Wednesday, October 27, 2010

All-Time Low Pressure Record Update

October 29 Update: The status of the pressure record has been updated as a result of further review.

10 PM Update: The National Weather Service reports that La Crosse, Wisconsin set an all-time low pressure record:
AT 553 AM ON OCTOBER 26TH...THE BAROMETRIC PRESSURE FELL TO   
971.4 MILLIBARS /28.685 INCHES OF MERCURY/. THIS JUST BARELY BEAT
THE PREVIOUS RECORD OF 971.6 MILLIBARS /28.691 INCHES OF MERCURY/
ON NOVEMBER 10 1998. THE TABLE BELOW CONTAINS THE FIVE LOWEST
BAROMETRIC PRESSURES AT LA CROSSE WI SINCE 1933.

LOWEST BAROMETRIC PRESSURE READINGS
AT LA CROSSE WI
1933 TO PRESENT

SEA LEVEL
SEA LEVEL PRESSURE
PRESSURE IN INCHES
RANK IN MILLIBARS OF MERCURY DATE TIME
---- ------------ ---------- ---- ----
1 971.4 28.685 10/26/2010 553 AM
2 971.6 28.691 11/10/1998 150 PM
3 971.9 28.700 04/03/1982 900 AM
4 973.6 28.750 11/11/1940 700 PM +
5 973.8 28.756 01/11/1975 500 AM

+ ARMISTICE DAY STORM
It was the second-lowest pressure ever recorded at Wausau, Wisconsin, and the fourth-lowest at Green Bay:
...2ND LOWEST PRESSURE EVER RECORDED IN WAUSAU TODAY...
...LOWEST OCTOBER PRESSURE ON RECORD AT WAUSAU TODAY...

AN INTENSE AUTUMN STORM DROPPED THE PRESSURE TO 28.65 INCHES
AT 805 AM THIS MORNING AT WAUSAU. THIS IS THE 2ND LOWEST PRESSURE
EVER RECORDED IN WAUSAU AND IS THE LOWEST PRESSURE ON RECORD FOR
THE MONTH OF OCTOBER. PRESSURE RECORDS HAVE BEEN KEPT IN WAUSAU
SINCE 1950.

HERE ARE SOME OF THE LOWEST OCTOBER PRESSURE READINGS AT WAUSAU.

RANK PRESSURE DATE / YEAR
-----------------------------------------------------------
1 28.65 26 2010
2 28.93 30 1996
3 29.05 19 2007
4 29.10 18 2007

HERE IS A LIST OF THE LOWEST PRESSURE READINGS EVER RECORDED
AT WAUSAU.

RANK PRESSURE DATE YEAR
------------------------------------------------------------
1 28.58 APR 03 1982
2 28.65 OCT 26 2010
3 28.67 JAN 11 1975
4 28.69 NOV 10 1969
5 28.77 NOV 11 1998
6 28.88 MAR 02 2007

NOTE: PRESSURE RECORDS BEGAN IN 1950.

...4TH LOWEST PRESSURE EVER RECORDED IN GREEN BAY TODAY...
...2ND LOWEST OCTOBER PRESSURE ON RECORD AT GREEN BAY TODAY...

AN INTENSE AUTUMN STORM DROPPED THE PRESSURE TO 28.78 INCHES
AT 824 AM THIS MORNING IN GREEN BAY. THIS IS THE 4TH LOWEST
PRESSURE EVER RECORDED IN THE CITY AND 2ND LOWEST OCTOBER
PRESSURE ON RECORD.

HERE ARE SOME OF THE LOWEST OCTOBER PRESSURE READINGS AT
GREEN BAY.

RANK PRESSURE DATE / YEAR
-----------------------------------------------------------
1 28.76 19 1937
2 28.78 26 2010
3 28.95 30 1996
4 29.05 19 2007
5 29.11 27 1995

HERE IS A LIST OF THE LOWEST PRESSURE READINGS AT GREEN BAY.

RANK PRESSURE DATE YEAR
-----------------------------------------------------------
1 28.45 APR 3 1982
2 28.69 DEC 14 1920
3 28.76 OCT 19 1937
4 28.78 OCT 26 2010
5T 28.80 FEB 11 1932

5T 28.80 NOV 10 1940
5T 28.80 JAN 11 1975
8 28.88 NOV 10 1998
9T 28.89 NOV 19 1957
9T 28.89 NOV 11 1998

NOTE: PRESSURE DATA BEFORE 1949 WAS TAKEN FROM AVAILABLE SOURCES.
NOT ALL MAXIMUM AND MINIMUM PRESSURE EVENTS MAY HAVE BEEN DOCUMENTED
BEFORE 1949.
12 PM Update: The Minnesota State Climatology Office reports:
On October 26, a large storm system dominated the continental United States. This is one of the strongest non-tropical storms on record for lowest minimum pressure in the United States. The lowest pressure found so far with the October 26 storm was 28.20 inches at 5:13pm at Bigfork in Itasca County. This shatters the old Minnesota lowest pressure record of 28.43 that was set in the November 10, 1998 storm at both Austin and Albert Lea. The strongest Great Lakes area storm in terms of pressure was the "Great Ohio Blizzard" of Janaury 26, 1978. The pressure minimum of this storm was 28.05, which was likely measured in southern Ontario. Thus, it appears that the minumum pressure of 28.20 inches measured at Bigfork is the new record low pressure for a non-tropical strom in the Continental US (excluding tornadoes).

This storm rapidly intensified over the course of 24 hours. Aided by a strong jet stream, a strong low pressure system became better organized over central South Dakota on October 25. The low moved to the northeast and by noon on October 26, the center was over Hibbing. High Wind Warnings were posted from southeast Montana to Ohio. A Blizzard Warning covered a good chunk of North Dakota. Winds were gusting up to 59 mph near Hanley Falls at 1:15pm on the 26h.

To illustrate how strong of a storm this is, 28.20 inches is equivalent to a Category 3 Hurricane. The lowest pressure for the storm that sank the Edmund Fitzgerald on November 10, 1975 was 28.95 inches. Even with the Armistice Day storm, the lowest pressure recorded was 28.55 inches. Of course, pressure is only one measurement of a storm.

During the evening hours of October 26, snow became mixed with the rain over northern Minnesota, by daybreak on October 27, a white blanket of snow covered parts of northern Minnesota. The heaviest snow total found so far was near Twig in St. Loius County with 9 inches. The Duluth National Weather Service Office measured 7.4 inches. Not only snow, but heavy rains fell as well with this storm with 3.92 inches reported in three days at Wolf Ridge in Lake County.
Original post:
The National Weather Service issued a statement this morning on the all-time low pressure records set yesterday by the very intense storm centered in Minnesota. Note that the new Minnesota record, if confirmed, is almost 8 millibars lower than the old record. The usual spacing between isobars on a weather map is 4 mb.
THIS IS A PRELIMINARY STATEMENT ON THESE PRESSURE RECORDS. HERE IS   
WHAT WE KNOW SO FAR ABOUT THE LOW PRESSURE RECORDS SET ON OCTOBER
26TH:

AN UNUSUALLY INTENSE LOW AFFECTED THE STATE OF MINNESOTA. AT 513 PM
CDT...THE AUTOMATED WEATHER OBSERVING SYSTEM AT BIGFORK MINNESOTA
RECORDED A 954.96 MILLIBAR /28.20 INCHES/ PRESSURE. THIS BREAKS THE
ALL TIME MINNESOTA STATE RECORD FOR THE LOWEST OBSERVED PRESSURE.

THE PREVIOUS RECORD WAS 962.6 MB SET ON NOVEMBER 10 1998 AT ALBERT
LEA AND AUSTIN IN SOUTHERN MINNESOTA. THE RECORD WAS INITIALLY
BROKEN SHORTLY AFTER 10 AM AS THE LOW PASSED BY AITKIN MINNESOTA.
HOWEVER...THE LOW CONTINUED TO INTENSIFY INTO THE AFTERNOON.

DULUTH
THE LOW PRESSURE RECORD AT DULUTH WAS SET AT 1113 AM
WITH A PRESSURE OF 960.72 MILLIBARS /28.37 INCHES/. THE PREVIOUS
RECORD WAS 964.3 MILLIBARS WHICH OCCURRED ON NOVEMBER 10 1998.

INTERNATIONAL FALLS
THE LOW PRESSURE RECORD AT INTERNATIONAL
FALLS WAS SET AT 345 PM WITH A PRESSURE OF 955.98 MILLIBARS /28.23
INCHES/. THE PREVIOUS RECORD WAS 971.9 MILLIBARS ON OCTOBER 10 1949.

WISCONSIN
THE LOW PRESSURE RECORD FOR THE STATE OF WISCONSIN WAS
SET IN SUPERIOR AT 1115 AM WITH A PRESSURE OF 961.06 MILLIBARS
/28.38 INCHES/. THE PREVIOUS RECORD WAS 963.4 MILLIBARS WHICH
OCCURRED AT GREEN BAY ON APRIL 3 1982.
Image (click to enlarge): Surface weather map at 4 pm CDT, October 26, approximately 1 hour before the all-time record low barometric pressure observation

2 comments:

John said...

I was alerted to a link for weather data in Birchdale, MN on Oct 26 by a tweet from MPRWeather: http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=MN026. That link shows a few readings at 27.99 beginning at 17:04. Is this not considered an official reading?

CapitalClimate said...

Thanks for the link. Those readings did get right on down there. However, that is a mesonet station. Mesonet is a voluntary network of privately maintained stations which supplement the regular reporting locations, known as METAR. METAR stations have a 4-character identifier, beginning with "K" in the U.S. (For example, Big Fork MN is KFOZ.) If the mesonet readings can be shown to meet quality control standards, they could possibly be certified to break the record.

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