Welcome to MetStat’s Extreme Precipitation Blog

Welcome to our blog on extreme precipitation.  We will do our best to update this as often as possible to highlight some of the recent extreme precipitation events across the United States.
Enjoy!

Southeast Montana storm of June 5-6, 2015

By | Extreme General Storm Precipitation, Extreme Local Storm Precipitation, MetStorm, Uncategorized | No Comments

Conditions on Friday night into the early morning hours on Saturday were prime for thunderstorms to develop in eastern Montana. A north-south oriented trough coupled with a surface stationary front instigated these thunderstorms, which ended up producing heavy rain, hail, and strong winds in southeastern Montana (see Weather Prediction Center’s surface analysis map below). The Storm Prediction Center issued a severe thunderstorm watch over the eastern half of the state from 4pm-midnight, with the southeast corner of the state in a flood warning.

ussatsfc2015060603
ww0259_overview_big_wou

 

ww0259_warnings

MetStorm™’s 24-hour analysis estimated that an astounding 7.72″ of rain fell just to the east of Broadus, Montana. While there were no rain gauges in the storm center, Weather Decision Technologies’ (WDT) Polarimetric Identification System (POLARIS) Quantitative Precipitation Estimate (QPE) from mosaicked and quality controlled radar data (used in MetStorm™) along with the National Weather Service’s estimated precipitation indicate this amount was valid. Over 7 inches of precipitation in 24-hours is an exceptional amount of rain to fall in such a short time. We were left asking ourselves how rare this event actually was.

P_allsites_201518_googlemap

MetStorm™’s Average Recurrence Interval (ARI) product can tell us just how uncommon this amount of precipitation was over this duration for this area. As of June 2015, MetStorm™’s maximum frequency is 1000-year, so if the maximum ARI for a storm is 1000.5 years, it indicates that the storm was over the 1000-year threshold MetStorm™ has. Below is the 24-hour ARI map for this storm. The storm cells to the east of Broadus and south of Powderville have over a 1000-year return period associated with them, meaning that they have less than 0.1% chance of occurring in any given year and that this storm was remarkably rare.

ARI_metstorm201518_24hr_max_ppt

Please note that the maps presented here are preliminary and will be updated when new data become available.  If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at media@metstat.com or through our contacts page at http://metstat.com/contact-us/.

Thanks for visiting our blog today!

-MetStat Team



Front Range, CO 3-hour Average Recurrence Interval for June 4-5, 2015

By | Extreme Local Storm Precipitation, MetStorm, Uncategorized | No Comments

The Front Range in Colorado has been very active this week with severe storms. In fact, there have been several severe thunderstorm, tornado, and flash flood watches and warnings issued since Wednesday of this week.

These storms were initiated from a surge of moisture and energy from remnants of Hurricane Andres meeting up with a shortwave trough and surface pressure system located over eastern Colorado (as seen in the WPC surface analysis below).

ussatsfc2015060503

The expedited moisture influx has resulted in very high rainfall rates and amounts for eastern Colorado and neighboring states. The mass curve plot below demonstrates just how intense this storm was, with nearly all of the precipitation falling within about 5-hours.

mass_curve_40.2362-105.1937_201517_Zone1

From a climatological standpoint, this event has been determined to be fairly rare. In the Front Range of Colorado alone, the maximum 3-hour Average Recurrence Interval (ARI) for yesterday’s rainfall was around 164 years (see MetStorm’s ARI map below). In frequency terms, a storm of this magnitude for this area and duration has only a 0.61% chance of happening in any given year.ARI_metstorm201517_3hr_max_ppt

With more rain and thunderstorms in the forecast, the flood threat continues through the weekend. Make sure to check back to see any updates and more of our near real-time precipitation analyses from MetStorm!

Please note that the data presented here is preliminary and will be updated with final information as all data is available.  If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at media@metstat.com or through our contacts page at http://metstat.com/contact-us/.

Thanks for visiting our blog!

-MetStat Team



6-hour ARI for Rainfall that Produced Flash Flooding in Austin, TX and Surrounding Communities, May 23-25, 2015

By | Extreme Local Storm Precipitation, MetStorm, Uncategorized | No Comments

The previous week has been incredibly active for the state of Texas, including widespread flooding in Austin, TX and the surrounding area over Memorial Day Weekend.

The surface analysis at 00Z on May 24th (7 pm CDT on May, 23) shows very cold (high) cloud tops across nearly the entire state, with several squall lines embedded within, ahead of an advancing cold front on the Texas-New Mexico border.

ussatsfc2015052400

As seen by the mass curve for the storm center, located to the west between Austin and San Antonio, TX, a majority of the precipitation fell in a very short period of time starting during the evening on Saturday, May 23rd. Nearly 10.5 inches of rain fell over a 6-hour period from 2200 UTC on 5/23 to 03 UTC on 5/24 (5pm to 10 pm CDT)

mass_curve_30.0953086504425-98.3480932539683_201513_Zone1

These high rainfall rates at the storm center are associated with a Maximum Average Recurrence Interval (ARI) of over 1000 years! This is to say that, statistically, an event of this magnitude has less than a 0.1% chance of occurring in any given year.  While total rainfall was not nearly as high over the metro areas of Austin and San Antonio, the city of Austin still has Max. ARI values nearing 50-years, which relates to a 2% chance of an event taking place any given year. It is important to note, however, that these ARI values are of the rainfall only and are not indicative of the recurrence interval with the associated flooding.

 

ARI_metstorm201513_6hr_max_ppt

Please note that the data presented here is preliminary and will be updated with final information as all data is available.  If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at info@metstat.com or through our contacts page at http://metstat.com/contact-us/.

Thanks for visiting our blog today! Come back soon for updates to these latest MetStorm™ analyses and for more posts to come!

-MetStat Team

(edited: 6/3/2015 )



Houston, TX 6-hour Average Recurrence Interval for May 25-26, 2015

By | Extreme General Storm Precipitation, MetStorm, Uncategorized | No Comments

Over the past week, Texas has been inundated with heavy rain which has lead to devastating flooding in dozens of counties. This blog post will focus on the heavy rain event that occurred on May 25-26, 2015 centered in Houston, Texas.

The surface analysis map produced by the Weather Prediction Center shows the complexity of weather features that went into this event. A combination of surface features including a west-to-east oriented trough, a squall line, and two couplets of surface high and low pressure centers all can be seen in Oklahoma and Eastern Texas in this 21Z surface analysis.

ussatsfc2015052521

 

As of 8AM May 29, 2015 all data including hourly and daily gauge, satellite, and radar data have been processed through MetStorm™. What is shown below is  only preliminary as we are still making adjustments via our quality control process.

The maximum 6-hour precipitation, shown below, depicts a 6-hour maximum at each grid point. This being said, each grid point can be displaying a different 6-hour window of precipitation for the 24-hour storm duration. For the Houston, Texas storm, MetStorm™ calculated the maximum 6-hour precipitation to be 12.43″.

metstorm201514_6hr_max_ppt_201514

The Average Recurrence Interval, or ARI, uses this maximum 6-hour precipitation grid to calculate the frequency of occurrence for each point at a 6-hour frequency. MetStorm™ uses frequency grids from NOAA atlas volumns as well as other published studies and matches the precipitation amount to the frequency of occurrence. It should also be noted that the ARI calculation is not restricted to a 6-hour duration; it can be calculated for 1-hour, 2-hours, 3-hours, and so on.

ARI_metstorm201514_6hr_max_ppt

The Houston, Texas 6-hour ARI revealed that the amount of rain that fell was climatologically significant, with an ARI of ~931 years. A common misconception about ARIs is that by saying this is a 931 year event, that it can only happen once in 931 years. This is untrue. From a climatological stand point it is simply the average number of years expected between events of this magnitude. An alternative way to understand ARIs is to think of them as a frequencies.

1/931=0.001 or 0.1%

So there is a 0.1% chance that in any given year there will be a rain event of this magnitude for this duration and location.

If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at info@metstat.com or through our contacts page at http://metstat.com/contact-us/.

Thanks for visiting our blog today! Come back soon for updates to these latest MetStorm™ analyses and for more posts to come!

-MetStat Team



Average Recurrence Interval for Hebron Nebraska storm of May 6-7, 2015

By | MetStorm, Uncategorized | No Comments

It has been a very active week with extreme weather in the Central US, providing ample opportunity to showcase more of MetStorm™’s unique analitics. Today’s post will highlight the record precipitation Wednesday through Thursday in Eastern Nebraska with the MetStorm™ Average Recurrence Interval Analytic. The record rainfall and significant rainfall rates caused widespread flooding through Eastern Nebraska, according to the Hastings, NE WFO. A narrow band of precipitation oriented southwest-to-northeast moved northeastward, causing the same areas to be overwhelmed with precipitation over a short amount of time. In addition to the heavy precipitation, this same event also produced several tornadoes.

Average Recurrence Interval (ARI) – also known as a return period – is a representation of precipitation amount per unit time as average number of years (climatologically) between equivalent events for a specific locations. It helps convey the rareness of rainfall and high impact storms. Here is the ARI map for the Hebron, Nebraska storm (updated 5/12/2015):

This storm has an impressive maximum ARI of over 1000 years for a 6-hour duration. MesoWest station Big Sandy Creek at Alexandria, NE, recorded 9.71″ in just 6-hours, an example of just how much rain needs to fall for this high of an ARI in this location to occur. This event is climatologically significant as this map suggests, which indicates it is a rare phenomenon for over 9 inches of rain to fall over just 6 hours in this location.

If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at info@metstat.com or through our contacts page at http://metstat.com/contact-us/.

Thanks for visiting our blog, we hope you enjoyed today’s post! Come back soon for updates to these latest MetStorm™ analyses and for more posts to come!

-MetStat Team



Depth-Area-Duration Curves for Oklahoma City Metropolitan Area – Storm May 5-7, 2015

By | MetStorm, Uncategorized | No Comments

In this post we will give a first look at MetStorm’s™ Depth-Area-Duration (DAD) product with the recent flooding event that occurred in the Oklahoma City Metropolitan Area (updated 5/14/2014).

Heavy rains began across the state of Oklahoma on May 5 and the Storm Prediction Center had indicated Oklahoma City, OK was in an area of marginal risk for convective activity on May 6. As forecast, the OKC Metro Area experienced several severe thunderstorms, some associated with tornadoes and record-breaking precipitation.  A CoCoRaHS COOP station at Oklahoma City received 9.07 inches of rain between May 5-7, to the southwest, Tuttle, OK received 9.88 inches during the same time.

SPC Day 2 – Convective Outlook Valid 06/1200z to 07/1200z

MetStorm_20159_DAD_Curves_Zone_1

 

MetStorm’s™ Depth-Area-Duration analysis shows that over the total 48-hour time period, an average of 3.83 inches of rain fell over an 10,000 square mile area – over 16 times the size of just Oklahoma City, OK. At a single point, 4.22 inches fell in only one hour and 13.52 inches over the 48-hour time period. These point values are not station verified, but rather a result of the radar-estimated quantitative precipitation in an area with sparse rain-gauge coverage.

Depth-area-duration (DAD) plots provide a powerful, objective, easy-to-understand three-dimensional (magnitude, area size, and duration) perspective of storm precipitation.  Historically, storm DAD analyses have been computed to aid in the computation of probable maximum precipitation (PMP) estimates that influence the design and operation of structures such as dams, nuclear power plants, flood retaining structures, and levees.  DADs require accurate, high-resolution precipitation depths in time and space, particularly in areas with the heaviest precipitation.  Unlike point precipitation observations, a DAD provides the areal magnitude of a storms precipitation.  A DAD makes it possible to compare the areal size, magnitude and duration of a precipitation event to other historic storm DAD’s and DAD threshold’s for flooding or other consequences.  For over a century, DADs have been used to  characterize extreme precipitation associated with storm events; MetStorm will continue this legacy as new extreme events occur, thereby adding to an ever growing database of extreme precipitation events to support better, safer and more-optimized infrastructure designs.

If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at info@metstat.com or through our contacts page at http://metstat.com/contact-us/.

Thanks for visiting our blog, we hope you enjoyed today’s post! Come back soon for updates to these latest MetStorm™ analyses and for more posts to come!

-MetStat Team



Storm Total Map for Crescent City California Storm of March 22-25, 2015

By | MetStorm, Uncategorized | No Comments

A very useful tool produced by MetStorm™ is the total storm map. This map uses the latest and greatest data from Weather Decision Technologies POLARIS quantitative precipitation estimates (PQPE), real-time and ghcn daily precipitation gauges, and satellite data from NOAA STAR’s Hydro-estimator. It seamlessly blends together these three sources to create a cohesive product which is an ideal solution for viewing precipitation.

In today’s post we will give an example of MetStorm’s™ total storm map product using a storm that occurred in Crescent City, California on March 22-25 2015. 

This storm was a result of a weak atmospheric river leading to a series of pacific low pressure systems moving through the area, supplying significant moisture and lift for the storms, as seen below in the US surface analysis and satellite composite maps.

sfc_analysis_20150323 sfc_analysis_20150324

The Eureka National Weather Service office posted a station list detailing the 72-hour storm total precipitation for various stations in the area. This list of stations can be found here. The highest recorded precipitation according to this page was 4.40″ in Gasquet Ranger Station with a close second of 4.13″ at Camp Six Raws Near Gasquet.

One of the many advantages of MetStorm™ is its ability to interpolate between stations using the PQPE and satellite data, allowing for additional rainfall amounts to be estimated. This is especially beneficial for areas in complex terrain. For the Crescent City, California case, MetStorm™ estimated up to 6″ of rainfall over the area for the 72 hour period (shown below). This area of the country is fairly mountainous, and it is fair to assume that there are not enough rain gauges to sample various elevations; so it’s realistic that MetStorm™ estimated higher amounts of rainfall for this area.

P_allsites_20153_googlemap

The applications for this map can be for media inquiries, situational awareness, and emergency management; just to name a few. The integration of the high quality data sources is key in its success at analyzing precipitation in a variety of situations, whether it be in the mountains, plains, or anywhere in between MetStorm™ can handle it all.

If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at info@metstat.com or through our contacts page at http://metstat.com/contact-us/.

We hope you enjoyed today’s blog post! Come back soon for more exciting information and examples of MetStorm™!

-MetStat Team



Mass curve plot for the Louisville, KY storm of April 2-4, 2015

By | MetStorm, Uncategorized | No Comments

With higher intensity storms from the changing seasons, there are more storms to process through MetStorm™. One of the more recent storms to occur in Louisville, KY provides a great opportunity to showcase one of the analytics MetStorm™ generates – the mass curve plot.

But first, the Louisville, Kentucky storm set up and background.

This storm was initiated by a passing cold front which extended from eastern Canada through the Central Plains. As it was moving through the Ohio River Valley the cold front transitioned to a stationary front leading to training thunderstorms and widespread flooding. The following surface analysis map is from the Weather Prediction Center’s Archive page. One feature in particular to point out is the squall line analyzed over Kentucky, which happens to coincide with where the highest precipitation totals were measured.

sat-sfc

It should also be noted that this storm set new records for Louisville and Lexington. The previous record for maximum daily precipitation was 4.08″ recorded in 1970 at Louisville, KY and 3.21 recorded in 1908 at Lexington, KY. The new maximum daily precipitation is now 5.64″ and 5.17″ for Louisville and Lexington, respectively, recorded on April 3, 2015.

And now, the moment you have been waiting for – MetStorm’s™ mass curve plot!

mass_curve_38.12375-85.32375_20154_Zone1

This plot represents both the incremental and accumulated rainfall for the storm’s maximum grid cell. The timing of the storm is determined from a combination of hourly station data from a plethora of sources and radar estimated rainfall from Weather Decision Technologies Polarimetric Radar Identification System Quantitative Precipitation Estimates, or POLARIS QPE (These sources and others will be discussed in future blog posts!). The left y-axis displays the incremental rainfall amounts, where the right y-axis displays the accumulated rainfall amounts. Both variables are displayed in inches (inner scale) and millimeters (outer scale). The x-axis shows the precipitation amounts through time in UTC. Currently the time scale for this plot is hourly; however, in the near future this will be changing to a 5-minute time scale resolution.

In the recent Louisville, KY storm, it is evident by the mass curve that there were two distinct periods of heavy precipitation. The first pulse of precipitation of just over 2 inches occurred around 6Z on the 3rd, where the second pulse of just over 1.5 inches occurred around 21Z on the 3rd.

This plot is a useful tool that shows in multiple ways the timing of precipitation for storms. The applications for this product vary widely from emergency management to hydrologic modeling validation and calibration to flood responses, forensic cases, insurance claims, situational awareness, and many more.

If you are interested in this product, or any other product from our MetStorm™ Precipitation Analysis tool, please contact us at info@metstat.com or through our contacts page at http://metstat.com/contact-us/

We hope you enjoyed today’s blog post! Come back soon for more exciting information and examples of MetStorm™!

-MetStat Team



About the MetStorm™ Precipitation Analytics

By | MetStorm, Uncategorized | No Comments

Today’s blog will focus on the capabilities that MetStorm™ and what it has to offer.

To reiterate from our previous “Welcome!” blog post, MetStorm™ offers unique storm precipitation analytics which include a depth-area-duration (DAD) table and plot, average recurrence interval map, and mass curve table/plot for the storms’ center.

Here are general descriptions for each of these analytics:

  • Depth-Area-Duration (DAD) table and plot
    • DADs represent various areal rainfall depths for a given duration from a storm event at different area sizes
    • DAD domains require uniform topography and precipitation timing to produce accurate and realistic results
    • DADs are commonly used in frequency analyses and Probable Maximum Precipitation (PMP) analyses for various applications including hydrologic modeling, stochastic modeling, and other engineering design applications
  • Average Recurrence Interval (ARI) map
    • Also known as and referred to as return period
    • ARIs represent a current precipitation event (amount per unit time) as the average number of years (climatologically) between equivalent events for a specific location (see an article on Forecasting ARI maps co-authored by our very own Tye Parzybok for more information about ARIs)
    • Generally speaking, ARIs help convey the rareness of rainfall and high impact storms
  • Mass Curve table and plot
    • A 2-D area plot displaying the hourly rainfall amounts as a function of time at the storm’s maximum grid cell
    • Also includes a summation line plot overlay to show enhanced timing of the storm and when the precipitation tappers off
  • Station Catalog
    • A complete listing of the rain gauge data used and their metadata (latitude, longitude, elevation, etc.)

A subset of these analytics will be available for free here on our blog for significant storms, the total MetStorm™ package can be available upon request.

If you have more questions/comments, feel free to send us an email at info@metstat.com or send a message through our contacts page! As always we hope you enjoyed our blog post today, come back soon!

-MetStat team



Welcome! Intro to MetStorm™

By | MetStorm, Uncategorized | No Comments

Welcome to our blog on extreme precipitation.  Our focus with this blog is to highlight important precipitation events that have either significant Average Recurrence Intervals (ARIs) or have significant flooding and showcase our MetStorm™ product and its capabilities.

MetStorm™ is a near real-time precipitation analysis tool that uses innovative algorithms to integrate real-time precipitation gauge, radar-estimated precipitation, and satellite data into a set of analytics that describe storms.

These unique storm precipitation analytics include a depth-area-duration (DAD) table and plot, average recurrence interval map, and mass curve table/plot for the storms’ center. A free subset of these analytics are available here on the blog for significant events, and more detailed and expansive set can be available upon request.

To learn more about MetStorm™, please visit our website at http://metstat.com/solutions/metstorm/

We hope you enjoy our blog, come back soon!

-MetStat Team