PREDICT Ensemble Discussion
Posted by JAC on 8/20/2010, 9:49 am
Date(UTC): 2010/08/20 09:48
Author: Ryan Torn
Submitted at(UTC): 2010/08/20 10:12
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Current Conditions/Review of Yesterday's Forecast:
PGI27L about to make landfall farther north than the ensemble
was predicting even a day ago. System continues to appear weak
and have low OW values.  PGI30L still weak and difficult to
track in most of the ensemble members because the circulation is
small. PGI31L appears roughly in the correct place, but still
is characterized by few members with OW values greater than 2.
PGI33L has a small compact circulation at the initial time with
10% of members having OW values greater than 2.

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DAY 1 (Next 24 hours) Outlook:
PGI27L makes landfall over Mexico, moves over Yucatan.
Thereafter, the ensemble has a difficult time following this
system.  PGI30L is difficult to track during this time.  The OW
values in PGI31L increase to beyond 2 for all members by 24 h
and some members show this system going through genesis by the
end of the period.  Over the past several runs, the model has
been very aggressive in trying to develop an organized system
out of the trough north of the ITCZ, so I am cautious that this
process will happen as quickly as the model predicts.  PGI33L
does not change much during the past 24 h, but it is located
along the lateral boundaries of the domain, so I do not trust
the ensemble as much.

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DAY 2 (24 - 48 hours) Outlook:
PGI31L appears to become a full-fledged TD in almost all of the
ensemble members by 48 h and the system starts to propagate to
the west, reaching 35W by the end of the period.  Both the
circulation and thickness anomalies reach genesis criteria for
all members by 48 h.  PGI33L just south of Cape Verde with a
large amount of variability in position, but few members with OW
values greater than 2 by this time.

Similar to yesterday, the ensemble is trying to develop
something out of the convection to the NE of South America.
This is obviously a large model error that will be investigated
sometime soon and should be ignored.  It is encouraging that the
ensemble is less aggressive with developing this system compared
to yesterday since most members have OW values less than 2 by 48
h.

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Extended Outlook:
PGI31L reaches 40W by 72 h and appears to be a well-developed
tropical system.  PGI33L has a large amount of variability and
actually starts to rotate around PGI31L in many of the ensemble
members.  Very few members have OW values greater than 2 for
this system.  The spurious system shows up in the southern
Caribbean, but has few members with OW values greater than 2.
80
In this thread:
Data coming in on 95L - JAC, 8/20/2010, 8:14 am
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