zone.

There is spectacular kayaking at the point to the south. There is fairly good fishing but fishing is forbidden within 5 miles of the reef. There is also some of the best shallow water diving in Baja on the lower reef.

 

Bahia de Los Angeles

This spectacular, huge island-studded bay has a small but devoted windsurfing community. If you are driving and you only have a week in Baja, this is your first and last stop. The air and water are far colder than sites far to the south. The winds are moderate here and the passage of even relatively weak Highs to the north will bring good north winds. Despite its beauty, the only sailors that stop here are those who are unwilling to drive for one or two more days to warm water. Typically the winds blow 2 to 4 days per week. The road can sometimes be rough the last 40 miles.

L.A. Bay is easy to find. Just turn left at the well-marked turnoff and head east to the Sea of Cortez. La Gringa, as it’s called by the locals, offers good flat-water sailing from your campsite across the La Gringa Bay to the point. Camping is currently $3.00 per day per car. The beach is sand and cobblestones. Set up camp in a high spot to avoid inundation during real high tides as the water comes in from behind you via a low spot. The waters inside are great for beginners and intermediates. Advanced sailors can head outside and towards the islands. The small unattractive village offers basic supplies and some food items. The market on the right side of the road has a telephone.

 

Punta Arena / Playa de Los Naranges

Located at the mouth of spectacular Bahia de La Conception these sites offer mostly light wind sailing in the 5.5 to 6.0 range. Great camping and boating. You can buy fresh seafood at the fish camp. Lots of long-term non-windsurfing campers. Typically the winds blow 2 or 3 days per week.

To find Punta Arena, pass the Punta Chivato turn off. The road will continue along a coastal plain heading towards Conception Bay. As you ascend the first hill just before the bay look for a wide graded area on the left with a dirt road leading eastward. There will be a sign saying Punta Arena. Follow the road for about 4 miles. There will be a maze of dirt roads at times. Keep on the central road at the 3 way fork. If you come out at a sandy beach with lots of RVs you are at the wrong place. Your destination is about a half mile to the east but you may not be able to drive there along the beach. Head back into the desert and take the next right until you come to a sandy beach with thatched shelters with concrete pads.

 

 

 

 

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Watching the Gulf of Mexico for Potential Tropical Development

By WeatherFlow meteorologist Shea Gibson
Tuesday, October 2, 2018

As we start the month of October, we are still very much in an active portion of the hurricane season, which does not formally end until November 30th of each year. The Tropical Cyclone Climatology graph below represents where we currently are on the timeline in the Atlantic basin. Even though we are transitioning downwards, October has shown some very powerful hurricanes in the past.
Examples:

  • Hurricane Matthew 2016 – highest winds ~165 mph
  • Superstorm Sandy 2012 – highest winds  ~115 mph
  • Hurricane Wilma 2005- highest winds ~183 mph
  • Hurricane Mitch 1998 – highest winds ~180 mph
  • Hurricane Opal 1995
  • Hurricane Hazel 1954


This morning, the NHC highlighted an area of disturbance in the western Caribbean Sea with 0% chance for development next 48hrs and 20% chance next 5 days.

Several criteria stand out as potential enhancers for this disturbance – and the threat for the Gulf Coast is definitely high should we get any significant development:

1. PWAT increase (precipitable water) as moisture piles up across the Caribbean along an Easterly trade wind surge.

2.  TCHP (tropical cyclone heat potential) is VERY high there as Sea Surface temps are very warm and very deep – lots of surface fueling there and extending to its north from the western Caribbean into the Gulf of Mexico.


3. Broad area of low pressure development ongoing – all it takes is aggregation of T-storms to create rotation of the atmosphere over that area.

4. MJO (Madden-Julian Oscillation) – this is an area of atmospheric coupling of tropical deep convection and atmospheric circulation – it pulses eastwards over the Indian / Pacific Oceans and signals over the Atlantic basin as well during “Phase 8” (which it is now). In short….this is like a steroid enhancer for tropical activity if the conditions are right.
Latest MJO evolution report as of 10/1/18: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf

ONE major limiting factor is that upper shear is strong over this area and will continue to be strong for the next several days. If or when this disturbance lifts north away from it, the Gulf of Mexico waters are very warm and ripe for development.

We will need to keep a close eye on this and any other tropical waves that attempt to develop in this part of the Atlantic basin. With such an abundance of surface fueling, a good portion of the setup for rapid intensification is there. We saw what happened to TX last year as Harvey intensified quickly into a Cat 4 storm before hitting the coast, so it is always good to have a plan at all times.

Stay safe and let’s hope we transition through the rest of the hurricane season without anymore land-falling storms!

Shea Gibson
WeatherFlow Meteorologist
SE Region/ East Coast / Tropics
Facebook: https://www.facebook.com/WeatherFlowCHAS/
Twitter: @WeatherFlowCHAS

Sources for this blog:
NOAA/NHC/ NCEP:
https://www.nhc.noaa.gov/
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf
WeatherBell Analytics: http://models.weatherbell.com
CIMMS TC Page/ SSEC (Space Science & Engineering Center
University of Wisconsin – Madison):
http://tropic.ssec.wisc.edu/real-time/mtpw2/product.php?color_type=tpw_nrl_colors&prod=natl&timespan=120hrs&anim=anigf
http://tropic.ssec.wisc.edu/real-time/atlantic/winds/wg8shr.GIF

 

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ENE Wedge Upset by Yet Another Short Wave

Blog by WeatherFlow meteorologist Shea Gibson 8/25/18

Concerning yesterday’s drop in winds and shift offshore along the Charleston beaches, there was a solid ENE build near 20kts that dropped significantly for locales north of the Charleston harbor entrance and slipped offshore a bit. When something like this happens, there is usually a “short wave” involved that interferes with the local gradient, which has effects on the directions and speeds. A short wave is sort of a buckle or “kink” in the atmosphere where either a trough or an old front exists. It usually attempts to develop an area of surface low pressure, which ultimately affects surface winds.

Here is the IOP Pier archive from Friday, August 24 showing the drop in speeds and shift in direction.

Folly Beach showed something similar, but not quite as affected.

So why the shift and drop in speeds? This time, it was a short wave of Low pressure in association with an old front well offshore that buckled towards the coast and temporarily disrupted the local ENE gradient. This also upsets the local Sea Breeze oscillations and squashes the local build temporarily until the short wave dissipates or moves away.

This is the typical scheme for the oscillations, so when a short wave interferes either offshore or onshore, it takes away the dynamic forcing (stronger winds along the barrier islands) and weakens the lower pressure at the coast.

So next time you are out and this happens, you’ll know at least one major reason why it could be occurring. As forecasters, we sometimes mention the possibility as these features can be rather sneaky at times. This one definitely caught me off guard…so this is a lesson learned not to turn my back on the Gulf Stream with an old front over it.

Until next time, stay safe out there!

Cheers,

Shea Gibson
WeatherFlow Meteorologist
SE Region/ East Coast /Tropics
Twitter: @WeatherFlowCHAS

 

Outside Sources: SPC Mesoanalysis: https://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=17

 

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Severe weather in the Northeast

Thunderstorm season in the Northeast US is off to an eye opening start after yesterday’s severe weather outbreak. A strong squall or line of thunderstorms passed through MA down to NJ in the late afternoon and evening bringing damaging winds and localized hail. 

 

 

In the radar image below, note the gust front ahead of the thunderstorms and the high dBZ signatures (in purple) over CT as thunderstorms barrel through. Dime to golf ball sized hail was reported in parts of NY and CT.

WeatherFlow stations recorded several gusts around NY and CT exceeding 60 miles per hour!

Honorable Mention: WeatherFlow station, Eaton’s Neck Lighthouse measured a 50 knot gust (~57.5 mph).

Let’s remind ourselves to stay safe when severe weather approaches and heed the watches and warnings issued by your local NWS offices.

This image was taken in Milford, Ma before thunderstorms passed through. These are mammatus clouds, formed by cold dense air sinking downward into warmer air causing groupings of ominous lobes. These types of clouds are often seen out ahead of thunderstorm clouds and are therefore harbingers of imminent severe weather. Source: WF Forecaster Tim Nicholas.

Sources:
Wind data courtesy of WeatherFlow
http://www.spc.noaa.gov
http://www2.mmm.ucar.edu
College of DuPage: http://weather.cod.edu/

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Cape Verde von Kármán Vortex Streets

By WeatherFlow meteorologist Shea Gibson 5/12/18

One of the great things about the new GOES-16 satellite imagery is the ability to see microscale events in high definition far beyond our coast to the east over the Atlantic ocean.

Check out these ripples called  “von Kármán vortex streets” created from NE flow across the Cape Verde Islands just west of the African Coast. This is caused by the separation of moisture over the mountains of these island as the winds blow across them.

This process is very much like how wind would whip across a powerline and create the vortices on the other side, giving it the ripple-like effect (and that “singing” effect as well).Just as a FYI….another hot-spot for this to occur is Jeju Island off the coast of the Korean peninsula during strong cool Northerly winds across its tall volcano peak.

Just another one of those neat-o things that occurs in the atmosphere that lets us know how the surface and atmosphere can work together to create beautiful patterns. Until next time, take care and keep up with our forecaster blogs at http://blog.weatherflow.com/ – make sure to toggle the varous regions for lots of valuable information from our team!

Shea Gibson
WeatherFlow Meteorologist/Wind Forecaster
Outreach & New Station Projects
SE Region/East Coast
Twitter: @WeatherFlowCHAS

Sources:
https://weather.msfc.nasa.gov/GOES/
GREarth: http://www.grlevelx.com/grearth/
https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street

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