Categories
Weather

Breezy Day

A 68 MPH wind gust was reported on the Ravenel Bridge today.

The Ravenel continues to be a rough ride this evening thanks to a tight pressure gradient between high pressure to the northeast and a stationary front (the front that’s cooled us off back to the upper 60s) to the south.

Categories
Weather

Five years since the Ides of March Outbreak

KCLX Level II radar image at 8:29 PM March 15, 2008, as seen through GR2Analyst. A supercell thunderstorm near Moncks Corner had just produced a tornado in the Strawberry neighborhood (between Moncks Corner and Goose Creek) while a forward flank downdraft from a supercell heading over southwest Charleston County was entering downtown Charleston (where I was living at the time). Radar estimated maximum hail size of 1.5 to 2 inches with these storms in addition to intense rotation.
KCLX Level II radar image at 8:29 PM March 15, 2008, as seen through GR2Analyst. A supercell thunderstorm near Moncks Corner had just produced a tornado in the Strawberry neighborhood (between Moncks Corner and Goose Creek) while a forward flank downdraft from a classic supercell heading over southwest Charleston County was entering downtown Charleston (where I was living at the time). While the tornado threat was greatly reduced near the coast, spotters reported quarter-size hail with storms near Johns Island, while baseball-size hail later fell on Hilton Head Island.

Today marks five years since supercells packing tornadoes, strong straight-line winds, and large hail ravaged South Carolina and Georgia in an incredibly unusual atmospheric setup for mid-March known as the Ides of March Tornado Outbreak. (Typically, our most favored time for tornadoes is April and May, according to a National Weather Service research study.)

The March 15 outbreak introduced me to the concept of a Particularly Dangerous Situation Tornado Watch, an enhanced type of severe weather watch more common in the Plains and in Dixie Alley (MS/AL). (Indeed, it was this outbreak which triggered my most intense study into meteorology as well as watch and warning dissemination and spurned on the creation of @chswx a few weeks later.) Here is the archived watch, PDS Tornado Watch 120, at the Storm Prediction Center website.

Three supercells from this event stand out for me: one spawned a EF1 tornado in the Strawberry mobile home community, causing $250,000 in damage and injuring several people (source). It struck a little too close to home for comfort; my parents live just a few miles south of Strawberry in Goose Creek and were very fortunate to dodge that bullet. A second supercell over Hollywood brought very strong winds to where I was living in downtown Charleston at the time — believe it or not, it was the first classic supercell thunderstorm I had ever been in! I didn’t see any hail but the wind was fierce — reminiscent of Hugo videos — with driving heavy rain. On Hilton Head Island, the third supercell produced baseball-size hail at the Hilton Head Airport causing severe damage to aircraft.

In the end, tornado damage up to an EF3 rating was found in several parts of the state (particularly on NWS Columbia’s turf). The Charleston metro area dodged a big bullet as a seabreeze had moved through earlier in the day which helped cut off needed surface-based instability for tornado formation closer to the coast.

Level III image from the afternoon of 3/15/2008 as supercells move through the Midlands of SC.
Level III image from the KCAE WSR-88D captured on the afternoon of 3/15/2008 as supercells moved through the Midlands of SC. (Please excuse the radar branding. Old inside jokes don’t hold up well in historical contexts…)

For more information, including a great technical discussion of the ingredients that led to such a rare outbreak, read NWS Charleston’s summary of the event; I also recommend their research paper (PDF) as it gets really deep into the meteorology. It also explores the challenges of issuing storm-based severe weather warnings in such a widespread severe weather situation (especially since storm-based, polygon warnings had just rolled out).

Fortunately, this March has been very calm and I’m pretty sure we all prefer it that way.

Categories
In Brief Weather

Tornadic Roadblock

This video was shot Tuesday evening by Drew Cavanaugh in central Florida, where several tornado warnings were issued due to strong rotation on radar and reports of funnel clouds, including this video. Nothing like driving down the road to see a tornado kicking up ahead of you to perk you right up.

Hat tip to more people than I can name over on Google+.

Categories
In Brief Weather

Dual-pol upgrade complete at the Charleston radar; products not flowing yet

The Charleston radar is running again after the dual-pol upgrade.

Dual-polarization data isn’t flowing to most people yet — based on my experience with the upgrade at Sterling, VA earlier this year, a day or two of calibration is still needed before the products are turned on over the Level III data stream (which serves a majority of the radar apps out there, including GRLevel3 and RadarScope). Dual-pol moments are available over Level II, though I’ll wait to rely too heavily on them until NWS gives the data its public blessing.

Categories
In Pictures Weather

It’s cool to be getting a few scans of live Level II dual-pol data from the Charleston radar site tonight, presumably as testing continues on the upgrade. This particular screenshot shows the Correlation Coefficient product, which essentially helps a radar operator identify what’s precipitation and what isn’t. One way meteorologists use the CC product (called RHO in GR2Analyst due to its roots in mathematics) is to help identify possible debris signatures associated with severe storms (including tornadoes) (warning: PDF).

Note to my fellow weather nerds and enthusiasts: While it’s fun to look at, this data needs calibration and won’t be reliable until NWS says it’s live. You also won’t see it in RadarScope or GRLevel3 (2.x) until that time. Stick with Columbia, Wilmington, and the other surrounding radars for now.

For more, take a look at NWS Charleston’s Facebook post earlier Sunday.

Categories
Weather

What’s influencing our weather today?

ABC 33/40 in Birmingham covers the concept of “high pressure wedge” — such a weather pattern is in force today.

We’ll see more high pressure wedges as the winter rolls on. If you love this cooler weather, it won’t be around to see tomorrow; if you hate this cooler weather, it’ll be much nicer tomorrow (with a thinning cloud deck to boot).

Categories
In Brief Weather

The Weather Channel continues to make its case for naming winter storms

The Weather Channel is having a Google+ Hangout to discuss the naming of winter storms tomorrow at 1 ET.

Noteworthy: Several feet of snow have been dumped on northern Minnesota by an unnamed early-season winter storm.

Categories
In Brief Weather

The Weather Channel to Name Winter Storms

Watch out, Winter Storm Q will transport you to another dimension!

I am still kind of on the fence about this. It makes me feel better that there is National Weather Service precedent for naming winter storms — Buffalo has been doing this for a while, so it seems — but I think I would prefer if this initiative originated with NWS. I’m not sure how I would approach it on @chswx in the event a powerful winter storm affected Charleston’s weather (we usually don’t get snow from them but the strongest ones can cause severe weather). I have always tended to take the lead from the NWS to avoid the potential for mixed messages, and I have a bad feeling that’s exactly what’s going to happen here.

Categories
In Brief Weather

Mysteries of the IntelliStar 2, revealed

I’ve had a fascination with The Weather Channel’s local forecast computers since infantile amnesia set in, so reading this post about the tribulations of the IntelliStar 2, the forecast computer that drives the Local on the 8s programming for The Weather Channel’s high definition simulcast, was a fun read. Apparently the project was in trouble for a while (which is why it took The Weather Channel so long to bring a truly local forecast to the HD channel). The hardware specs are wild:

There ended up being 2 boards and a daughter card to make the I2HD work. The two main boards are PCIe boards and are very complicated. There are several instances of embedded linux running across the boards.

Again, the software was developed in-house. The new renderer was purchased from a 3rd party and integrated into the system (VizRT). The device driver was also done in house. The high level software is written in C#/F# running on Windows Embedded Standard (due to business requirements not present for [IntelliStar 1]).

It’s a pretty complex box doing complex things — constantly ingesting a satellite feed with radar and text products from The Weather Channel and the National Weather Service while driving high definition output 24/7. (Via TWC Today.)

Categories
In Brief Weather

RadarScope 1.1 for Mac

RadarScope 1.1 for Mac is out. RadarScope has been my go-to radar app on iOS since I got my iPod touch back in 2009, and quickly became my go-to solution for a Mac-native radar viewer. Version 1.0 was fairly solid but was missing some of the AllisonHouse and Spotter Network integration features the iOS version had. No worries, though, as 1.1 adds those back (lightning data being, for me, the most critical) along with some welcome UI tweaks to more easily control the radar display. While I still bring out GR2Analyst in my Boot Camp partition for heavy-duty analysis, I always keep RadarScope open in a Space for quick reference, and thanks to the improvements in 1.1, I’ll use it even more extensively. RadarScope is $30 and available in the Mac App Store (AllisonHouse data is subscription-based — I have had the $10/month “Storm Chaser” plan for many years and it has proven invaluable).