June 2012 PWS Report

June 2012 was very active and this activity was broken up into patterns that hung around for about a week each. This included an extreme precipitation event that led to moderate flash flooding during the morning rush hour of the 15th. Additionally, the precursor to Hurricane Chris brought unexpected severe weather for Father’s day, along with a record low temperature.

Climatologically, June 2012 was cooler than average and managed to have above normal precipitation – continuing the trend that began in May. Despite the above normal monthly precipitation ending the short term drought, Bermuda remains in a long term drought as the year-to-date precipitation at the end of the month was still 8.05″ below normal so the water table remains under strain.

The first week in June was characterized by unsettled weather with rain being observed every day compliments of a nearly stationary frontal system. Dry spells occurred as waves of low pressure developed around areas of stronger convection and moved along the front; shifting the boundary slightly north or south in the process.

The cloudiness, rain, and sometimes thunderstorms along with cooler airmasses from the north associated with these semi-stationary fronts allowed temperatures to stay fairly cool for the first half of the month. I recorded 0.82″ of rain from June 1st to 9th; slightly below average (we average about an inch a week). So although it rained nearly every day – only small amounts managed to accumulate.

The front cleared away allowing pleasant weather from the 10th to the 14th of June. Although, since we were behind a cold front, temperatures remained well below average – with high temperatures not even reaching 75F some days!

The Royal Gazette photos of flooding in Pembroke parish. Bermuda Weather Service Radar Image of heavy rain June 15th 2012 7:53am.

The really extreme period began on the 15th with another stationary front parked over Bermuda. 2.5-3 inches of rain fell in about 3 hours from 6am – 9am. This led to moderate flash flooding as it coincided with high tide which was around 6:30am. As a result some roads quickly became impassable and were closed to traffic. Reports of 4 feet of water across low lying areas particularly in Pembroke near The Canal and Mill’s Creek were common. Cars had to be abandoned as they stalled in the high water. Later that day, the front drifted to the southeast and the weather cleared up. I recorded 3.09″ of rain that day and the high temperature struggled to a weak 73.2F.

The Precursor to Hurricane Chris at the height of the storm. Bermuda Weather Service Radar June 17th 2012 3:23pm

The next major weather event was that same weekend! Father’s Day Sunday June 17th. The same stationary front that brought the flash flooding on the 15th developed a wave of low pressure along it. This low pressure was poorly analyzed and so poorly forecast by our best forecast models, and so it caught quite a few by surprise. It was just too small for the models to pick up on. However, it did form and it quickly moved northeast crossing the island around 2:30pm. A mesoscale convective complex (an organized cluster of thunderstorms) existed at the head of the extra-tropical low pressure system; this is what crossed this island. As it did so, reports of low level cloud rotation and doppler radar velocities showing rotation prompted the Bermuda Weather Service to issue a Severe Weather Warning.  The Bermuda Weather Service observed sustained winds at 40kts (46mph) with gusts reaching 56kts (64mph) along with a minimum pressure near 1006mb. I observed similar pressures and a max gust to 42mph.

The level of organization of this low suggests that it was in the process of transitioning from an extra-tropical storm to a sub-tropical storm as it crossed the island. The storm still had frontal characteristics which is likely why the National Hurricane Center didn’t classify it as anything Sub-Tropical or Tropical at the time. It later detached from its frontal boundary and became Hurricane Chris to our distant northeast.

Post-Tropical Storm Debby about 90miles north of Bermuda, the cyclone brought strong winds as it passed to our near north. (Bermuda Weather Service Radar Image June 29th 12:03pm)

The island managed to dry out for about a week before yet another slow moving/stationary front draped itself across the area on the 26th. Through the end of the month, this stationary front brought 0.97″ of rain. The front finally cleared away late on the 29th as the Post-tropical remnants of Tropical Storm Debby rolled up the front like a yo-yo taking the front with it. The Post-tropical storm maintained enough of its energy to bring strong to near gale force winds to Bermuda (sustained at 31kts/36mph, gusting to 37kts/43mph) , however, it lacked sufficient convection to bring significant rain with only a few light showers being observed. The Bermuda-Azores ridge of high pressure nudged in overnight on the 30th to start July off dry.

It should be noted that the 2012 Atlantic Hurricane Season set a record for the earliest fourth named storm when Tropical Storm Debby formed in the Gulf of Mexico, however, with the unfavorable conditions of El Nino developing – this activity probably isn’t an indicator for the pace of this hurricane season.


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