Scientific Forecaster Discussion
Southeast Alaska forecast discussion
National Weather Service Juneau Alaska
613 am akdt Tuesday Apr 28 2015
Short term...hurricane force low due west of Prince of Wales
Island early this morning has resulted in High Wind Warning for
zones 27 and 28 through early this afternoon. As expected, winds
increased very rapidly and this was observed upstream in Canadian
observations from haida gwaii, hecate Strait, and coastal British
Columbia. Observations from Annette early on during this event
indicating wind gusts in excess of 70 miles per hour. Wound up issuing a
hurricane force wind warning for Clarence Strait as well.
Confirmed report of water spouts in hecate Strait and Prince
Rupert sound. Observed wind speeds are being augmented by storm
motion to the north of at least 35 kts. Suspect winds over zone 27
will be a little lower than what is being observed in zone 28 due
to the proximity of the cyclone center. Strong winds expected over
zone 26 later this morning. In addition to hazards already
mentioned, gale force winds will spread north over the Inner
Channels through this evening. Currently have only small craft
winds in place for northern Lynn Canal, but gales there are not
out of the question. Additionally, have updated the forecast to
include strong winds for Juneau and Skagway later today.
In addition to extremely high wind gusts, periods of heavy rain are
expected. No flooding concerns because the area of heavy
precipitation will move through the area so quickly.
Used a blend of Gem and European model (ecmwf) for updates to pressure and winds.
Pop and quantitative precipitation forecast from GFS and European model (ecmwf) with a little help from Gem.
Overall forecast confidence is above average.
Long term... / Wednesday to Monday / with the upper level trough
moving east into western Canada, the zonal jet stream will move
across the North Pacific and into the northern British Columbia
coastline essentially through Friday night. At the surface, high
pressure will nose into southern British Columbia...meanwhile a
broad area of low pressure will extend from west of Hudson Bay
across northern Canada to the Bering Sea. This area of low pressure
has 2 to 3 low centers in association with it making some of the
flow patterns confusing.
Early Wednesday we will see the remains of the surface trough of
what is left of the Tuesday system dissipate along the Panhandle
coast. The next incoming short wave will be moving into the
western Gulf of Alaska Wednesday night and the weather associated
with this one will be moving into the Panhandle Thursday. Aloft
expect minor vorticity lobes in small short waves to move across
the Gulf into the weekend.
Overall model agreement is fair through the weekend although there
are some minor timing and positioning issues. Used a blend of
models this morning for my adjustments with ec being one of prime
sources. In the extended time frame, little in way of modifications
were done as the wpc was the main source of forecast input for
those time frames.
Aviation...severe turbulence and low level wind shear associated with the
hurricane force low will move north with the storm. Thunderstorm
activity is expected in the wake of this low as the atmosphere
public...strong wind from 1 PM to 4 PM akdt this afternoon for
High Wind Warning until 1 PM akdt this afternoon for
Strong wind from 1 PM akdt this afternoon through this
Marine...Storm Warning for pkz036.
Gale Warning for pkz013-031>035-041>043.
Small Craft Advisory for pkz012-021-022-051>053.
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