Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » General Discussion » Forecast accuracy?

Posted by
76Trombones


Users avatar

Posts
362
Registered at
2009-08-03 18:04:56
2013-04-12 13:57:19 - Forecast accuracy?
SOL mostly uses "real-time" winds and forecasts based on the National Oceanic and Atmospheric Administration's (NOAA) models. There have been a few questions in chat about how reliable the forecast is, and if it's reasonable to make long term strategy decisions based on the predicted winds.

There are a few ways to look at this, and "weather forecasters" in general get a bad rap because the average person is most interested in what will happen on *their* commute home or for the bbq on the weekend than the actual weather systems. The forecaster is usually the guy who gets a minute and a half on the morning talk/news show.

We had some unusual weather for the balloon race, and had to switch gears about halfway through. The image below is a composite of the May 11, 1200utc forecast taken from SOL's Wx for the week prior, starting at the top.



It's pretty obvious that the weather predicted on the 4th is quite different from what we ended up with, but certainly the last 4 days are very close. What happened? Is the 7 day forecast wildly inaccurate?

Leading up to this sequence there were three lows in the N Atlantic - one well N, one SW of the finish and a more powerful one following. Each major system is well defined, but how they merge can get messy. In the earliest forecast, the SE low moved onshore - allowing the following one to quickly move NE.

By Friday, you see evidence of a dramatic slowing, but the prediction is still for a merge to the NE. This is where a bunch of us started to worry - if the earlier pattern held, we'd have a fast and safe approach to the finish, but it was looking like we'd have to loop in from the SE. The SE approach was very risky, as any shift back would leave boats stranded. I posted an analysis Friday evening in which the speeds in the NOAA model were called into question. The UK Met model showed the low lingering S of Ireland, and indeed this is what ended up happening.

By Sat, it was obvious that we were in a new pattern - remembering that it was always one of the options... The critical system was pulled down, giving us the Southerly winds eventually needed to finish.



--- Last Edited by 76Trombones at 2013-04-13 00:05:10 ---
Attachments

Please login to post a reply.

Races

Next Race: 00d 00h 00m

Current Races:

Regata dell’Accademia Navale 2026

Welcome to Sailonline’s partnership with the City of Livorno (Leghorn say the English) in cooperation with the local yacht clubs and the Italian Navy, offering all the online opportunity to race the famous Regata dell’Accademia Navale - 630nm in length. Starting and finishing in Livorno, this year the race takes you the length and breadth of the Tyrrhenian Sea via little Mortorio (Mortoriotto) off Sardinia to Capri and home again to Livorno. This race also counts towards Sailonline’s Magical Mediterranean Series and the SuperBuddy title. Online, you will be sailing a Mini 6.50, to give you a match against several of the real-life entrants, which you will be able to track on-screen!
Race #2020
INFO by brainaid.de
Mini 6.50 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: MED - SUPBUD - SYC
Race starts: Apr 25th 10:00 Registration Open!

▶ Flash
GO TO RACE

Guess Gotland TIMED Race 2026

The Guess about Gotland is do we helm our First 27 solo east or west of the island in this 140 nm race. This is a TIMEDrace so you may RE-REGISTER HEREto try again after finishing a run. You will have 13 days and 11 hours to test your skill and decision making after the race opens.
Race #2030
INFOby brainaid.de
First 27 solo Particulars
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
TRQ2 - TRCH - SYC
RACE CLOSE: Saturday,
2 May at 23:00 UTC
Race starts: Apr 19th 12:00 Registration Open!
▶ Flash
GO TO RACE

Rommel by Balloon 2026 - Through the Sahara


Generalfeldmarschall Johannes Erwin Eugen Rommel may have been that chivalrous, gallant tank commander of legend, led astray by the Prussian military traditions of loyalty and chain of command, but one thing he wasn’t, was mad. So, let’s do it anyway – not stick to the coast and the battle for logistical superiority – but depart the oases of Siwa south west into the desert for Agadez and its uranium. And let’s go by balloon, it’s only 2500km (1250nm)!
Race #1973
INFOby brainaid.de
SOL Balloon PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: BOL - SYC
RACE CLOSE: Sunday,
May 3 at 2300 UTC.
Race starts: Apr 07th 13:00 Registration Closed
▶ Flash
GO TO RACE

Falklands to Tasmania 2026

Welcome to yet another all-new route. This next race is part of our Ocean Championship as well as the ROW series. Falklands to Tasmania, is like last year's island to island. It’s one of the longer ones 6400nm, more than half way around the world (and the Antarctica). It starts the 2026 OCQ2, and will be sailed in our Steinlager 2, contrary to prior notice.
Race #2021
INFO by brainaid.de
Steinlager 2 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: OCQ2 - ROW - OCCH - SYC
RACE CLOSE: Thursday,
May 7 at 2300 UTC.
Race starts: Apr 06th 11:00 Registration Closed
▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member KaSToR
  3. Sailonline Yacht Club Member CriticalHippo
  4. Sailonline Yacht Club Member rafa
  5. Sailonline Yacht Club Member Panpyc
  6. Sailonline Yacht Club Member rumskib
  7. Sailonline Yacht Club Member CollegeFund
  8. Sailonline Yacht Club Member sassy63
  9. Sailonline Yacht Club Member Sax747
  10. Sailonline Yacht Club Member bonknhoot

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client