Weekend Weather for the Northeast (Hans)
FIG. 1. 6 HR Total Precipitation at 2100 UTC on 01 Nov 2014 FIG. 2. 700mb Heights, RH and Omega at 1500 UTC on 01 Nov 2014
FIG. 3. 500mb Geo Abs Vort Adv (GEO) at 1500 UTC, same day FIG. 4. 850mb QG Temp Forcing (Laplacian) at 1500 UTC, same day FIG. 5. 900mb Frontogenesis/Frontolysis at 1500 UTC, same day
For the long term, the event of interest is of the weather impacting the northeast this Saturday, Nov. 1st by midday (1500-2100UTC). The 6 hour precip impacting the New York City (and the greater Northeast) area (See Figure 1) shows over an inch of rain by the afternoon hours. Looking at omega (See Figure 2), a local maximum of rising motion can be seen over NYC. Looking at the following three values of both the forcing terms of the QG omega as well as for frontogenesis, the forcing behind this rising motion can be better understood.
With a large trough off to the west of this area, there is VORT MAX (See Figure 3) to the southwest of New York City providing positive vorticity advection (PVA). The second QG forcing term shows (See Figure 4) positive horizontal temp advection impacting the NYC area.
As for frontogenesis, with westerly flow along the east side of this point of interest (just off the coast) traveling across the isotherms and northerly unobstructed flow to the west side of the point of interest, a strengthening of the temperature gradient can be seen (See Figure 5).
Together, these forcings are allowing for rising motion over the northeast and especially impacting the NYC area with well over an inch of rain for this upcoming Saturday.
by Hans Taylor