By January 7, 2019 Read More →

Severe weather warning

From Jerusalem weather forecasts FB page:

Not so thrilling chance of snow Tuesday night – here are all the fun details:
(TLDR FORECAST at the bottom)

Ok, hey everybody! I know it’s been a while. That’s partly due to being busy with other work, but also due to the lacklusterness of all of the snowstorm potential we’ve had so far.

As many of you read before, there were indications a few weeks ago that the first week of January could be a snowy and wintery period. The CFS long-range model had consistently forecasted a cold Russian trough diving south toward Israel thanks to a warm air ridge over Europe. So indeed, this weather pattern did develop, but we just didn’t cash in the opportunity. The ridge over Europe developed too west (thanks to a negative NAO) and the resulting cold air trough dug down too positive – which is a technical way of saying that it slanted westward away from us sending most of the cold air into Greece and Turkey. As I’ve said many times, getting snow in Jerusalem is tough – it requires so many factors falling into place just right, and often, those factors don’t – hence the reason why statistically speaking – Jerusalem receives accumulating snow once every 4 years.

But with that said, there’s a small chance we’ll see our vibe shift slightly more snowy with a storm approaching tomorrow Tuesday night into Wednesday morning. Now before I go into it, let me just say this will most likely not be a memorable storm at all. I will even say that chances of it just being a cold rain with some ice mixed in is much more likely to happen than there being snow.

BUT – there are some significant factors in place that warrant a post, and let me explain why. If you look at the two pictures I posted, you will first see the upper-level 500mb heights forecast map for late Tuesday. You can see our important warm air ridge over Europe, and then the cold air trough from the north diving south toward Israel. Notice though, that the trough looks unrefined, and has a curvy feature due to a low-pressure system or shortwave positioned inside it over northeast Europe. This wave of energy, unfortunately, limits just how south the bottom part of the trough can dig into Israel and is also forecasted to continue this bad trend of diving too far west/positively tilted in the following days after our storm. So not only does this limit the southward motion of the upper-level cold, but it also forces the trough to pull westward from us for several days after Tuesday.

However, since there is still some downward motion to the trough, it is successfully able to push a lot of significant lower level cold at 850mb into Israel – and this is what you see in the second picture. This means that we’ll have our coldest temps so far this winter on the ground level this coming Tuesday into Wednesday. However, whenever we don’t experience the right amount of upper-level cold that we need, storms do not produce powerful convective precipitation that results in memorable snows. Often, in these situations, much of the precipitation in the atmosphere overhead does start off as snow (since the 850mb is below 0 and 700mb levels are around -10, which is sufficient for snow formation), but that cold does not get drawn down to the surface since the precipitation ends up being more sparse and the storm overall is just less “energetic.” This usually just leaves us with a good ole cold rain, mixed with ice.

This is certainly why I am just not so pumped about the snow potential for tomorrow. However, just to be positive, I’ll throw in a couple of doses of optimism just for fun. Firstly, the models have trended toward keeping the northern storm in the cold air trough further north reducing the impact of the southern part of the trough diving down towards us. As a result, I have seen the 500mb temps trend colder the past few days, and there is still a chance they can trend cold enough to better produce the copious amounts of precipitation we’d need for a good storm.

Secondly, the storm is coming in a more westerly motion than our previous storm yesterday, which came in more northwesterly. Northwesterly storms typically pick up dust from the south and dry out much of the air before the precipitation arrives, keeping most of the precipitation north of Jerusalem (that’s why it was dusty yesterday morning and afternoon before the rain arrived and why most of yesterday’s precipitation occurred north of us). But with this upcoming storm and it’s westward motion, this is less likely to happen and the center of Israel/Jerusalem should receive more precipitation.

So, what’s my FORECAST?

TUESDAY MORNING – AFTERNOON: Winds will grow stronger, and cloud cover will increase. Temps will noticeably drop.

TUESDAY NIGHT – WEDNESDAY MORNING: Precipitation will begin falling as early as 6pm but will be at it’s strongest between 10pm to 6am. There is a 60% chance it will fall as rain mixed with ice pellets. There is a 30% chance, especially when precipitation falls down the heaviest, that it will turn into a clean wet snowfall, but with no accumulation. There is a 10% this event will be nothing but a cold rain the entire time.

WEDNESDAY MORNING and onward: Wednesday morning will be very cold, cloudy, with a small chance for rain from time to time. Onward into Thursday and beyond, temps will warm up and skies will be clear. There is no chance for rain or snow the rest of the week.

Quick and hopeful point to end off: There are a lot of indications that after this week, a cold and wintery weather pattern will return, and I am more hopeful than not that we’ll have another snow potential to start tracking. Stay tuned 🙂

Enjoy tomorrow and the rest of your week. And of course, don’t forget to pray for snow ❄️❄️⛄️⛄️🌨🌨 

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