Na strani organizatorja je kar nekaj poročil o problemih, ki jih imajo tekmovalci na svojih plovilih. Andrea Carraci je izgubil jambor, Francisco Lobato po neverjetnih hitrostih, ki jih je dosegal v preteklih dnevih, močno pada po lestvici, že včeraj smo poročali o problemih Isabelle Joschke…

Ker se približujejo Zelenortski otoki, je morda čas za besedo ali dve o taktiki okoli njih in potem do prečkanja Ekvatorja. Kot že rečeno, prva skupina, v kateri bo, upamo, tudi Kristian, bo prišla v Zelenortske otoke jutri popoldne. Pravila pravijo, da morajo na desni strani pustiti skrajni zahodni otok ter na levi skrajni vzhodni otok. Naš načrt je, da se otok Santa Lucia pusti na desni strani, se izogne vetrovne sence otoka Santo Antao in potem nadaljuje zahodno proti prečkanju ekvatorja. Statistično najboljša točka prečkanja je med 30 in 31 stopinjami zahodno. Zakaj statistično? Zelenortski otoki so skrajna točka, kjer se jadralci z nekaj sreče še držijo napovedi, ki so jo dobili na startu. Na osnovi izkušenj prejšnjih Transatov in simulacij, ki smo jih naredili, je potrebno prečkati Ekvator tako, da se v JV pasatih na istih uzdah v veter prebije mimo naslednje obvezne točke, otočka Fernardo de Noronha, ki ga morajo pustiti na desni. Omenjen interval prečkanja Ekvatorja je kompromis med več vetra zahodno na poti do Ekvatorja, širino intertropske konvergenčne cone, ki je ponavadi proti zahodu ožja in kolikor toliko ugodnega kota jadranja v JV pasatih. Intertropska konvergečna cona je izredno trd oreh za napovedovanje, tako da počakajmo z napovedmi, od jutri naprej pa bomo sproti komentirali različne opcije in kako se vreme obnaša glede na klimatološke napovedi. Kar bo naredilo stvari še bolj težavne je zametek tropske nevihte, ki bo prečkala pot floti predvidoma v nedeljo. O njenemu učinku na vrstni red tekmovalcev je ponovno prezgodaj govoriti, zna pa biti, da se bodo tisti od zadaj lahko približali prvim.

Zaenkrat se Kristian do pike drži začrtanega scenarija in stvari gredo bolje. Predvidoma bo v naslednjih 24 urah prišel po lestvici še višje, saj lahko jadra direktno do začrtane točke prehoda. Hkrati bo imel dobro izhodišče za nadaljevanje, saj bo po Zelenortskih otokih vetra manj na vzhodu. Andraž se po dobrih dneh nekako ne pobere, pred prehodom na Zelenortske otoke pa se skuša v kolikor toliko močnem vetru premestiti proti zahodu. Vzhodna skupina se bo soočala s šibkejšimi vetrovi, kjer kot vetra postaja vedno bolj odločilen dejavnik. V drugi etapi Yves le Blevec vozi zelo blizu liniji najkrajše poti in to dovolj hitro, da je kar močno v ospredju.

Zadnje nekaj dni je kar nekaj vprašanj in negotovosti o vremenskem dogajanju okoli Zelenortskih otokov. Najlažje se o vremenskem dogajanju prepričamo na osnovi sekvence zadnjih satelitskih slik. Eden od virov podatkov je: http://www.weather.com/maps/maptype/satelliteworld/tropicalatlanticsatellite_large_animated.html

O tem, kakšni so dejansko vetrovi na Atlantiku, se lahko prepričamo na osnovi podatkov iz satelitov, ki so razmeroma točni. Poglejte si: http://manati.orbit.nesdis.noaa.gov/hires/ in kliknite na globalni sliki na mesto, ki vas zanima. Gre za podatke s senzorja QuickScat, ki meri odboj radarskih žarkov iz morske gladine, na osnovi oslabitve radarskih žarkov pa se lahko oceni smer
in hitrost vetra  na morski gladini. Podatki so posamezno točko na morju dostopni 2x dnevno.

Naslednji vir podatkov so napovedi meteoroloških modelov. Očitno je, da so na spletni strani organizatorjev dosptopni podatki iz ameriškega globalnega modela GFS, ekipo Adria4ocean pa podpira Agencija RS za okolje s produkti evropskega modela ECMWF. Napoved ECMWF za danes ob 12 h pa si poglejte na sliki v prilogi. Barvna skala prikazuje hitrost vetra v vozlih.

Jure

Reports of damages are constantly emerging on the official website. Today Andrea Carraci lost his mast and Francisco Lobato, after the incredible speed in the past few days is now droping down the rankings, and no to mention Isabelle Joschke, who now seems to be headed towards the Cap Verdes.

Speaking of which it’s time for a quick look at the tactics regarding the Cap Verdes and than crossing the Equator. As I said the ET of passing the Cap Verdes is tomorrow afternoon for the leading group – hopefully Kristian will be among them. The rules are that the westernmost and easternmost islands are the gate. So our plan was to leave Santa Lucia on starboard and thus avoiding the wind shadow of Santo Antao and than to proceed west to cross the Equator. Statistically it’s best to cross the Equator between 30 and 31 degrees west. Why statistically? Because the Cap Verdes are the furthest point of the way where skippers can still somewhat rely on the weather routing made at the start. Based on the past Transats and the simulations we made, one has to cross the Equator sailing on one tack in the SE trade winds passing the next way point, Fernando de Norronha (they have to pass it starboard). This is ofcourse a compromise between more wind in the west, the latitude of the Doldrums (which is usally more narrow in the west) and a favourable angle of sailing in the SE trade winds. The Dolodrums are really difficult to predict, so I’ll wait with my forecast for a few days. From tomorrow on I will comment the different options and the »behaviour« of the weather compared to the climatological forecasts that I made. Things will be even more difficult for the skippers because there is a tropical storm developing in the area the fleet will pass on Sunday. It’s to soon to predict the effect it will have on the fleet but it is entirely possible that the back of the fleet will be able to compensate some of the lost miles and time.

For now Kristian is sticking exactly to the plan and things are looking up for him. It is possible he will gain some places during the day as he can sail directly towards the agreed waypoint. Also he will have a good starting point for the next part because there will be more wind in the west. Andraž is doing worse than yesterday but it seems he is also making his way through to the west before passing the Cap Verdes. The eastern part of the fleet will have less wind and a more important factor is becoming the angle of sailing. Yves Le Blevec is sailing very close to the Rhumb line and fast enough as he is by far in the lead at the moment.

There have been quite some questions and doubts regarding the weather near the Cap Verdes. It is easiest to be sure of the weather if we check the latest satelite reports. One of the sources is: http://www.weather.com/maps/maptype/satelliteworld/tropicalatlanticsatellite_large_animated.html

To check out the winds in the Atlantic you can visit http://manati.orbit.nesdis.noaa.gov/hires/ for accurate data. Just click the area you are interested in. This data is acquired by QuickScat sensor, which measures the rebound of the radar beams from the seasurface. Based on this they can measure the wind speed and direction at seasurface. The information is available twice daily.

The next source of information are meteorological models. The official website obviously uses the American global model GFS, team Adria4ocean’s models are provided by Environmental Agency of Slovenia (European model ECMWF). The ECMWF for today is the attached photo. The color scale is wind speed in knots.

Jure Jerman

This entry was posted on Thursday, October 11th, 2007 at 2:02 pm and is filed under Transat, Vreme. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.