Regional Specialized Meteorological Center (RSMC) Products

The following are RSMC products that were created during a routine monthly test between RSMC Washington and RSMC Montreal. (For example RSMC Washington products click here). These products would have been distributed to the IAEA, the WMO, and the designated recipients had this been a real emergency. The maps on the left are from RSMC Washington, while those on the right are from RSMC Montreal.

JOINT STATEMENT

The following is a Joint Statement between RSMC Washington and RSMC Montreal that would have been provided a few hours after the maps were issued to help the recipient interpret model differences.

JOINT STATEMENT
RSMC MONTREAL AND RSMC WASHINGTON EXERCISE
November 5, 1996, 1800 UTC
TEST RESULTS COMPARISON

SITUATION
A possible radiological release into the environment may have started around 1000 UTC at the Pickering, Ontario nuclear plant (43.82N, 79.07W) on November 5, 1996. The event has not been confirmed by the IAEA and no additional information is available at the moment.

The dispersion models were executed by RSMC Montreal and RSMC Washington using the standard default scenario with a release time of 1000 UTC, November 5 1996. Both RSMCs used the 0000 UTC data to run their models.

METEOROLOGICAL SITUATION
The primary amplification of a trough during the forecast period occurs over the U.S. Great Plains. This allows southerly winds at all levels to develop with time. However, initially a very strong short wave shows up at all tropospheric levels and continues into the stratosphere. This wave supports weak overrunning precipitation near the release site. The wave is also interacting with a stationary front that is stalled east-west along and near 44N, between two regions of surface high pressure. The AVN model forecasts precipitation over the release location between 0600 and 1200 UTC November 5. GOES-8 IR imagery shows the brightest cloud tops near the release location and radar echoes are indicated over the region at this time. Surface observations at Muskoka, Ontario (44.58N/79.18W) were not available until 1100 UTC November 5, when rain was indicated and was continuing; Toronto, to the south, had not indicated any rain. This event is complicated by precipitation in the region.

TRAJECTORIES
Corresponding trajectories from RSMC Montreal and RSMC Washington are similar. Both 3000m trajectories move in a general east-northeast direction, however the Washington trajectory is slightly north of the Montreal trajectory. The 1500m trajectories arrive over the coast of eastern Newfoundland at 00 UTC on November 8, however the Washington trajectory took a much further northward path to arrive at this location. Finally, the 500m trajectories are very similar throughout the forecast period. In both models, there is no indication of large ascending or descending motion of the air parcels.

Trajectories are consistent with the strong shortwave moving rapidly east- northeastward and escaping the developing southerly winds as the upstream trough of low pressure develops out through the U.S. Great Plains. This is true, except for the lowest levels, as indicated by the 950 hPa trajectory, which becomes involved with the developing southerly winds.

It should be noted that one set of initial trajectories should only be used to evaluate the general flow field calculation of the meteorological model and not the computed exposure patterns since the exposure calculation is composed of many trajectories representing the release over the entire 6 hour period as well as the pollutant's subsequent dispersion.

EXPOSURE/DEPOSITION
RSMC Montreal used its Global model to run its atmospheric transport and dispersion model while RSMC Washington used its AVN model. Both models were run with the 0000 UTC data. Both models cover the 72 hour period ending 0000 UTC November 8. Note that the first 24 hour exposure map covers the period from 0000 UTC November 5 through 0000 UTC November 6 although the release began at 1000 UTC November 5.

EXPOSURE: Results from both RSMCs again show very similar patterns of exposure out to 48 hours (0000 UTC November 7), however some small differences in exposure patterns are noted during the final 24 hour period. The corridor of maximum exposure extends north of Toronto during the first 48 hour period, reaching the eastern shore of James Bay by 0000 UTC November 7; from 48 to 72 hours both models indicate the exposure pattern will extend east- northeast covering most of northern Quebec and Newfoundland. Maximum values (10-9 Unit s/m-3) are just to the north of the source at 0000 UTC November 6 due to relatively light wind speeds in the vicinity of the release; Washington values are about one-half those of Montreal. For the second 24 hour period the position of the maximum value (10-10) is forecast to be about 200 km north of Toronto in both models. The maximum values predicted by both models are about the same.

In the last 24 hour period (0000 UTC November 7 to 0000 UTC November 8), the exposure pattern is forecast to extend generally from the southern end of Hudson Bay east to the Atlantic coast. The RSMC Montreal model indicates some transport to the south over the Gulf of St. Lawrence, extending southward over the Atlantic Ocean to 40N. The RSMC Washington model indicates that some low exposure values are possible in an area to the west of Hudson Bay. The position of the maximum value in both models is forecast to be north of Toronto at about 53N (east of James Bay). However, the maximum value predicted by RSMC Washington is an order of magnitude less (10-12) than predicted by Montreal model (10-11).

GROUND LEVEL DEPOSITION: The total deposition pattern in both models corresponds well with the exposure patterns discussed above. Maximum values are forecast to be just to the north of the Toronto area and are the same in both models (10-11). Note that , in addition, RSMC Montreal forecasts an area of deposition to the east-southeast of Toronto extending across most of New England and Nova Scotia and to 35N, 50W.

SUMMARY
Both models suggest that the areas north of the source will be most affected in the first 48 hours; the affected area expands to cover essentially all of Quebec and Newfoundland in the following 24 hours. The RSMC Montreal also indicates that New England and Nova Scotia may also be affected by deposition. Due to forecast light winds and precipitation in the vicinity of the release and the forecast of little movement of material during the first 24 hour period, interests should monitor the weather for possible changes which could alter the exposure and deposition patterns. Until sufficient monitoring information becomes available, both meteorological and radiological, it is suggested that any actions follow the most conservative model predictions.

END