By Robert K. Peters, Ph.D. - National Weather Service Cooperating Observer
The month of April 2011 was much warmer than normal, and saw near normal rainfall. It was, in fact, the sixth warmest April on record. Compared with April 2010, the month was 4.3 deg. Warmer, and 2.65 inches wetter.
Year-to-date rainfall at momth's end was nearly identical in 2010 and 2011: 11.88 inches in the former and 11.35 inches in the latter. The thirty-day outlook for April 2011 had called for near normal temperatures and near normal precipitation.
The month began warm and breezy under upper air high pressure. A cold front and storm system crossing on the morning of the 4th brought thunderstorms some of which were severe and rainfall of between one and two inches.
Temperatures cooled through the morning of the 6th, but warmed again thereafter under returning upper air high pressure. Strong winds blew on the 6th and 8th as low pressure deepened along the lee slope of the Rocky Mountains, and the eastward-moving surface high responsible for the cool temperatures of the previous two days shifted away from the region.
The year's first 90-degree high temperature came on the 10th as upper air high pressure controlled until a cold front came through on the morning of the 11th. This caused thunderstorms a few of which were severe near the Louisiana border. Temperatures cooled for a couple of days, warming again on the 13th with strong winds through the 15th. Another cold front arrived then, bringing more thunderstorms some of which were severe north and east of Tyler.
Temperatures cooled until the surface high pressure ridge, associated with that cold front, shifted east on the 17th. This resulted in gusty south winds beginning that afternoon.
A crossing upper air disturbance on the night of the 19th brought more severe weather north and east of Tyler, with rainfall occurring there. Tyler missed out.
A cold front made a brief appearance from the evening of the 20th through the morning of the 21st. Otherwise, Tropical Maritime air covered the region. Conditions were warm and windy most days between the 21st and 25th. An upper air storm and attendant cold front crossed during the 25th and 26th. This brought two rounds of severe weather, with a tornado outbreak on the evening of the 26th.
There was property damage in Van Zandt County. Three tornadoes crossed Smith County one from southwest of Lindale to near Hawkins, a second in northwest Tyler, and ahe third from southeast of Tyler to near Kilgore.
Neither of these touched down in Smith County, though there was considerable wind damage. Cooler temperatures followed, until another warming trend commenced on the 29th.
The reporting period for temperatures and phenomenon on each day is for the twenty-four hours ending at midnight hours GMT--6 p.m. CST and 7 p.m. CDT. The reporting period for precipitation is for the twenty-four hours ending at noon GMT--6 a.m. CST and 7 a.m. CDT. All times are given using the twenty-four hour clock, and are expressed in Greenwich Mean Time.
Observations are from NWS Station 41/9207/4 in Tyler, Texas. The term "normal" refers to averages from the standard climatic period 1971-2000.
MX MN OBS PCPN REMARKS
APRIL 2011, RECORDS AND SUMMARY: