Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
730 AM EST Sat Jan 21 2017

Valid 00Z Sun Jan 22 2017 - 00Z Sun Jan 29 2017

To commence the forecast period, a lobe of vorticity pinching off
from the mid-latitudes will drift eastward through the Hawai`ian
island chain through Monday. Thereafter, expansive ridging toward
the International Dateline should eventually lead to general
northwesterly flow early next week before a new area of troughing
forms east of the region by mid-week. Ensemble spaghetti plots
agree on keeping this system away from the islands. Toward the end
of the period, renewed height falls begin to take shape across the
Central Pacific which may bring a rather strong baroclinic zone
toward Kauai by perhaps next weekend. Overall, the 00Z ECMWF
ensemble system is quicker, but there is at least sufficient
agreement on the longwave pattern with variance in the details.

At the surface, an anticyclone to the north-northwest will foster
the development of moderate to occasionally strong northeasterly
flow this weekend. Forecast winds may reach the 25 to 30 knot
range during the height of the event. As this ridge translates
eastward, the winds will shift toward a more easterly direction
with a gradual slackening of this flow as the pressure gradient
weakens. Depending on the model, there may be a response to the
amplification in the mid-latitude flow. Regarding precipitation,
the best threat for showers will be through the middle of next
week before much drier air infiltrates into the region.


Rubin-Oster