Sanders

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TEAM 2 Sanders Li
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295K
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300K
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305K
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310K
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295K
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300K
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305K
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310K
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900mb
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850mb
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Map Synopsis The isentropic analysis clearly
depicts areas of rising and descending motion.
Rising motion is seen on the isentropic analysis
in the southern U.S. just to the north of the
Gulf of Mexico. Rising motion can also be seen
over northern New England. This is evident in the
GARP figures where the wind is crossing the
pressure surfaces from high pressure to low
pressure. The visible satellite image supports
this theory because there are clouds where rising
motion is occurring. The GARP figures also depict
areas of descending motion. This is occurring
where the wind is crossing the pressure surfaces
from low to high. In these areas of descending
motion the satellite image depicts no clouds.
Such a processes is occurring through the Mid
Mississippi River Valley and eastward through the
Ohio River Valley. The rising and descending
motion is seen best on the 300 K level although
it is visible on the levels just above and below
this. The GARP figures containing the RH fields
further support this notion. The RH is greatest
where rising motion is taking place and least
where descending motion is occurring. It is
interesting to note that the RH is greater on the
295K surface than at higher levels. This means
that the moisture is at lower levels. The 900mb
and 850mb maps further support this notion. WAA
is seen on the pressure map in the southern U.S.
just north of the Gulf of Mexico. This is the
same location that the isentropic maps depicted
rising motion. CAA is occurring on the pressure
maps over the regions were descending motion was
occurring on the isentropic maps. The level of
the moisture also corresponds between the
pressure and isentropic maps. There is more
moisture in the 900mb and 295k maps than there is
in the 850mb and 305k maps. This clearly
demonstrates that these two types of maps are
showing the same information but just in a
different manner. In the 900mb map there is a dry
area in the Gulf of Mexico, but on the 295K map
the same area has high RH. This is because the
isentropic map actually goes down in the altitude
as we go south, where there is more moisture than
above.
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Air is ascending from 1000mb to the 850mb
surface. This is a vertical distance of roughly
1.6km and occurs from SW IL to NE IL. Air is
descending from 420mb to 850mb over a vertical
distance of 5.5km over MT to SE SD. In the WAA
pattern air will continue to rise roughly to
550mb. In the CAA pattern air will fall until it
hits the surface. The isentropic analysis shows
that the RH in lower levels of the atmosphere is
quite low, between 40 and 60 at 900mb. This
means at the surface the RH will be even lower.
Even at high levels, above 600mb, the RH is just
above 80. Not much precipitation will be
produced by this system because any precipitation
in the upper levels will evaporate before it hits
the ground. We will probably see a lot of virga
on the radar as this system passes over the Great
Lakes.
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The wind on isentropic surface is close to
geostrophic wind, which means that even when air
is ascending or descending, there is not much
dynamic forcing in the synoptic scale, the
movement of the air parcel is largely in
geostrophic balance. The wind on 850mb is just
the wind at that pressure level. On the
isentropic map the wind follows the movement of
air parcel.