(meteorobs) Weather Prospects for the Transit of Venus - VIIi
Skywayinc at aol.com
Skywayinc at aol.com
Sun Jun 6 23:38:25 EDT 2004
The northern cold front that we've been concerned about for the past
week will apparently never get much farther south than the Canadian/New England
border; apparently it will push north as a warm front during Monday night . .
. widely scattered diurnal-type thunderstorms may pop-up during Monday
afternoon across northern New England and upstate New York.
I've just taken a gander at the new 00Z run of the ETA model.
As noted earlier . . . on the ETA, moisture in three levels of the
atmosphere are depicted. For 8 a.m. on Tuesday, the middle and upper levels (R2
and R3) of the atmosphere are still forecast to be quite dry across much of
the Northeast US, the Great Lakes States and Ohio Valley. However, the lowest
level -- the R1 -- is forecast to be very moist.
The R1 level depicts that part of the atmosphere between 1000 and 965
mbs . . . or roughly between sea level and 1,500-feet.
That is where most observers will likely be on Tuesday morning!
It has been my experience, that once the relative humidity in the R1
level exceeds 80%, that scuddy low-level cloudiness tends to be prevailent.
Obviously, the higher the humidity level, the thicker and more extensive is the
cloudiness. This type of cloudiness usually burns off/thins out as the Sun
climbs higher into the sky.
The good news is that the projected humidity values from the new ETA
run for the R1 layer have dropped by an average of 5 to 10% for many of the 20
cities that I had listed earlier. The biggest drops were in Dayton, Ohio
(15%) and Philadelphia (13%). This may be a signal that the low-level cloudiness,
may not be quite as thick or widespread as had been earlier suggested.
Below are the updated relative humidity values for the R1 level for 20
selected cities off of the latest 00Z run of ETA FOUS output. Next to each
value is the difference in percent compared to the previous ETA run of Sunday
afternoon. Once again, above the R1 level (above 1,500-feet) , the R2 and R3
levels have humidity values that are only about half as much!
Location RH for R1 level Difference from 12Z
Albany 80% -6
Burlington 78% +2
Boston 76% -4
Philadelphia 83% -13
Williamsport 92% -5
New York (La Guardia) 83% -9
Portland, ME. 80% -7
Caribou 79% -7
Bangor 83% -7
Concord 76% -2
Bufallo 74% +1
Pittsburgh 78% +2
Cleveland 69% -8
Dayton 79% -15
Indianapolis 88% -4
Charleston, WV 71% +1
Washington, DC 92% -5
Norfolk 95% +4
Chicago 81% +2
So, while low cloudiness is still a bit of an issue for many localities, it
might not be quite as bad as had earlier been thought.
I hope to issue one final outlook sometime late in the day on Monday
-- joe rao
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