Predictability

Tough forecast day for SPC in light of the disappearance of the spring forecast experiment model suite. I know I felt the loss of NCARs model when I was making my forecast for Minnesota and Iowa.

The story starts with obscenely high values of dew points across the midwest ... 80+ dew points in Iowa and above 75 just about everywhere else. A potent little low was forecast to move through the area around the Twin Cities with a moderate risk of tornadoes given the extreme instability and large vertical shear.

What was more obvious today was that the hodograph curvature would be decreasing through the day as the cold front advanced eastward. A remnant MCS was forecast to depart the area and another was forecast to erupt in its wake. The NSSL model had a hard time with that component of the forecast, instead developing the convection along the cold front and slightly ahead.

The hard part was utilizing this model run to determine what role the remnant MCS would play in terms of any leftover boundaries, the role of the associated cloud field to the west, and the cold front even further to the west. As it turned out, the departing MCS gave way to another MCS accompanied by damaging winds and tornadoes. The cold front lit up in sections appearing to be linear but isolated enough to warrant tornado warnings before collapsing. About 5 hours later as the front passed the Twin Cities it lit up again.

All in all it was a hard forecast because the model simulation was not quite capturing the episodic nature of the convection. This is one forecast where the model was working against the forecasters despite the somewhat strong forcing for ascent. The details were absolutely lacking in the model forecast and this case will be a prime candidate for further research into why this happened.

This radar image sums it up nicely with the western most convection marking the cold front and accompanied by TOR warnings, Then the cloud field marked by the 25-30 dBz echo, then the isolated convection which exploded into the MCS over the Twin Cities, and the remnant MCS is off to the east.

Updated: MCS

Here is the update of the MCSs that occurred over the last 5 weeks (May 28 - July 4) at 0645 UTC:
If I counted correctly, something like 26 systems (of various sizes) over that span,
not including multiple MCS events, or the fact that multiple systems could be identified on radar under one cloud shield.

The precipitation anomaly for the last 30 days still indicate 8" swaths from NE through IA. Lets recall the radical flooding in OK City on 14-15 June (which also has their 30 day anomaly above 5"). KS also participated in the events but it was much less a focus for extreme  precipitation totals.

60 day anomalies were significantly less revealing the reduced May rainfall in Ia, NE and northern KS.

Compared to 2008 and 2009, June 2010 was literally the summation of the last two Junes. In 2008, 8" anomalies were common in IA and northern MO and a small part of eastern KS. In 2009, 8" anomalies were common in western NE and a sliver in KS, NE and MO (1 small corridor). 2006 and 2007 were very different from these last 3 years, but 2005 was similar to 2009.

Iowa is currently in flood mode with 35 of 99 counties under some kind flood watch or warning. Interestingly, the Iowa Environmental Mesonet reported that DSM had 22 days of measurable rain and more is on the way this week. up until the 22nd the IEM reported the highest mixing ratio average for the state since 1902!

The complete scientist

http://blog.agu.org/sciencecommunication/2010/06/29/complete-scientists/

A classic argument between being just a scientist and being an applied scientist. It is worthy of considering, since science is not just done for pure fun and amusement by the curious. We are, afterall, interested in using science for the betterment of society. Knowledge gains are practical too, since they provide a foundation from which applied science may be constructed.

I took issue with little in this blog post, but I have my 2 cents:
1. The requirement to go out and be social! I like this point but it is far from practical for your average university professor or average young scientist. These are people busy building not just their knowledge base and communication skills, but also their reputation in the scientific community. They are busy expanding their career and acquiring future funding. There is seldom time for such outreach activities. This is not to say they should not be doing outreach, but rather that their time is better spent in the construction and development phase of their career.  Personally I would much rather the elder scientists participate in outreach activities and from what I see, this happens fairly regularly.
 

2. watches and warnings are not intuitive. Oh yeah:
person 1: watch out, their might be a something bad around the corner.
person 2: warning, anvil is about to fall on your head from that coyote!

Seems pretty intuitive to me. watch = prepare, warning=action. See the difference?

The confusion lies in the perception of risk that is built into those words from the culmination of life experiences. I was watching "After the catch" about a fisherman from LA who survived Katrina. He did not evacuate and he almost payed dearly. He thought: I survived before and this one wont be so bad. the gist of his story is his wife floated away, to be found alive 6 hours later, and most of his family held onto trees until they got in a boat.

This type of story is common. The forecasting community recognizes these types of social behavior but there isn't too much to do yet. I do know that an NWS office issued tornado warnings when the eyewall of a certain storm was passing through LA. They wanted the gravity of that situation understood in plain words: all hell is about to break loose if you can hear this message (and in particular, if you havent already realized the gravity of the situation). Kudos to you NWS. 

Breaking the myth of how poor weather forecasts used to be and educating the public on how good they are is difficult to do. I was in an airport a while back and a random conversation ensued: "As a meteorologist I get to keep my job precisely because the forecast was wrong". May seem strange, but bad forecasts imply there are tools we need to improve and situations we need to learn from. The publics perception is that we are always wrong (not precise). But that is the entire point we need to convey ... being precise is not what makes a good forecast. Knowing the evolution is much better that getting all the numbers correct*.

*getting all the numbers correct serves a different purpose: Farmers want to know how the heat will affect crops, or how much rain to expect. People in general want to know what the temp will be and how humid and how sunny. But being precise isnt what is promised. A range is always better since local variations will always be present.

Interesting Iowa weather

 Radar imagery from the morning of the 27th showed what could be either a gravity wave, bore, or cold outflow. The two waves seen as finelines of about 25 dBz are over AMW and approaching DSM.

The time series from the roof of the ISU Agronomy building:
http://mesonet.agron.iastate.edu/plotting/iemcc/?year=2010&month=6&day=27

The time series shows a small drop (1.2F in 5 minutes) in temperature and dew point, a brief recovery, then a second drop (3F in 7 minutes). The third drop is actually the outflow boundary from the storms to the west, not the north. So it is plausible that the bore or gravity wave arrived first followed closely by the outflow boundary. 

The temp and pressure relationship was non-existent for the 1st "wave" (dp = 0), but strong for the 2nd (dp = 0.5 hPa). the wind speeds in the 2nd wave peaked after the min pressure occurred during the t fall. The last wind speed increase occurred in the wake of the 2nd wave but prior to the rapid, small pressure oscillations. I wonder if the pressure sensor is affected at particular wind directions.