Earl Fiona Interaction
Posted by JAC on 9/2/2010, 6:58 am
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http://catalog.eol.ucar.edu/cgi-bin/predict/htmlwrap?file_url=/predict/report/weather/20100901/report.weather.201009011400.discussion.html

Earl and Fiona remain embedded in regions of high precipitable
water (PW) and appear to be partially interacting as the
distance between them decreases (image 2). A PW loop for the
last 36 h (not shown) reveals that an area of high PW values
(>55 mm) was stripped away from Fiona and pulled to the
northwest where it appears it could be ingested into the eastern
side of the Earl circulation and possibly "turbo-charging"
Earl (an "earl-y" bird special at the Café Vapor Maximus?).
Our interpretation of prior GFS runs that quickly pulled Fiona
north-northwestward, weakened it, and ingested it into the outer
circulation of Earl is that the model mistook the convection
associated with this northwestward moisture surge as a weakening
and dissipating Fiona whereas in reality Fiona slowed, moved
more westward, and retained its TC status. An infrared image for
1200 UTC 1 Sep shows convection around Earl and Fiona and the
convection to the northwest of Fiona that was previously
stripped away from Fiona (image 3).

Objective satellite techniques (ADT, AMSU) estimate that the
maximum surface winds in Fiona this morning to be approximately
50 kts. The broad circulation of high PW has been slightly
siphoned off by Earl and the moisture and convection is being
drawn into Earl may be the signature responsible for the GFS
capture of Fiona as noted above. Early morning convection has
subsided and cloud tops are gradually warming, with little new
convection and the vorticity and divergence aloft are diagonally
stacked with the strong upper level northeasterlies (image 4).
Although it appeared for a while that Fiona possessed a partial
eye signature in the Martinique radar, the eye appeared to open
up, and was likely only a rain structure that imitated an eye
(not shown) after satellite investigation.











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Earl Fiona Interaction - JAC, 9/2/2010, 6:58 am
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