22 June 2010 Chase - Southern PA and Northern MD

Jason Foster and I just got back from chasing... was about 4-5 mi south of the reported tornado in SE PA. We didn't see the rotation or tornado (we were on I-76), but we did see the nice wall cloud that spawned it. Note that the TOR producer was not actually the cell that got TOR warned later on :P Pics and screen grabs coming soon.

Things we experienced today:
- Beautiful wall cloud.
- Two double rainbows, one of which was literally right at the ground.
- Dime sized and maybe a couple nickel sized hail (as we "core punched" the second cell that formed to our south).
- Estimated 60-65 mph wind gusts (as we were standing outside filming the tornadic storm).
- A large tree down in Cecil County, MD blocking a road just south of Rt. 1 (which we reported).
- Vivid CG lightning from three different cells.

We drove through an area with a pretty bad road network, especially during "rush hour," so we weren't able to catch up to the TOR warned southern cell after an hour of pursuit. All in all, we did see a lot of interesting things, got on the only chaseable tornadic cell of the day (so far), so it turned out to be a pretty good chase day.

Jan 23-25 Verification

Verifications for the January 23-25 storm.

All SPC forecasts are from the Day 3 Outlook of Jan. 20-22. My forecast was made on the 20th (3-5 day outlook).











AGAINST THE SPC:
My TX/LA severe threat could have been cut down to 5% since nothing happened. There was a strong line of elevated storms that moved through the area, but since it was not surface-based, the severe winds did not reach the surface. The same deal happened in PA/NJ, in which a strong line of storms moved through the region, but they were not surface-based. All in all, a pretty good forecast compared to the SPC day 3 outlooks.

AGAINST THE REPORTS:
The one NY report was for a mudslide, and not actually for damaging winds. Other than that, my Slight Risk encapsulated all of the severe reports, and my winter forecast was pretty good as well.

OVERALL:
4.5/5. Coverage was excellent, but was too extensive in a couple of areas. However, given the potential for severe weather in these areas, it was an excellent forecast.

Jan 20-22 Verification Part 2

I'm having a bit of difficulty overlaying stuff for the verifications, so just eye-ball these first couple...

All SPC verifications will be as close to when I made my original forecasts. Originally done on the 18th, my forecast was a 3-5 day forecast, which gave the SPC a slight advantage since their forecast for the 21st is one day fresher and the 22nd is two days fresher.

NOTE: I only forecasted for the Southeast, so ignore the reports I missed out west.











AGAINST THE REPORTS:
I dropped the ball on the TX/OK/LA storms, which turned out to be the most critical reports of the storm. I did not anticipate the storm system to come together as early and as far west as it did, which is why my severe risk did not include these reports. Subsequent analyses would have fixed this error, but as I was only doing one forecast, this is what I've got. Besides one report in KY, I was able to grab the northern extent of the reports.

AGAINST THE SPC:
The SPC beat me with the TX/LA storms, and was right about the lower risk in SC. However, their northern extent of of the risk area was off quite a bit. They remedied this by the Day 1 Outlook, but I beat them to the punch.

OVERALL:
I'd give the overall rating of my forecast a 3/5. It encompassed most of the reports, but it missed the main event, and could have been more concise along the East Coast.

Wx Discussion... Jan. 23-25 Central and Eastern US

JANUARY 23-25, 2010
CENTRAL AND EASTERN US SEVERE AND WINTER WEATHER THREAT

A powerful storm is currently that is currently soaking the West Coast will also have a significant impact in the Great Plains eastward to the East Coast. The timing and placement of this storm is pretty consistent between the GFS, ECMWF and CMC model forecasts, which gives me fairly good confidence in this forecast. If the current forecast verifies, we could see severe weather as far north as eastern PA and NJ. This will be dependent upon when the storm occludes, which will be the big determining factor to the northern extent of severe weather.

A strong LL southerly jet will force warm, moist air to migrate northward ahead of a long area of concentrated ML vorticity, which will run north-south over almost the entire N-S length of the US. The UL jet will orient itself SW-NE and provide a great area of lift and will also act to strengthen the center of low pressure as it makes its way from the Central US up through the Great Lakes.

Given the current setup, we could see Slight risks for severe weather extending from the southern US in eastern TX and eastward through most of FL, going north up through parts of MO and extending NE through KY west of the Appalachians. The precip. will redevelop east of the Appalachians and affect most of the east coast up through most of NJ. There will likely be a Slight risk issued for areas east of the Appalachians extending from Central FL up to the DC area, with a See Text from DC up through eastern PA and most of NJ.

Eastern PA and NJ may be in for a strong wind event, should this storm have a favorable development. Most of the ingredients are in place for a severe wind outbreak across this region, which will be created by a well-organized line of storms forming along the cold front near the triple-point where the occluded, cold and warm fronts meet. These events are mostly dynamically-driven, and can be a surprise to many people in this region given the unexpectedness of severe weather during the winter months. Warming at the surface will be the main thing to watch in PA and NJ as this storm develops, as it's temp. relative to the ML and UL temps. will make or break the severe threat in this region.

Now, with all of this exciting severe stuff going on, we cannot discount the winter weather that will be associated with this system. The storm will sit in the Central US for a bit before heading east, which will give it ample time to wrap moisture around the northern and western parts of the center of low pressure. This will cause a wintry mix and a good amount of snow over the northern Great Plains and the western Great Lakes region. The possibility of widespread mixed-precip. over these areas could be disastrous, depending on how far south the rain/snow line reaches during this event. The same areas getting hit by winter weather from the current storm could see additional accumulations of frozen precip. However, areas affected ahead of the center of low pressure may be spared the worst, as rain and wet snow will be prevalent, making travel and cleanup considerably easier.

Here's a map for you all to enjoy:



The 5% (i.e. "See Text") and Slight risks are made using SPC risk standards.

Jan. 20-22 Verification, Part 1

VERIFICATION, PART 1:

Here are this morning's SPC severe weather outlooks:





It looks like my area of slight risk was excellent, with the exception that I did not bring the risk area far enough west. Understandable, considering the timing of the storm was still a bit off at the point of my forecast. Also, the SPC does not have SC in the Slight risk, but I'm not a big fan of that call.

More verification with actual storm reports will be posted later.

Wx Discussion... Jan. 20-22 Southeast

(This was originally posted on a forum by me on the 18th...)

This is the first of hopefully many weather discussions written by yours truly. To keep myself updating more often, I will not include images, as they take extra time to put on the site, and I do not want to deal with that every thread.

These posts will contain technical discussions, with some words abridged on a consistent basis, such as low/mid/upper level, weather indices, and geographic regions.

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JANUARY 20-22, 2010
SOUTHEAST SOAKER AND SEVERE THREAT

Strong dynamics will come together over eastern TX and LA late on the 20th to produce widespread heavy precipitation over parts of the SE on the 21st and part of the 22nd. A strong LL jet will inject moisture into the SE ahead of a small-but-significant area of ML vorticity. The system's development on the morning of the 21st will be brief, but significant. Strong UL divergence created by the UL jet, along with a negatively-tilted trough axis, will complete the formula for strong dynamics over the SE.

Aiding the chance for severe weather across the SE will be the strong ML and UL lapse rates that will manifest as the dry UL air associated with the Mexican Plateau is advected over the SE. However, the prefrontal thermodynamic instability will be limited by precip. and lingering clouds that will form during the late morning and early afternoon hours, which will weaken the lapse rates out ahead of the area of greatest dynamic lift.

So what does this mean for the SE? Extensive cloudcover will keep severe weather damped, but areas with clearer conditions and more favorable LL and ML lapse rates could see rapidly-developing storms with the potential for damaging hail, strong winds and isolated tornadoes. The 21st will most likely have a Slight Risk for severe weather, extending from MS to FL and northward through TN west of the Appalachians and through SC. The northward extent of the severe weather will be highly dependent upon the strength of the LL jet.

Ample moisture, along with the strong dynamics, will create broad areas of 1-2" of rain across the SE, with localized rainfall approaching 6" in areas that are already struggling with the high rainfall amounts of recent months.

UPDATE:

Added a picture for the severe description: