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Heat Wave for Central Part of the States

Dean Baron said:
Im hearing that here in Minneapolis we broke our official dewpoint record. I dont see a PNS yet but I saw on FB the international airport was reporting a dp of 82 or 83. This is at least the third day in a row i've seen dewpoints well in to the 80s somewhere around the state.
Click to expand...

Yeah, I don't doubt that. Like I was saying if I looked around for some other stations rather than just the MCW airport one here I'm sure were in the 80s dewpoints again in the area for the 3rd day in a row. Although, the old discussion about this same thing we had back in 2005 like the link Gphillips posted, many of these stations are located almost out in corn fields or right near in a rural setting. I know of many around this area so you can get sort of a crazy microscale evapotranspiration on stations like that.

I'm noticing now that KORC is historically one of these spots with the higher readings, that one is out in Orange City so I'm not sure where the site is but it looks to be south of town somewhere.
 
True, and these readings always have to be taken with a grain of salt. That said, I dont remember ever feeling this humid all day long for so many days in a row, and its not over yet. 90/70 is going to feel cold compared to this
 
The Minneapolis-St. Paul 4 pm ob shows a temperature of 95 F, a dewpoint of 82 F, and a resulting heat index of 118. According to a recent PNS from MPX, this sets the all-time record high dewpoint on hourly observations at the airport (with such dewpoint observations dating back to 1945). Newton, IA, had a 99 temp, 84 dewpoint, and 128 F heat index at 3 pm.

For what it's worth, the 4 pm Supercell Composite was >66 NW of MSP (even NW of STC), with a peak Sig Tor (CIN) ~12 just north of the Twin Cities.
 
Yet again, evening hits and the dewpoint goes up. 95/81 here right now, that is 3 days straight of at least an 81 degree point in MCW.
Click to expand...
This diurnal trend is pretty common. After peak heating, as the surface begins to cool, near-surface stabilization increases. The sun is still out, however, and near-surface relative humidity is typically the lowest that it will be during the day (as a result of mixing during the afternoon), so evapotranspiration can remain quite significant (lots of crop activity, plenty of very moist soils from a wet winter and spring, etc.). With decreased vertical mixing, however, that additional water vapor no longer gets mixed upward as quickly. As a result, the near-surface specific humidity / dewpoint / mixing ratio rises. When the sun comes back up tomorrow morning, differential (in the vertical) diabatic heating will begin to mix out the near-surface stable layer, and the upward flux of moisture will commence again (often leading to a reduction in the surface dewpoint).
 
Record cold for the state of Oklahoma five months ago now we are setting up for some summer records................108 so far the high in Tulsa and things are getting very dry with only .36 rain



PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE TULSA OK
1242 PM CDT TUE JUL 19 2011

ARZ001-002-010-011-019-020-029-OKZ049-053>076-200500-
BENTON-CARROLL-WASHINGTON AR-MADISON-CRAWFORD-FRANKLIN-SEBASTIAN-
PUSHMATAHA-CHOCTAW-OSAGE-WASHINGTON OK-NOWATA-CRAIG-OTTAWA-PAWNEE-
TULSA-ROGERS-MAYES-DELAWARE-CREEK-OKFUSKEE-OKMULGEE-WAGONER-
CHEROKEE-ADAIR-MUSKOGEE-MCINTOSH-SEQUOYAH-PITTSBURG-HASKELL-
LATIMER-LE FLORE-
1242 PM CDT TUE JUL 19 2011

...RECORD HOT SUMMER SEASON UNDERWAY...

THUS FAR FOR THE SUMMER SEASON...FROM JUNE 1 THROUGH JULY
18...SEVERAL LOCATIONS ACROSS EASTERN OKLAHOMA AND NORTHWEST
ARKANSAS HAVE SET OR APPROACHED ALL TIME HIGH TEMPERATURE
RECORDS...AND ARE ALSO ON PACE FOR ONE OF THE HOTTEST SUMMERS.

FORT SMITH ARKANSAS HAS THE HIGHEST AVERAGE TEMPERATURE
OF 87.1 DEGREES. THE SECOND WARMEST AVERAGE TEMPERATURE FOR THE
SAME PERIOD IS 85.6 DEGREES FROM 1934.

TULSA OKLAHOMA IS CURRENTLY RANKED THE SECOND WARMEST...WITH AN
AVERAGE TEMPERATURE OF 86.5 DEGREES...WITH 1980 BEING THE
WARMEST...WITH AN AVERAGE TEMPERATURE OF 86.7 DEGREES.

THE MCALESTER AIRPORT ALSO HAS THE WARMEST AVERAGE TEMPERATURE SO
FAR THIS SUMMER...WITH AN AVERAGE TEMPERATURE OF 85.9 DEGREES. THE
SECOND WARMEST YEAR FOR THE SAME TIME PERIOD IS 1954...WITH AN
AVERAGE TEMPERATURE OF 84.1 DEGREES.

THE BARTLESVILLE AVERAGE TEMPERATURE SO FAR THIS SUMMER...IS 82.7
DEGREES...WHICH RANKS IT IN 5TH PLACE...BEHIND 1934 WHICH HAD AN
AVERAGE TEMPERATURE OF 85.3 FOR THE SAME PERIOD.

LASTLY...FAYETTEVILLE HAS AN AVERAGE TEMPERATURE SO FAR THIS
SUMMER OF 80.4 DEGREES...WHICH TIES 1980 FOR THE WARMEST AVERAGE
SUMMER TEMPERATURE THROUGH JULY 18TH. THE SECOND WARMEST YEAR FOR
THE SAME PERIOD WAS 1954...WITH AN AVERAGE TEMPERATURE OF 79.9 DEGREES.

ON A SIDE NOTE...THROUGH JULY 18...FORT SMITH HAS HAD 14
CONSECUTIVE DAYS AT OR ABOVE 100 DEGREES. THE RECORD IS 17
CONSECUTIVE DAYS...FROM JULY OF 1934.

DIFFERENT SITES CONTAIN DIFFERENT YEARS OF DATA...GOING BACK AS FAR
AS 1892. SOME DATA DURING THOSE YEARS MAY BE FROM DIFFERENT
LOCATIONS...AS EQUIPMENT HAS MOVED...AND COULD HAVE SOME MISSING
DATA. THESE TEMPERATURE RECORDS ARE FOR THE SOLE PURPOSE TO
COMPARE THIS SEASONS UNUSUALLY HOT WEATHER TO PAST RECORD HOT
SEASONS
 
Interestingly tomorrow seems to bring somewhat stronger southwesterly flow into our area, this should aid in a bit better mixing than we have seen today. Problem is that actual temps could end up a little higher, right now I'm ok with that as long as we can get those dewpoints down there.

Appears the streak of 80 degree dews will end at 3 days in a row here.
 
Checking 500-hPa heights around the country, it appears that the ridge is weakening slightly and shifting a little more to the east. Early this week OAX reported a 00UTC 500-hPa height of 600 dam. The past two evenings, the 00 UTC soundings all have 500-hPa heights in the central plains decreasing slightly. Granted, they are still extremely high (> 596 dam), but it appears each subsequent evening the highest heights are 1 dam lower than the day before.
 
I'm liking the forecast for early next week...just gotta make it through tomorrow and Thursday!

I'd be really happy if this MCS would bring a decent thunderstorm to southeastern WI. Seems there's been one almost every day for the last week to our west and/or north, but it has either weakened or turned away as it approached.
 
Finally a better start to the morning here, only a 70 degree dewpoint right now. As I mentioned in a previous post, we finally will not reach the 80 degree dewpoint today. At least we shouldn't anyway.
 
Josh Richardson said:
One other thing Jeff, not sure if you saw my post before but I did see a reading one year from Onawa IA that was 101/87. Still can't remember for the life of me what year that was, I remember talking about it with Mike H. as he's from that area...other side of the river basically.
Click to expand...

I saw that post, Josh. Given some of the documented measurement errors with non-ASOS sensors (see some of the entries at http://mesonet.agron.iastate.edu/onsite/news.phtml?q=dew+points) I figure that measurement was not accurate, especially since the Onawa sensor is an RWIS sensor.

If you follow some of the RWIS sites around the state on the IEM you'll see how badly they can err. The Tama RWIS station along Highway 30 on the Benton-Tama County line and the Colfax RWIS station in Jasper County, for example, frequently show dew point values that simply can't be representative or accurate, like 84/84 or 96/90 (as I've seen in past days).
 
Josh Richardson said:
Interestingly tomorrow seems to bring somewhat stronger southwesterly flow into our area, this should aid in a bit better mixing than we have seen today. Problem is that actual temps could end up a little higher, right now I'm ok with that as long as we can get those dewpoints down there.

Appears the streak of 80 degree dews will end at 3 days in a row here.
Click to expand...

I saw that too when looking at 12Z upper air analyses. Looks like warmer 700 mb temps are moving over. Usually that implies things will mix out a little deeper, resulting in slightly lower dewpoints, but warmer temperatures at the same time.
 
Jeff Duda said:
I saw that post, Josh. Given some of the documented measurement errors with non-ASOS sensors (see some of the entries at http://mesonet.agron.iastate.edu/onsite/news.phtml?q=dew+points) I figure that measurement was not accurate, especially since the Onawa sensor is an RWIS sensor.

If you follow some of the RWIS sites around the state on the IEM you'll see how badly they can err. The Tama RWIS station along Highway 30 on the Benton-Tama County line and the Colfax RWIS station in Jasper County, for example, frequently show dew point values that simply can't be representative or accurate, like 84/84 or 96/90 (as I've seen in past days).
Click to expand...

Good to know thanks, I always wondered why certain ones were so skewed. I just assumed they were out in the middle of a corn field or something, lol.
 
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