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Plymouth State College: A climatology of heavy rainfall producing tropical cyclone remnants over the eastern United States

Final Report


Overall Tropical Cyclone Remnants Partners Project objectives:

Plymouth State College (PSC) Team:

We constructed the Event Database through study of the NOAA Daily Weather Map series and NOAA Storm Data publications. We also constructed the Precipitation Database by use of a number of data sources from the National Climatic Data Center (NCDC) and NOAA Forecast Systems Laboratory (FSL). We then generated a series of 24-hour rainfall charts for each of the events.

Lessons learned: We developed a local conversion script in order to convert the datasets into a more usable format.

National Weather Service (NWS) Team:

We constructed the upper air database utilizing data from CD-ROMs via NCDC and software from FSL. The U.S. surface data was constructed from CD-ROMs from NCDC. The needed Canadian data was not a part of the CD-ROM set and was obtained through the NCDC.

Lessons learned: 1) We developed a software package (C++) to convert the data into a more GEMPAK-friendly format. 2) The Canadian data format required additional scripting to convert into proper format and units for GEMPAK usage. 3) We discovered some bugs in the upper air retrieval software and worked with the FSL programmer to solve these problems by testing software fixes.


Most of the exchanges between the two teams were coordination calls and visits by the Project Leader (SR) to PSC. The Project Leader presented a seminar on the project, preliminary findings and progress to the PSC Student Chapter of the AMS in the spring of 2000. We have also produced a poster to be presented at the 2001 AMS Annual Meeting on the findings from one event, Hurricane Fran from 1996, and a poster at the 2000 National Weather Association (NWA) Meeting on the progress of the study. The manuscript from this project will be in the conference pre-prints.

We have also begun a manuscript detailing the project and our findings for future publication, likely in the National Weather Association Electronic Journal of Operational Meteorology. Our preliminary work has spurred interest from other NWS offices in the terrain study that is ongoing.


Reynolds, S.D., N.A. Stuart, D. Riley, J.P. Koermer, and M.P. Shuman, 2000: "A Climatology of Heavy Rainfall Producing Tropical Cyclone Remnants in the Eastern U.S." Poster presentation at 25th Annual National Weather Association Meeting, Gaithersburg, MD.

Shuman M.P., J.P. Koermer and S.D. Reynolds, 2001: Heavy Precipitation Events from Tropical Cyclone Remnants in the Eastern United States. Preprints, Amer. Meteor. Soc. 81st Annual Meeting, Albuquerque, NM, Amer. Meteor. Soc.


4.1 Benefits to the University resulting from the collaboration

Benefits: 1) Student researchers were exposed to some of the problems that operational forecasters deal with on a daily basis, as well as getting a first taste of conducting research with multiple research partners. 2) TCR events have been categorized for further in-depth study to determine excessive rainfall versus non-excessive rainfall events. Four events (Hurricane Fran, Tropical Storm Beryl, Hurricane Opal and Tropical Storm Jerry) were found to have significant precipitation enhancement from topographic effects, while 5 additional events appeared to have at least some enhancement. We will be using these categorizations in further study of these events.

An additional future benefit will be maps generated using the Halvorson technique to determine favored areas of topographic enhancement. This technique inputs a low-level wind velocity into an algorithm and with the use of high resolution digitized United States Geological Survey maps, a graphical output of these favored areas can be produced.

Problems encountered and subsequent resolution:

First student researcher did not work out well...did not put the effort forth that was necessary.
- Resolution: Original student was replaced during the spring of 2000.

Precipitation data was incomplete and in difficult format to convert into a usable format for study and graphics generation.
- Resolution #1: Programmer from PSC Computer Services was enlisted to assist in program and script generation to convert data into usable format.
- Resolution #2: New datasets were obtained from NCDC that were more complete and in more usable format.
- NWS team obtained Precipitation CD-ROM set from FSL/NCDC to complete missing datasets.
4.2 Benefits to the NWS office resulting thus far from the collaboration

Benefits: We have discovered a few useful track forecasting techniques and preferred areas of heavier rainfall. One particularly promising heavy rainfall potential technique is to utilize the 500-300 hPa average Omega field to help pinpoint deep layers of vertical motion which seem to coincide with the heaviest rainfall with these phenomena. A track forecasting technique that shows promise is to utilizing a low-level equivalent potential temperature field (i.e. 850 hPa) in concert with an upper level equivalent potential vorticity field (i.e. 200 hPa). We will be studying these techniques further to determine usefulness for all TCR events.

We are in the process of developing a web site that will contain event documentation as well as some of the generated datasets, including surface analyses, upper air plots, soundings, and observed rainfall. Terrain maps will be added at a future date. We will post the web address once the site has been established (goal is by March 2001).

Problems encountered and subsequent resolutions:

We would like to thank the COMET Outreach Program and all of their partners for making this project possible. We ultimately planned on doing much more than we could have expected to accomplish in a 12-month period, given that the NWS researchers were all operational meteorologists. This research is continuing, although our funding period is complete.