Ending a five-day spell of intense heat and dry conditions, lightning illuminated Israeli skies, and heavy rains caused chaos.
Rains poured all over the country on Wednesday night and Thursday, accompanied by isolated thunderstorms and unseasonable drops in temperatures, according to Israel Meteorological Services.
The downpour led to flash floods and road closures across the South, sending police search and rescue teams scrambling to rescue stranded drivers.
In the early morning, a group of around 200 students from Hadera and their parents were stranded at Masada after the flooding blocked off their exit route. They were eventually evacuated to nearby Kfar Hanokdim.
At the height of the storm, Highway 90 into Eilat was closed for hours, blocking the entrance to the city. Also on Thursday, as flooding swept through the Arava, a mother and daughter were moderately hurt when their car overturned near Yotvata.
Although rainy periods in May are not unusual – and in fact occur nearly ever year – these episodes tend to occur only locally and involve no more than a few millimeters of rain, Dr. Amos Porat, director of the IMS Climate Department, told The Jerusalem Post on Thursday. The Thursday rains, however, were occurring on a widespread scale and were “exceptional with large amounts,” he said.
“The rainfall and thunderstorms we have experienced are a result of a very unstable atmosphere caused by warm air at low levels of the atmosphere accompanied by an upper air trough with cold air,” Porat said.
“We received a lot of humidity and cloudiness from the tropical areas of Africa.”
In meteorological terms, a trough is an elongated region characterized by low atmospheric pressure, whereas a ridge is such an area with high atmospheric pressure.
Unlike during winter storms, in which cold air masses move in from Europe, in this case, tropical air masses moved in from eastern Africa or potentially even as far as the Indian Ocean, Dr. Baruch Ziv, a climate scientist at the Open University, told the Post. Lightning frequency was very high, a typical component of tropical storms, and the intensity of the rains were extreme, Ziv added.
The strong storms carried with them widespread thunder and lightning and drenched the country with rain almost nonstop from Wednesday night through Thursday morning, IMS data, provided by Porat, said. Up until Thursday afternoon, the largest amount of rains fell in the Shfela region, with about 50-80 mm. accumulating there. In most monitoring stations stretching from the North to the northern Negev, between 20-50 mm. piled up, the data said.
The station at Tzora, in the Mateh Yehuda Regional Council, received 82 mm. of rain, the maximum amount of rain accumulated in a single May day in Israel since 1963, when 93 mm. fell in Afula, according to IMS.
“This event was exceptional or even unique for May,” Ziv said. “I think that there was not even one rain station in Israel that didn’t get rain.”
Despite the rains of the past two days, northern portions of the country in particular still face large deficits in rainfall since the beginning of the season – only accumulating about 50-70 percent of their average annual rainfall, the IMS said. In the Center, the deficit is smaller, with those areas receiving between 70-85% of average annual rainfall. From the Ashdod and Hebron areas and southward, areas received typical rainfall amounts, the IMS said.
When the air becomes warmer, it contains more water vapor, and therefore has an increased potential for rain, Ziv explained.
“The intensity of this storm may be related somehow to global warming,” Ziv said.
As the tropical air masses become warmer, the potential intensity of such storms becomes higher, he added.
“I think that one tendency that we see nowadays is that storms in the beginning and the end of the rainy season tend to be more intense,” Ziv said.
He stressed, however, that “we need more time to be convinced about the significance of such findings.”
Wednesday night and Thursday’s rainy conditions followed days of spring heat-wave conditions – known in Hebrew as sharav – which typically occur in the March through May months and are different from summer heat waves, Porat explained. Sharav heat waves are characterized by warm and dry conditions, including in coastal areas, which typically involve relative humidity of less than 20% and temperatures of 30-35°C, or sometimes even up to 40°C, he continued.
“The heat waves are caused by depressions from northern Africa or a Red Sea trough with low level southeasterly to southwesterly winds, bringing warm and dry air from the deserts,” Porat said.
While Porat stressed he would not call the four-to-five-day heat wave exceptional, he said that such spells typically last only one or two days in the spring.
Due to the inclement weather, the National Road Safety Authority reminded drivers on Thursday to exercise additional caution on the roads and remember that moisture and winds make driving conditions more difficult. On slippery roads, drivers are advised to reduce their speed by 20 km/h and maintain a greater distance between vehicles, the authority said. Sudden braking, as well as passing, should be avoided, and lights should be turned on, the authority added.
Meanwhile, the Kanat - Insurance Fund for Natural Risks in Agriculture estimated that the heavy rains have caused millions of shekels worth of damages to crops. The fund reported receiving dozens of calls from farmers on Thursday, most citing damages due to hail and rain. Hail mainly affected fruit crops, such as grapes, apricots, peaches and nectarines in the Lachish region, the fund said.
Rains heavily damaged hay grown for animal feeds.
Showers and isolated thunderstorms, as well as hail in some cases, were expected to continue throughout the day on Thursday, with drops in temperatures around the country and risk of flash floods in eastern and southern wadis, IMS forecast data said.
For Friday, the IMS forecasted partly cloudy and slightly warmer conditions, with isolated showers expected in the North until the afternoon. Saturday would likely feature partly cloudy skies with slightly warmer temperatures, and similar, perhaps clearer conditions would continue on Sunday, the IMS added.