WEATHER

You al­ways re­mem­ber your first time…

SAIL - - Contents - By Robin Urquart

Strate­gies for avoid­ing and weath­er­ing squalls

Our first en­counter with a big squall was sail­ing from San Diego to Ense­nada, Mex­ico. We left at 0200 to en­sure we’d get into Ense­nada be­fore our 1300 haulout time. The Na­tional Weather Ser­vice had fore­cast con­sis­tent 15-20 knot winds from the north­west, which was per­fect for the 60-mile run down the coast. We hoisted sails as soon as we were out of the San Diego Har­bor chan­nel, keep­ing a reef in the main­sail as is our pol­icy for night sail­ing. The wind was ex­actly as pre­dicted, and we cruised across the bor­der un­der a moon­less sky.

A short while later, as we were ad­mir­ing the lights of Ti­juana, we no­ticed the wind less­en­ing, then back­ing to the west. “That’s weird,” I thought as I moved to trim the sails. In­stan­ta­neously, we

were laid down by a 35-knot blast out of the south­west, the sails flog­ging wildly as the boat rounded up. Shocked we sought to get the boat un­der con­trol. With our full genoa out and only one reef in the main, we were grossly over-can­vassed.

Af­ter let­ting out the main­sheet I set about reef­ing the head­sail as white spray flew over the bow. Once the head­sail was furled to the sec­ond reef point and with the main trav­eller to lee­ward, the boat stopped want­ing to round up, and the mo­tion be­came more com­fort­able. The rain then ar­rived, and the wind dropped to an even 30 knots. As we scorched along at 7.5 knots, my wife, Fiona, and I both looked at each other and said si­mul­ta­ne­ously, “Squall!”

WHAT IS A SQUALL? The of­fi­cial def­i­ni­tion for a squall, ac­cord­ing to the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion (NOAA) is a “strong wind char­ac­ter­ized by a sud­den onset in which the wind speed in­creases at least 16 knots and is sus­tained at 22 knots or more for at least one minute.” A squall can also be de­fined as an area of strong, lo­cal­ized con­vec­tion in which wind­speed in­creases sub­stan­tially for a du­ra­tion last­ing any­where from a few min­utes to a few hours.

In our ex­pe­ri­ence in the Pa­cific Ocean, squalls usu­ally blow in the 20 to 30-plus knot range and last an av­er­age of 20-40 min­utes. Based on data gath­ered from Lat­i­tude 38’s Pa­cific Pud­dle Jump over the last five years (2012-2017), the av­er­age high­est wind­speed en­coun­tered on the cross­ing is a lit­tle over 32 knots and is al­most al­ways ex­pe­ri­enced in squalls. There have been re­ports of squalls in the 50-knot range, but this is rare, with 82 per­cent of boats re­port­ing max­i­mum en­coun­tered wind­speeds of 40 knots or less.

Ten thou­sand miles later and af­ter avoid­ing and ex­pe­ri­enc­ing count­less squalls, Fiona and I have be­come much more adept at rec­og­niz­ing and re­spond­ing to this in­ter­est­ing weather phe­nom­e­non. Squalls, al­most by def­i­ni­tion, are too small and lo­cal­ized to be fore­cast pre­cisely. How­ever, ar­eas of the kind of in­creased ac­tiv­ity that can form a squall line can be seen on weather radar and will be in­cluded in a lo­cal area fore­cast.

VIS­UAL CHAR­AC­TER­IS­TICS There are a few key in­di­ca­tors to look for when try­ing to iden­tify a squall: namely clouds, rain and waves.

Cu­mu­lonim­bus clouds: The first sign of a squall is typ­i­cally a large cu­mu­lonim­bus cloud built up with a dark, flat bot­tom. How­ever, not ev­ery cu­mu­lonim­bus cloud will have a squall un­der it, which is why it’s im­por­tant to look for other in­di­ca­tors as well.

Virga: The sec­ond in­di­ca­tor of a squall are gray streaks un­der­neath said cloud. These streaks are called virga and are the re­sult of rain evap­o­rat­ing be­fore it hits the ground. As the rain evap­o­rates it also steals heat from the sur­round­ing air cre­at­ing pock­ets of cold air that can de­scend rapidly, caus­ing strong gusts at sea level.

Rain: A dark slab of rain un­der a cloud is usu­ally a good in­di­ca­tor that strong wind will be present, es­pe­cially in the trop­ics and sub-trop­ics. The rain is of­ten at a slant, as a re­sult of the wind within the squall com­plex. Squalls, how­ever, of­ten move side­ways to this slant, so don’t as­sume the cloud is drag­ging the rain be­hind it.

Waves: Another good in­di­ca­tor to look for are white caps on the sur­face of the wa­ter near large clouds—a sure sign that strong lo­cal­ized winds stir­ring things up.

Radar: Of course, these fea­tures are im­pos­si­ble to see at night, which is why we of­ten use radar to iden­tify squalls af­ter dark. This tac­tic works be­cause radar re­flects off con­densed wa­ter (rain), ei­ther in the cloud or at sea level. Ei­ther way, where there is rain, there is likely to be strong winds. A squall will ap­pear as a hairy blob on the radar screen.

HOW TO AVOID SQUALLS

Avoid­ing squalls fol­lows nat­u­rally from be­ing able to rec­og­nize them. How­ever, just be­cause you know what a squall looks like, that doesn’t mean you will au­to­mat­i­cally know where it is go­ing. In fact, squalls of­ten do not fol­low the pre­vail­ing winds, but rather move at an angle to them. In ad­di­tion, large gusts can oc­cur as far as two-miles away from the squall’s cu­mu­lonim­bus cloud, so be sure you don’t wait for it to get too close, or you may find your­self caught un­pre­pared.

If it is light out, we usu­ally start by tak­ing a bear­ing on the squall. We might use a com­pass, but mostly we just line it up with a stan­chion or through a dodger win­dow. If we hold the same

If a squall is ap­proach­ing, the first step is to reef the sails. Ex­pect in­creased wind­speeds at least 50 per­cent higher than the pre­vail­ing con­di­tions and re­duce can­vas ac­cord­ingly

head­ing and the angle on the squall doesn’t change, then we know we are on a col­li­sion course: it’s the same prin­ci­ple at work as when avoid­ing other ships.

A few times we’ve tried rac­ing ahead of a squall even though we knew it would be cut­ting things close. We’ve had mixed suc­cess with this strat­egy, hav­ing been caught as of­ten as we’ve es­caped, and we now pre­fer to let a squall roll by while we slow the boat or al­ter course to avoid it.

If we are sail­ing at night in a squally area, we gen­er­ally run a radar sweep ev­ery 20 min­utes, mak­ing sure the “rain scat­ter” mode is turned off or at min­i­mum. Radar can be es­pe­cially good at track­ing a squall’s move­ment. It’s also good at pro­vid­ing early warn­ing that one is in the area. We sweep at a range of 12 and 24 nau­ti­cal miles, al­though due to the cur­va­ture of the Earth, it is dif­fi­cult to iden­tify rain at sea level be­yond 15 nau­ti­cal miles. If a squall can be iden­ti­fied at, say, 9 miles away, then slow­ing the boat down just half a knot can mean the dif­fer­ence be­tween getting drenched and stay­ing dry.

Another strat­egy we’ve found use­ful when open-wa­ter sail­ing is re­ly­ing on a self-steer­ing wind­vane to keep the boat at a con­stant angle to the wind, so that as the wind shifts with the squall the boat shifts with it. This has meant some­times sail­ing at right an­gles or worse to our orig­i­nal course as we skirt the pe­riph­ery of a squall wait­ing for it to blow it­self out. How­ever, if you’ve got a way dis­tance to go, a fivemile de­tour is no big deal. This ap­proach also re­quires very lit­tle ef­fort on our part, mak­ing it per­fect for sin­gle­hand­ing at night.

The same ef­fect can be achieved with an au­topi­lot that is set to wind angle as op­posed to course head­ing. How­ever, don’t get com­pla­cent. Squalls are no­to­ri­ous for sud­den wind­shifts, which can re­sult in an ac­ci­den­tal gybe and cause sig­nif­i­cant dam­age.

SAIL­ING IN A SQUALL

No mat­ter how hard you try to avoid squalls, even­tu­ally you will have to sail through one. Sail­ing in a squall doesn’t have to be an es­pe­cially in­tim­i­dat­ing ex­pe­ri­ence. In fact, it can of­ten be quite re­fresh­ing as it helps spirit you on your way. At the same time, though, tak­ing some pre­cau­tions early on and know­ing what to ex­pect will pay div­i­dends in terms of keep­ing both your boat and your crew safe.

If a squall is ap­proach­ing, the first step is to reef sails. Ex­pect in­creased wind­speeds at least 50 per­cent higher than the pre­vail­ing con­di­tions and re­duce can­vas ac­cord­ingly. The adage “reef early and reef of­ten” is a good one to fol­low. Be­ing caught over-can­vassed is a chal­leng­ing and un­en­joy­able ex­pe­ri­ence to say the least, not to men­tion po­ten­tially dan­ger­ous for the boat and rig.

That done, make sure ev­ery­thing on deck and in the cock­pit is well se­cured. It is also a good pol­icy to put on foul­weather gear or at least have it close by, as the cool rain can cause a chill, even in the trop­ics. The first strong gusts of wind as­so­ci­ated with a squall are al­most al­ways the strong­est. You’ll typ­i­cally feel this wind be­fore you feel the spat­ter­ing of rain.

Once the rain hits, the wind usu­ally lessens some­what, but can still be gusty. De­pend­ing on where you are, how high and large the cloud is and the ini­tial pre­vail­ing con­di­tions, the wind will typ­i­cally be any­where from 25-40 knots. Of­ten be­fore and af­ter a squall the wind will be very light, prompt­ing us to turn on the en­gine to make head­way af­ter the squall has passed.

Many sailors rec­om­mend that you sail with the squall, or “go with the blow.” As is the case with the wind­vane strat­egy, this will al­most as­suredly take you off course. But stay­ing on the pe­riph­ery is usu­ally prefer­able to sail­ing through the heart of a large squall, in par­tic­u­lar. The rea­son for this is that the wind shifts in a squall can of­ten be un­pre­dictable, forc­ing you to have to trim sails, or even tack or gybe mul­ti­ple times: a tremen­dous amount of ef­fort that is hardly worth it given the squall will likely blow it­self out within 20 min­utes to an hour any­way.

Some­thing to watch out for on those oc­ca­sions when you do find your­self caught up in a squall is round­ing up and out of con­trol. For ex­am­ple, your sailplan may be work­ing just fine on a run in 30 knots. But then a wave slews round your stern, or a gust hits, and the next thing you know the boat is turn­ing up into the wind, com­pletely out of con­trol.

In fact, we’ve ex­pe­ri­enced a num­ber of squalls in which the wind and waves over­pow­ered the rud­der in as lit­tle as 35 knots of wind. The prob­lem was the main­sail was over­pow­er­ing both the rud­der and the head­sail. There­fore, when run­ning in front of a large squall, a triple reefed main and reefed head­sail may be the best sailplan. You might even want to try sail­ing un­der stay­sail or reefed head­sail alone, since keep­ing the nose of the boat down­wind will make the trip both more com­fort­able and a good deal safer.

Many cruis­ers rec­om­mend that the best thing to do is sim­ply mo­tor through a squall with a triple-reefed main­sail or a reefed roller­furl­ing stay­sail up for sta­bil­ity. Some­thing to re­mem­ber, though, is that with this kind of an un­bal­anced sailplan the rud­der can still have prob­lems keep­ing a good grip. That said, if you don’t mind burn­ing diesel, this method will gen­er­ally keep you on a more-or-less con­stant head­ing and also keep you mov­ing in the lighter airs af­ter the squall has passed.

Of course, the most con­ser­va­tive ap­proach is to drop all sails and mo­tor through the squall zone. How­ever, while this tech­nique can be a good one with a smaller sea state, when the waves get up to 10ft or more, mo­tor­ing into or even across them be­comes a daunt­ing and not very com­fort­able prospect. At this point it is bet­ter to get some sail up.

Ul­ti­mately, there are a many fac­tors at play in squall sail­ing, in­clud­ing sea state, wind­speed, boat bal­ance, the num­ber of crew, the air and wa­ter tem­per­a­ture, and rig. The ex­act so­lu­tion will there­fore be dif­fer­ent for ev­ery boat and a mat­ter of play­ing around with what works best for you and your crew. A con­ser­va­tive ap­proach is a good place to start. Af­ter a few squalls it will quickly be­come clear what works best and what doesn’t.

What­ever you do, there’s no rea­son to be afraid aboard a well-found boat. While it’s good to ap­proach a squall with re­spect, there is no rea­son to fear it. With good avoid­ance tech­niques, boat and crew prepa­ra­tion, and the right sails, ev­ery squall can be man­aged. Con­sider it a lit­tle burst of ex­cite­ment on an oth­er­wise placid day. s

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