781 
fxhw60 phfo 220135 
afdhfo 


Area forecast discussion 
National Weather Service Honolulu HI 
400 PM HST Sat Nov 21 2009 


Synopsis... 
the high pressure to the northeast will weaken Monday and Tuesday 
and the associated surface ridge will move nearer to the islands. 
This will also slightly weaken trade winds. Except for scattered 
showers that mainly affect the windward or mountain 
areas...remaining areas should enjoy mostly sunny days through the 
first part of the coming week. 


&& 


Discussion... 
satellite imagery showed a band of showers moving onto the central 
islands this afternoon. Showers are also expected to move over the 
windward Big Island later tonight and into the morning. Some showers 
will also blow across leeward sides of the smaller islands through 
Sunday morning but conditions should dry before midday Sunday. High 
clouds have nearly cleared The Big Island...and the upper trough 
will shift east of The Big Island by Sunday afternoon. The afternoon 
balloon soundings are stable and precipitation amounts are not 
expected to be very significant. 


A general trade wind weather pattern is expected into the beginning 
of next week. Conditions will be stable under ridging aloft and the 
continuing influence of the high to the northeast. Trade winds will 
decrease to moderate strength Monday and Tuesday when a low 
presently in the far western Pacific moves into the central North 
Pacific as a very strong low late Sunday. The surface high will 
shift eastward and the surface ridge will move to about 200 miles 
north of Honolulu. 


Models show a cold front moving toward our islands Tuesday night and 
Wednesday but stalling before it can reach Kauai. Models do not 
depict enough support in the upper atmosphere to push it down across 
the main Hawaiian islands Wednesday or Thursday. Instead the low 
moves up to the Gulf of Alaska and a new surface high moves in 
behind again strengthening the trade winds. There is a 
chance...according to models...of some moisture being drawn up from 
the southeast onto The Big Island Wednesday and Thursday. 


The present forecast reflects a trade wind climatological pattern. 


&& 


Marine... 
very strong storms forecast to move across the North Pacific next 
week Promise to generate multiple high surf episodes. A high surf 
advisory was issued for north and west Kauai and Niihau and for 
North Shores of Oahu Molokai and Maui for surf that should be rising 
Sunday morning on Kauai and move down the island chain during the 
day. The first signs of long period swell energy began arriving on 
buoy 51001 about 200 miles northwest of Kauai Saturday afternoon. 


The strong storm responsible for this expected swell moved up to the 
western Aleutian Islands Thursday night and then experienced a 
secondary low that extended the fetch area. This will serve to 
prolong the high surf episode through Monday...and possibly into 
Tuesday. Another low that will move into the central North Pacific 
late tomorrow and Monday will produce an even larger northwest swell 
Tuesday night with the peak Wednesday. The swell will then continue 
as a large north northwest swell into the second half of next week. 


&& 


Hfo watches/warnings/advisories... 
Small Craft Advisory until 5 PM HST Sunday for Kauai Channel- 
Kaiwi Channel-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big 
Island leeward waters-Big Island southeast waters. 
High surf advisory beginning 6 am Sunday until 6 am Tuesday north 
and 
west Kauai and Niihau and North Shores of Oahu Molokai and Maui. 


&& 


$$ 


Hoag