Visible satellite loop of Hurricane Irene impacting the D.C. area while spinning off the mid-Atlantic Coast

Hurricane Irene caused extensive damage (amounting to perhaps around $10 billion) and loss of life (in the tens of people) after making landfall in North Carolina on August 27 as a category 1 storm. Though much discussion is already underway about whether or not Irene was “overhyped,” particularly in the New York City area, there is little denying this was a rare event for much of the coast north of North Carolina. In D.C., the effects were relatively minor, though still rather significant for a tropical system in this area. National Airport recorded a gust to 60 mph and had one hourly observation of sustained winds to tropical storm force. The daily rainfall in D.C. on the 27th was the highest August daily total in 4o years (since the similarly tracked Tropical Storm Doria) and the 3.83″ total helped boost D.C. to its wettest August in a long while. At its peak, several hundred thousand locally (and north of 5 million on the East Coast) were left without power after a number of trees (among other items) fell and toppled power lines.

2011 American Weather Conference presentations

The first American Weather Conference was held at BWI this weekend. Though it was the first American Weather Conference, it was the 7th we have put on. The prior six were known as the “Eastern U.S. Weather Conference.”

The conference is both a gathering for people who love weather to hang out with each other, and a learning experience for many involved. Over the years we have been fortunate enough to consistently line up the top professionals in the business. This year was no exception.

Following a Friday of workshops by Wes Junker and Will Schwartz (that I unfortunately missed due to work), the main event of Saturday provided quite the show. Featured speakers (in order of appearance) included Bill Read, the director of the National Hurricane Center; Brian LaSorsa of NWS Baltimore/Washington; Brad Panovich of WCNC-TV; Mike Smith of WeatherData; and a conference regular, winter weather expert Paul Kocin.

Below are videos of the presentations. They are not close to fancy, and I originally shot in HD but lowered way down to cut upload time. As far as I can tell though, they work!

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The highest low temperatures in Washington, D.C.: A look at 80F+ overnight readings

This post has been updated to cover all 80-degree or higher lows in Washington through early August 2011. Graphs will be updated to include this year once it is apparent there is no risk of further 80-degree lows.

The once rare 80F+ low has been appearing more often of late. 2011 has easily turned into the leader of the pack on consecutive days and overall totals.  Prior to 2011, there have never been more than two 80 degree or higher low temperature days back-to-back at Washington. A previous record streak of two days happened most recently in 2010, when DCA recorded 80F for a low on the 7th and 8th of July.

From July 21-24, 2011 D.C. recorded its warmest stretch of lows ever, with four days in a row 80F+. Temperatures actually spent about 128 hours above 80F, from 7:52 a.m. on July 20 through just after 4:00 p.m. on July 25. In the climate records, this will be counted as a four-day stretch — even though the hours match up to five days — due to the 80F morning low  of the 25th not standing through midnight. As an encore performance, 80-degree plus lows returned for the final three days of July 2011, bringing the record total to seven for the month and year.

The warmest low on record at D.C. is 84F and it occurred on July 23rd and July 24th, 2011 as well as on the 16th of July in 1983. There have been 42 days (including the seven in 2011) 80F+ lows going back to when daily records I have access to begin in 1872. Before 1930, there were only 3, and they all happened in 1876. The sample and averages are still quite small, with a 1930-2010 average of 0.4 days per year and a 30-year average of 0.7. But looking at the graph, and now considering 2011, one gets the sense these high-end low temperatures are becoming more of a norm, if also still erratic.

The trends do continue, and in some ways are more apparent thanks to increased data samples, into categories such as 75F+ lows and similar. In an urban environment like D.C. the question arises whether the increased frequency of such lows points to larger climate change or, more simply, a growing urban heat island effect. It is worth at least noting that Baltimore’s climate record includes much more numerous 80F+ readings during the earlier history where D.C. lacks them. In part, this may be due to the Baltimore station initially being in the city prior to moving to a more rural setting at BWI.

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Washington, D.C. thunderstorm days: Examining the last 30 years of data

In the July installment of a year-long series of D.C. climatology posts on Capital Weather Gang, I included a graphic showing the averages for thunderstorm days by month in Washington over the last 30 years. Why 30 years? That’s the National Climatic Data Center standard for climate normals, and they just released a new set. This information, however, comes from additional research through daily records posted on the Weather Underground.

Thus far, I have only looked at the last 30 years, but may build back as far as I can at some point. Either way, this post will be updated at least a bit with data already obtained, but see below for some of it for now:

D.C. averages 32.8 thunderstorm days per year. 18.8 occur during meteorological summer (June-August). July is barely the statistical winner, though for real purposes it is tied with June for the most thunderstorm days per year. The curve is almost surprisingly normal, with a quicker drop off in fall than rise in spring thanks to lacking upper-level cold air of the winter prior that gives spring an extra boost in both storms and severity of storms.

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Day 2-?? don’t look so good for storms. Headed to Kansas…

We ended up in Texarkana (on the Texas side) last night after almost 24 hours — and over 1,200 miles — of driving. Now we’re back on the road headed toward Kansas, where we will be meeting with Mike Smith of WeatherData tomorrow.

Rather than get into the details about the next few days or the outlook for those next few days (little of which I actually know for certain right now), here’s a short unedited clip of a severe thunderstorm we ran into just after crossing the Tennessee line into Arkansas. There was some rotation in the cell on radar, but we did not see anything. A funnel clouds was apparently reported close by and the storm had a tornado warning while passing through parts of Memphis.

Additionally, there was a large supercell that formed in northeast Texas with a tornado reported, however that has not been verified by the Storm Prediction Center thus far. Overall, the energy proved to be a little too far displaced from the small warm sector in southern Arkansas to result in too much out of the ordinary despite good potential.

I’m hopeful that by Friday (perhaps Thursday but return flow won’t be great) there will be more storm action.

Asperatus in the morning in east central Tennessee

Small pictures don’t do it justice, click image for a larger (still perhaps too small!) version. Pretty cool stuff out ahead of a dying squall line this morning.  Currently sitting in the car with rain falling along with the occasional flash of lightning.

We’re currently headed through Tennessee on the way toward hopefully intercepting some severe weather in and around Arkansas later today, where the Storm Prediction Center has a slight risk for severe weather and has recently upped tornado risk from 5% to 10% — more on that later as we figure out where we’re going.

Leaving for “the storms” imminent: How do things look?

Before beginning: No, not everything here will be about weather! Just maybe most of it for the next few weeks…

The final countdown is on to the departure for two weeks of storm chasing. The plan is to leave Maryland around the crack of dawn on Sunday and head west (our South?) [Midday update: Leaving tonight it seems. Going to be a race to Arkansas area for storms tomorrow].

In the wake of one of the greatest and saddest tornado outbreaks in recent history that has become the deadliest since the Great Depression, it sort of makes me wonder exactly why I want to go storm chasing. Being that it was the second major tornado outbreak in a month full of tornadoes, it also makes me wonder if 2011 has already shown its best hand and will bluff from here out.

The pattern is changing up a bit, at least on certain levels. The past few weeks have seen a very positive North Atlantic Oscillation (NAO) which has been shown to correlate with increased activity over the Southeast U.S. When you add in remnant effects of a La Nina (also shown to produce tornado outbreaks in the Southeast), the tale of this month and the multiple cities hit is hopefully one not to be repeated anytime soon.

That said, tornadoes hit where they hit regardless of who is watching, and I still want some storms to follow around the empty spaces of the central U.S.!  Let me start the “analysis” by saying I’ve done more model watching in the day 8-16 range for this trip than I would ever do normally, as guidance in that range is a bit of a fantasy.

It’s been a roller coaster ride. Even at this late date I find myself vacillating in thought from “wow, we’re going to be busy” to “hey, it could be a cool story to tell about the quiet period of the record 2011 tornado season.”

There are some unknowns with this pattern changeup. If we go into a negative NAO, there should be a tendency for East Coast toughing, which could be somewhat problematic in that it keeps wavelengths short across the country and promotes at least temporary upstream or even West Coast ridging. So, at the very minimum, it seems the first week out there is not screaming “major” storm.

At the same time, the active jet stream partially behind all the severe weather this season appears to continue mostly unabated, with waves of storminess at varying strength and in varying positions every few days.  There could easily be at least one break of 2-3 days with little to no activity, but there is other stuff to do out there… I think.

There is potentially something of interest on the way out, especially if we went the southern route. The problem is that cooler air has invaded a good portion of the country following the last big storm — at least one shot of even cooler air is ahead as the negative NAO induced Greenland Block flexes its muscle.  It appears any severe weather would be fairly deep into the South and perhaps not that energetic, though it’s still evolving and models are keying in more heavily on this system now.

It’s likely that there would be at least some break after that initial system (perhaps a several day one?), though energy continually wants to spill into the northern Plains, and the models have had trouble with the strength of this energy for months now until the short range. However, it’s pretty early for activity up there, especially with the trough orientation fairly fast from northwest to southeast.  Hopefully the dryline will activate on quieter days, but the drought over Texas and growing north might complicate that.

The northwest flow, as modeled, could ultimately transition into a situation where convective systems form along it as warm air begins to advect back north heading toward or into next weekend. That could provide a more generalized storm risk each day, though the storms could be fast moving, and perhaps mainly non-tornadic in nature.

There are indications that by next weekend things could be more interesting in an “outbreak” sense. The question is if it’s still a fantasy or something real. The idea of more troughiness through the Rockies and into the Plains has been pushed back a little already, from near the 5-6th to the 7th-8th, but it’s been there on many runs.

On varying runs, this trough is modeled by the GFS to dig deep through the Rockies and spawn a surface low pressure somewhere near the Texas Panhandle into Kansas before strengthening and traversing east.  In a scenario like that, a significant tornado event would be possible.

Another potential scenario spit out is weaker, but consistent troughiness over the southwest and into the Rockies. This may allow for a regular feature of a weaker low pressure somewhere just east of the Rockies, which would at least promote the risk of storms through the period by drawing moisture in from the Gulf and creating instability plus some turn to the atmosphere.

The “no storm of consequence” scenario is a bridge we can cross if we get there. I’m cautiously optimistic, but perhaps slightly less so than a week ago. It could just be nerves…

Quick look at atmospheric conditions for a significant D.C. area tornado

A small composite mean sample of days with significant tornadoes in and around the Washington, D.C. area at various heights of the atmosphere is below. From low level (near surface — 850mb) to cloud  level (700 mb) and then into the mid-and-upper levels (500mb). These can be useful to compare a modeled setup to see if there is any extra risk of more than the garden variety activity.

Hopefully I’ll return to this in more depth as it’s something I’ve been meaning to do.

This post is part of a Washington, D.C. climatology series, both on and off site, that will be maintained at semi regular intervals.

Evening satellite loop of the April 27, 2011 tornado super outbreak

At least 141 tornado reports (as of 1:45 a.m. April 28), on top of 61 on the 26th. Many communities in Mississippi, Alabama, Tennessee and Georgia (maybe others still ongoing), including parts of large cities such as Tuscaloosa and Birmingham, have been devastated. This should go down as one of the largest tornado outbreaks on record, and solidify April 2011 as the month with the most tornadoes ever. There were even tornadoes confirmed around D.C., with more potentially on the way into the morning…

April 27, 2011