The Weather Centre: 05/18/11

Wednesday, May 18, 2011

May 18: Storm Initiation Imminent

Visible Satellite has detected bowing updrafts in Texas through Oklahoma, an indicator that storms may be about to initiate.
We will keep you on alert and update you when storms begin to develop.
The dryline is located right along this bowing.

Weather News: April 2011 Ranks 7th warmest since 1880 (May 18)

The NOAA Has ranked April 2011 as the 7th warmest on record since record keeping began in 1880. Below is the NOAA Press Release.

Global Temperature Highlights – April

The combined global land and ocean average surface temperature for April 2011 was the seventh warmest on record at 57.76 F (14.29 C), which is 1.06 F (0.59 C) above the 20th century average of 56.7 F (13.7 C). The margin of error associated with this temperature is +/- 0.13 F (0.07 C).
Separately, the global land surface temperature was 2.02 F (1.12 C) above the 20th century average of 46.5 F (8.1 C), which was the sixth warmest April on record. The margin of error is +/- 0.20 F (0.11 C). Warmer-than-average conditions occurred across most of the southern United States and northern Mexico, much of central South America, Europe and Siberia. Cooler-than-average regions included most of Alaska, western Canada, the northwestern United States, southwestern Greenland and most of Australia.

The April global ocean surface temperature was 0.70 F (0.39 C) above the 20th century average of 60.9 F (16.0 C), making it the 11th warmest April on record. The margin of error is +/- 0.07 F (0.04 C). The warmth was most pronounced in the eastern Atlantic Ocean, the northwestern Pacific and across the Southern Hemisphere mid-latitudes.
The average temperature was the warmest on record for April across the United Kingdom. Germany reported its second warmest April since records began in 1881.

Global Temperature Highlights – Year-to-date

The combined global land and ocean average surface temperature for the year to date (January – April 2011) was 0.86 F (0.48 C) above the 20th century average of 54.8 F (12.6 C), making it the 14th warmest on record. The margin of error is +/- 0.16 F (0.09 C).
The year-to-date worldwide land surface temperature was 1.33 F (0.74 C) above the 20th century average — the 17th warmest such period on record. The margin of error is +/- 0.36 F (0.20 C). Warmer-than-average conditions were particularly felt across the southern half of Greenland, Siberia, northern Mexico, the southern United States and across Africa. Cooler-than-average regions included central Canada, the northern United States, western Russia, Kazakhstan, Mongolia, extreme southeast Asia and most of Australia.

The global ocean surface temperature for the year-to-date was 0.68 F (0.38 C) above the 20th century average and was the 11th warmest such period on record. The margin of error is +/-0.07 F (0.04 C). The warmth was most pronounced across parts of the most of the western Pacific Ocean, the tropical Atlantic Ocean, the North Atlantic near Greenland and Canada, and the southern mid-latitude oceans.
La Niña conditions continued to weaken in April for the fourth consecutive month, although sea-surface temperatures remained below normal across the central and eastern equatorial Pacific Ocean. According to NOAA’s Climate Prediction Center, La Niña will continue to have global impacts as the event continues to decline, but by late spring neither La Niña nor El Niño conditions are expected to prevail in the region.
Effective May 2, 2011, NOAA updated its monthly mean temperature dataset, which is used to calculate global land surface temperature anomalies and trends. The Global Historical Climate Network-Monthly (GHCN-M) version 3 dataset replaced GHCN-M version 2. Beginning with this month’s Global State of the Climate Report, GHCN-M version 3 is used for National Climatic Data Center climate monitoring products. More information on this transition can be found at:http://www.ncdc.noaa.gov/ghcnm.

Polar Sea Ice and Precipitation Highlights

The average Arctic sea ice extent during April was 5.7 percent below average, ranking as the fifth smallest April since satellite records began in 1979.

The April 2011 Antarctic sea ice extent was 7.7 percent below average and was fourth lowest April extent since records began in 1979.

Northern Hemisphere snow cover extent during April ranked as the 15th smallest on record, while the snow cover extent over North America was the 10th largest and Eurasian snow cover was the fifth smallest April snow cover on record.

Average rainfall across Australia was 18 percent above average during April. However, for the first month since June 2010, below-average rainfall was reported in the states of Queensland, South Australia and New South Wales. This broke a streak of nine consecutive months with above-normal rainfall in those states.

May 18: Tornado Watch #306

This watch is in effect for Central Oklahoma until 11 pm CDT.
DISCUSSION

Tornadoes, Hail to 3 inches in diameter, and damaging wind gusts upwards of 70 mph are possible.
In the next hour, isolated thunderstorm development is expected along a dryline. The area is moderately unstable and weakly capped at this time. Deep Layer shear will strengthen as a 50kt mid level jet stream moves into the area. Low level shear and vertical wind profiles will become quite conductive for supercells at this time. The primary hazard is large hail, but tornadoes are possible.

May 18 Severe Weather

DISCUSSION
Strong forcing in the South Central High Plains and weaker forcing around the dryline in Texas. Initial surface based storm development will begin in the Colorado area, where forcing is stronger.
Severe Hail and perhaps a tornado possible.

Farther south, deep convective development could yield a strong severe threat with large hail and supercells. Later tonight, increase in storms likely in Kansas.