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The Oklahoma Climatological Survey is proud to announce the Fall 2007 edition of its seasonal climate series "Oklahoma Climate," available online at: http://climate.mesonet.org/seasonal_summary.html.
Enjoy some stuffing with the following great stories:
At one point this summer, 2007 looked poised to challenge 1957 as Oklahoma's wettest year on record. Bolstered by the wettest June since 1921, the statewide average rainfall through the end of July was more than eight inches above normal, and ranked as the third wettest such period on record. A strange thing happened as July faded on the calendar, however - the rains stopped. There were still deluges from time to time, of course. A rather indelible event will remain in Oklahoma's collective memory after a visit from an erstwhile Tropical Storm in September left 100-500 year rainfall amounts in west central and central Oklahoma. The flooding from that event was devastating, as were the rising waters of the spring and summer. Despite that dose of tropical moisture, Oklahoma returned to the dry pattern of the previous two years that saw drought ravage the state's winter wheat crop and diminish reservoir levels to some of their lowest on record. The August 1-November 20 period was the 22nd driest since 1921, about three inches below normal. The dryness varied across the state, but the southern tier of counties along with the Panhandle was hit the hardest, with drought designations from the National Drought Mitigation Center returning to the state for the first time since late March.
Central Oklahoma did manage to wrest away 1957's moniker as wettest year on record, however, with more than a month left in the year. As of November 20, Central Oklahoma had an average precipitation total of 49.60 inches for the year thus far, besting 1957's annual total of 49.14 inches.
Prospects for widespread precipitation look a tad underwhelming for the next few months. La Nina conditions have developed and strengthened in the equatorial waters of the south pacific, which could keep Oklahoma and the rest of the southern U.S. warm and dry though the winter months into early spring. An unfortunate consequence of the abundant rains of 2007 coupled with continued drying will be an increased risk of wildfires. Vegetation which grew at a rapid rate with the available moisture has now gone dormant and could act as a dangerous fuel source, should fires begin.
Overwhelming observational evidence indicates that the earth is warming, and that the cause of that warming is mostly anthropogenic (caused by humans) in nature. Further, the vast majority of scientists that actually study climate change believe that warming will continue for the foreseeable future.
Of course, climate change has become a highly contentious topic in public discourse, with the waters being muddied by extreme viewpoints and concerns. So where does the truth lie, and what are the implications for Oklahoma? The Oklahoma Climatological Survey (OCS) has been mandated by the Oklahoma legislature to provide climate information and expertise which could be of value to the public, as well as to state policy- and decision-makers. In that regard, OCS has conducted a review of current assessments of climate change research in order to craft a definitive statement on global climate change and the implications for Oklahoma - detrimental and beneficial alike. The statement is based purely on the findings of the vast majority of scientists that study climate change.
A round of strong to severe thunderstorms associated with a cold front pushed Oklahoma City's rainfall total for the year to 53.34 inches according to the National Weather Service, and established 2007 as Oklahoma City's wettest year on record. This breaks the old record of 52.03 inches set in 1908 with more than two months left in the year. Oklahoma City records date back to 1891.
According to data from the Oklahoma Mesonet, the year-to-date statewide average rainfall total of 37.44 inches through October 15 ranks as the 6th wettest since 1921 at more than seven inches above normal. That is still well behind 1957's total of 42.66 inches for the same period. The Oklahoma Mesonet site at Minco has recorded 54.20 inches of rainfall since the beginning of the year to lead the state.
Central Oklahoma sits at more than 17 inches above normal for the January 1-October 15 period with an average total of 47.94 inches. That puts the central region at just about an inch behind its record annual total of 50.56 inches set in 1908.
The September 2007 Monthly Climate Summary is now online at: http://climate.ocs.ou.edu/monthly_summary.html.
Highlights:
The Oklahoma Climatological Survey is proud to announce the Summer 2007 edition of its seasonal climate series "Oklahoma Climate," available online at: http://climate.mesonet.org/seasonal_summary.html.
Enjoy these stories on a rainy day:
It's just not supposed to work that way. Tropical storms are not supposed to reform over land. Then again, with all the rain earlier this year, maybe it thought Oklahoma was the ocean. In what is about as rare of a weather event as anyone will ever witness, Tropical Storm Erin reformed over southwestern and central Oklahoma during the late afternoon and overnight August 18-19.
Shortly after 5 pm on Saturday, the remnants of Erin, which had been downgraded to a tropical depression, started to show signs of new life. Two brief tornadoes were reported in western Oklahoma, near Cordell. As the evening progressed, the storm continued to wrap up, bringing torrential rainfall across southwestern Oklahoma and slowly spreading eastward and northward across the state. Beginning at 1:15 am on the 19th the Mesonet (http://www.mesonet.org) site at Watonga, near the center of the circulation, reported severe winds nearly continuously for two hours. During this time, sustained wind speeds over 40 miles per hour were reported. Had that occurred over open water, Erin would have been upgraded to a tropical storm. Wind gusts over 70 miles per hour were recorded at the Watonga and Fort Cobb Mesonet sites, and the Watonga Airport topped the list with an 82 mph gust.
Erin continued to wrap up during the overnight hours, eventually forming a new eye, centered just north of El Reno at about 5 am. The circulation persisted for several hours, driving bands of moisture counter-clockwise around the eye. The slow-moving system dropped more than five inches of rainfall along its path, with over an inch common in a larger area from Erin's outer 'bands'. Of the Mesonet sites, Fort Cobb picked up the highest total - 9.24 inches. However, a CoCoRaHS (http://www.cocorahs.org) observer reported 11.00 inches northwest of Geary, noting "the amount was MORE than 11 inches. When I went out to check the gauge this morning, it was full, had clearly overflowed during the night, and I spilled some of the contents getting the gauge off the post. The majority of the rain occurred between 11 pm and 4 am."
Oklahoma has a long list of natural hazards we face year-in and year-out. Now it looks like we can add tropical storms to the list. It will be interesting to see whether our sure-to-be disaster declaration will be labeled as such, or get lost amongst the many other "severe storms and flooding" events in our history.
The rainfall added by Erin was yet another blow to an already water-slogged state, especially for central Oklahoma. Rainfall totals averaged over the central Oklahoma region stands at 43.14 inches since the beginning of the year, 19.09 inches above normal - easily the wettest on record for the area. The previous mark was set in 1957 with a January 1-August 20 total of 36.90 inches. Statewide, the year thus far is the 4th wettest on record with 31.96 inches, 8.42 inches above normal.
The summer season through August 20 is the wettest on record statewide with a total of 15.46 inches, 6.71 inches above normal. Central Oklahoma is 14.45 inches above normal for the June 1-August 20 period with 23.23 inches of rainfall.
To watch Tropical Storm Erin as it moved across Oklahoma, download WeatherScope from our Software (http://climate.ok.gov/software/) website and then click here
Oklahoma's previous bouts with tropical systems | ||||
| Year | Month | Tropical Storm | South Region | Comments |
| 1996 | September | Fausto | Pacific | 6+
inches rain; minor flooding along North Canadian. |
| 1995 | August | Dean | Gulf of Mexico | 12-16
inches in parts of OK; interacted with weak, stalled cold front; major flooding along much of Salt Fork of the Arkansas River in Grant and Kay Counties; flooding also occurred on Cimarron, Washita and Arkansas Rivers. |
| 1988 | September | Gilbert | Gulf of Mexico | Interaction
with slow-moving front; 4+ inch rains fell onto saturated soils; flooding on creeks and rivers. |
| 1986 | September- October |
Paine | Pacific | Up
to 20 inches in north-central OK; massive flooding on Cimarron. flooding on the Arkansas River; ground was already saturated by rainfall associated with remnants of Pacific Hurricane Newton; estimated damages of $350 million; 52 counties declared disaster areas. |
| 1983 | October | Tico | Pacific | Up
to 17 inches rain in southwest and central OK; Red River at Burkburnett and Terral rose to highest stage in 60 years; widespread flooding of smaller rivers and creeks. |
| 1981 | October | Norma | Pacific | Up
to 24 inches of rain in south-central OK (Monthly total of 25.8” at Madill is greatest for any station during any month in OK history). |
| 1961 | September | Carla | Gulf of Mexico | Up
to 9 inches of rain fell across central and north central Oklahoma. |
| 1900 | September | Unnamed | Gulf of Mexico | The
remnants of the hurricane that devestated Galveston inundated eastern Indian Territory with flooding rainfall. |
Mother Nature launched a dastardly and unprovoked attack on our cool summer, and now she has set her sights on our wet summer as well. Prior to August 5, the 119 Oklahoma Mesonet sites had recorded triple-digit temperatures three times. In the 10 days between August 5 and August 14, however, those same sites have recorded temperatures of at least 100 degrees 390 times. The statewide average temperature for August 1-14 was 82.0 degrees, 1.4 degrees above normal. The statewide average high temperature, which has been creeping up daily, was 96.1 degrees for the same time period. Nighttime temperatures have been inching downward as the state begins to dry out and the length of daylight hours decreases. Through those 14 days, the average nighttime temperature was 2.1 degrees above normal. Temperatures normally reach a high of around 94 degrees in mid-August, decreasing steadily to around 90 degrees at the beginning of September. The highest temperature in the state thus far has been 106 degrees recorded at the Hooker and Webbers Falls Mesonet sites on August 12 and 13, respectively. That's a far cry from the summer's coolest high temperature of 67 degrees, recorded at Boise City way back on June 14. It could be worse; for the same period in 2006, the Mesonet had recorded triple-digit temperatures 1079 times, with a high of 109 degrees twice.
Since the 100-degree temperatures ramped up in earnest on August 5, Oklahoma has recorded a measly 0.05 inches of rainfall on average statewide. In fact, as of the morning of August 15, the statewide average precipitation for the month thus far was 0.30 inches, more than an inch below normal and the 8th driest such period since 1921. Most of that rainfall occurred at a few locations. Slapout received 3.2 inches during that period while Byars had three inches. Nearly 50 of the Oklahoma Mesonet's 119 stations recorded no rainfall during those 15 days. The statewide average for the 30-day period from July 16-August 14 was 1.05 inches, which is the 10th driest such period on record. That is contrasted with the 60-day period from June 16-August 14, where the statewide average was 10.49 inches, more than four inches above normal and the 5th wettest on record.
Oklahoma's flirtation with a Canadian-style summer came to a crashing halt as triple-digit temperatures replaced the flooding rains of June and July. The main culprit in the journey back to normalcy is an upper-level ridge of high pressure that has become entrenched over the Southern Plains. The ridge has effectively stifled the widespread rains that the state saw for much of the summer and at the same time allowed temperatures to soar into the 100s with increasing frequency. Prior to August, the Oklahoma Mesonet's 117 observing stations had recorded only three 100-degree temperatures, the highest of which was 103 degrees at Goodwell on July 8. Those same 117 stations have recorded temperatures of more than 100 degrees 37 times between August 5 and August 8. Most of those extreme temperatures have occurred in extreme western Oklahoma and the Panhandle, which have been drier than points east. The highest temperature in the state, through August 8, has been 105 degrees at Buffalo, reported both on August 7 and August 8.
The upper-level ridge made the return to of Oklahoma's normal summertime weather an inevitability - heat, heat and more heat. The abundant precipitation of the previous two months have helped keep air temperatures down somewhat as the sun's rays work primarily to evaporate moisture from the surface. As the surface begins to dry, however, and vegetation loses its greenness, more of the sun's energy will be used to heat the ground. The heat that western Oklahoma has been seeing will begin to creep eastward, spreading eastward across the state.
Unfortunately, as the moisture from the ground is evaporated, it increases the humidity of the air near the surface. This adds to Oklahoma's normal hot and humid August conditions. Heat indices have been in the 105-110 degree range across portions of northern Oklahoma, prompting excessive heat warning and heat advisories from the National Weather Service.
A current heat index map from the Oklahoma Mesonet can be found at: http://www.mesonet.org/data/public/mesonet/maps/realtime/current.heat.gif
Incredibly, only three triple-digit temperatures have been recorded by the Oklahoma Mesonet's 119 observing sites during 2007. Of the nearly 12,000 high temperature observations reported by the network, the lone 100-degree readings were: 103 degrees at Goodwell on July 8; 101 degrees at Hooker, also on July 8; 100 degrees at Tipton on June 19. Results from previous years indicate that 2004 had the next-lowest total through July with 117 reports of triple-digit temperatures from the Mesonet. The highest total of 2520 came during the drought-induced heat of 1998. Last year's total through July was 1565.
Oklahoma's cool and wet summer continued through July according to preliminary data from the Oklahoma Mesonet. The statewide average temperature for the month was three degrees below normal to rank as the 11th coolest July since 1895. Cool summer months are normally associated with above normal precipitation and that was exactly the case this July as well. The statewide average rainfall totaled nearly four inches, more than an inch above normal, to rank as the 24th wettest July on record. The greatest area of surplus precipitation occurred from the southeastern tip of the state up through central Oklahoma. The southeast led the state with an average of more than eight inches, nearly five inches above normal - the 4th wettest July for that area.
This year's June-July period ranks as the wettest on record for the state with a surplus of more than six inches. Central Oklahoma led the state with a surplus of more than 11 inches. The Panhandle, on the other hand, was more than an inch below normal and experienced its 23rd driest June-July on record. Central Oklahoma had its wettest January-July on record with a total of 38.52 inches, nearly 16 inches above normal. Statewide, the June-July period ranks as the 13th coolest on record, more than two degrees below normal. The year thus far ranks as the 53rd coolest.
| July 2007 Mesonet Statistics | ||||||
| Climate Division | Avg Temp | Departure | Rank | Rainfall | Departure | Rank |
| Panhandle | 77.7 | -1.9 | 32nd Coolest | 1.67 | -0.85 | 31st Driest |
| North Central | 78.9 | -3.3 | 12th Coolest | 3.10 | 0.12 | 52nd Wettest |
| Northeast | 78.9 | -2.0 | 28th Coolest | 3.05 | -0.11 | 57th Driest |
| West Central | 78.1 | -3.6 | 8th Coolest | 2.39 | 0.26 | 49th Wettest |
| Central | 79.1 | -2.9 | 19th Coolest | 5.69 | 3.12 | 10th Wettest |
| East Central | 78.6 | -2.7 | 18th Coolest | 5.12 | 2.14 | 23rd Wettest |
| Southwest | 79.3 | -3.9 | 7th Coolest | 1.93 | -0.25 | 53rd Driest |
| South Central | 79.0 | -3.7 | 7th Coolest | 4.79 | 2.25 | 14th Wettest |
| Southeast | 78.1 | -2.8 | 8th Coolest | 8.40 | 4.82 | 4th Wettest |
| Statewide | 78.7 | -2.9 | 11th Coolest | 4.03 | 1.29 | 24th Wettest |
How wet is it? Or is the real question "how dry was it?" Comparing the drought of the previous two years to the flooding rainfall of 2007 is indeed like comparing apples and oranges, with one notable exception - both hazards have been disastrous for those affected. The 2006 wheat crop was decimated by drought while the 2007 crop languished in fields too wet for machinery. The drought conditions of 2005 and 2006 spawned destructive wildfires while the torrential rains of this year have flooded homes and businesses across the state. The most unfortunate similarity is the cost in lives, however, whether it be those who were lost fighting wildfires or to the rising floodwaters. With those similarities noted, the statistics between the two periods could not be more striking.
According to data from the Oklahoma Mesonet, the statewide average rainfall through July 16 has already eclipsed the yearly rainfall amounts of both 2005 and 2006. The statewide average rainfall for the year thus far, through July 16, is 29.05 inches. The yearly totals for 2005 and 2006 were 26.93 inches and 28.59 inches, respectively.
The regional averages are even more outlandish. Central Oklahoma currently leads the state with an average of 37.76 inches - the wettest on record for that part of the state, 16.65 inches above normal. Compare that with identical periods from 2005 and 2006 when the averages were just 16.85 inches and 14.13 inches, respectively.
As a final exclamation point, consider the rainfall statistics from the Oklahoma Mesonet site at Minco, which has recorded 44.00 inches of precipitation through July 16. The same periods from 2005 and 2006 combined added up to 23 inches, a little more than half of this year's total. In fact, to match this year's total, you have to go back all the way to February 24, 2005 - that's February 24, 2005, through December 31, 2006. In other words, it took the rainfall from the previous 676 days at Minco to match this year's total accumulated in 197 days.
Oklahoma City might be considering changing its name to Seattle, given how much rain we've had recently. Friday morning's rains mark 17 consecutive days of rainfall in Oklahoma City, according to the National Weather Service. This breaks the previous record of 14 consecutive days, from May 29 through June 11, 1937. Although, if we went farther back in history, we hear the real record is 40 days (and nights)! Then again, maybe we're just trying to convince the Seattle Supersonics basketball team to move to Oklahoma City.
Since the most recent rounds of rainfall began in Oklahoma on May 24, the state has tallied 9.42 inches of rain (through June 27), on average, which is more than four inches above normal for the period. Central Oklahoma leads the way with an average of 13.38 inches. Now anybody who deals with Oklahoma weather knows that things are rarely average - some places get more and some get less. The "more" side of it totals as much as 19.72 inches at Minco and more than 18 inches at Marena, Medicine Park, Apache, Chickasha and Kingfisher.
All this rain makes it kind of hard to remember how dry it had been. When you figure the rain total for the last 365 days, it comes up just a bit above average. Southwest, west central, and central Oklahoma come up on the wet side and southeast comes up a bit below normal, with the state overall showing a surplus of 3.94 inches. The recipe? Take about 6 really dry months, about 3-4 near-normal months, and a couple of incredibly wet months and you have "normal," just like you would expect in Oklahoma!
Track your rainfall at http://climate.mesonet.org/rainfall_update.html
May 24, 2007 through June 27, 2007 | |||||
| Region | Total Rainfall |
Departure
from Normal |
Percent
of Normal |
Rank
since 1921 (of 87) |
Wettest
on Record |
| Panhandle | 3.16" | -0.35" | 90% | 35th driest | 7.90" (1962) |
| N. Central | 8.77" | +4.01" | 184% | 6th wettest | 11.94" (1957) |
| Northeast | 10.76" | +5.18" | 193% | 5th wettest | 13.84" (1957) |
| W. Central | 7.32" | +2.58" | 154% | 9th wettest | 10.36" (1995) |
| Central | 13.38" | +7.81" | 240% | 1st wettest | 12.41" (1957) |
| E. Central | 8.56" | +2.67" | 145% | 11th wettest | 12.44" (1935) |
| Southwest | 9.21" | +4.19" | 183% | 4th wettest | 11.20" (1987) |
| S. Central | 12.80" | +7.18" | 228% | 1st wettest | 11.07" (1987) |
| Southeast | 8.72" | +2.85" | 149% | 12th wettest | 11.87" (1935) |
| Statewide | 9.42" | +4.24" | 182% | 2nd wettest | 9.79" (1957) |
After two years of severe drought, Mother Nature turned the spigots on in relief but seems to have forgotten to shut them off. Consequently, flooding has become the hazard of choice during the past three months. Oklahoma's statewide average precipitation total for the year thus far ranks as the 19th wettest since 1921, 1.40 inches above normal. Much of that bounty is buoyed by the northwestern half of the state. The north central, central and west central regions are all experiencing year-to-date totals ranked within the top-ten wettest. The last 90 days have been particularly wet, with the state enjoying its 13th wettest such period. West central, central, and north central totals are all ranked in the top-six wettest during that same time frame. Not all areas of the state are sharing in the moisture surplus, however. The eastern third of the state has continued to dry out over similar periods. The southeast and east central sections of the state are nearly three inches below normal since the beginning of the year to rank as the 26th- and 29th-driest on record, respectively. The two-year precipitation statistics reflect the just-broken drought with virtually the entire state, save for the west central section, showing precipitation deficits. May 2005-May 2007 for southeastern Oklahoma is the driest such period on record.
It's somewhat standard for Oklahoma's severe drought episodes to end with a deluge instead of a trickle. The state's most notable droughts, the 1930s Dust Bowl and the 1950s, were both broken in a spectacularly wet fashion. The Dust Bowl episode was whittled away in early 1941 before being blasted from existence by a statewide average rainfall of 11.32 inches in October, the wettest Oklahoma month on record. The 1952-57 drought, considered the state's worst statistically, ended rather abruptly in May 1957 with heavy rains and major flooding on the state's largest river systems. That year still stands as the wettest in Oklahoma history at 48.21 inches.
The Oklahoma Climatological Survey is proud to announce the Spring 2007 edition of its seasonal climate series "Oklahoma Climate," available online at: http://climate.mesonet.org/seasonal_summary.html.
Enjoy these stories on a rainy day:
Governor Brad Henry proclaimed May as Flood Awareness Month, and apparently not a day too soon. In just the first eight days of May 2007, Oklahoma posted a statewide-averaged rainfall total of 3.53 inches. By comparison, May 2006 only recorded 3.03 inches - for the entire month. The normal May rainfall is 5.21 inches. In short, it took only eight days to surpass the total from the drought-plagued month of May 2006.
This rain comes on the heels of a wet April, which helped Oklahoma erase the last vestiges of a 2-year-long drought. On April 3, the U.S. Drought Monitor ended drought designations, although lingering effects still remained in pastures and reservoirs. With the May rainfall, the reservoir issue has nearly been resolved. Lake Thunderbird near Norman, which just a few weeks ago was nearly 30% below it's normal conservation level, is now nearly full. Lake Altus-Lugert, which had been less than half-full, is three-quarters full, great news for cotton-growers in southwest Oklahoma that rely upon the irrigation lake in the summer.
If there was any doubt about the recovery from drought in Oklahoma, this past week has put that to rest. Soil moisture at nearly every Mesonet site is saturated, the Keetch-Byrum Drought Index is virtually zero statewide and wildfire potential is almost non-existent. In the last 30 days, the driest part of the state (the Panhandle) has 114% of normal rainfall. Statewide rainfall totals place Oklahoma as the 7th wettest on record over the past 30 and 60 days and the 13th wettest year-to-date (through May 8). Even more incredible, every region of the state except the northeast is at or above normal for the water year (beginning October 1), and the northeast missed by only 0.03 inch. Oklahoma has not experienced a Spring like this since 1999.
As so often occurs in Oklahoma, we switched from one hazard to another. Instead of fighting wildfires, Oklahomans must now remember safety rules for floods. According to the National Weather Service, "each year, more deaths occur due to flooding than from any other thunderstorm related hazard. Why? The main reason is people underestimate the force and power of water. Many of the deaths occur in automobiles as they are swept downstream. Of these drownings, many are preventable, but too many people continue to drive around the barriers that warn you the road is flooded. Whether you are driving or walking, if you come to a flooded road, Turn Around Don't Drown. You will not know the depth of the water nor will you know the condition of the road under the water."
Earlier, Governor Henry proclaimed March as "Flood Insurance Month," part of a state campaign to spread the word about the availability of affordable flood insurance through the Federal Emergency Management Agency's National Flood Insurance Program (NFIP). According to the Oklahoma Water Resources Board, Oklahoma currently boasts 376 NFIP member communities, which consist of municipalities, counties, and tribes. Gavin Brady, State Floodplain Manager, notes that "implementation of sound floodplain management and building strategies, particularly through the NFIP, is the most effective way for communities to avert potential flood damages." However, he encourages communities to go "above and beyond" minimum NFIP standards, consistent with the national Association of State Floodplain Manager's ongoing 'No Adverse Impact' initiative. Brady points out that 87% of homes in Oklahoma's designated floodplains have no flood insurance.
As we continue to monitor rainfall patterns, we should pause and realize how vulnerable we remain to the effects of water, both too little last year and too much now. Water management is a critical issue for Oklahoma, both in managing excess to limit damages and preserving sufficient resources for the dry times. Climate change scenarios suggest that this will only get worse in coming decades. All Oklahoma citizens are encouraged to participate through local community planning and through the state's Comprehensive Water Plan process, to assure that we will become less vulnerable to these risks in the future.
Ashton Robinson Cook: Storm Prediction Center SCEP student
Spring can be the most violent season for Oklahoma weather. With spring in full swing, Oklahomans may be wondering about the prospects of the upcoming tornado season and whether El Niño or La Niña can increase or decrease probabilities of a tornado in an area.
El Niño and La Niña are part of a more complex climate system termed El Niño Southern Oscillation (ENSO). This climate phenomenon is driven by abnormal sea surface temperatures in the equatorial Pacific, with shifts in weather around the entire world attributed to ENSO. El Niño is the warm phase of this climate phenomenon, denoted by abnormally warm sea surface temperatures. La Niña is the opposite; it involves significantly cooler than average sea surface temperatures in the region. The third ENSO phase, Neutral, indicates sea surface temperatures that are near the climatologically normal level.
ENSO has its most pronounced effects on U.S. weather during the winter months. In a winter El Niño, warming of the equatorial sea surface temperatures forces a stronger than average subtropical jet to develop across the southern tier of the U.S. The jet tends to bring cooler, wetter conditions to the southern tier of states, including Oklahoma. In contrast, winter La Niña conditions tend to diminish the presence of the subtropical jet and displace it farther to the north. Generally, this results in drier, warmer conditions in Oklahoma. Although the effects are less clear during the spring months, cooler and wetter conditions generally prevail throughout the spring in El Niño months, with drier conditions noted during La Nina and Neutral months.
So are there similar shifts noted in spring tornado activity?
There is very little evidence that ENSO is responsible for shifts in spring tornado activity in Oklahoma. A brief analysis of tornadoes occurring in Oklahoma during spring and early summer (April, May, and June) between 1950 and 2005 reveals only very small shifts in tornadic activity across the state. Figures 1 and 2 indicate that some of the tornadoes during the La Nina phase seem to have longer tracks compared to tornadoes in El Niño phase events, especially across central and northern Oklahoma. Although the shift is evident, it is not very pronounced. Tornadoes occur in all parts of the state regardless of ENSO phase. In addition, it is difficult to determine a solid meteorological basis for this shift as distinct shifts in weather patterns (such as the climatological positions of jet streams, fronts, and drylines) during the spring months have not been determined.
A further analysis reveals that stronger tornadoes (rated F2 or higher in the Fujita Scale) occur slightly more frequently in the La Niña phase of ENSO (30.9%) compared to the El Niño phase (21.6%). While strong tornadoes are also a more frequent occurrence in Neutral phases (29.6%), it is difficult to draw valuable comparisons between Neutral ENSO phases and others because the Neutral phase occurs nearly twice as often (28 spring seasons) as both El Niño (13 spring seasons) and La Niña phases (15 spring seasons). As expected, the Neutral phase contains nearly double the tornadoes (1015) that either the La Niña (525) or El Niño phase (547) contains, indicating that the frequency of tornadoes across Oklahoma is not affected by ENSO phase.
In short, it appears that the effect of ENSO on spring Oklahoma tornado activity is minimal. The entire state has equal chances of experiencing tornadoes regardless of the ENSO phase. While stronger tornadoes occur less frequently in the El Niño phase compared to other phases, strong and even violent tornadoes (rated F4 or F5) have been observed in all three phases.
Sources:
Hart, J. A., and P. Janish, 1999: Severe Plot v. 2.0 Oklahoma Climatological Survey: http://climate.ok.govThe Oklahoma Mesonet is participating in the annual FFA state convention at the Cox Convention Center in Oklahoma City, April 24-25. Oklahoma FFA assists students interested in careers in more than 300 areas, ranging from agri-science to biotechnology to turfgrass management. The convention attracts thousands of students from all counties in the state. One stop in the exhibit hall is the Oklahoma Mesonet booth, where Al Sutherland and Laura McKay will be demonstrating how weather information is harnessed to help the state's agricultural industry deal with Oklahoma's weather.
Weather is no longer something that farmers and ranchers passively accept. Through technological advancements, they are now able to continuously monitor weather conditions on the local level and apply it to their practices. Results include increased production, reduced pesticide and fertilizer costs, and environmentally-friendly practices. One of the tools they use is the Mesonet's AgWeather page, http://agweather.mesonet.org/. AgWeather combines real-time information from the Oklahoma Mesonet with a variety of agricultural application models, market information, and Oklahoma State University Extension fact sheets to provide a comprehensive source of information for all varieties of businesses. We invite you to visit with Al and Laura at the booth, or to stop by the AgWeather website.
Natural HazardsConferences
Oklahoma faces a wide variety of natural hazards. One of these, heat stress, will be highlighted in two events this week.
On Tuesday, April 17, the "Never Leave Your Child Alone" news conference will focus on heat deaths resulting from leaving children unattended in automobiles. The Oklahoma City Fire Department, Safe Kids Worldwide, and General Motors are teaming up on an information campaign this summer to draw attention to what is an easily presentable cause of death. Since 1998, at least 11 Oklahoma children have died from heat stroke when left unattended in closed vehicles, some for as short as only a few minutes. Even when the temperature is as low as 70 degrees, the temperature inside a vehicle can rise 19 degrees in just 10 minutes. Children are especially vulnerable, because their body temperatures rise at a rate of three to five times faster than an adult's. The news conference will occur at 3 p.m. at the Oklahoma City Police/Fire Training Center, 800 N. Portland. For further information, contact Tony Young with the Oklahoma City Fire Department, (405) 297-3314.
On Wednesday, April 18, hazards will be the topic of a day-long conference held at the National Weather Center. The second "Climate & Loss Mitigation Conference", hosted by the Oklahoma Insurance Department, will feature speakers and breakout sessions focusing on climate-related hazards, how those might change because of global warming, what impacts this might have on the insurance industry, and things we can do in our communities to make ourselves less vulnerable to both projected hazards and the hazards we already face. Registration is as low as $15 for seniors and students or $30 for the general public, and includes lunch. The conference is co-sponsored by the Oklahoma Climatological Survey, State Farm Insurance, and American Farmers and Ranchers Insurance. Additional information is posted at http://www.oid.state.ok.us/ or call (405) 325-2541.
Return of Deadly Tornado Ends Record Absence
March 29, 2007
The two confirmed tornado deaths on March 28 near the small town of Elmwood in Beaver County are the first in the state since April 11, 2001, according to statistics from NOAA's National Climatic Data Center. The nearly six-year span of 2178 days is the longest interval between killer tornadoes since accurate statistics began in 1950 and eclipses the previous record of 1457 days, which occurred between May 7, 1995, and May 3, 1999. The fatalities mark the first official tornado deaths in Beaver County, although additional records list a fatality near Balko in Beaver County on May 20, 1949. Beaver County's last tornado occurred on September 21, 2006 near Turpin.
Oklahoma's last tornado fatality occurred four miles east of Coalgate in Coal County a little after 4:30 pm on April 21, 2001, after a mobile home was thrown 200 yards and disintegrated, killing one. Oklahoma's 3028 tornadoes since 1950 have resulted in 265 deaths, over 4000 injuries and more than $3 billion in damage. The state's 27 tornadoes during each of the last two years are little more than half the annual average of 53.
Heavy rainfall in the northern one-third of the state has helped ease severe drought conditions in north central Oklahoma. The Oklahoma Mesonet site at Foraker recorded 5.31 inches of rainfall during the event, with 5.14 inches of that total occurring on the 20th. General amounts between 3-5 inches fell in Grant, Kay, Noble, and Osage Counties. Unofficial reports and radar estimates of 6-7 inches came in from the Newkirk and Red Rock areas. Flash flood warnings were issued by the National Weather Service for Kay and Noble Counties due to the heavy rains. Roads in and around Blackwell, Newkirk and Ponca City were reported under water on the 20th.
Much of north central Oklahoma remains in severe drought conditions according to the National Drought Monitor. The rest of the western half of the state is categorized as abnormally dry or in moderate drought conditions.
The Oklahoma Climatological Survey is conducting a workshop for public safety officials. The Spring Full Certification Course is March 13-16, 2007 at the National Weather Center in Norman. Completion of this course will deem the student as a Full Participant in OCS's OK-First program.
Grand Prize Winner
February 16, 2007
Dr. Matthew Haugland and Dr. Ken Crawford met with the Governor Brad Henry and Lieutenant Governor Jari Askins at the Oklahoma State Capital to honor Dr. Haugland for winning the Grand Prize at the National Collegiate Inventors Competition. The National Collegiate Inventors Competition recognizes and rewards innovations, discoveries and research by college and university students and their faculty advisers. Haugland's entry, titled "The Uncoupled Surface Layer Model," is based on his research of weather observations in microclimates. The Grand Prize carries a monetary value of $25,000 which Dr. Haugland intends to use to start his own private company based in Oklahoma.
The Oklahoma Climatological Survey is proud to announce the Winter 2006-07 edition of its seasonal climate series "Oklahoma Climate," available online at: http://climate.mesonet.org/seasonal_summary.html.
Thaw out with these stories:
If this has seemed like a long, cold winter, that's because it has been. OCS and KWTV News9 looked at past winters to see just how this winter compared. Digging back through snowfall records for Oklahoma City from 1948 to present, we've learned just how this winter stacks up to some of the memorable ones from the past.
Even though this winter has been cold (38.9 degrees average temperature from December 1 - February 15), it is far from the coldest. In fact, of the past 60 years, this year is so far tied for 29th coldest - roughly the middle of the pack. However, it may seem colder because Oklahoma City just came off its 3rd warmest winter on record, a balmy 43.2 degree average temperature. You have to go back to 2000-2001 for a colder period, when the average temperature was a chilly 35.0 degrees.
But cold is only part of the story. If it seems like we've had more snow or ice events or the snow/ice has stuck around longer than usual, that is indeed the case. As of February 15, Oklahoma City reported 19 snow days (days with at least 1 inch of snow falling or on the ground). This ties for the 5th most since 1948, and there are still another 4-6 weeks in which additional snow may be possible. The record is 25 days, set in 1948.
The snow/ice also has stuck around longer. The 13 days from January 12-24 where snow (or ice) either fell or was on the ground is the 3rd longest period of consecutive snow-days in modern records. The longest period was 18 days in 1978.
So this winter has definitely been tough, but what was the worst winter? Hands-down, that distinction goes to 1978-1979. That winter was the coldest (30.4 degrees), 2nd for the most number of snow days (23), had 6 snow events, and had 18 consecutive days with snow on the ground. This came right on the heels of the winter of 1977-1978, which otherwise would have been considered the worst winter in modern times. As spring came in 1978, folks were probably grateful to have that winter put behind them, but they had no idea that it could get worse just one year later.
The National Weather Center will host a kick-off event for the Pioneer Multi-County Library System's Big Read event, featuring "The Grapes of Wrath" by John Steinbeck, on Friday, Feb. 9. Scientists will give talks, followed by a reception and tours of the NWC facility, located at 120 David L. Boren Blvd. Geographers and meteorologists from the College of Atmospheric and Geographic Sciences will discuss weather conditions of the Dust Bowl compared with today, accuracy of the conditions portrayed in the book, human impact and farming practices during the Dust Bowl and how these issues affect us today.
Speakers include Gary McManus, a climatologist from the Oklahoma Climatological Survey. Gary will discuss the climate of the Dust Bowl era, and the conditions and practices that led to the Dust Bowl disaster.
John Steinbeck's The Grapes of Wrath is not merely a great American novel. It is also a significant event in our national history. Capturing the plight of millions of Americans whose lives had been crushed by the Dust Bowl and the Great Depression, Steinbeck awakened the nation's comprehension and compassion.
Visit the Big Read website at http://www.bigreadok.com for more information, including registration, online discussions, and updates leading up to the event. Registration for this event is limited to 500. Due to the demand, the presentation in the auditorium will be presented twice: 5:45 and 6:45 p.m.
State Climatologist to Speak on Climate Change
January 30, 2007
Global warming may be the furthest thing from our minds these days, but just a few months ago, it felt very real. State Climatologist Ken Crawford will join climate experts on a panel discussion focused climate change and its implications for Oklahoma. The panel will discuss the current scientific understanding of the dominant causes of climate change and its effects locally, nationally and internationally. This coincides with the February 2 release of the first volume of the Intergovernmental Panel on Climate Change (IPCC) fourth assessment report, "Climate Change 2007: The Physical Science Basis".
Dr. Crawford, Regents Chair Professor of Meteorology at The University of Oklahoma, will be joined by renowned climate experts Dr. Robert Corell, Director of Global Change Programs at the Heinz Center in Washington, DC, and Dr. David Karoly, Williams Chair Professor of Meteorology at the University of Oklahoma. Dr. Corell served as the Chair of the Steering Committee for the Arctic Climate Impact Assessment, an international effort completed in 2005 to evaluate the effects of climate variability and climate change in the Arctic. Dr. Karoly was a lead author and review editor of the forthcoming IPCC report. Also appearing on the panel will be Dr. Mark Shafer, Director of Climate Information from OCS, who will look at climate change from a political and policy perspective.
The IPCC report assesses current scientific knowledge of the natural and human drivers of climate change, observed changes in climate, the ability of science to attribute changes to different causes, and projections for future climate change. Panel members will each give a short presentation, followed by a question-and-answer period. Please join us on Friday, February 2, at 1:30 p.m. at the National Weather Center in Norman. For accommodations based on disability, or more details, please contact the School of Meteorology at (405) 325-6561.
Ice Storm!
January 12, 2007
Freezing rain is a distinct wintertime hazard in Oklahoma. Ice storms are extended freezing rain events, lasting several hours to days at some locations, with heavy ice accumulations. The US National Weather Service considers an ice storm with greater than 0.25 inches (0.63 cm) of ice accumulation a significant episode that would trigger an ice storm warning. The resulting ice cover can down power lines and limbs, causing millions of dollars in damages and widespread power outages. These events make automobile travel very treacherous, especially on secondary roads, where the ice can linger for several days. Significant icing events occur with nearly the same frequency as heavy snow events, especially in the southeastern half of the state. While ice accumulation is usually less than an inch, storms that deposit several inches can occur once or more per decade. The consecutive winters of 2000-01 and 2001-02 each featured a major ice storm that deposited more than three inches of ice in 24 hours across much of southeast and central Oklahoma. For the electric utility industry, an ice storm strikes in two waves: first from the initial ice accumulation and wind stress; then later from stresses caused by the rapid recoil of power lines when accumulated ice melts and falls.
FREEZING RAIN FORMATION
Freezing rain is most commonly found in a narrow band on the cold side of a warm front, where surface temperatures are at or just below freezing (Figure 1).
Whether freezing rain forms from the cold rain or not depends critically on the characteristics of the surface cold air layer. If the layer is too thick or too cold, it will refreeze the rain into ice pellets, or sleet. If the cold layer is too warm or too shallow, the rain will continue to the ground as normal rain and will not freeze unless the temperature of the ground or some other surface it contacts is well below freezing. Often small temporal or spatial differences in air temperature and in droplet size result in freezing rain mixed with sleet, snow or non-freezing rain.
Much-needed rain and snow visited the state during December, lessening
drought conditions and providing welcome relief to most of Oklahoma.
Between 3-6 inches of precipitation fell over a good portion of
the state, while the Oklahoma Panhandle suffered through a couple
of bouts of nasty winter weather. That helped the Panhandle region
to its wettest December on record, more than three inches above
normal. The state as a whole fared well with the 12th wettest December
on record. Drought conditions remained severe in parts of north
central Oklahoma, which largely missed out on the heavy precipitation.
The year ended as the 23rd driest on record statewide at eight
inches below normal. The year’s final month was also the
27th warmest on record, helping the year itself to finish as the
2nd warmest.
An inch of freezing rain and up to 5 inches of snow in
the state’s
three western-most counties on the 19th made for treacherous driving,
as well as leaving thousands without power. Still smarting from that
wintry blast, a full-fledged blizzard hit the Panhandle on the 29th.
Eighteen inches of snow and drifts of up to 6 feet brought much of
Cimarron and Texas counties to a standstill. An ice storm hit the
rest of the Panhandle, once again leaving thousands without power
and destroying over $1 million of power poles and lines.
| Temperature | |||
| AVG. | Depart. | Rank (1892-2006) | |
| Month (December) | 41.9°F | 2.9°F | 27th Warmest |
| Year-to-Date (Jan-Dec) | 62.2°F | 2.5°F | 2nd Warmest |
| Precipitation | |||
| Total | Depart. | Rank (1892-2006) | |
| Month (December) | 3.67 in | 1.65 in | 12th Wettest |
| Year-to-Date (Jan-Dec) | 28.69 in | -8.00 in | 23rd Driest |
The Oklahoma Climatological Survey is proud to announce the Fall 2006 edition of its seasonal climate series "Oklahoma Climate," available online at: http://climate.mesonet.org/seasonal_summary.html.
Beat the Heat with these great stories:
The beneficial rains of the past several weeks have brought nominal to significant improvement across drought-ravaged Oklahoma. With this relief, the National Drought Mitigation Center (NDCM) lowered the drought severity across most of the state by one to two categories. This past week, NDMC lowered southern Oklahoma's drought designation from "exceptional" - the most severe category - to "extreme". Unusually heavy rains in the Panhandle improved that area's drought impacts from "extreme" to merely "abnormally dry".
Despite the above normal rainfall of August, however, the drought is still labeled as "severe" or "extreme" over a sizable portion of southern and western Oklahoma. Much of the remainder of the state remains in "moderate" drought conditions. In effect, while short-time impacts have lessened, the drought is still dominated by long-term effects due to precipitation deficits that began in earnest in late February of 2005. In some areas of the state, the true drying-out period began much earlier. In the southeast, for instance, the dry period extends back to early 2003.
Statewide average precipitation statistics from the Oklahoma Mesonet ranked the March 1, 2005, through September 10, 2006, interval as the driest-such period on record, 19 inches below normal. While the drought has ebbed and waned over that time, its impacts became especially severe early last fall. Effectively wiping out more than half of the state's wheat crop, the worst harvest in more than 50 years, the drought also provided Oklahoma its worst wildfire season on record. More recently, the western half of the state enjoyed above normal rainfall in August and early September, while the eastern half of the state had very little rainfall. Southwestern and west central Oklahoma experienced their 23rd wettest such periods on record, while the Panhandle enjoyed their 6th wettest.
The long-term drought conditions result in a more difficult road to recovery. Rain that falls in areas with deficits in the tens of inches over the last several years has several levels of water supply to replenish, from soil moisture, surface water, to deep wells and aquifers. And, as evidenced by the Oklahoma Mesonet's soil moisture observations, even short-term improvements can be fleeting if not quickly reinforced by more precipitation.
The latest seasonal drought outlook from the Climate Prediction Center calls for varying degrees of improvement across the northwestern two-thirds of Oklahoma through November, and drought persistence across the southeastern one-third.
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