HMT Forecast Sun 2/17/2008 2000UTC
West coast ridge remains with us for the next few days. PACJET is set up
westward of 145W and progressing to the east. The low we are looking forward
to presently near 165E is rotating around a more stationary low over the
The progression of short waves is similar to what we saw yesterday. The first
wave coming in remains dry on Tuesday as it undercuts the ridge.
The next wave is on track for Wed Feb 20 with about .25" in the GFS between
00Z and 18Z.
The atmospheric river we've been looking at is still there with important
details changing from day to day. The latest GFS run has the best setup at
18Z Wed reaching from 135W all the way to the Philippines. However it breaks
up as pieces of it reach the CA coast with the ensuing short waves. We get
25-30mm of IWV impinging on the SRN half of CA at 12Z Fri.
The main low we've been tracking looks a bit weaker at 12Z Thu compared with
yesterday's run as it rotates into NW BC. We still have the PACJET with more
of a spread out appearance along the W coast of North America. We then have
short waves reaching NRN CA every 24-36 hours embedded within the jet. The
first one now looks to be between 03Z Thu and 02Z Fri with just about .45" in
the GFS. The ECMWF looks about 6 hours slower with this wave.
There is a clearer demarcation between the two short waves on Thu/Fri compared
with yesterday's GFS run. The later wave looks to be the stronger of the
two coming ashore between 15Z Fri and 08Z Sat with about .8" of precip. So
the sum of the two waves comes out slightly less than in yesterday's run.
Since the flow is fairly zonal the temperatures remain moderate being about
0C at 850mb dropping down to -2C at the end. The ECMWF looks a bit faster
with this second wave.
Next in the progression of waves is from 03Z Sun to 06Z Monday with about
1.35" and is more than in yesterday's run. What remains of the atmospheric
river though is down by LA at 12Z Sun. This system digs more than the Thu/Fri
ones and brings down more cold air with 850mb temps dropping from 0C down
Overall we will want to maintain watching the details of the short waves
and atmospheric river with an IOP possibly commencing between Thu and Sun.