Sep 30, 2011

Typhoon Roke and Stronger Mid Latitude Storms

You can't always trust the barometer. On September 16th, Madison, WI (KMSN) reported a pressure of 30.34"/1027.7 mb and light rain. A shortwave trough was moving directly over a surface high and was still able to produce some light rain even as it encountered an increasingly confluent flow over the Great Lakes.

On September 19th, a 964 mb storm prompted hurricane force wind warnings for the Gulf of Alaska:
Same storm two days later:
This is category 4 Typhoon Roke on September 20th south of Japan with 115 knot (135 mph) winds:
It was a category 2/90 knot (105 mph) storm when it made landfall in southern Japan around 4:30Z on the 21st.
Tokyo was hit with 90 mph winds and 260,000 households lost power.

On September 20th, a 998 mb low produced a 75 mph wind gust at Bullhead, SD and a 66 mph gust at Pierre, SD.
Yesterday (September 29th), this 992 mb storm prompted storm warnings for Lake Superior and Lake Michigan:
Winds gusted to 60 mph at Sturgeon Bay Airport, 69 at Stannard Rock Lighthouse (Lake Superior), 69 at Sister Bay (Door County, WI), and 71 at Green Bay Lighthouse. At 3:50 AM toady, Buoy 45007 in south central Lake Michigan, 43 miles ESE of Milwaukee, reported 23 foot waves.

Sep 17, 2011

Tornado Warning for Grant County OK

A tornado warning is in effect for Grant County, Oklahoma:
This is on a day with only modest mid-upper winds:
850 mb winds however, were around 30 knots:
This is a good case study of the importance of low level shear in tornado formation. A sounding was taken today at Lamont, OK at 17Z (noon CDT) today, which happens to be in Grant County. While there is little shear from 900 mb to 200 mb, the shear from the surface to 900 mb is significant, leading to an SRH value of over 300:
SPC mesoanalysis indicates less than 40 knots of 0-6 and 0-8 km shear, but well over 20 knots of 0-1 km shear:
When the thunderstorm cell moved into this area of increased low level shear, the tornado warning was issued. Helicity was also enhanced in this area:

Sep 16, 2011

Hurricane Katia and Frost

On September 5th, a Gulf of Alaska storm reached 955 mb:
This is Hurricane Katia passing between the Lesser Antilles and Bermuda as a category 3 on September 5th:
It was upgraded to category 4 only for the advisory at 3Z September 6 (10 PM CDT Sept 5) with winds at 115 knots and minimum central pressure 946 mb. Katia on the morning of the 6th:
Morning low temperatures on September 5th were as low as 30F in the Minnesota Arrowhead. On September 15th, International Falls had a low of 19. This was the first time that station had a temperature below 20 for the month of September. Frost advisories (blue) and freeze warnings (light blue) were issued from the Northern Plains to New England:
There was a photo of frost from Sugar Grove, Illinois (west suburb of Chicago) from the 15th on the WGN weather blog.

On September 15th at 21Z (4PM CDT), Tropical storm Maria was upgraded to a hurricane. This may be questionable because the minimum central pressure was 987 mb and the only reasons given in the discussion were satellite and radar imagery. This is how Maria looked at 2145Z (just 45 minutes later):
If hurricane force winds were present, it may have been partly from Maria's movement to the NNE (30 degrees) at 40 mph.

Sep 12, 2011

Hurricane Irene and Strange Tropical Storms

Three more very questionable tropical storms were named in August. The area of convection south of Newfoundland in this water vapor image was named Tropical Storm Franklin:
It was first named a depression on the 12th at 21Z, at 36 latitude, then named a tropical storm on the 13th at 9Z, at latitude 37.9.

The small cluster of convection seen in the upper center of this visible image was named Tropical Storm Gert at 18Z on August 14th (15 minutes after the time of the image):
This small swirl of shallow convection just north of Bermuda was named Tropical Storm Jose on August 28th (not the large area of deep convection to the south):
Since it is almost impossible to see, here is a closer view:
An image from 7 hours earlier (18:45Z) shows a very small area of deeper convection, and this was only 6 hours after it was first named at 12Z.
This tropical wave near the Lesser Antilles on August 20th was what later became Hurricane Irene just a few hours before it was declared a tropical storm:
Hurricane Irene moving past Hispaniola on the 22nd:
Moving through the Bahamas on the night of the 23rd:
Near peak strength as a category 3 on the 25th:
As Irene approaches North Carolina on the 26th, there does appear to be some dry air entrainment:
Radar imagery from North Carolina on the morning of the 27th shows a loosely organized eye:
On the evening of the 27th, after crossing North Carolina, Irene moved out into the Atlantic again:
Irene was dumping heavy rain over a huge portion of the East Coast:
Many people have said that the intensity of Hurricane Irene was exaggerated after the first landfall. Buoy 44009, 26 nautical miles southeast of Cape May, NJ reported winds at 45 mph with gusts to 63 at 5:50 PM EDT on August 27th. Winds at 40 mph with gusts to 54 were reported as late as 11:50 AM EDT on the 28th. Buoy 44014, 64 nautical miles east of Virginia Beach reported winds at 47 mph with gusts to 65 at 6:50 PM EDT. Winds at 45 mph with gusts to 54 was reported as late as 3:50 AM EDT on the 28th. According to Hurricane Irene discussion number 31, issued at 11 PM EDT on August 27th by the National Hurricane Center, a reconnaissance flight reported 700 mb flight-level winds of 92 knots, and the stepped frequency microwave radiometer (SFMR) estimated 66 knot winds in a small area over 100 nautical miles east of the center of Irene. The buoy measurements were taken and the discussion was issued when Irene was over open waters between the Outer Banks of North Carolina and the Delmarva Peninsula. Discussion 32, issued at 5 AM EDT, August 28 noted a gradual weakening of Irene, but also that the minimum pressure was still 958 mb, and that hurricane force winds from aloft may be brought down to the surface in the convective environment. Discussion 32 was issued while Irene was near the New Jersey Coast, and the last to keep Irene at hurricane strength.

On August 15th, Auckland, New Zealand was hit with record cold and the heaviest snow in 50 years.

Sep 11, 2011

July 2011 Heat Wave and Hurricanes

This is category 3 Typhoon Ma-on on July 16th in the West Pacific south of Japan:
Its peak strength was category 4 with winds to 115 knots (135 mph) on July 15th. It later struck southern Japan on July 19 as a category 1.

On July 16th, a dangerous heat wave prompted the issuance of excessive heat warnings (shown in violet) across most of the Midwest:
On July 17th, the 500 mb geopotential height at Omaha, NE (KOAX) was 6,000 meters:
SPC's mesoanalysis showed 9,000 CAPE in southeast North Dakota:
This produced a tornado in LaMoure County which was rated a high end EF3 despite being in a very rural area (population only 4,139 for the entire County).

By July 20th, the heat wave had spread into the Great Lakes:
And by the 21st, the East Coast:
At 21Z (4PM CDT) on July 20th, another questionable tropical system was named. Tropical Storm Cindy began at 35.2 latitude, 53.8 longitude and then moved to the northeast. It can be seen at the right edge of this water vapor image:
Meanwhile in the East Pacific, category 4 Hurricane Dora developed an enormous eye:
It reached a peak strength of 929 mb and 135 knot winds 11 hours later ( July 21, 15Z).

A July 29 marathon race in western Montana was canceled because of snow cover so deep that it covered the signs which mark the trails.

This is Typhoon Muifa from July 31st:
It was category 5 on July 30th with winds at 140 knots.