Thanksgiving Gales Possible

A strong cold front crossed the island with extensive and slow moving shower activity on Monday. The very active front brought between 0.50″ and 0.75″ of rain to the island on Monday – much needed rains as November has been relatively dry so far. Behind the front, today strong north-northeasterly winds are ushering in cooler and less humid weather, with some lingering post-frontal isolated passing showers.

Strong north-northeasterly flow is expected to continue through Wednesday. This flow then veers overnight Wednesday into Thursday, becoming more northeasterly. This is in response to either a wave or an area of low pressure forming along Monday’s cold front which, by Wednesday night, has stalled to the south through east of Bermuda. This wave then pushes westward towards Bermuda, crossing the island on Thursday night. There is potential for heavy rain, thunder, and gales to develop in the northeasterly flow ahead of the wave or area of low pressure. Such an area of adverse weather could impact the island on Thursday.

The official forecast (from the Bermuda Weather Service) for the second half of this week should therefore be monitored closely for updates if or as this system develops.

Hurricane Kate Passes to the Northwest

Hurricane Kate north of Bermuda yesterday morning, at the time Kate was racing away to the east-northeast at 40-45mph.
Hurricane Kate northeast of Bermuda yesterday morning, at the time Kate was racing away to the east-northeast at 40-45mph.

Kate strengthened into a Hurricane and passed about 250miles northwest of Bermuda in the predawn hours of Wednesday morning. A broken band of showers slowly moved across the island during the day along with strong southwesterly winds with gusts to gale force, particularly in higher elevations with exposure to winds from that direction. By sunset, a weak cold front associated with the non-tropical low that steered Kate northeastward crossed the island with another brief period of shower activity. Kate has since transitioned into a post-tropical cyclone and is expected to bring strong and gusty winds and heavy rain to the UK in the next three to four days as a non-tropical cyclone.

Radar imagery showing a band of showers south of Bermuda just after the weak cold front passed at around 5pm. (Radar Link)

Northwesterly winds have now settled in and are strong at times. Less humid and slightly cooler weather has developed in the flow behind the cold front. A brief warm-up on Friday will be followed by another cold front by Friday evening with much cooler and much less humid air. Expect a narrow band of brief showers to blow through Friday evening with winds shifting from southwest to west. Well below normal temperatures settle in for the weekend, again with strong westerly winds veering northwesterly – some post-frontal shower activity could develop as much cooler continental air moves over the still warm waters of the western Atlantic.

Afternoon high temperatures will likely struggle to reach 70F on Sunday following Friday’s front. Northwesterly flow begins to veer to the north then northeast and diminish from strong to moderate by Monday keeping cooler than normal weather in place. High pressure slides in from the west on Monday so, while remaining cool, more settled weather develops.

Follow the Bermuda Weather Service for the latest official forecast information.

Tropical Storm Kate to Pass to the North

Kate 10 Nov 2015 1815 UTC
Tropical Storm Kate racing northeastward in the southwestern Atlantic. Kate is expected to pass to the north of Bermuda early on Wednesday.

Tropical Storm Kate formed early yesterday morning. The storm tracked north of the Bahamas Islands, clearing those islands by late Monday night, turning northward. Kate continued to recurve and is accelerating northeastward and strengthening. The National Hurricane Center’s forecast as of 11am expects Kate to pass north of Bermuda Wednesday morning as a minimal hurricane. This is a relatively high confidence forecast, taking Kate more than 150nm north of Bermuda. Because Kate is a small storm, small differences in the actual track will therefore have little bearing on the impacts in Bermuda.

Kate has strengthened and developed a more robust circulation than originally expected. This will delay it being absorbed by a non-tropical low until after Kate passes Bermuda.

Expect southerly winds to increase from moderate to strong, then veer to the southwest overnight. Shower or possibly thunderstorm activity associated with rain bands far removed from the center of Kate could bring gusts to tropical storm force (>34kts or >39mph) on Wednesday morning. Winds could briefly peak at sustained tropical storm strength in the northern marine area and in elevated areas of the island with exposure to southwesterly winds, particularly around any squallier showers or thunderstorms.

Following Kate’s passage, a cold front rolls through Wednesday night and winds veer to the west, ushering in cooler and less humid weather. Kate serves as a reminder that Hurricane Season runs from June 1st to November 30th for a reason.

See the Bermuda Weather Service and the National Hurricane Center for the latest official information.

Cold Front and Possible Tropical System

A warm day today with temperatures near record highs in the low 80s F comes to an end this evening as a cold front pushes through from the northwest. This brings showers and periods of rain along with a period of much cooler weather. Southwesterly winds ahead of the front shift sharply northerly, then continue to veer becoming easterly and strong at times on Monday as today’s front becomes stationary near to the south of the island.

With the now stationary front to the near south of Bermuda, cloudiness, showers, or patchy rain remain in the area through Tuesday. Another frontal system begins to develop along the US East coast on Tuesday morning and pulls the stationary front northward. Winds veer from easterly to southeasterly during this time, remaining mostly moderate. The frontal system is expected to move east-northeastward beyond Tuesday.

RGB Satellite imagery centered on the tropical low that the NHC is monitoring for development. The small low is just north of the Turks and Caicos Islands.
RGB Satellite imagery centered on the tropical low that the NHC is monitoring for development. The small low is just north of the Turks and Caicos Islands.

Meanwhile, a tropical low currently just north of the Turks and Caicos Islands is being monitored by the National Hurricane Center for the possibility of tropical depression or storm formation as it tracks west-northwestward. As of their 3pm update, the NHC is giving this tropical low a ‘high’ 70% chance of becoming a tropical cyclone either tonight or tomorrow should the current pace of development continue. Aircraft Reconnaissance is scheduled to investigate the low tomorrow morning as it begins to impact the Bahamas Islands. By Tuesday, the potential tropical storm will begin to turn to the north then northeast as the frontal system developing along the US East coast begins to change the regional steering flow.

Cooler drier air around the frontal system and cooler sea surface temperatures along the potential tropical storm’s track beyond Tuesday will likely result in a weakening trend. It is likely that the frontal system absorbs whatever is left of the potential tropical storm. But the possibility exists that a weakening tropical cyclone could pass close enough to Bermuda to bring strong winds and gusty showers on Wednesday as the weakening potential tropical storm and cold front move through. Much cooler and less humid weather can be expected for Thursday.

Follow the Bermuda Weather Service and the National Hurricane Center for the latest official forecast.

Strong Weekend Cold Front

Terra MODIS Satellite imagery for Monday morning showing cumulus field behind the cold front - typical of cold air blowing over warm water.
Terra MODIS Satellite imagery for Monday morning showing cumulus field behind the cold front streaming across the Atlantic toward Bermuda – typical of cold air blowing over warm water.

Sunday night saw the passage of a strong cold front with little fanfare save for a wind shift and increase. Winds shifted to the north and increased to strong with gale force gusts early Monday morning ushering in a much colder airmass. The airmass originated in southeastern Canada and was responsible for the first snow of the season in that region and the Northeastern United States. Temperatures fell through the morning and struggled just below 70F around midday, then continued to fall overnight and fell to record lows, which are around 65F for this time of year – 64.2F at the airport and 63.8F at my PWS.

October Cold Front 2015 Temp
October Cold Front 2015 Dew The last week’s Temperature and Dew Point trace from my PWS.

Perhaps more notable than the increased winds and lower temperatures was the drop in humidity. While midday temperatures fell from around 80F on Sunday to around 70F on Monday, the dew points fell from near 70F on Sunday to around 50F on Monday.

This much cooler and less humid weather will not stick around. Winds have since shifted to the east-northeast as high pressure extends a ridge north of Bermuda. Low pressure forming to the south of the island in the next day or two should be monitored as it will strengthen the pressure gradient across Bermuda thus increasing those east-northeasterly winds to strong again and introducing chances for rain or showers by Friday. Keep up to date with the official forecasts from the Bermuda Weather Service.

Joaquin to Pass Bermuda Tonight

Hurricane Joaquin RGB 4 OCT 2015 1415UTC
RGB Imagery at 14:15UTC this morning showing hurricane Joaquin nearing Bermuda from the southwest. You can see that the satellite presentation of Joaquin has deteriorated with an eye no longer evident and a smaller central dense overcast region – symptoms of a weakening hurricane.

Hurricane Joaquin has left the Bahamas and is now embedded in a well defined generally northeastward flow. Yesterday morning saw a second peak in intensity as Joaquin moved away from the Bahamas, but the hurricane has since weakened as expected. As of the noon update from the National Hurricane Center, Joaquin had weakened to a category two hurricane with 110mph maximum sustained winds and a minimum central pressure near 957mb. The center of Joaquin is expected to pass roughly 60 miles to the west and northwest of the island.

  • The Bermuda Weather Service issued a Hurricane Warning for Bermuda and the surrounding marine area yesterday and that remains in effect. This means that hurricane conditions (sustained winds greater than 74mph or 64kts) are expected in part of the warning area generally within 36 hours of issuance.
  • Hurricane Joaquin Surface Wind Field noon 4 Oct 2015As of noontime, it looks like sustained tropical storm force winds (>39mph or 34kts) are already occurring in the marine area and at elevated and exposed areas. Sustained winds should continue to increase this afternoon, exceeding 60mph (50kts) at times with higher gusts as Joaquin makes its closest point of approach. Elevated areas exposed to southeast, south, and southwest winds, particularly in the west end could see a period of sustained hurricane force winds with higher gusts tonight. Expect isolated to scattered power outages and mainly vegetative damage with some isolated minor structural damage possible in areas of highest winds. It doesn’t look likely that Joaquin will make a direct hit on Bermuda tonight, but in the event that happens, be prepared for significantly higher winds.
  • Dangerous sea states are developing now and some minor coastal flooding is possible in areas of onshore winds. Heavy showers of rain have occurred and should become more steady this afternoon as the center of Joaquin gets closer. Unofficial rainfall totals near 2″ have been reported on some wunderground personal weather stations since last night. Additional accumulations of 1-3 inches are possible as Joaquin passes and could lead to flooding in low-lying areas particularly around high tide. As with any tropical cyclone, there is the threat of isolated tornadoes in the heavier squally showers in the outer bands.
  • Continue to monitor official updates from the Bermuda Weather Service and the National Hurricane Center regarding the track and intensity of Joaquin and any changes to expected impacts.

Hurricane Joaquin a “Threat” to Bermuda

Hurricane Joaquin OCT 02 2015 2015UTC
RGB imagery of the Eastern United States and Western Atlantic showing the current location of Hurricane Joaquin in relation to the steering, deep-layered cut off low to its west. Joaquin’s approximate 5-day track is drawn on. Image as of 20:15UTC October 2 2015

The forecast track of Hurricane Joaquin has shifted further eastward as the model guidance suite has shifted further east and the models are beginning to show less spread between each other. As noted in previous posts, the scenario where Joaquin took a path either out to sea and possibly brushing Bermuda was always on the table and so it is a little bit misleading to say that Joaquin is only now just becoming a ‘potential threat’ or ‘threat’ to Bermuda. A Tropical Cyclone forecast to pass within 400 nautical miles of Bermuda is classified as a ‘potential threat’ while any Tropical Cyclone forecast to bring adverse weather to Bermuda is classified as a ‘threat’. Today, confidence has grown around this scenario and Joaquin could begin to spread tropical storm conditions across Bermuda as early as Sunday evening as it passes some distance to the west of Bermuda. This is reflected by the Bermuda Weather Service issuing a Tropical Storm Watch for Bermuda in their 4:30pm forecast.

Joaquin remains a major hurricane this afternoon. It continued strengthening yesterday morning, reaching category four strength and became one of the most intense hurricanes to make a direct hit on the Central Bahamas in the modern record as pressures fell as low as 931mb. Maintaining category four strength overnight and through this morning, an astounding 36+ hours of sustained hurricane or major hurricane conditions should be coming to an end on the Central Bahamas islands in the next few hours as Joaquin begins to track northward. These conditions include potentially life threatening storm surge, topped with large and battering waves, along with torrential rains over several tidal cycles.

National Hurricane Center 5-day forecast track for Hurricane Joaquin.
National Hurricane Center 5-day forecast track for Hurricane Joaquin. Current Watches and Warnings are highlighted.

As of the 6pm advisory from the National Hurricane Center, Hurricane Joaquin remains a major hurricane but has weakened slightly and now has maximum 1-minute sustained winds near 125mph and a minimum central pressure near 942mb.

  • Joaquin is expected to continue northward out of the Bahamas as it feels the southerly flow around a mid-latitude system over the Southeastern United States. Joaquin then turns more northeastward on Saturday and begins to approach Bermuda before turning back northward on Sunday and passing to the west of Bermuda on Sunday night. On Monday, Joaquin gets caught in the mid-latitude westerly flow and returns to a northeasterly track and accelerates into the Central far North Atlantic.
  • Joaquin has likely either already peaked in intensity, or will do so in the next 12-24 hours before environmental conditions begin to become less favorable for a major hurricane. By Saturday evening, expect a steady weakening trend to begin and last through transition to a powerful post-tropical cyclone just south of Atlantic Canada on Monday night.
  • As the hurricane passes to the west of Bermuda, following the NHC forecast track as of 6pm, expect southeasterly winds to increase to tropical storm force while veering to the south on Sunday through Sunday night. Winds continue to veer to the southwest then begin to decrease below tropical storm force on Monday. Expect squally showers with a chance for thunder as the outer bands of Joaquin cross the island. Further, hazardous sea states will develop over the weekend and last into Tuesday due to rough southerly swells. Keep in mind that tropical storm force winds extend up to 180 nautical miles from the center of Joaquin.
  • A Tropical Storm Watch means that the onset of tropical storm conditions (sustained winds over 39mph or 34kts) is possible in the next 48hours. Continue to monitor updates and changes to the Bermuda Weather Service & National Hurricane Center products and forecast as more information becomes available and forecast confidence improves in the approach of Joaquin. There is still a higher than normal level of uncertainty in this forecast and small changes in the track now could result in dramatically different conditions in Bermuda as Joaquin passes.