Gales developed on Friday as a small low pressure passed just under 80 km to the north. This low was one of a series of small-scale low pressure systems that tracked from west to east along a quasi-stationary front near Bermuda last week.
Ahead of Friday’s low, that quasi-stationary front lifted northward across the island with patchy light rain showers on Thursday night. This was accompanied by an increase in temperatures and humidity as southwesterly winds strengthened early Friday morning. Southwesterly winds briefly increased to gale force (sustained >34 kts) with unofficial gusts over 45 kts reported at automated weather observing sites. Winds then dropped off slightly, veering through to northerly as the front moved across Bermuda from west.
Cooler air then blew in as winds veered to the north on renewed gales behind the front. Storm force (>48 kts) gusts were recorded around the island, with a peak official gust of 49 kts at the airport, the second highest official gust observed in May since 1949*. High winds resulted in diverted flights (Royal Gazette/Bernews), delayed start to Relay for Life (Bernews), and several boat incidents (Bernews).
Very little rain fell from this system. Much of the shower activity was confined to the north of the island (along the front near the centre of the low), and south of the island (along the front). Pressure fell to 1000.7 hPa as the low passed the island, the lowest pressure observed in May since 2007**.
* Only 6th May 1978 had a higher gust at 50 kts, but the record is incomplete prior to 1996.
** This statistic is not recorded prior to August 2006.
After each season, the National Hurricane Center prepares ‘post-storm reports’ on each tropical cyclone that formed in the North Atlantic and Eastern Pacific basins. These reports include data collected in real-time that may not have been available during operational analysis, and therefore can sometimes lead to revision of track or intensity. This was the case for 2014’s Hurricane Fay.
Today, the National Hurricane Center released its report on 2016’s Hurricane Nicole. Their analysis on observations from Bermuda suggest that widespread category one conditions occurred on the island with isolated areas seeing category two conditions. Aircraft reconnaissance measurements near the time of closest point of approach to Bermuda indicate that Nicole was still a category three hurricane with maximum sustained winds near 105 kts (120 mph). The island received impacts from the left-front quadrant of Nicole’s eyewall, missing these strongest winds (located in the right-front quadrant) and thus this was classified as a strike.
Hurricanes are centers of extreme low pressure. Winds spiral inwards, towards centers of low pressure and in the northern hemisphere, this manifests as a counter-clockwise circulation. Observations from Bermuda indicated that winds backed (turned counter-clockwise with time) from an easterly direction to a northerly, and then northwesterly direction suggesting that the center of circulation remained to east of the island and therefore did not make landfall, despite Bermuda entering the calm eye of the hurricane.
Nicole’s impacts on Bermuda were also remarkable in that the hurricane made for one of the top-5 wettest meteorological days on record at the airport, and the Bermuda Weather Service was able to release a weather balloon in the eye that measured the highest precipitable water here since 1973 at 2.93″.
Notable for an erratic early track and meteorological evolution (including two periods of rapid intensification), Hurricane Nicole will go down in the record books as the fourth early-October hurricane impact on Bermuda in three years. Once Nicole passed Bermuda, the cyclone underwent a complex transition into a powerful extratropical cyclone in the North Atlantic where it continued to produce storm force winds for several days.
Bermuda is now well into its ‘winter’ season where changeable weather associated with gales is commonplace. Yesterday’s cold front brought a brief warm and humid spell with southwesterly gales and thunderstorms that brought heavy rain to the island.
Locally severe wind gusts, mainly confined to the marine area, were also observed. The Crescent Buoy, in the northern marine area, measured a peak thunderstorm gust of 54 kts. Winds on island appear to have remained below severe levels (i.e. < 50 kts) with a peak gust of 43 kts measured at the airport prior to any thunderstorm activity.
A well anticipated multi-day heavy rain event last weekend ended with a May’s worth of rain nearly everywhere. A band of deep, tropical moisture with total precipitable water amounts near 2 inches aligned over the island from Thursday night through Saturday afternoon. A cold front, turned stationary front remained draped nearby with associated small scale areas of low pressure developing along the front leading to isolated and brief periods of enhanced winds. The front and lows led to persistent shower and thunderstorm activity through much of the weekend resulting in some event disruption and nuisance flooding.
Officially, 3.82″ of rain was measured at the Bermuda Weather Service as a result of this rain storm. This agrees well with island-wide reports generally near 4 inches, including my PWS which measured 3.95″. In an average May, the island sees roughly 3 inches of rain.
A blocked upper level flow pattern is currently developing. This will allow an upper trough to become stationary over the Eastern United States. Meanwhile, an associated cold front slides across the Western Atlantic today, becoming stationary near the island Thursday night. Convergent surface flow in an environment of deep layered moisture ahead of and along the stalling front will help to focus and maintain a region of shower and possibly thunderstorm activity near Bermuda.
High pressure remains in control Wednesday as it begins a retreat to the east. Pressure gradient between the high pressure to the east and advancing low pressure to the west lead to strengthening southerly winds on Thursday. Thursday night sees an initial band of showers ahead of the cold front. The cold front becomes roughly stationary nearby with waves of shower activity persisting through the day on Friday and into Saturday morning. The front then resumes its progression to the east, clearing shower activity as it exits the area.
Model guidance supports rainfall totals for the ~48 hour period Thursday night through Saturday morning of 2-4″. Depending on where the most persistent organized shower activity sets up, over 6″ of rain is possible in this period. Any persistent downpours contributing to these totals could lead to flooding, particularly around high tide and in low-lying areas.
March 29th saw a slow moving cold front push through Bermuda from northwest to southeast. Lines of thunderstorms associated with the front tracked across the island dropping very heavy rain in a short period leading to some morning flooding issues. Lightning strikes associated with those thunderstorms resulted in isolated electricity, and communications interruptions on Tuesday. Further still, one of the thunderstorms produced a waterspout off the west end of the island that was caught on film – a fairly rare occurrence with only 5 days per year seeing either a funnel cloud or waterspout/tornado from the airport for the period 2000-2015, mainly in August or September.
This heavy rain event followed a string of daily record high temperatures with temperatures in the mid-70s. Highs of 75.9ºF, 76.5ºF, and 76.5ºF broke records on the 26th (previously 75.8ºF set in 1999), 27th (previously 75.2ºF set in 1999) and 29th (previously 75.0ºF set in 1989) respectively. This warmth came with unseasonably high humidity as dew point temperatures held steady near 70ºF or oppressive levels through much of that period. This warmth and moisture likely played a role in fueling the thunderstorms observed on the 29th.
Experimenting with R-code and unofficial reports from Wunderground, I’ve put together this graphical depiction of the distribution of rainfall across the island. Apparently, the heaviest rains fell in the west end where over four inches of rain was reported in spots while parts of the east end saw less than an inch. Unfortunately, there are no rain reports on Wunderground from Hamilton or Sandy’s Parishes. Gaps in report coverage limits how accurately this map represents how much rain actually fell, so I’ve indicated where each report was made.
This heavy rain event follows another event with islandwide totals of over an inch of rain just two days earlier. The combination of these events has made March 2016 unusually wet, and has officially (at the airport) brought 2016’s year to date values roughly a month’s worth of rain above average.
The 17th of February saw a very wet and active frontal system move across the island. With steady rain and embedded heavier showers and isolated thunderstorms. The widespread rains generally totaled more than two inches across the island, with the central parishes seeing the greatest totals. The 2.11″ of rain that fell at the Bermuda Weather Service was a daily record total for the 17th, beating the previous record of 1.76″ set in 1987. The wettest February day at the airport saw 3.80″ of rain on 21 February 1981.
This rain came on the heels of some of the coldest air of the season. The frontal system responsible for all this rain also ushered in a cold air mass in it’s wake with strong winds and below normal temperatures with lows around 55ºF on the 19th.
A quieter pattern is in store for the next five days with generally light to moderate winds and temperatures recovering to the low 70s, follow the Bermuda Weather Service for the latest official weather.
Below are Wunderground personal weather station reports for the meteorological day on the 17th. These are unofficial except where noted.
A cold front and associated pre-frontal trough to the west of Bermuda is expected to reach the island early tomorrow with heavy rain, showers, and possible thunder.
Strong southerly flow ahead of the frontal system has allowed temperatures to climb into the low-70s and dew points to recover into the mid-60s after a cold and blustery weekend. Further warmth and moisture should continue to stream into place tonight. Showers with heavy rainfall rates are becoming increasingly likely, beginning early tomorrow morning. Over an inch of storm total rainfall is possible, mostly falling tomorrow. This could lead to some isolated flooding in low-lying areas, especially if this heavy rain occurs around the time of high tide.