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.

Major Hurricane Joaquin in the Central Bahamas

Hurricane Joaquin, in an impressive bout of rapid intensification, strengthened from a tropical storm to a category three, major hurricane yesterday. As of the 12pm advisory today, Joaquin had strengthened some more and had 125mph maximum 1-minute sustained winds, with a minimum central pressure near 942mb as reported by continued aircraft reconnaissance flights into and around the storm. Joaquin is still a category three hurricane and there is potential for additional strengthening today.

Hurricane Joaquin 11am 1 Oct 2015
An estimated wind field of tropical storm and hurricane force winds, past track of Joaquin, and latest watches and warnings for Hurricane Joaquin as of 12pm ADT 1 October 2015. See: National Hurricane Center

Hurricane Warnings are in place for the Central and Northwestern Bahamas Islands and Tropical Storm Warnings are in effect for the rest of the Bahamas and for the Turks and Caicos Islands. Hurricane conditions are already occurring on some of the central Bahamas Islands where Joaquin has either already made a direct hit or will in the next 24 hours. The main threat from Joaquin in the Bahamas appears to be the violent winds, particularly in the Hurricane Warned areas. Additionally, heavy rain related flooding and storm surge flooding are also significant threats. Joaquin is expected to spend another 12-24 hours drifting southwestward then northward through the Bahamas before exiting the archipelago to the north on Friday afternoon, so a long duration event of hurricane conditions with torrential rains and storm surge is possible on some of those islands. I wouldn’t be surprised if the geography of some of the low lying islands that take a direct hit are dramatically altered by this hurricane because of its duration and severity.

Hurricane Joaquin 1445UTC 1 Oct 2015
RGB Satellite imagery of Hurricane Joaquin over the Central Bahamas at 14:45UTC this morning.

The future of Joaquin still remains unclear despite efforts to improve the model guidance initialization with increased upper air observations. Multiple aircraft missions into and around Joaquin combined with extra weather balloon launches around both the hurricane and the mid-latitude system that is expected to steer Joaquin have been made in hopes to improve the model initialization and therefore produce a more confident and consistent forecast. As of last night’s model runs, however, model guidance continued to show an unusually high level of spread in the potential track of Joaquin. This likely will be the case until around tomorrow afternoon. By the time the system over the central United States begins to approach and interact with Joaquin (~24 hours from now), the model guidance will probably get a better handle on how it will impact Joaquin’s path.

Hurricane Joaquin is expected to continue strengthening as it drifts into the Bahamas, potentially becoming a category four hurricane by tonight. This strengthening is supported by high sea surface temperatures, decreasing vertical wind shear, and a very moist environment. Potential convective structural changes that are common in major hurricanes could result in weakening or at least fluctuations in intensity as Joaquin exits the Bahamas on Friday night. Over the weekend the approaching mid-latitude system could impact Joaquin’s intensity by either resulting in weakening, or resulting in deepening and extratropical transition – again this remains unclear due to the unusual model guidance disagreement.

The most recent National Hurricane Center track follows somewhat of a consensus or mid-point of the forecast models and takes Joaquin northward into New England by Tuesday. However, it should be noted that there are still three distinct potential tracks for Joaquin once it exits the Bahamas and any threat to land thereafter from Joaquin will likely begin on Monday:

  1. A turn to the north then northeast – either out to sea, or with possible impact to Bermuda.
  2. Almost due north – either then turning and going out to sea, or impacting New England and Atlantic Canada.
  3. A turn to the north, followed by a turn to the northwest with possible impacts in North Carolina and the Mid-Atlantic states.

The eventual solution seems to depend on how far Joaquin drifts into the Bahamas, this will impact the timing of when the approaching mid-latitude system from the Central US begins to impact Joaquin, and subsequently will impact where Joaquin goes. Each of these scenarios has support from traditionally reliable model guidance and so essentially everyone in those mentioned regions should monitor the progress of Hurricane Joaquin and for updates in track confidence and alterations in the track forecast as they come. However, it appears that regardless of track, South and North Carolina through the Mid-Atlantic states could see significant flooding as the approaching mid-latitude system interacts with deep tropical moisture already im place. See: National Hurricane Center | Bermuda Weather Service for the latest official information.

Tropical Storm Joaquin

27-30th 2015 Late September Rain Storm

Showers and rain continue in Bermuda as the stationary front continues to lift across Bermuda. Today, scattered showers and downpours are resulting from deep tropical moisture and low level convergence along a stationary front between easterly flow around high pressure to the north and southeasterly flow around newly formed Tropical Storm Joaquin, located to the southwest of the island. Storm total rainfall since the stationary front entered the picture on Saturday are 2.50″ to over 4.00″ in central and western parishes, accounting for more than half of this September’s total rainfall.

29 Sep 2015 1945UTC RGB Annotations
This evening’s RGB enhanced satellite imagery of the Western Atlantic showing Joaquin and its five-day forecast track from the National Hurricane Center – keep in mind that the 3 to 5 day period is currently an unusually low confidence forecast for Joaquin.

Joaquin has shown signs of organization today as strong northwesterly vertical wind shear abated, deep convection developed, and Joaquin continued to be embedded in a moist environment. Investigatory flights into the tropical cyclone have found that a relatively fast pace of strengthening has coincided with the improved organization. As of the 6pm advisory Joaquin had 65mph maximum 1-minute sustained winds and a minimum central pressure near 990mb.

This is a marked change from Monday when there was little forecast model support for Joaquin to strengthen. Vertical wind shear pushed the cyclone’s deep convection off to the near southeast of the surface center. This decoupled the cyclone, which means that instead of the surface circulation being vertically aligned with the mid and upper level circulations, it was tilted toward the southeast with altitude. Because low level steering flow was weak on Monday, and remains weak today, the deep convection was able to ‘pull’ the low level circulation southeastwards underneath the mid and upper level circulations while the cyclone as a whole drifted to the west. This convective re-alignment was poorly caught by the suite of forecast models yesterday.

Now that Joaquin is becoming more organized, forecast models will have a better handle on the cyclone’s short term track. A continued slow track to the west-southwest over the next 2-3 days will take Joaquin towards the northern Bahamas Islands. Joaquin’s environment will remain at least marginally favorable, if not increasingly favorable for additional development during this time. As a result, it is likely that Joaquin will become a hurricane as it approaches the Bahamas, and as of the 6pm update this evening, this scenario is now being reflected in the National Hurricane Center official forecast. While a landfall or a direct hit on any of the Bahamas Islands is not certain, tropical storm conditions are quite possible and Watches or Warnings might be required for the Northern and Central Bahamas within the next 12 hours.

The question then becomes: how far west-southwest does Joaquin go before being picked up by a quickly deepening mid-latitude system? As of the latest forecast model guidance, there appears to be several reasonable scenarios as both this mid-latitude system approaching from the northwest and the remnants of Ida approaching from the east make the steering pattern exceedingly complex – the location, amplification, and timing of both systems will have bearing on the track of Joaquin past day 3.

One scenario takes Joaquin north then northwestward into the United States East coast somewhere either in the Mid-Atlantic or Northeastern regions. Another scenario takes Joaquin northward between the US and Bermuda then out to sea. A further scenario takes Joaquin northward then northeastward toward Bermuda. Because there is so much spread in the potential track of this system, this is an unusually low confidence track forecast, particularly after day three. Hopefully, aircraft observations today will improve the accuracy of the model guidance and increase confidence in a single forecast track scenario.

Further, because Joaquin is not expected to be within 400 nm of Bermuda in the next 72 hours, the storm is not currently a threat to Bermuda at this time. However, because the potential exists for this storm to turn towards Bermuda after 72 hours it is imperative to follow updated official information from the Bermuda Weather Service and National Hurricane Center as the forecast evolves.

Japan Met Agency Radar of Typhoon Dujuan south of the Ryukyu islands over the weekend.
Japan Met Agency Radar of Typhoon Dujuan south of the Ryukyu islands over the weekend.

Recently, in the Western Pacific, Typhoon Dujuan made a direct hit on the southernmost Ryukyu islands of Japan, then a landfall in Taiwan both as a category four equivalent typhoon, followed by a second landfall in eastern China as a much weaker tropical storm. Peak wind gusts measured at 130-180mph occurred in those islands of Japan and parts of coastal northeastern Taiwan where several feet of rain also fell. Quite impressive that such measurements were possible in real time as instruments and/or communications typically fail well before winds reach that level of ferocity – a testament to the strength of local infrastructure that hopefully represents the general state of affairs in those impacted regions.

Wet and Windy Weather Weekend

Sep 28 15 1345 UTC RGB Annotated
Satellite image showing the easterly surface flow with moist southerly mid level flow over running it with connections to tropical depression 11. The stationary front to the south is serving as a focus point for the convection.
Skew T 2015092812Z Analysis
Another view of the two layered flow can be seen in this morning’s skew-t diagram for Bermuda. Low level easterly flow (surface to 4000m) with southerly through southwesterly mid level flow just above it. This is a very moist airmass through the entire column – a measure of that is the precipitable water (PWAT) which is highlighted in green as 50.81mm.

Saturday evening saw a slow moving cold front slide southwards across Bermuda. The front brought gusty showers and downpours as it crossed the island and, as it became stationary to the near south of the island, ushered in near gale force easterly winds with gale force gusts and significant rains.

Rain and shower activity continue today as deep tropical moisture flows around both the remnants of tropical storm Ida to the distant southwest and newly formed tropical depression 11 to the distant southeast. TD11 is expected to both remain weak and not have direct impacts on Bermuda. This moist flow is then lifted by the stationary front to the near south of the island, serving as a focus for shower activity to form and spread northward across the island. Significant rainfall totals from this long duration event are expected, with some areas already seeing over 2″ of rain since Saturday night, and an additional 1-4″ of rain possible as the stationary front lifts northward through Wednesday.

A strong pressure gradient (between the high pressure to the north of Bermuda and the two tropical systems to the south) behind the front is responsible for the continued near gale force easterly surface flow in Bermuda. Locations at elevation with easterly exposure have seen frequent gusts over gale force and sustained winds to gale force at times. A Gale Warning is in effect for sustained winds at elevation and in the marine area reaching gale force (>34kts, 39mph) at times today.

Expect near gale/gale force easterly winds to slowly veer southeasterly and decrease from near gale force to strong tonight. Winds continue settle out of the southeast on Tuesday and remain moderate to strong through the rest of the work week.

For the latest official forecast see the Bermuda Weather Service. For the latest official information on TD 11, see the National Hurricane Center, and the Bermuda Weather Service’s Tropicals Page.

Pacific Earthquake and Tsunami

A relatively inactive cold front crossed the island late on Tuesday ushering temperatures closer to normal and much lower dew points that fell into the low 60s for a time. This was a welcome change following a spat of unusually warm and humid weather that had heat index values over 100F common during the peak of the day. That cooler drier post-frontal flow has since veered through north and northeast and has settled out of the east-southeast. This flow is allowing a slow increase in humidity and temperatures this weekend.

Additionally, a low over the Southwestern Atlantic is being monitored for tropical or subtropical development by the National Hurricane Center. As of 3pm local time, the NHC was giving this area a 40% chance for development in the next five days. At this time, it appears that this low will track slowly northeastward and track just offshore of the US East Coast over the next five days. This is currently a low confidence situation on whether or not something (sub)tropical forms, and where the area of unsettled weather goes regardless of formation. Updates from the National Hurricane Center and the Bermuda Weather Service should be monitored for the latest official information on this system.

Elsewhere in the Atlantic, weak Tropical Depression 9 is tracking northwestward over the Central Atlantic, where it is expected to become a remnant low in the coming days. Following closely behind is Tropical Depression 10, which formed this morning. TD10 is expected to fare somewhat better than TD9 as it tracks generally west-northwestward into the Central Atlantic. TD9’s deep convection and has somewhat moistened the environment around TD10 and has shifted some of the vertical wind shear to the west. Further, TD9’s circulation has helped to steer the dry, dusty and therefore inhibitive Saharan Air Layer a little further to the north of TD10. So in some ways TD9’s demise has helped make the environment somewhat more conducive for development for TD10. The NHC expects TD10 to become a tropical storm in the next day or so as it tracks west-northwestward with gradual strengthening through the next five days.

The 8.3 Magnitude Earthquake struck around 2300UTC 16th September. A few hours later we see the water level fluctuate abnormally and dramatically between 8 feet below normal to 13 feet above normal. Smaller waves continue to impact the area as of September 18th, likely resulting in dangerous currents and water level changes.
The 8.3 Magnitude Earthquake struck around 2300UTC 16th September. Just over an hour later we see the water level fluctuate abnormally and dramatically between 8 feet below normal to 13 feet above normal at Coquimbo, Chile. Smaller waves continue to impact the area as of September 18th, likely resulting in dangerous currents and water level changes.

Meanwhile, in the Southeastern Pacific a “Great” earthquake struck just off the coast of Chile overnight on Wednesday and it generated a notable Tsunami. The tsunami peaked along the adjacent coast of Chile where tsunami waves combined with the incoming high tide (high tide is about 2ft above mean sea level) reached as high as 13 feet above mean sea level and inundated several coastal areas. Sizable tsunami waves were also measured in Hawaii where tsunami waves up to 4 feet above mean sea level were measured, and a small but measurable tsunami was also measured in places as far away as Alaska and Japan.

Water level data found at – Sea Level Station Monitoring Facility converted to feet from meters.

Low Southeast of Bermuda to Watch

8 Sep 15 1145UTC RGB
RGB Satellite imagery showing the broad area of low pressure roughly centered to the southeast of Bermuda.

A broad area of low pressure formed along a stationary front about 300 miles to the southeast of Bermuda over the weekend. Last night, the stationary front began to show signs of dissipating and the low began to show signs of consolidating. The National Hurricane Center has been monitoring this low and as of 9am local time this morning, has given it a medium 40% chance of becoming a tropical cyclone by Thursday morning. Deep convection has been able to persist over the eastern part of the surface circulation over the last day or so, but it hasn’t been able to develop well defined surface circulation probably due to moderate vertical wind shear and nearby dry mid-level air.

However, starting later today, the vertical wind shear that has been slowing development is expected to diminish. As the environment improves, it should allow for further organization of the low as it remains nearly stationary to the southeast of Bermuda over the next day or so. By Thursday morning, the low should begin moving to the north and pass well to the east of the island. If a tropical cyclone does form, it should track far enough to the east of the island to keep adverse weather at bay.

At this time, expect moderate to strong east-northeasterly winds to continue into Thursday morning with isolated showers. On Thursday, winds then back through the day, settling from the southwest by Friday afternoon as the low passes to the east then northeast. Isolated to scattered showers continue in the area, clearing into Friday. For the latest official information: Bermuda Weather Service | National Hurricane Center.

Elsewhere, Tropical Storm Fred dissipated over the east-central Atlantic and its remnant energy is tracking towards the Azores, and Tropical Storm Grace is tracking quickly westward across the central Tropical Atlantic. Grace is struggling with the nearby dry and stable air associated with the Saharan Air Layer to the near north of this system. As a result, Grace is expected to become a remnant low before reaching the northeastern Caribbean in the next four to five days. Grace is not a threat to Bermuda over the next three days.