Associated with differences in the precipitation patterns are differences in the genesis and subsequent evolution of the coastal cyclone. These are shown in the graphic below.
Note that the coastal low development occurs later and further east in the EtaX than in the operational Eta (24 hours, 12 UTC12/30/00), much closer to the HPC analysis. At 36 hours, the rapid deepening phase is complete, with the coastal storm again further north and east in the EtaX than in the operational Eta, consistent with its further north and east precipitation pattern, but still too slow.
Mean sea level pressure comparison, Eta vs. EtaX vs. HPC
verification
|
Model |
Eta |
EtaX |
Verification |
|
24 hrs. |
 |
 |
|
|
36 hrs. |
|
|
|
The 12 hour 500 hPa forecast heights and vorticity from the Eta and EtaX are
shown below. A visual inspection shows that both models, although cycled on
their own first guesses, are virtually identical. Because the dynamics forcing
cyclogenesis are indistinguishable prior to interaction with the coastal front,
we must look to other causes to explain the difference in location and timing
of the precipitation and storm development.
500 hPa heights and absolute vorticity comparison, Eta vs.
EtaX
|
Model |
Eta |
Etax |
 |
|
12 hrs. |
 |
 |
