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  • 1.  What weather websites offer recent rain event's Storm Frequency?

    Posted 07-20-2016 11:32 AM


    Does anyone know of a weather related website that performs frequency analysis on recent rain events?  Particularly for rain events in South Mississippi.  Thanks


    Matthew W. Hosey, EI | Engineering Intern
    Waggoner Engineering, Inc. | 2510 14th Street, Suite 1200 | Gulfport, MS 39501
    office: 228-206-1115 | mobile: 228-697-0908 | fax: | Matthew.Hosey@...



  • 2.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-21-2016 09:57 AM

    go to NOAA Atlas 14.  If you use of the data is for design or something that may require governmental approval then you might need to check with your local government or state DEQ to ensure they are accepting atlas 14 for return frequencies.  They may only accept TP40 or some other return frequency analysis.

    Good luck!

    NOAA Altas 14

    Jennifer Morreale P.E., CFM, M.ASCE
    Project Engineer
    Hubbell Roth & Clark
    Detroit MI
    (248) 454-6828

  • 3.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-22-2016 03:05 PM

    Thanks Everyone,

    So far it looks like the NOAA Atlas 14 site is the winner.  This is exactly what I was looking for, and couldn't find on my own without spending a bunch of time (than NOAA site can be a bit overwhelming).  Sorry I didn't respond yesterday, but I was out in the field all day yesterday. 


    I should have given more background about my project and why I'm needing this info.  I'm doing a conceptual drainage plan for one or our coastal counties in Mississippi.  Basically the county has given us about 70 problem sites (about half are drainage related and the other half are dredging related) and we have to analyze each site, propose a solution and cost estimate for each.  The most common problem we are finding is old culverts that are undersized.  So obviously I'm doing hydraulic analysis on each one to determine what size it should be.  I thought it would be a good idea to support the hydraulic analysis with some recent storm info, but discovered that it is quite laborious to do this accurately.  That's where my forum question comes into play.  I was certain there must be a way to get a rough estimate, but was unsuccessful in finding the right sites to help with this. 


    Again thank you all so much.  It's great having this forum at our expense.  I've got some more questions I'll be posting soon that are more personal research topics I want to know more about than project related questions.  Hope everyone has a great weekend.


    Matthew W. Hosey, EI | Engineering Intern
    Waggoner Engineering, Inc. | 2510 14th Street, Suite 1200 | Gulfport, MS 39501
    office: 228-206-1115 | mobile: 228-697-0908 | fax: | Matthew.Hosey@...



  • 4.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-24-2016 06:17 PM
    Edited by Jennifer Morreale 07-24-2016 10:54 PM

    It looks like your original post and subsequent post are somewhat completely different (in concept). If you want actual rainfall data then you can go to the following website:


    this website will allow you to query NOAA rain gauges closest to your site. The available sites might be too far from your study area and/or data not recent enough. Typically, local government or county government have a more robust rain gauge network where you could request data from them. If possible, try to obtain the lowest increment of rain they record (like 5-minute intervals). Once you have that data you can sum each duration interval to determine the max 5-minute, max 10-minute, max 15-minute…(and so on to max 24-hours or max 10-days…even up to max 60-days) in order to determine your largest return frequency compared against the first link that I sent. And when I say “sum each duration”…if, for example, you have 5-minute data, then you would have 12 possible values for a peak 1-hour increment as you would sum from 0:00 to 0:55, then 0:05 to 1:00, then from 0:10 to 1:05 and so on to give max peak hour. You would need to do this for every duration interval to determine max. This would allow you to say that the rain event on a particular date was an X-year return frequency.

    Having said all of that…it sounds like you might need to develop your hydrology first though. If your culverts are in a FEMA designated floodplain, then you can look up the area in a Flood Insurance Study (FIS) to get flow rates in 10-year, 50-year, 100-year and 500-year intervals. (also, if in fema floodplain then you will likely have to submit a LOMR if changing the floodplain).  If you are not in a FEMA floodplain then you have to determine areas tributary to each culvert and then use something like TR55 to develop your peak Q for your design event (check with your state DEQ though because, for example, in Michigan we fill out a drainage request online and the MDEQ provides us the discharge rates from 2-year to 500-year return frequencies). As for your design event…that will depend on your state and local government…might be 100-year.

    I could be wrong, but I think you’d only want recent rainfall data if you had a dynamic model of your drainage system with stream gauges and you wanted to calibrate your model using rainfall data compared to stream gauge data (or some metered data). With a calibrated model you would simulate the design event (like 100-year, 24-hour) and see how your system performs.  I’m not sure what else you would do with recent rainfall data in relation to the redesign of your culverts.  Actually, the only other use would be to prove that the recent rain events that caused flooding were beyond the design event.

    Hope this helps.

    Jennifer Morreale P.E., CFM, M.ASCE
    Project Engineer
    Hubbell, Roth & Clark
    Detroit MI
    (248) 454-6828

  • 5.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-21-2016 02:19 PM








    Trevor W. Timberlake, PE, CFM

    Engineer Supervisor - Dam Safety & Floodplain Management

    Arkansas Natural Resources Commission

    101 E. Capitol Ave., Suite 350

    Little Rock, AR 72201

    Office: (501) 682-3981   Fax:  (501) 682-3991


  • 6.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-21-2016 04:56 PM
    Jennifer has referenced NOAA Atlas 14 and Trevor refers to the Metstat web site. Metstat does it's analysis on a fairly routine basis. NOAA's Hydrometeorological Data Center does this type of analysis on an ad hoc basis for really big cases. HDSC are the same folk who publish NA14. They publish their studies on the page AEP Analysis for Selected Storm Events. I'd like to make a couple of points relevant to this type of analysis:
    1. Both Metstat and NOAA's HDSC use NA14 as the source for rainfall frequency info for these analyses. HDSC's analyses aren't done immediately, but with about 1-3 days of the event to ensure that the rainfall information is based on optimal estimation using radar, point gauges and sometimes satellite information.
    2. There really isn't such a thing as a "Storm Frequency". NA14 and other documents of it's type present depth and intensity thresholds for various frequencies and durations at point locations. The duration term is the contiguous time period over which rainfall is accumulated. The accumulation may be for part of a storm, for one or more storms, or for n storms plus parts of storms at the beginning and/or end of the duration (accumulation) period. The rainfall frequency is for a specific point which doesn't move, unlike a storm which does move. Probable Maximum Precip computations used in estimating Probable Maximum Floods do compute accumulations for storms, They account for the movement of the storm and the variable area of the storm.)
    3. It may be important to know the frequency of say: the most intense 6 hour or 24 hour or 2 day duration during the event, and these may all give different frequencies. For example, the Colorado event of September 9-16, 2013 had rainfall frequencies more rare than 1 in 1,000 AEP for durations of 7 days, whereas worst case 6 hour events had AEPs of only about 1 in 50. See Figure 1 of the document. So you really need to be quite specific about what you'll use the information for when asking this type of question.
    4. Note that TP40 is obsolete for all areas except Texas and HDSC is working on a NA14 update for that area. Some states have not yet recognized that TP40 is obsolete.

    Geoff Bonnin

  • 7.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-21-2016 07:55 PM

    I dont know of any sites that specifically give automatic analysis of a storms frequency, however, if you know the rainfall amount and the duration of the storm, you can do your own analysis by grabbing the precipitations frequency estimates (also known as the Intensity-Duration-Frequency relations) from the NOAA Atlas 14 web site:  http://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=pa

    All the best.

    Bob Holmes

    Robert R. Holmes, PhD, P.E.,  D. WRE,F. EWRI, F. ASCE  || U.S. Geological Survey 
    National Flood Hazard Coordinator                         || http://water.usgs.gov/floods/
    bholmes@..." target="_blank">bholmes@...              || 573-308-3581           || https://profile.usgs.gov/bholmes      

  • 8.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-22-2016 06:03 AM

    I am not aware of any sites that give you the frequency of precipitation event on the fly.

    What I do is determine the precip frequency for any location using this site - this should give you the statistics of rainfall over any precip duration. I set this to MS - so hope it comes through.  Just center your cursor over the centroid of your watershed.

    PFDS: Contiguous US

    Noaa remove preview
    PFDS: Contiguous US
    View this on Noaa >

    I then go to the AHPS cite and look for the precipitation rain event that you are interested.

    AHPS Precipitation Analysis

    Weather remove preview
    AHPS Precipitation Analysis
    National Weather Service Advanced Hydrologic Prediction Service (AHPS)
    View this on Weather >

    Go to the location your are interested in, then go to the bottom to specify the date you are interested in, and read the precipitation color bar on the to determine the precip over the 24 hr period.

    Here is a screen shot of the precip on March 19 over New Orleans, showing about 5 inches for that day. From the PFDS site, find the 24 hour duration row, go right until you see the column that has 5 inches.  Then go up the column to find the frequency in years.  Good for only 24 hr duration storms - but better that waiting!  Good luck

    David Williams Ph.D., P.E., D.WRE, HG, F.EWRI, F.ASCE
    David T. Williams and Assoc.
    Fort Collins CO

  • 9.  RE: What weather websites offer recent rain event's Storm Frequency?

    Posted 07-25-2016 03:40 PM

    As Geoff Bonnin and Trevor Timberlake mentioned, we (MetStat) are continuously translating near real-time 1-, 2-, 3-, 6- and 24-hour gauge-adjusted radar-estimated precipitation into its equivalent Average Recurrence Interval (ARI).  We base our ARI results off the NWS MPE as well as QPE derived from MetStormLIVE (a high-resolution gauge-adjusted Dual-Pol radar-estimated precipitation product); these results can be seen here. We have an extensive archive, so if you need an ARI analysis for a specific duration/location, let me know. Similar to HDSC, we highlight extreme storms in our blog that often feature ARI analyses/maps.

    We also create 6- and 24-hour ARI forecast maps out 5 days based on the WRF model four times a day. These are premium products, but are excellent for situational awareness of future extreme events. Below is a graphic of the maximum 6-hour ARI over the next 5 days.

    Hope this helps.  Please reach out if you have any further questions.

    (David -- we're practically neighbors in Fort Collins -- let's get together sometime!)

    Tye Parzybok A.M.ASCE
    President/CEO & Chief Meteorologist
    Metstat, Inc.
    Fort Collins CO