Fading surf will give way to a small new swell arriving late in the day and through the overnight into Sunday, but wave heights will likely only reach a couple of feet overhead at best. Windswell along our east and northeast facing shores will be back on the rise over the next several days, potentially triggering another advisory Monday into Tuesday. The incoming northwest swell was generated by a low several days ago, but it was on a rapid track toward the east-northeast, greatly limiting any fetch aimed in our direction and most of this swell is coming out of the west-northwest. However, a secondary fetch developed shortly after, but again, this energy was not aimed well in our direction. Another area of low pressure developed near the dateline Thursday, but this too was not aimed well in our direction. This energy should simply help to keep head-high surf active through Tuesday or possibly Wednesday of next week. The models continue to show a low forming south of Kamchatka Sunday and early next week. A long-lived, but unimpressive fetch is expected to set up, aimed well toward Hawai`i. The resulting swell should arrive Wednesday around small to moderate levels. High pressure north of the islands should keep strong upstream and local tradewinds blowing through mid-week, likely building the local windswell to advisory levels by late Sunday or Monday morning. Nothing more than background swell is expected out of the southern hemisphere through the period. Not a lot of swell should be expected this week, but at least we won’t go flat.
Windswell along the east and northeast facing shores should rise to 3-5 foot levels today, building to overhead levels Sunday and advisory levels by Monday. North and northwest facing shores should increase to overhead levels later in the day today, around 4-6 foot, but will likely start off at smaller levels. Upper West shores should only come in around 1-4 foot, but select breaks may pull in larger sets. South facing shores have no swell to mention and will remain flat at 0-2 foot.
Wind and Tide Information
Low tide at Kahului was 0.8 foot at 12:43 AM just after midnight, rising to a high of 1.2 foot at 4:54 AM early this morning, then dropping to a low of -0.2 foot at 11:33 AM shortly before noon, before once again rising to a high of 2.1 foot at 7:16 PM early this evening
The sunrise was at 06:01 am this morning and will set at 06:47 pm this evening. The Moon is currently 19 days old, and is in a Waning Gibbous phase. The next Last Quarter will occur at 7:53 AM on Tuesday, April 22nd.
The east-northeast to northeasterly tradewinds will remain breezy to strong around 15-25 mph today, with an increase expected Sunday and through the first half of the upcoming week. Windspeeds should decrease a little over the second half of the week, but will still be at breezy to strong levels throughout the forecast period.
Sunset: 6:46 PM
Weather Outlook for Saturday
A trade wind weather pattern will continue through the next several days across Hawaii, thanks to high pressure north of the state. Showers will favor windward and mauka areas with a few showers possible over some leeward locations.
Showers have become rather sparse over the state during the past several hours, with radar and rain gauge data showing only very light rainfall amounts across some windward areas. The 12Z soundings show a lowering of the inversion as expected, with the base down to between 5700 and 6700 feet, from about 9000 feet 12 hours earlier. This is consistent with mimic-tpw satellite data which indicate a drier airmass spreading into the state from the east. Earlier model data suggested that this drying would take place primarily in the 850-700 mb layer, again consistent with the 12Z raob data. Satellite imagery depicts abundant high level cloudiness streaming northward across the state, to the east of a mid/upper level trough centered several hundred miles to the southwest. At the surface, a 1023 mb high is centered well northeast of the state, with a stronger 1028 mb high building eastward from the dateline north of 30°N.
For today, expect shower coverage to remain fairly sparse with light rainfall amounts even across windward sections, as stable and dry conditions continue. Tonight, satellite and model data indicate that another area of higher moisture will be moving into the state, although model soundings show the inversion remaining fairly low. With brisk trades in place, the influx of additional low level moisture should be sufficient to increase shower activity once again across windward/mauka areas, with some spillover into leeward.
Sunday through Monday night, rather strong high pressure will pass north of the state, causing trades to increase further. Aloft, guidance indicates that the mid/upper trough to our southwest will shear apart, with the mid level trough moving to the west southwest and away from our area, while the weakening upper level trough drifts slowly to the east northeast. A deep dry layer will persist across the state in the mid levels, with a mid level ridge building just to our north. Therefore would expect the only impact to our sensible weather from the upper trough to be periods of high level cloudiness. Active trade showers will continue across windward/mauka, with some spillover to leeward due to the strength of the trades.
Trades should return to more moderate levels Tuesday through Thursday, as the first surface high shifts further to the northeast and is replaced by a second slightly weaker high to our north. Would expect little change in the weather pattern across Hawaii with showers continuing mainly across windward sections.
Central Valley (Kahului, Spreckelsville):
Mostly cloudy. Isolated showers after midnight. Lows 63 to 71. Northeast winds 15 to 20 mph. Chance of rain 20 percent.
Leeward West (Lahaina, Ka`anapali):
Mostly cloudy with isolated showers. Lows 63 to 72. Northeast winds 15 to 20 mph. Chance of rain 20 percent.
Windward West (Wailuku, Waiehu):
Mostly cloudy with scattered showers. Breezy. Lows 55 to 73. East winds 15 to 25 mph with gusts to 40 mph. Chance of rain 50 percent.
Windard Haleakala (Hana, Haiku, Makawao):
Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Breezy. Lows 66 to 71 at the shore to around 52 at 5000 feet. East winds 15 to 25 mph with gusts to 40 mph. Chance of rain 70 percent.
Leeward Haleakala (Kihei, Wailea, Makena):
Mostly cloudy. Breezy. Lows around 67 at the shore to around 52 at 5000 feet. Northeast winds 15 to 25 mph with gusts to 40 mph.
Mostly cloudy with isolated showers. Windy. Lows around 47 at 7000 feet to around 41 at the summit. East winds 25 to 30 mph. Chance of rain 20 percent.
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