Scott's May 2007

Mid-Atlantic Radar

Scott's May, 2007 Blog
(blog descends chronologically)

My Mini-Chase...And...
Talkin' Tropics This Week?
Wednesday, May 30

Curious thing about storm chasing...I've driven hundreds of miles to see nothing more than some rotation under a Towering Q and then there's days like today when the storm comes right to your door!

What at first appeared as a slow moving Pulse non-severe thunderstorm blew up this afternoon in my neck of the woods...prompting a quick little "chase" around my home town.

Here's the radar as depicted by WeatherTap's nifty RadarLab HD (high definition) software. The red borders and shading denote a Severe Thunderstorm Warning. The black "x" is where our office and weather station is located...right under the purple (61 dBz) thunderstorm. This storm moved slowly and dumped 1.76" of rain in our gage and produced 47MPH gusts before crossing I-81.

I logged just 24 miles on this "chase" and was treated to tropical storm-like rain and wind gusts, numerous downed limbs and a torrent of pea-size hail (Lexington reported severe criteria hail of .75 inches). The entire region is quite dry so flash flooding was not triggered by this storm.

The conditions log from our wx station tracks the storm. The image above was taken at 4:58PM; note as the strongest part of the storm passed that over one inch of rain fell in fifteen minutes!

Time          Wind    Gust     RH     Temp     Dew Pt    SLP        Rain
4:45pm        8         11        45       77.2       54.2      30.16       0.03
5:00pm      28         39        65       67.6       55.5      30.16       0.60
5:15pm      17         26        75       64.4       56.3      30.16       1.61
5:45pm        4          5         82       65.8       60.2      30.16      1.78

Here in the East, this has not been a good year for storm chasing, so I'll take whatever I can get...especially if it is on my street!

TROPICS: Two named Pacific storms off Mexico have heated up the tropics and there is a very slight chance for some action in the Gulf of Mexico and over Florida into the weekend. Here's a look at the models (click graphic for current maps):

Models are suggesting a surface trof down by the Yucatan Peninsula will keep tropical moisture heading up over Cuba, the Eastern GOM and eventually Florida. A wave of Low Pressure on Friday just off Florida and this will produce needed rainfall for the Sunshine State. Whether or not there is any organization at the surface is much in doubt...upper level wind shear is forecast to remain savage with more important mid-level shear a most inhospitable 40-60 knots. So, I think the eastern Gulf is the place to watch, but organized tropical development is not anticipated.

Big rains may still plague Florida into the weekend before the system heads away from the US early next week. The Western Atlantic will then draw our attention.

Scattered Storms Threaten Memorial Weekend BBQs...And...
Tropical Depression 1E Forms in Pacific.
Sunday, May 27

Scattered showers and thunderstorms will develop this afternoon and again on Monday over the Northeast before popping up east of the Mid-Atlantic mountains today. Severe parameters are low although the atmosphere is more unstable today than yesterday. Scattered t-boomers or small, localized downpours should get going along the Appalachians this afternoon, generally heading northeast later into this evening. Many folks will see no precip but should be prepared for any rain or storms that do develop. Little bit more steering today than previous two days so precipitation should not sit in one location for a lengthy period of time. Better opportunity for stronger storms and heavy rain will be north of the Mason-Dixon Line from Indiana to Upstate New York. A Stationary Front now hung over the Lakes and Northeast will begin heading south as a Cold Front...ahead of this boundary is where warm moist air collides with advancing cooler air. I don't see much a threat for tornadoes, but heavy rain, vivid lightning and strong winds are possible in some storms.

For Memorial Day, the Front approaches the Mid-Atlantic and pop-up storms will again be a threat along the Northeast I-95 Corridor as well as the Mid-Atlantic states. Nothing severe expected but do have indoor alternatives for Memorial Day activities, especially late afternoon and evening.

High Pressure builds in by Tuesday with slightly cooler temps before another Cold Front approaches next weekend.

TROPICS: The season's first Pacific storm has formed well southwest of the Mexico coast and is Tropical Depression One-E ("E" denotes Pacific Basin). This is forecast to become Tropical Storm Alvin (Allllllvin!) and is forecast to track west due west away from land. We're running model maps on this event at our "Premium Service" hurricane model maps section. Info here.

Have a happy and safe Memorial Day weekend. Please keep in your thoughts those who are serving and have served to protect our freedom to appreciate this day of remembrance.

Coastal Mischief Coming...And...
A Brief Hasta la vista.
Thursday, May 17

Mischief is in the making off the Mid-Atlantic coast. An Upper Level Low (ULL) over the Great Lakes will cross the Mid-Atlantic on Friday, get over water and head toward New England. Meanwhile, surface Low Pressure over the Bahamas moves up and organizes off the VA/NC border. Cold air aloft and warmer (tropical) Low Pressure at the surface can prove interesting. Coastal waters are too cold for a tropical cyclone...but a decent Nor'easter is possible (Invest 91L???). Models are in good agreement, among them the GFS, NOGAPS and UKMET all spinning up a Low off the Virginia Capes and coming in around Cape Cod this weekend.

Showers and thunderstorms could pop up most anywhere across the region north of the NC/VA border on Friday. Heavier rain and the potential for coastal flooding loom from the Jersey Shore into New England, especially if the storm cranks and hangs just off shore.

As advertised in yesterday's blog, temps cooled off today and will by much cooler Friday and Saturday before warmer air marches back on Sunday.

This will be my final update here at the blog until next Thursday (5/24). I'm attending a weekend camping event prior to a three day conference, and won't be in the office until late Wednesday. I try to get all travel completed by June 1; the "official" start of hurricane season. The plan is to begin "Pre-Season" subscriptions for our Premium Service hurricane model maps later next week...so check things out now by clicking here.

See y'all next week.

Severe Possibilities Today
Wednesday, May 16

A Cold Front is marching toward the Mid-Atlantic/Northeast and should crank up rain, some gusty winds and possibly strong to severe thunderstorms. Timing is everything and the timing looks good for storms east of the Blue Ridge this afternoon and evening. Ahead of the Front, strong SW winds are heating up the surface with dewpoints approaching 60° (and climbing). Prime heating of the day coincides with the boundary passage, so were I able to chase today, I'd be somewhere between Route 29 and the I-95 corridor. Small chance for tornadoes from the Chesapeake up into southern New England while strong to severe boomers are the risk for the Mid-Atlantic. Shear is marginal, but sufficient at least for the opportunity of Supercell development. Check in with our Severe WeatherCenter for real-time information.

Much cooler air filters in behind the Front on Thursday and Friday. Low Pressure will develop off the coast and should be far enough east to not gum up the weekend, but clouds will filter in over eastern locations. Temps begin to rebound on Saturday. Next Cold Front approaches late Sunday...not certain if it makes it to the Mid-Atlantic or how much moisture will accompany the boundary.

Andrea Redux?
Saturday, May 12

See this morning's Special Tropical Disturbance Statement for remnant Low of Andrea undergoing some redevelopment. This is the potential chicanery referenced in Thursday's blog below.

Last model run on this event was yesterday afternoon and shows the general path this disturbance is expected to track:

Hurricane Hunters will not fly out to due to "resource issues". Not certain if the flight was scrubbed yesterday and the plane or a crew is not available. Nonetheless, that's an interesting comment.

Andrea could be back as a named depression again today... so we'll keep her online at the HurricaneCenter and see how this pans out. I'm skeptical much happens as wind shear will resume at 20+ knots by Sunday. The potential NE/ENE track could bring the system close to Bermuda, but should not impact the mainland US other than "Surfs Up" (borrowing a phrase from The Beach Boys). For several days we've talked about a trof crossing the Eastern US; that will keep whatever develops away from the coast.

Current satellite:

Any updates on this system will appear here and at our HurricaneCenter.

18Z Model Map from this afternoon:

Convection does not appear to be holding together as the day progresses and shear will increase shortly; therefore I'm not bullish this becomes a "Andrea" a second time. That said, it is not an impossibility so we'll continue to monitor and publish model maps on this event right here.

Anemic Andrea May Be A "Miss" With Little Rain To Moisten The Drought.
Thursday, May 10

STS Andrea is about 100 miles due east of JAX this morning with a minimum surface pressure of 1002 mb ...she's barely a tropical storm. There isn't much rain on the western (Florida) side of the cyclone and dousing rains are not expected to help with fires in Florida and Georgia. Virtually all precipitation is displaced well to the east of the broad center of circulation. Unfortunately, winds coming around Andrea have shifted and fanned some fires so she hasn't delivered the hoped for "benefits" of a storm.

Winds are from the northwest and shear is increasing to 25-30kts so she won't strengthen today...in fact...the storm is weakening. Of note is the adjusted forecast track that has shifted south and east away from Florida. This morning's 6Z messy model map also shows this trend:

Most models and all ensembles turn the weakening cyclone away from land; if this verifies, Andrea will be a "miss". Assuming the center retros east closer to convection the storm will not come in along the Florida coast. Current information on this event is at our HurricaneCenter.

Mid-Atlantic Severe: The nearly Stationary Front currently located from Lake Ontario into the Tennessee Valley and over to Texas will ebb toward the area today. Severe parameters are low to barely marginal but the trof could help trigger some showers or a few non-severe thunderstorms today...especially over interior locations of the region and western/central PA. Any precipitation probably holds off for the area until mid-afternoon.

Rain and storms should develop later Friday into Saturday morning, but this right now it does not look anything more than garden variety storms. We'll keep an eye on things and update here as needed.

Andrea was downgraded to a Subtropical Depression at 11AM EDT by TPC/NHC. As noted earlier this morning, she'll be little to no help with fire and drought relief. Breezy conditions will hamper fire fighting efforts while pushing some fires and plenty of smoke to the south. No changes to earlier discussion: Andrea will weaken, miss the coast and probably be absorbed and swept away by an advancing trof coming down from the Northwest.

Mid-Atlantic Severe Update: A few thunderstorms should pop up along and just east of the mountains later this afternoon. These storms probably don't reach severe criteria, however if they poke along (nothing is moving very fast in the atmosphere at this time), isolated gully-washing rains are possible.

At 11PM EDT the Tropical Prediction Center/National Hurricane Center issued the final Forecast Advisory on Andrea. The depression is morphing into a remnant Low and likely will loop around in advance of an approaching Cold Front that will sweep off the East Coast on Sunday night. High Pressure builds in behind the front and while most improbable, we'll watch for any chicanery early next week offshore along the boundary.

This will be the final update on this event. Good timing as I'm on the road Friday so a quick word as we head into the weekend. The previously mentioned Cold Front *finally* reaches the Mid-Atlantic late Saturday into Sunday morning. Ahead of this front, a trof will hang across Virginia on Friday, so late afternoon or evening showers and perhaps some thunderstorms may fire up. Storms should be widely scattered and not approach severe limits. The action should be isolated and scattered on Saturday before winds pick up with building High Pressure. Mother's Day looks terrific across much of the region!

Invest 90L Currently Being Investigated. Subtropical Storm Andrea Later Today?
Wednesday, May 9

Hurricane Hunters are out and should determine if this is warm (tropical) or cold core (subtropical). This appears cold core and Advisories on Subtropical Storm Andrea could be posted as soon as 11AM EDT today.

Models from 6Z this morning:

Very little to steer this storm right now but heavy surf and wind are the major features at this time. Local interests should continue to monitor developments. If the storm becomes "Andrea", we'll have the latest info at our HurricaneCenter. This system is partially blocking the boundary to the West that is associated with the ongoing severe weather in that area and we'll see how both systems pan out here in the East later this week. Urgently needed rain from Invest 90L/Andrea should move inland later today. Check our Severe WeatherCenter for watches and advisories...especially along the coast.

Another update here at the blog late this afternoon. Quick comments at our News Feed that you can subscribe to for free.

12Z Model Map:

Updated 12Z Model Map to depict additional models and TPC/NHC track coordinates for subtropical Storm Andrea:

Please visit and refer to our HurricaneCenter for official forecast track information.

Updated 18Z Model Map:

Very little movement (easily gleaned by all the squiggly model lines). See why some model maps are called "spaghetti"? ;) Essentially a 40-45MPH cyclone providing a prolonged buy glancing blow to FL, GA and SC. Andrea shouldn't strengthen much, if any, although there have been showers and minor thunderstorms spun inland all the way up to near Danville, VA. This has ground to a halt the now Stationary Front looping from the Lakes down to Texas.

Andrea ebbs toward Florida tomorrow (note most models languish the storm just offshore). This weather gridlock means the boundary to our west won't approach the Mid-Atlantic until late Friday...so the forecast will likely delay the showers and some thunderstorms until late
Friday and Saturday.

However, Andrea's counter clockwise spin and a slowly advancing Cold Front may squeeze out some instability across the lower Mid-Atlantic on Thursday. Think it possible to be scattered thunderstorms but but probably stable enough to keep the action below severe limits. We'll see how it looks on Thursday with another discussion. Have a good night.

Invest 90L Could Become Subtropical Storm Andrea!
Tuesday, May 8

The "blob" off the Southeast US continues to nicely organize today, with convection pulling in toward a visible center. The system is now Invest 90L (Area of Investigation) and a hurricane hunter flight is scheduled for tomorrow morning.

Models indicate this may already be a tropical storm sporting winds over 40 knots near the center. Significant strengthening is not expected. As noted in previous blog, this may not become a true tropical (warm core) cyclone so it could be classified as "subtropical" storm Andrea.

Our Premium Service hurricane model map subscriptions will not begin until approximately May 25th; however we are tracking the system and I'll post *freebie* model maps here!

I will update model maps...so please check back over the next day or so.

Current Infrared Satellite view (click graphic for more images):

If Invest 90L becomes our first named storm of the year you'll find real-time info at our HurricaneCenter.

This evening's 0Z models (click map for subscription info):

Convection on Tuesday night not all that impressive. There's still some hope that at least a little rain gets into the parched Southeast...but this is a double edged sword because of increasing winds. No named storm tonight and we await seeing if the hurricane hunters bring a Recon flight in on Wednesday...this is still pending. Next update will be Wednesday morning. Have a good night.

EF-5...And...SPECIAL TROPICAL DISTURBANCE STATEMENT.
Tuesday, May 8

I was away on business from last Friday until last night and had no access to all the weather tools I depend on to keep an eye on weather events. On Sunday, I heard a comment about a big tornado in Kansas, but knew not the extent of this outbreak until yesterday. The Greensburg, KS tornado was the first "F5" using the new enhanced Fujita Scale...thus it was classified as the first "EF-5" . This already has caused confusion as the old scale was based on damage caused by a tornado; the new enhanced scale uses 28 different indicators to more precisely estimate wind speed. The Fujita Scale previously rated a wind gust of 262MPH or higher to be an an "F-5" while the "EF" Scale baseline for a '5' is a 3 second 200MPH gust. The enhancement is now taking into account the type of construction found in the damage field. The Greensburg tornado was rated approximately 205MPH...old scale this would be a very strong "F-3"; however the extent of damage to sturdy structures (schools, Post Office) and extent of damage to the water tower change the rating to an "EF-5" using the new scale. Nonetheless, this was a devastating tornado and the first recorded F-5 in the US since the Moore/OKC, OK tornado in 1999..

Video from the Stafford County, Kansas tornado on Saturday:

As the Greensburg tornado departered, storm chasers drove into town. Here's what they saw:

Models last week were jumping on a Gale Center "blob" to develop off the Southeast US coast and this has begun to organize. Here's a map showing some models forecast track from 6Z this morning (click graphic for more maps):

Models generally agree this NON-tropical Low Pressure center will drift west toward the coast with tropical storm force winds just off the coast from GA up to OBX. Buoys have ranged from 15 to 25 foot seas...impressive! In fact, QUIKSCAT this morning showed 50 knot winds. The National Hurricane Center issued their first Tropical Disturbance Statement for 2007 this morning and it is possible the hurricane hunters may fly out to investigate on Wednesday morning. Folks along the coast from Florida up to the Eastern Shore of DE should keep an eye on this system.

It is possible this could develop into a subtropical storm, but probably would need to do so by Wednesday evening. This system will push rain and perhaps a few thunderstorms over inland Georgia and the Carolinas. We'll continue to monitor developments.

Related Links:
Our HurricaneCenter (quiet now, but you never know...Andrea may be lurking)
Premium Service Model Map subscription information

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