Need help to understand the weather

[zeehag]

while you all are awaiting for the real el nino to hit, you may want to know it set in for the second year last may. we are in a super el nino year, and winter should be interesting.
the el nino current has become stronger than any other year, even 1997, which was the last worst one. so.... while you state you are waiting for the real el nino to set in--- you are in it already. el nino is may one year to june the next.
enjoy.
observations are much more accurate than someones words. learn to read satellite pix and anomaly current information.
learn to know what each satellite pic will bring you.
read passage weather, weather underground and learn what the physical signs of the satellite fotos actually are.
learn what the marching elephants are.
learn to read the skies so you know what is coming at you so it isnt a surprise. there is nothing surprising about weather--it is all obvious if you know what to look out for.

[gamayun]

Originally Posted by zeehag

....learn what the marching elephants are.

Is this a Mexican term? Do you mean undulatus clouds? I was introduced to these wavy clouds when I moved to California and someone said that they show up about 3 days before a storm. I don't know how accurate that is, but several times since I've noticed them and a storm was a few days out.

Reading about the weather and reading the weather are so very different things

[zeehag]

Originally Posted by gamayun

Is this a Mexican term? Do you mean undulatus clouds? I was introduced to these wavy clouds when I moved to California and someone said that they show up about 3 days before a storm. I don't know how accurate that is, but several times since I've noticed them and a storm was a few days out.

Reading about the weather and reading the weather are so very different things

is what the seas do when storm growing for ye. saw it in gom when i was sailing there.

[belizesailor]

Originally Posted by gamayun

Is this a Mexican term? Do you mean undulatus clouds? I was introduced to these wavy clouds when I moved to California and someone said that they show up about 3 days before a storm. I don't know how accurate that is, but several times since I've noticed them and a storm was a few days out.

Reading about the weather and reading the weather are so very different things

Not Spanglish, its what the seas can look like on the horizon in some weather situations. For example, if you stand on the beach in SE FL and look East across the Gulf Stream and you see what looks like pacaderms marching on the horizon....then its a bad day to cross the Gulf Stream.

Various cloud types can be useful for short term indications of weather. Some common ones to research:

Cumulus (see also "Sea Breeze/Land Breeze")
Cirrus (see also "Mare's Tails")
Altocumulus (see also "Mackerel Sky")
Mammatus
Cumulonimbus

[monte]

Marching elephants. Never heard that one before. I have a question though. Yesterday when sailing North, approaching the top of Guadeloupe at around 10am, I saw what appeared to be waves breaking across the horizon, from one side to the other. It was consistent and when I looked through the binoculars it had the same appearance. Apparently 6' waves breaking for a an area of maybe 4 miles across, and 5 miles distant. Some kind of optical illusion obviously, but one seen by bare eyes as well as binoc's. I've seen. This a couple of times before. Any Idea what causes that effect? It's a bit weird, especially when you are scanning the horizon to try interpret the sea state ahead

[belizesailor]

Originally Posted by monte

Marching elephants. Never heard that one before. I have a question though. Yesterday when sailing North, approaching the top of Guadeloupe at around 10am, I saw what appeared to be waves breaking across the horizon, from one side to the other. It was consistent and when I looked through the binoculars it had the same appearance. Apparently 6' waves breaking for a an area of maybe 4 miles across, and 5 miles distant. Some kind of optical illusion obviously, but one seen by bare eyes as well as binoc's. I've seen. This a couple of times before. Any Idea what causes that effect? It's a bit weird, especially when you are scanning the horizon to try interpret the sea state ahead

Yes, thats unusual. The obvious would be a shoal, but I assume you would have seen that on the chart.

Uncharted shoal? Ive discovered some that way that were not noticeable in calm weather.

Or current/wind/another intersecting wave train?

Refraction on the horizon can do strange things, but Ive never seen it look like breaking waves.

[wrwakefield]

Originally Posted by monte

Marching elephants. Never heard that one before. I have a question though. Yesterday when sailing North, approaching the top of Guadeloupe at around 10am, I saw what appeared to be waves breaking across the horizon, from one side to the other. It was consistent and when I looked through the binoculars it had the same appearance. Apparently 6' waves breaking for a an area of maybe 4 miles across, and 5 miles distant. Some kind of optical illusion obviously, but one seen by bare eyes as well as binoc's. I've seen. This a couple of times before. Any Idea what causes that effect? It's a bit weird, especially when you are scanning the horizon to try interpret the sea state ahead

Monte,

Perhaps you were seeing a construct of a Fata Morgana mirage? [Slightly different from other mirages we might be accustomed to...]

Here is an image showing the distant wave phenomena.

I've also seen the pseudo breaking waves at 60+°N typically when there is a cold air layer on the water... Another common one is distant floating ice appearing as very tall [200+ meters?] pillars- like a distant fence of granite or a floating Stonehenge... That one I actually welcome since I'm forewarned about ice ahead...

Here's hoping the surf isn't really up...

Cheers!

Bill

[belizesailor]

Originally Posted by wrwakefield

Monte,

Perhaps you were seeing a construct of a Fata Morgana mirage? [Slightly different from other mirages we might be accustomed to...]

...

Ive seen Fata Morgana mirages of boats/lights/coasts/islands... I assume if conditions were right then one could be created from breaking waves ashore...maybe that was what Monte saw?

[monte]

Thanks Bill. That looks a lot like it. I have seen it a couple of times around the Caribbean. Definitely not shoals but it always makes me double check the chart! I've been surfing my whole life so I'm pretty used to seeing waves a long way off, as well as through binoculars. It really looks like overhead close out sets! Not really the kind of conditions I'd like to sail into...
A good description here..
http://www.wired.com/2015/01/fantast...-fata-morgana/
The first pic is similar to what I saw. Oddly there also appeared to be ships beyond the waves and amongst them. As we drew closer the waves disappeared and the ships turned into local fishing boats...
I'm not crazy...honest!

[monte]

Originally Posted by belizesailor

Ive seen Fata Morgana mirages of boats/lights/coasts/islands... I assume if conditions were right then one could be created from breaking waves ashore...maybe that was what Monte saw?

There weren't really breaking waves other than some walking elephants with some white capping normally associated with the 2-3m swell and 25kn winds. We were in the lee of the island at the time and headed out into it so I was curious about the conditions ahead. Forecast was for rough seas and a small craft advisory but it was pretty decent sailing conditions in the end. Honestly when I saw the Fata Morgana I was thinking, ok.. A few more miles but if they're really breaking above head height I'm turning around before the first one breaks...

[Alan Mighty]

Originally Posted by KD on Tropic

Am off to Thailand to sail around the East coast riviera islands of Koh Chang, Koh Mak, Koh Kood etc. in a weeks time.... never a bad place to sail due to lots of protected areas should the weather turn.... so as a safe haven to learn in... it is perfect.... and this where I would like to get the practical side of "Understanding the Weather class 101" done.

For Ko Mak, Ko Chang etc, I think you need Weather in Southeast Asia 115, not Weather on Temperate Continental Coasts 101.

Here's my quick take on Weather 115 (if I had more time I would have written more concisely):

That's because the weather at latitude 12 degrees N has a different mix of pattern and chaos, requiring different rules of thumb, than the weather in a temperate clime such as the Melbourne VIC near latitude 38 South or the Melbourne FL near latitude 29 North (by which I mean I don't know which Melbourne is your home).

1. The weather in the Gulf of Thailand is part of the Asian-Australian Monsoon system, a seasonal weather system with two monsoon seasons (named after the prevailing wind) and two intermonsoon seasons.

Every December thru early March in SE Asia is the NE monsoon in the N hemisphere (and in N Australia, the NW monsoon). So you can expect Northeast winds around Ko Chang et al.

The strength of each monsoon is both forecast and monitored. The Asean Specialised Meteorological Centre does some of that reporting and forecasting. You can find the current forecast at: Regional Climate – Seasonal Outlook | You'll note that Ko Chang et al are in the zone predicted to enjoy (if that is the word) below normal seasonal rainfall.

One of the very best sites observing and reporting on the Asian-Australian monsoon system is at U of Hawai'i: Monsoon Monitoring

At that U Hawai'i website, charts A and B related to the NE monsoon experienced at Asian end of the Asian-Aus monsoon system. And chart C relates to the NW Monsoon experienced in N Australia (and the parts of the Maritime Continent (aka the Great Archipelago aka Maritime SE Asia) S of the Equator. You'll see that so far in January 2016, the NE monsoon in the Indian subcontinent and in SE Asia is weaker than average. But the NW monsoon in N Australia is stronger than average (big mobs of rain in N Queensland and the NT).

2. Another pattern is imposed on the cycle of NE Monsoon - Intermonsoon - SW Monsoon - Intermonsoon. That other pattern is the Madden-Julian Oscillation (MJO). You can read more at Wikipedia or other info sources. But here's a quick run-down:

- If you look at the red data curve on chart C from that U of Hawai'i website. you'll note that the strength of the current monsoon cycles up and down about every 40 - 50 days. That's the same pattern observed by Roland Madden and Paul Julian in 1971 when they were working at the National Center for Atmospheric Research in Boulder, Colorado. Madden and Julian traced it to a pulse of convection that starts at about the East African/Indian Ocean coast and proceeds eastward at about 10 knots, crossing the Indian Ocean, then thru the Maritime Continent, then across the Pacific Ocean (where it can sometimes speed up to 30 knots as it loses its rain into the Pac, stays at a stable speed other times and produces other effects, and at still other times dies away to nothing in the Pac O), and sometimes into the Atlantic. O (where it is associated with Atlantic hurricanes and the West African monsoon).

- That pulse of convection is a double pronged thing, usually a dry prong of uplift that delivers sunny and dry weather followed by a wet prong of uplift that delivers squally and wet weather.

- The pulse of convection is generally strictly tropical, directly affecting latitudes 10 N to 10 S. But the pulse can reach intro sub-tropical zones (e.g. the Pineapple Express in Hawai'i).

- To date no one has mastered forecast of the Madden-Julian Oscillation (hence it's other name, the maddening Julian Oscillation). Nine of the richer economies on the planet run 15 supercomputers, each doing their best to come up with a prediction of the MJO. The US Climate Prediction Centre refuses to call a winner and instead runs a website which shows you each of the 15 predictions for the two weeks. You can find those predictions at the CPC's CLIVAR program website: CPC - Climate Weather Linkage: Madden - Julian Oscillation

You'll see a table with 15 cells, each labelled with abbreviation of a prediction centre (BOMM = Australia's BOM, E for Europe, J for Nippon, T for Taiwan, N for the US, CM for Canada Met, UK for Britain, CPTC for Brazil). Rest your pointer over one of the cells (e.g. the TCWB, which is one of my favourites for its accuracy in the NE monsoon) and you'll see a red curve, dotted with past dates, leading up to a green line that is the prediction for the 14 days since the model was last run. The deal is to look at which zone (Indian O, Maritime Continent, etc) has a peak (where the curve is far from the central circle. So if TCWB etc show a green peak in zones 3 or 4 (E Indian O and W Maritime Continent) when you expect to be in Ko Chang, then expect to see squalls, rain, etc.

3. GRIBs are of course useful. If you use software such as zygrib, download the latest GRIBs for your cruising area of Ko Chang, Ko Mak et al. Make sure to configure zygrib or the GRIB viewer of your choice to see CAPE (Convective Available Potential Energy) and CIN (Convective INhibition) forecasts. If CAPE is >1.5 kJ/kg, expect updrafts (as explained above) with squalls, rain etc. If CIN is > 200 J/kg, a capping layer may counter the updraft effect. If CIN is < 50 J/kg and CAPE is > 1.5 kJ/kg, then reef early and set your anchor firmly.

4. At latitude 12 degrees N (i.e. Ko Chang et al) don't waste your time looking at sea level pressure synoptic charts. Synoptic charts and the associated rules of thumb (Buys Ballot and so on about Lows on your Left) that are fine in temperate latitudes are not worth much in the tropics.

Instead of synoptic charts (with isobars of sea level atmospheric pressure), in the tropics streamline charts are the more useful tool. The US Navy Fleet Numeric Ops Center has a neat website that delivers great forecasts into the near future. But the easy choice for the Gulf of Thailand (remember to pronounce it ThaiLand, with the capital letters being point of pronunciation emphasis), is the daily Regional Weather Chart issued each afternoon from the Singapore National Environment Agency. See: Singapore Weather Information Portal - Regional Weather Chart

The lines are surface streamlines (i.e. the direction of wind at 10 metres above sea level, which will be close to the metacentre of your sailplan). At selected points you'll see a wind barb (the usual deal, a half fleche for 5 knots, a full fleche for 10 knots), the expected temperature in Celsius, and an icon for expected weather conditions (a black dot for overcast, a white dot for clear sky, etc).

Of course, around Ko Chang, Ko Mak etc, you'll have other local conditions (island effect wind conditions, sea breeze etc) so don't expect any general prediction to be accurate at micro levels.

Al

[Alan Mighty]

Originally Posted by Alan Mighty

- That pulse of convection is a double pronged thing, usually a dry prong of uplift that delivers sunny and dry weather followed by a wet prong of uplift that delivers squally and wet weather.

Oops. I failed to proof read.


That should read: "That pulse of convection is a double pronged thing, usually a dry prong of downdraft that delivers sunny and dry weather followed by a wet prong of uplift/updraft that delivers squally and wet weather."


My bad.


Al

[wrwakefield]

Originally Posted by monte

Thanks Bill. That looks a lot like it. I have seen it a couple of times around the Caribbean. Definitely not shoals but it always makes me double check the chart! I've been surfing my whole life so I'm pretty used to seeing waves a long way off, as well as through binoculars. It really looks like overhead close out sets! Not really the kind of conditions I'd like to sail into...
A good description here..
Fantastically Wrong: The Bizarre Mirages That Once Scared the Bejesus Out of Sailors | WIRED
The first pic is similar to what I saw. Oddly there also appeared to be ships beyond the waves and amongst them. As we drew closer the waves disappeared and the ships turned into local fishing boats...
I'm not crazy...honest!

Hi Monte,

I'm glad you didn't have to report an uncharted shoal...

My understanding of Fata Morgana illusions is they are dependent upon ducting associated with a temperature inversion- which makes them different from the typical mirages. the link you provided was useful to enhance that understanding.

I'm also glad you have no concerns regarding your sanity. [I don't either...] After all, mirages present equally to all; it is the shared interpretation(s) and subsequent action(s) that may bring to question the observer's state-of-mind...

Cheers!

Bill