Wednesday, December 31, 2014

Weather It Is (The Plot Deepens)

Good Afternoon:

We've had a nice winter day and Thursday's weather should even be a bit nicer: even warmer with lots of sunshine and continued light winds.

However, our weather map will take a turn towards winter, which should begin in the north late Friday and spread to the center of the country by late Saturday afternoon. The winds will also pick up and there could be some wind gusts above advisory levels.  Rain amounts from Shabbat into Monday morning should generally be between 25-50 mm in many locations.

Looking further ahead, the more significant system we spoke about the other day is starting to become better resolved by the global ensemble model.  This involves a a ridge of high pressure building into central Europe with extremely cold air dropping down from western Russia, potentially forming a deep winter trough and winter storm in the eastern Mediterranean.

Unlike the approaching storm, which will approach from the west, the energy for this storm will approach from the north. This would preserve the unusually cold air features of this very winter-like system, as it will be passing over land instead of sea.

Since last night, the forecasts probabilities of a wintertime (snow) storm have increased from about 20% to 35%.  Concurrently, all the ensemble members now show a 500 mb pattern indicating trough formation in our area, meaning that the models have latched onto a signal that could mean a return to whiteness for us. The timing for this system is Tuesday into Thursday of next week.

Yet, a 35% chance is not a certainty; in fact, it is less than half. On the other hand, the area of the world from which this system will originate is not well sampled (observed), so any signal (especially of this probability 9 days in advance) is worth watching.

One might wish for greater certainty, but half of the weather excitement of living in Israel is waiting for whatever weather event "mother-nature" has in store.

Sincerely,

Barry Lynn

Tuesday, December 30, 2014

Weather It Is (High Clouds and then the Storm)

Good Morning:

The sky is streaked with high clouds ahead of our next winter storm.  As previously mentioned, the separation between the northern and southern Jet Streams has come to an end and we are seeing cold air (previously locked up in northern Europe) stream southward.

The interaction of the southern and northern streams has brought gale force winds to the Mediterranean, as well as severe winter cold to central Europe.  The stormy weather will move eastward towards our area by the end of the week.  Shabbat will likely be rainy and windy, with a small chance of rain mixed with snow at the highest elevations.  A ridge of high pressure will then build into western Europe which will allow the trough of lower pressure to strengthen over the eastern Mediterranean.  This will allow the coldest air of the winter season to spill southwards and possibly develop a an even stronger winter storm that will last several days. (In any case, next week looks to be a wet week.)

While we know it will be wet and windy, we don't know yet how cold it will get as the storm possibly reintensifies early next week. This will depend on just much the ridge to our west sharpens, which itself will depend on the influx and movement winter time system over the western Atlantic.

In summary, we know it will be quite wet with strong, possibly gale force winds.  Will it snow on the Hermon -- yes.  Will it snow elsewhere, most likely not -- but there's a chance it will.

Barry Lynn

Friday, December 26, 2014

Weather It Is (A Wave and a Crash)/

Good Afternoon:

The weather has been quite pleasant -- and no one is complaining. Yet, it is hard to beat the calendar and he calendar says we're headed towards January.

The past month was a bit odd weather-wise.  We had frequent rain, but not particularly very much.  The weather was more like late fall in NY than early winter in Israel.  This was in response to a split in the jet stream, where the southern stream was active but unable to tap the cold air associated with the northern jet stream.

This may be changing towards late next week -- perhaps just in time for my next (isn't it always?) birthday.  The split pattern should end and a deep trough will form over western-central Europe and move  -- like a wave -- eastward. It appears that some rain should occur with this system as temperatures dive down into the single digits.  Just how cold we'll get remains to be seen, but right now it looks most probably  to be just rain.  We'll need a bigger wave and bigger crash on our shores to bring more than this.

Shabbat Shalom,

Barry Lynn

Saturday, December 20, 2014

Weather It Is (Some Rain)

Good Evening:

We're looking at low pressure moving into our area during the next couple of days.  There will be a chance of showers into Tuesday morning, with lighter showers Sunday into Monday, and heavier rain more likely Monday afternoon into Tuesday morning.

The weather pattern, however, is showing a bit of split flow.  The low pressure is swinging around broad high pressure over northern Africa and Southern Europe.  This broad area of low pressure will then build further eastward, and all of our winter "cold" will be shunted to the northern reaches of Europe for several days thereafter.

It won't be until the end of this week before the high pressure area begins to take on a more north-to south orientation, which will allow for cold air to seep southward again. This will allow for a stronger trough of low pressure to develop over the central Mediterranean.  The high pressure system may then nose to the east, bringing even more cold air into the trough.  Whether it makes it as far as our way remains to be seen.

Chanukah Samaech,

Barry Lynn

Wednesday, December 17, 2014

Weather It Is (The Weather Starts to Feel Cooler)

Good Evening:

There was a nip in the air today; yet, the air is going to get a lot nippier soon.  Temperatures are headed downwards as our next storm begins to take shape in the eastern Mediterranean.

The problem: we're not really sure just exactly how this next storm is going to develop.  There will be a slight chance of showers on Shabbat, and then the energy associated with the next storm will move into our area early next week. Still,  it's not clear how much phasing of the northern and southern jet streams will take place.

Some of the Global Ensemble members are showing quite a lot of phasing and a lot of cold air streaming southward.  However, there is no trend yet in the overall ensemble so we can't really commit to any type of scenario just yet.  The less said, the better.

In fact, my wife was quite pleased when she heard that the doctor told me to try "not to speak," as I am suffering from a bit of laryngitis. She didn't really say why, but she seemed quite sure of herself about this.

It's interesting: the "whole" point of feminism was to give women a chance to be more than just a homeowner, much more, in fact.  One consequence was that the husbands should take on the "womanly" tasks like cooking, wash, etc.  Yet, it doesn't really seem that my wife is too pleased that I took my mother and sister's encouragement to be pro-feminism, and I wonder if this is simply because I have invaded her "turf."  After all, did women (who were queen (or is that king?) of the kitchen really want to share their domain with someone else?

If so, why in one of my nicknames "Maetzben?"  (Something bothersome, for those who don't know this word.) I seem to get this a lot when I try to help in any way other than taking out the trash or cleaning the dishes.

It's tough to be a husband in today's modern age, but I have to admit that I can put up with the criticism in order to be a little creative in the kitchen.  After all, I can make the perfect pizza even if I can't make the perfect weather forecast.

Chanukah Samaech,

Barry Lynn

Sunday, December 14, 2014

Weather It Is (A Weather Review and Forecast)

Good Morning:

Today's rainy weather should generally leave between 10 and 25 mm of rain along the coastal regions.  There will be occasional lightning during the day as well.  There will be lesser amounts in the center of the country and up north.

Looking head, we see the possibility of another system approaching towards the end of the week.  At this time, it is not clear (from the ensemble data) how much rain should fall with this system. There is the possibility for significant rain, but it is equally as likely that rain will be generally light. 

I'd like to bring a greater understanding with regard to the recent heavy rain/lightning event that impacted the Jerusalem area Friday evening. There was also heavy rain and lightning from Beer-Sheva to the Dead Sea Basin.  This event was not forecast using the GFS forecast data from the previous night (the 0 GMT data), but only with the 6 GMT data (and an ensemble model). If you'd like a better understanding about the predictability of weather, please read on.

While speaking about the potential for terrorist attacks against the United States, Donald Rumsfeld -- then the Secretary of Defense -- stated: "There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know."

This quote is very relevant because it describes the state of the art with regard to weather forecasting.  It also provides an opportunity for improvement. 

1) Things we know we know: these are synoptic Systems often seen as areas of low or high pressure on the weather map.  This is the type of situation we forecast quite well and well in advance with our high resolution model (1.3 km single ("deterministic") forecast) a couple of weeks back, where there was heavy rain (> 100 mm) from Ashkelon eastward to Jerusalem. 
2) There are things we know we don’t know: the location and intensity of rainfall in a previous synoptically driven convective rain were forecast more accurately with our 4 km ensemble forecast.  In this situation, the coastal cities received localized heavy rain amounts of > 25 mm in three hours.
3) There are things we don’t know we don’t know: these are weather systems that originate in small convective clouds, and are smaller than the resolvable synoptic grid.  That is, they won't appear in the forecast grid of the synoptic scale model, even though they can (with a "fine eye")  be seen by satellite or in a lightning detection network.   Yet, these convective events  nevertheless grow up-scale to become mesoscale convective storms.  Once they reach the mesoscale, they are often resolvable by the global models presently in use today.   This is the event of Friday evening. It became apparent only with the 6 GMT forecast information -- that is, it grew upscale (with large enough size) to be "seen: (resolved) on the GFS forecast grid. Our high resolution forecast of this significant rain event became available just prior to the event, and was forecast only with our high resolution 4 km ensemble.  The deterministic model did not forecast this event.

There are avenues available for forecast improvement.  The use of satellite information or a lightning network might allow for the forecast of these events several hours in advance. 

Barry Lynn

Thursday, December 11, 2014

Weather It Is (Not Much, But It's Winter)

Good Morning:

Today's temperatures will be quite pleasant.  Then, a weak area of low pressure will approach the eastern Mediterranean bringing a chance of showers.

High pressure remains anchored over the eastern Atlantic ocean. This allows for areas of low pressure to move across the sea, but without a good supply of cold air these systems weaken as they move eastward.  We see no change for the next week or so, just more wintertime temperatures than the past few days.

The other day I asked my wife to go for a walk, and promised her that it wouldn't rain on us.  Her reply: "that's what you said last time."  Sometimes, I really wish I was a doctor of medicine instead of  atmospheric science (and environment).  First, it is a lot easier to fix an earache, rather than a rainy day.  Second, imagine my triumph when the kids ask me if they have an earache, and I can confidently answer: "yes, you do! -- now take your medicine and you'll be better no-time."  Instead, I get questions like: "will it rain today?"  "Possibly," I answer.  "Not good enough!" -- I get back.

The worst is right before a possible snow-storm.  I go to sleep and I toss and turn until morning. I open my eyes and, yes, it did snow.  I'm thrilled -- but only until I realize that I was just dreaming.  It gets worse: I even started dreaming that I woke up, pinched myself, just to be sure, and then...

It makes me to want to retire, or at least switch fields of work.  Did you know I make amazing Yogurt? The best in the land.  This is both satisfying and a way of developing deep friendships -- at least with my friends: Lactobacillus bulgaricus and Streptococcus thermopiles.


Have a good day!

Barry Lynn




Friday, December 5, 2014

Weather It Is (Looking Ahead)

Good Afternoon:

It appears that our late fall/early winter weather will be changing.  Temperatures should start heading downwards and it will feel more like winter by early next week.

At the same time, weak low pressure should approach the area on or about Tuesday bringing showers, but no significant rain.

Temperatures will snap upwards for a day or two, but then head down to even cooler levels by the start of Chanukah.

We don't see any real cold air in the forecast, but it should start to get wetter, and significant rain may occur early the following week.

Where is the rain of yesterday?  Looking at the weather map shows strong high pressure over the eastern Atlantic.  Storms forming to the east of this eventually transfer southern Europe, but a kink in the jet stream prevents any real cold air from spinning up these storms, so they dissipate as they approach.

Sometimes, positive interactions among weather systems leads to amplification, while other times systems weaken.  The same can occur during social interactions, and one should try to steer clear of the situations or times when it takes more than one to make a real argument. On the other hand, one good mood or smile can also make a difference.

Shabbat Shalom,

Barry Lynn

Monday, December 1, 2014

Weather It Is (Rumors)

Good Evening:

We just received a frantic call about next week's snowstorm.   The problem is that we're not speaking, writing, or even hinting about a snowstorm next week.

In fact, the next two days will be really nice as temperatures warm by about 6 degrees.

It's what happens (or might happen) starting early next week that seems to be causing the panic.
We see that a storm might develop next week, and that sometime next week it might rain.  We also see a 10% chance that the northern jet stream will phase with the southern jet stream and bring us unusually cold temperatures.

However, unlike last year when it just a question of how cold, now it's a question of whether it will be cold or not, let enough cold enough for snow.

So, let's stop the rumors, the panic, and frantic preparations, and just wait to see how the weather plays out -- so no worries just yet.

Barry Lynn