Real time Gravity wave page
Purpose:
initiated December 17, 2002  updated July 19, 2003
Clock requires Netscape

This page is updated daily between 18 and 19 UTC while tsc is updated hourly.

Whats new: added a plot of the lid strength index.

adding a real time simple Time to space conversion of surface observations. Observations include AWOS data taken at 20 minute intervals and also any special reports. The TSC analysis uses a time window of +/- 1 hour and the spatial analysis is constructed with a Barnes scheme. The grid spacing is computed with gempak and then doubled to remove noise since there is no temporal weighting.

Other links:
NCSU IGW analysis system
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email jimmyc symbol iastate.edu if you have used and like using this page, or if you want something added!

If the LAP (height) ~= Delta NBE then the assumption for balance is violated. This also applies to the Jacobian of the wind field.

At this early stage, it appears that the Lap (height) is correlated with the Delta NBE, but this is not a sufficient condition for gravity waves...I will include a plot of the Jacobian of the wind field since this is supposed to be the 2nd largest term...maybe that will be a good discriminator.


ETA Laplacian  of the geopotential height field (contoured) and Laplacian of the virtual temperature field (shaded)
The images below all follow the same 4 panel structure:
Top 2 panels left to right: current day 00 hr and 12 hr forecast
Bottom 2 panels left to right: 24 hr and 36 hr forecasts

Flow imbalance is calculated as the residual of the non-linear balance equation as shown by Zhang et al. (2002). Duct factor is calculated as in Koch and Siedlarz (1999).
Delta NBE = Lap (geo hght) + Beta * U - f *zeta - 2 * J(u,v)
                           10^-8          10^-10        1*10^-8       10^-8
Duct factor = Theta (800) - Theta (950) + Theta e (800) -Theta e (400)

500 hPa flow imbalance (contoured),500 J(u,v) (green contour), low level duct (shaded), and surface pressure (blue contour) is shown at 996, 1000, and 1004 hPa :

RUC211 duct factor (shaded) and surface pressure (contoured) for 12, 15 18, and 21 UTC of the current day:

Meteorograms and surface data:


Current Surface Potential Temperature gradient (shaded) and surface potential temperature (contoured) every 4 C

Lid Strength Index after Carlson (1980) : Lid strength in Celsius to the left, pressure difference between inversion level and the most unstable parcel pressure to the right. Blue is current radiosonde launch while black is 6 hours behind. Plotted also is the lid breech temperature (take the lid temperature down to the sfc dry adiabatically). LSI (black contour) and CIN (blue dashed)
 

CAPE/CIN/ DCAPE analysis from Emmanuel (1994?) MUCAPE (black) and DCAPE (Blue dashed)

Most probably CAPE and CIN (parcel with least CIN provided CAPE is greater than 250 j/kg)

  A Time to space conversion analysis of real time surface data (altimeter setting converted to pmsl ); Observation counts are shaded below 3. This is a measure of how well the barnes scheme handled the data (where extrapolation was necesary)AND how much data got into the scheme (It isn't always the schemes fault!) We have also added a 1km radar mosaic image to each plot. If you are interested in the technique and details of the real-time system, click here for my preprint at the 84th AMS annual meeting in Seattle.

Date YY/MM/DD TT Forecast Region  Gravity wave? How detected:
 02/12/18 00-12UTC IA, MN no surface wave detected (no) initial band , synoptic scale WV
02/12/21 12-00UTC OK, KA (tul) no surface wave detected (no) band Tulsa in clear air radar 18 UTC
02/12/24  00-12 UTC TX, LA, AR (deq,arg,dtn) wave at back of precip shield (dfw) LZK and dfw radar
02/12/25  12-12 UTC off long island coast ack possible wave (?) ack obs
02/12/31  18-00 UTC arkansas (arg) LA (shv,sgt) small amplitude back of precip (no) surface pressure spikes
03/02/01 23-?? UTC Hyannis, and ack,pvc, large amplitude, back edge of dissipating precip shield rapid p falls
03/02/16 16-00 UTC Wallops, Philly pressure pulse? Questionable pressure spike
03/02/22 12-00 UTC MKL, JAN possible wave, possible bust pressure spike
03/02/23 12-00 UTC tulsa ok no wave detected, lack duct not detected
03/03/26 00-12 TX corpus christie wavelike derecho event tied to convection
03/04/10 18-06 Virginia (FVX LKU OFP HNZ) solitary wave / convection? sfc p fall (unclear convective / wave)
03/10/17 22-06z
 kansas
 wavelike

A note on the meteorograms: When possible stations with 20 minute data will be shown. Although these meteorograms provide lots of information they do not contain enough. For example, on December 25, 2002 ACK had the sfc low go by. Just before this occurred the metar contained a remark, PRR (pressure rising rapidly) while in the midst of large hourly pressure falls. The next ob had the pressure decreased by 3 mb. This might be indicative of a gravity wave but it will be unknown until a large time series of 5 minute obs can be processed.

Generated by jimmyc@iastate.edu using GEMPAK and the 80 km ETA/RUC model grids.