Author Archives: David Reimer

Driest September On Record for D/FW

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While significant rains were observed across West and South Texas this month the same cannot be said for North and East Texas. On average D/FW International Airport receives 2.55 inches of rain during the month of September. The current driest September on record was set in 1984 with only 0.09 inches of rain in September. So far we’ve seen just 0.06″ of rain this month. With no precipitation expected through Wednesday this month is expected to set a new record low for rain during the month of September.

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The National Weather Service in Fort Worth has put together an excellent resource page regarding the ongoing drought and expectations for this fall. Be sure to check it out at http://www.srh.noaa.gov/fwd/?n=drought
We also have the 2014-2015 Winter Outlook for Texas published on our blog here.

Severe Storms Moving Towards Northwest Texas Panhandle

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Two supercell thunderstorms will move into Dallam and Hartley Counties in the Texas Panhandle around 7 PM. These storms have a history of producing large hail and damaging wind gusts across eastern New Mexico. These storms should maintain their organization as they move across the state line and could bring severe weather to the northwest Texas Panhandle this evening. Other thunderstorms southeast of Santa Rosa could approach the state line later this evening. They’re currently not severe but we’ll be watching them closely. A Severe Thunderstorm Watch remains in effect for the northwest Texas Panhandle and those in Dalhart should monitor the weather over the next hour as the severe storm east of Mosquero, NM moves closer. The storm 20 miles east of Mosquero looks particularly intense at this time and will approach the state line by 7 PM. One limiting factor for a more significant severe weather threat this evening is limited instability values. The atmosphere is moderately unstable across the Northwest Texas Panhandle but instability values decrease further east into West Texas and the Panhandle. For that reason we expect most storm activity to remain west of I-27/US-87 this evening. Storms that manage to get further east will begin weakening as they move out of the instability axis.

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2014-2015 Winter Weather Outlook for Lone Star State

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Let me first start by saying that seasonal outlooks are a tricky business. Meteorology itself as a science is relatively new dating back only a century. When compared to other sciences Meteorology is still in its infancy. While we’ve gotten fairly good at predicting weather within the upcoming three to five days we still can’t master forecasts over a week out. Hence the skill of forecasting upcoming seasons/months is still a new science. Nevertheless there are a few major indicators that can help give insight on what might be more likely to transpire down the road. One of the most, if not the most used, indicators are phases called La Nina, El Nino, and ENSO Neutral. I’m sure many of our followers are already aware of these phenomena, or at least have tried the El Nino cocktail at your local Chili’s restaurant.

The determining factor regarding an El Nino or La Nina is actually all the way out in the equatorial waters of the Pacific Ocean. When sea surface temperatures become unusually warm an El Nino typically develops. On the opposite end of the spectrum a La Nina usually develops when sea surface temperatures are unusually cooler. You might be asking yourself why the equatorial waters of the Pacific Ocean have anything to do with our weather. The answer is fairly straight forward when it comes down to our weather in Texas.

El Nino Winter Pattern Courtesy of JetStream/NWS

El Nino Winter Pattern
Courtesy of JetStream/NWS

La Nina Winter Pattern Courtesy of JetStream/NWS

La Nina Winter Pattern
Courtesy of JetStream/NWS

During an El Nino event Jetstream usually positions itself across the Southern United States including Texas. As disturbances in the atmosphere move with the Jetstream they can produce precipitation. The stronger low pressure systems that develop near the jet stream not only can bring precipitation to our state but cause more frequent cold air intrusions from the north (known as a cold front). During the winter season the result can be more frequent bouts of arctic air from the Canadian prairies and northern plains. A La Nina will typically keep the Jetstream further north across the United States leaving Texas and much of the Gulf Coast in a dry and warm pattern. A La Nina was in place back in 2011 when much of Texas was expecting record dry and an extreme fire season that we thought would never end. Fortunately we shifted out of La Nina into a neutral pattern where we had no La Nina or El Nino in early 2012. We’ve essentially been sitting there ever since until earlier this year when signs began to point towards the development of an El Nino.

Earlier this year, climate prediction models were forecasting the development of a strong to extreme El Nino. However the progress towards the development of an El Nino slowed this summer and confidence decreased. The latest forecast from NOAA and the National Weather Service predict a 65 percent chance that an El Nino will develop this fall and early winter. Based on current observations and the latest climate prediction models, the upcoming El Nino is expected to be a weak event. Don’t let that little tidbit discourage or get you down. Research has actually shown that parts of Texas actually fair better in terms of precipitation during a weak/moderate El Nino versus an extreme event. Every La Nina/El Nino is different just like each winter storm or tropical cyclone has its own unique characteristics.

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The Winter Outlook from the Climate Prediction Center is based on the expectation of an El Nino developing by late fall. Based on past experience with El Nino events along with long-range climate prediction models the outlook shows Texas having an above-average chance of precipitation this winter. Let me caution now that just because we have an above-average chance of precipitation does not mean we will receive rain all the time or break the drought. It just means the chance of being in a wetter pattern this winter is more likely than having a dry winter.

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Much of Texas is also highlighted in a zone where the chance of having below-average temperatures this winter is more likely than not. Like the precipitation outlook, that does not mean we’re going to experience record cold or be frigid all winter. I’m confident we’ll have times where temperatures are above average. As a whole, the outlook suggests we will have more frequent cold fronts this winter with temperatures at or below average seasonally verses above average.

So what does this mean for our chances of having winter precipitation? Well I’d say the chances of having winter weather events will probably hinge on the development of an El Nino along with how cold temperatures get to our north. Just because the Northern United States and Canada get cold in the winter does not mean that frigid air transports south all the time. Several factors such as the Arctic and North Atlantic Oscillation, along with snow cover to our north, will determine exactly how cold we get this winter and how many cold blasts we end up receiving.

Considering we’re expecting a more active Jet Stream across our area means we should have more chances for precipitation. Should precipitation fall at time where we have a sub-freezing air mass in place the result would be frozen precipitation. Typically speaking during past El Nino events we have had winter weather events in Texas. The 2009-2010 Winter Season was dominated by a moderate El Nino. We had the Christmas Eve Blizzard along with several high-impact winter storms during the first months of 2010 including the foot of snow in the D/FW Metroplex. The 2010-2011 winter season was dominated by a strong La Nina and the 2011-2012 season had a weak La Nina. 2013-2014’s winter was in a neutral phase. Regardless we’ve had winter weather events in Texas during El Nino and La Nina. Factors such as the jet stream, frequency of strong storm systems, and snow cover and arctic air to our north all play significant roles in winter weather.

For those interested in the full meteorological discussion from the Climate Prediction Center I’ve included it below on the blog.

Long-Lead Seasonal Discussion
Outlook for October – December 2014

The main factors that usually influence the seasonal climate outlook include: 1) El Nino and La Nina – which together comprise El Nino/Southern Oscillation or ENSO. Impacts of these events are summarized by separating 3-month observations from 3 or more decades into El Nino, Neutral, and La Nina sets, averaging each separately, and then computing anomalies. These are called “ENSO Composites”, which are used at times to subjectively modify the forecast. 2) Trends – Approximated by the OCN tool as the difference between the most recent 10-year mean of temperature or 15-year mean of precipitation for a given location and time of year and the 30-year climatological period (1981-2010). 3) The Madden-Julian Oscillation (MJO) – affects climate variability within seasons. 4) The North Atlantic Oscillation (NAO) and the Pacific – North American (PNA) patterns – which affect anomaly patterns especially during the cold seasons. These phenomena are considerably less predictable on a seasonal timescale than ENSO. 5) The Pacific Decadal Oscillation (PDO) – an ENSO-like pattern of climate variability affecting the Tropics and the north Pacific and North American regions, but which varies on a much longer timescale than ENSO. 6) Persistently dry or wet soils in the spring and summer and snow and ice cover anomalies in the winter. These factors tend to persist for long periods and act as a kind of memory in the climate system. 7) Statistical Forecast Tools – Canonical Correlation Analysis (CCA), Screening Multiple Linear Regression (SMLR), Constructed Analogue (CA) and Ensemble CCA (ECCA). 8) Dynamical forecast models – Including the NCEP Climate Forecast System (CFS). An experimental model forecast system, the North American Multi-Model Ensemble, comprised of several models and designated NMME, may also be used experimentally and subjectively until it is included into the consolidation. An international multi-model ensemble designated IMME is also available. 9) Consolidation (CON) – An objective, skill-weighted combination of the OCN, CCA, SMLR, ECCA, AND CFS forecasts is used as a first guess in preparing the forecast maps. This technique makes optimum use of the known skill of forecast tools.

Current atmospheric and oceanic observations are consistent with ENSO-neutral conditions with the likely transition to El Nino conditions in autumn and winter. A weak El Nino event is most probable, however there is a chance of either a moderate event or continued ENSO-neutral conditions into winter. A strong El Nino event is not likely to occur this year. Most dynamical and statistical model forecasts of east-central equatorial Pacific sea surface temperatures (SSTs) in the Nino 3.4 region (170W to 120W longitude and 5S to 5N latitude) indicate a weak El Nino (+0.5C to +0.9C) with peak anomalies in the early winter.

The temperature outlook for October-November-December (OND) 2014 indicates elevated probabilities of above-normal mean temperatures west of the Rocky Mountains, across the Northern U.S. from the Northern Rockies to the Northeast, in most areas east of the Mississippi, and for all of Alaska. Below-normal mean temperatures are more likely over areas of the Southwest including eastern Arizona, New Mexico and western Texas.

The OND 2014 precipitation outlook indicates enhanced probabilities of below-median precipitation over the Pacific Northwest including parts of Northern California and Nevada and over the Northern Rockies. Increased probabilities for above-median precipitation amounts are forecast from southern California eastward across the Southern Rockies and the Southern Plains, and along the Gulf and Southern Atlantic coasts up to North Carolina. The probabilities for above-median precipitation are also enhanced over southern Alaska.

In areas where the likelihoods of seasonal mean temperatures and seasonal accumulated precipitation amounts are similar to climatological probabilities, equal chances (EC) is indicated.

Basis and Summary of the Current Long-Lead Outlooks Note: For Graphical Displays of the Forecast Tools Discussed Below See: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing

Current Atmospheric and Oceanic Conditions

Atmospheric and oceanic conditions in the tropical Pacific are consistent with current ENSO-neutral conditions, while indicating the potential development of an El Nino. Observations for the second week of September show SST anomalies of +0.5C in the Nino 3.4 region, +0.7C in Nino 4, +0.4C in Nino 3, and +0.7C in Nino 1+2. SST anomalies increased in the east-central Pacific during the last month. The equatorial upper ocean heat content as indicated by the subsurface temperature anomalies to a depth of 300 meters has increased steadily during the last two months.

An area of suppressed convection represented by positive OLR anomalies was observed near the Date Line mostly north of the equator, and enhanced convection and negative OLR anomalies were observed over the Maritime Continent. Low-level (850-hPa) winds were near-average across most of the equatorial Pacific during the last month, and upper-level (200-hPa) easterly anomalies were observed over the east-central Pacific.

Persistent, strongly positive SST anomalies were observed over the North Pacific, along the Pacific Coast of North America, and westward across the subtropical Pacific Ocean. This SST pattern projects weakly onto a positive PDO. Positive SST anomalies were also observed along the Atlantic Coast and in the North Atlantic.

Prognostic Discussion of SST Forecasts

Most statistical and dynamical models continue to predict that an El Nino event will develop within autumn. Nino 3.4 anomalies are predicted to peak as a weak El Nino in early winter in many forecasts, with some model forecasts indicating a moderate or a strong event and some ensemble members remaining below +0.5C. The CFS Nino 3.4 ensemble members are similar to the multi-model ensemble forecasts of the NMME, currently indicating a peak anomaly of about +0.8C in winter of 2014/2015. Very few ensemble members predict a strong El Nino event. While few ENSO events have developed at this time of year, it is not unprecedented, and considered together, model forecasts and current observations continue to support the consensus ENSO forecast indicating a 60-65% chance of El Nino development in autumn or winter.

Positive North Pacific SST anomalies are forecast to persist through the boreal winter by many dynamical models including the NMME as an El Nino is forecast to develop. Positive SST anomalies along the Atlantic Coast are forecast to persist into winter. These sub-tropical and tropical SST anomalies are likely to impact the climate of North America in the next several seasons.

Prognostic Tools USed for U.S. Temperature and Precipitation Outlooks

The temperature and precipitation outlooks were influenced by potential impacts of an El Nino beginning with OND 2014 and continuing through MAM 2015. The seasonal outlooks are based primarily on dynamical model forecasts from the NMME and IMME, including the CFS, with adjustments made for potential model biases. The shift in probabilities related to positive Nino 3.4 anomalies in the range of 0.5C to 1.0C were considered. For outlooks from AMJ through OND 2015, decadal trends due to changes in the climate base state are the primary source of temperature and precipitation signals. The temperature forecasts of the NMME models appear generally to indicate a greater likelihood of above-normal temperatures across much of the U.S., while few areas of below-normal temperatures are indicated by the dynamical model forecasts.

Prognostic Discussion of Outlooks – OND 2014 to OND 2015

Temperature

The OND 2014 through MAM 2015 temperature outlooks indicate enhanced probabilities of above-normal temperatures for much of the west, particularly along the Pacific Coast. Temperature outlooks indicate enhanced probabilities of above-normal temperatures across the Northern U.S. through DJF 2014/2015, for parts of the Southeast through NDJ 2014/2015, and for parts of the Northeast throughout the year. These areas of enhanced probabilities for above normal temperatures are supported by most dynamical model forecasts, and are also consistent with impacts of a potential El Nino. Decadal temperature trends have enhanced the chances of above-normal temperatures in much of the Southwest, the Northeast, and the Southeast in the forecasts from MJJ through OND 2015. Enhanced probabilities of above-normal temperatures are forecast for Alaska through OND 2015. Through FMA 2015, this Alaska forecast is due in part to dynamical model forecasts for the persistence of above-normal North Pacific SSTs. The anomalous delay in Arctic Ocean and Bering Sea sea-ice cover for October and November in the last decade relative to the 1981-2010 climatology period results in greatly enhanced probabilities of above-normal temperatures for parts of Northern and Northwestern Alaska. An area of enhanced probabilities of below-normal temperatures is forecast for parts of the Southwest in OND 2014, extending across Texas into Southern Louisiana by DJF 2014/2015 and across parts of the Gulf Coast states in JFM and FMA 2015. The increased likelihood of below-normal temperatures continues into MAM 2015 for Southern New Mexico and Texas. This forecast is supported by the average impacts of positive Nino 3.4 SST anomalies during these seasons. Dynamical model forecasts for the same seasons indicate only weaker probabilities of above normal temperatures or near-normal temperatures, with few forecasts of below-normal. The outlooks were made by adjusting dynamical model forecasts by the most likely impacts of a potential warm ENSO event.

Precipitation

The OND 2014 through FMA 2015 precipitation outlooks indicate enhanced probabilities of above-median precipitation from parts of Southern California, across most of the Southwest and the Southern Plains, and along the Gulf and Southern Atlantic Coasts. Enhanced probabilities for below-median precipitation are indicated for the Pacific Northwest through FMA 2015, and from the Central Mississippi Valley into the Great Lakes region from NDJ 2014/2015 into FMA 2015. Probabilities of above-median precipitation are enhanced for Southern Alaska and parts of the Alaskan Panhandle through FMA 2015. These precipitation outlooks are supported by dynamical forecasts from the NMME and IMME, as well as by the potential impacts of an El Nino.

Probabilities of below-median precipitation are enhanced for parts of the Pacific Northwest in the JAS and ASO 2015 seasons due to decadal trends resulting from a changing climate.

Forecaster: Dan Collins

The Climatic normals are based on conditions between 1981 and 2010, following the World Meterological Organization convention of using the most recent 3 complete decades as the climatic reference period. The probability anomalies for temperature and precipitation based on these new normals better represent shorter term climatic anomalies than the forecasts based on older normals.

For a description of of the standard forecast tools – their skill- and the forecast format please see our web page at http:/www.cpc.ncep.noaa.gov/products/predictions/90day/disc.html (Use Lower Case Letters) Information on the formation of skill of the CAS forecasts may be found at: http://www.cpc.ncep.noaa.gov/soilmst/forecasts.html (use lowercase letters) Notes – These climate outlooks are intended for use prior to the start of their valid period. Within any given valid period observations and short and medium range forecasts should be consulted.

This set of outlooks will be superseded by the issuance of the new set next month on Oct 16 2014

1981-2010 base period means were implemented effective with the May 19, 2011 forecast release.

State Fair of Texas Opening Day Forecast

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It’s finally that time of year again where Big Tex is booming and the grease is flowing! While the traffic forecast may not look particularly pleasant for Friday the same can’t be said about the weather. A strong upper level storm system will be moving into the Western United States on Friday bringing chances for rain to drought-stricken parts of California. Meanwhile North Texas and the state as a whole be under the influence of an upper level ridge. A weak upper level low be in place across Southwest Texas which could result in a few showers and thunderstorms across the Hill Country and West Texas on Friday.

For the D/FW Metroplex and specifically Fair Park the weather forecast for Friday afternoon and evening looks like your typical late summer/early fall day. Temperatures will be in the upper 80s to perhaps around 90 degrees during the late afternoon before falling into the low to mid 80s by sunset and around 80 to 82 degrees by 10 PM. Besides a five percent chance for a passing shower during the afternoon/early evening hours sky conditions are expected to be clear to mostly sunny for the opening day of the State Fair of Texas.

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The above graphic is essentially a quick weather roundup for Dallas this weekend. Temperatures are expected to be near seasonal averages for this time of year this weekend. There will be a five to ten percent chance of passing shower/storm on Saturday and Sunday but again I think activity will remain west/southwest of the D/FW Metroplex. Winds will remain light and around 5 MPH through Sunday. Overall besides being a tad warm during the afternoon the weather is going to be a go for opening weekend at the fair!

Flood Warning for Hockley & Lubbock Counties till 9 PM

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A Flood Warning is now in effect until 9 PM for Hockley and Lubbock Counties in West Texas including Levelland, Lubbock, Idalou, Reese Center, and Wolfforth. This also includes the Texas Tech Campus. Very heavy rains on the order of nearly three inches an hour are falling from strong storms across the area. Typical flooding spots are likely already flooding with a bunch of the low-lying spots also expected to have problems.

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THE NATIONAL WEATHER SERVICE IN LUBBOCK HAS ISSUED A

* FLOOD WARNING FOR…
HOCKLEY COUNTY IN NORTHWEST TEXAS…
LUBBOCK COUNTY IN NORTHWEST TEXAS…

* UNTIL 900 PM CDT

* AT 659 PM CDT…SLOW-MOVING THUNDERSTORMS WITH TORRENTIAL
RAINFALL WERE CAUSING NUMEROUS INSTANCES OF FLOODING THROUGHOUT
LUBBOCK AND HOCKLEY COUNTIES. MANY FLOOD-PRONE ROADS AND STREETS
MAY BECOME IMPASSABLE IN THESE CONDITIONS. RAINFALL IN EXCESS OF
ONE INCH IN 20 MINUTES IS OCCURRING WITH THESE STORMS!

* RUNOFF FROM THIS EXCESSIVE RAINFALL WILL CAUSE FLOODING TO OCCUR.
SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE…LEVELLAND…
LUBBOCK…SLATON…IDALOU…RANSOM CANYON…REESE CENTER…TEXAS
TECH UNIV….WHITHARRAL…WOLFFORTH AND WOODROW.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

TOTAL RAINFALL AMOUNTS OF 2 TO 3 INCHES ARE POSSIBLE WITH THESE
STORMS. DO NOT DRIVE THROUGH WATERS OF UNKNOWN DEPTH!

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