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.

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.

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.

Active Tropics

The northern hemisphere tropics have taken another active turn. Starting in the Atlantic, after Danny dissipated in the northeast Caribbean, tropical storm Erika formed not too far behind in the central Atlantic. Erika then tracked mainly westward, following a similar track to Danny. Unlike Danny, however, Erika was a larger storm that struggled with wind shear its entire life. Erika tracked through the northeast Caribbean, crossed Haiti then Cuba where it degenerated into a tropical wave.

Erika’s heavy rains resulted in deadly flooding in parts of the northern Lesser Antilles islands. The remnants of Erika could cause hazardous flooding in parts of Florida and contribute to rainfall occurring across much of the southeastern United States over the next three days. As of 8am EST 30 Aug, the National Hurricane Center is giving the remnants of Erika a low chance of regeneration over the next 5 days as they track into the eastern Gulf of Mexico and then get drawn into an area of low pressure in the southeastern United States.

Tropical Storm Fred between the West Coast of Africa and the Cape Verde islands. Aug 30 2015 at 14:45UTC
Tropical Storm Fred between the West Coast of Africa and the Cape Verde islands this morning.

In an unusual turn, Tropical Storm Fred has formed to the southeast of the Cape Verde Islands. Typically it takes several days over the open water for African easterly waves to organize into tropical cyclones and by then they are to the southwest or west of the Cape Verde Islands. In Fred’s case, the robust wave emerged into the Atlantic and almost immediately became a tropical cyclone. Fred is forecast to track northwestward, through the Cape Verde Islands and steadily strengthen along that path. Fred is expected to be over the Cape Verde Islands by Monday afternoon. This has warranted the issuance of Hurricane Warnings for those islands.

Terra MODIS satellite imagery from yesterday showing the three Pacific hurricanes. Hawaii can be seen between Kilo and Ignacio.
Terra MODIS satellite imagery from 29 Aug 2015 showing the three Pacific hurricanes. Hawaii can be seen between Kilo and Ignacio.

Meanwhile, three major hurricanes are simultaneously churning up the waters of the Tropical Pacific ocean. From west to east, Hurricane Kilo formed in the Central Pacific and very slowly organized into a tropical storm then hurricane. Kilo is about to cross into the Western Pacific area of responsibility where it will be renamed a Typhoon. After that, Kilo is forecast to take a turn to the northwest, but then turn back towards the west by Wednesday, some fluctuations in intensity are expected as vertical wind shear fluctuates along the path. Kilo is largely in the open Pacific ocean away from populated land.

Hurricane Ignacio formed in the Eastern Pacific and tracked westward into the Central Pacific. Ignacio is expected to pass north of the Hawaiian Islands starting on Tuesday. Elevated surf seems to be the primary threat there, but strong winds and gusty showers are also possible and tropical storm conditions are possible in those higher elevations – tropical storm watches are in effect for several of the Eastern Hawaiian islands. Ignacio is expected to weaken as it passes north of the islands as vertical wind shear increases.

Finally, Jimena is tracking westward through the Eastern Pacific. On this track, Jimena is forecast to cross into the Central Pacific by Wednesday. Jimena is forecast to remain far from any land for the next five days.

All three of these hurricanes were at category four strength as of the 11am EST update from the National Hurricane Center and Central Pacific Hurricane Center.

None of the tropical cyclones out there are currently a threat to Bermuda within the next three days. Stay tuned to the Bermuda Weather Service for the latest official forecasts. For the latest on the above mentioned cyclones see: National Hurricane Center | Central Pacific Hurricane Center.

Hurricane Dolores, Typhoon Nangka, and Typhoon Halola

Tropical Storm Claudette quickly became post tropical Tuesday night south of Newfoundland where it was devoid of deep convection due to a combination of high vertical wind shear and low sea surface temperatures north of the Gulf Stream. Thus the Atlantic returns to quiet and no tropical cyclone formation is expected within the next five days. In Bermuda, a welcomed increase in the chances of showers with possible thunder will begin on Friday and potentially last through the weekend and into early next week. See the Bermuda Weather Service for the official forecast.

Meanwhile, the Pacific continues its active streak with three hurricane strength tropical cyclones impacting land simultaneously. Category three Hurricane Dolores last night passed over Mexico’s Socorro Island in the Eastern Pacific. The southern eyewall of Dolores brought sustained winds measured up to 80 mph with gusts as high as 115 mph to that island. Pressure fell as low as 968 mb as Dolores made its closest approach.

Hurricane Dolores over Soccoro
Microwave satellite imagery of Hurricane Dolores, showing the southern eyewall of the cyclone over Socorro Island at ~0130z. Peak winds were observed around this time. Naval Research Lab.

In the West Pacific, Typhoon/Tropical Storm Halola passed south of Wake Island. Halola formed in the Central Pacific and tracked westward into the West Pacific where it became a typhoon. Peak winds measured by the National Data Buoy Center (NDBD) at Wake Island reached 36 mph with gusts to 51 mph. Central-to-Western Pacific crossovers are unusual because so few tropical cyclones form in the Central Pacific. However, the above normal sea surface temperatures associated with El Niño tend to lead to a more active Central Pacific. A recent notable Central Pacific tropical cyclone was Hurricane Ioke in 2006, one of the most powerful tropical cyclones of Central Pacific origin on record. Ioke also passed over Wake Island and several low elevation atolls as a major tropical cyclone causing extensive damage in its path.

Halola is expected to continue tracking westward, deeper into the Western Pacific and slowly strengthen into a major typhoon over the next five days.

Finally, Typhoon Nangka is making landfall in Southern Japan as a category one equivalent typhoon. Heavy rainfall, particularly in the more mountainous areas has been accumulating for at least 36 hours now and the risk of flash flooding and mudslides is escalating as Nangka slowly approaches the coast. Hurricane conditions are expected to begin shortly on Shikoku and slowly spread northward with the typhoon. The main concern here is flooding – Tropical Storm Talas in 2011 took a similar approach to the coast with a similar intensity as Nangka and produced serious flash flooding and mudslides that resulted in dozens of fatalities.

Radar imagery from Japan showing the eye of Nangka just offshore of Shikoku  and heavy rains on the windward side of the mountainous regions.
Radar imagery from Japan showing the eye of Nangka just offshore of Shikoku and heavy rains on the windward side of the mountainous regions due to topographic enhancement. Japan Meteorological Agency.

See the Japan Meteorological Agency and the Joint-Typhoon Warning Center for more information on current Pacific tropical cyclone activity.

Rain in Sight

Monthly Actual vs. Normal year to date precipitation total for the airport. Normals based off of 1979-2000 climate period as is the climate records from the Bermuda Weather Service. Where there is brown, there is a deficit; where there is blue, there is a surplus of precipitation.
Monthly Actual vs. Normal year to date precipitation total for the airport as of July 9th. Normals based off of 1979-2000 climate period as is the climate records from the Bermuda Weather Service. Where there is brown, there is a deficit; where there is blue, there is a surplus of precipitation.

After a wet start to the year, mostly in February, Bermuda has fallen behind in precipitation. The Bermuda-Azores high has held a persistent ridge across the western Atlantic for the second half of Spring. As of July 9th, the airport was 3.81″ behind the normal year-to-date total precipitation. The last several days have featured a few hit or miss, passing isolated showers – no tank rain. However, an approaching cold front may change that. Keep in mind that a month’s worth of precipitation is 3-5 inches, and a week’s worth is around an inch.

A cell of high pressure to the southwest of Bermuda briefly allowed a period of light northerly winds over the last few days as a weak cold front dissipated in the area. Isolated areas of convergence and less stable air in the area led to isolated showers and thunderstorms for the middle of this week. Winds have since backed to the west and increased to moderate.

This weekend, another weak front is expected to become stationary in the area rather than dissipate. By early-morning Saturday, the cold front to the near north should enhance local convergence enough to produce isolated showers, a band of showers with a chance for thunder is possible Saturday afternoon along or just ahead of the front itself – depending on how well the boundary holds together as it approaches. The front then becomes stationary near the island, oriented from west to east as a wave of low pressure develops offshore of Virginia on Saturday evening. This keeps a chance for isolated showers and a risk for thunder in the area through Sunday.

The general expectation is for around 0.50″ of rain to fall from showers on Saturday and Sunday, but over an inch of rain is possible depending on the exact track and location of the heavier showers and thunderstorms ahead of and along the front as it approaches and becomes stationary. Since it has been very dry lately, this rain is very welcome.

Winds shouldn’t become an issue around this front. Expect today’s moderate westerly winds to continue into Saturday morning, veering northwesterly Saturday afternoon, and becoming light behind the front Saturday night. There is a slight chance for winds to become gusty in and around showers or thunderstorms, mainly ahead of the front. Winds remain variable at times on Sunday, but mostly light.

Monitor the progress of this weather with the Bermuda Weather Service and keep an eye out for possible Small Craft Warning and/or Thunderstorm Advisory.

The Tropics

The tropical Atlantic continues a quiet stretch after mid-June’s Tropical Storm Bill – no tropical cyclone formation is expected in the next five days. Meanwhile, the entire Pacific ocean has become very active; earlier this week there were three typhoons simultaneously in the West Pacific, a tropical storm in the central pacific and four other tropical disturbances with potential for tropical cyclone development.

Japan’s Himawari 8 satellite, the newest suite of sensors operationally observing the Earth caught (from left to right) Typhoons Linfa, Chan-hom, and Nangka on July 8th at 530UTC in its full disc visible band. This geostationary satellite has the highest spatial and temporal resolution of the current operational meteorological satellites in orbit. New York Times Article. NOAA is expected to launch a similar satellite next March – GOES R.

Part of this activity can be attributed to an unusually strong phase of the Madden-Julian Oscillation (MJO), another part to unusually warm equatorial Central and Eastern Pacific waters associated with El Niño, and yet another to the climatological upswing in West Pacific tropical cyclone activity this time of year. The Western Pacific is the most active region in the world for tropical cyclones and so it is not uncommon to have multiple intense cyclones at the same time. The MJO is a wave that circles the globe from west to east, and makes one revolution roughly every 30-60 days. It consists of a region of enhanced convective activity and a more inactive region. The amplitude of this enhanced and reduced convective pattern is typically highest over the Indian Ocean and West Pacific. Tropical cyclones are known to form more readily in the enhanced convective phase of the MJO. The warmer than normal equatorial Central and Eastern Pacific waters associated with El Niño is also known to aid in tropical cyclone development in those regions.

Linfa has since dissipated over southeastern China where it made a landfall as a category one equivalent typhoon. Chan-hom is approaching eastern China for a possible landfall near Shanghai and later likely impacting the Korean peninsula and Japan as a much weaker cyclone. Chan-hom became a typhoon near Guam, Rota and Saipan bringing torrential rains there, then passed between Okinawa and Miyakojima as a category four equivalent typhoon within near hurricane conditions on Okinawa. Nangka has weakened from a brief run at Super typhoon status yesterday thanks to a concentric eye-wall cycle and some increased wind shear. Nangka is expected to continue westward for the next few days before being steered northward – possibly threatening Japan.

Tropical Depression 7 in the Caribbean – a Potential Threat

Tropical Depression 7 forms in the Northeast Caribbean. GOES Floater RGB imagery of the depression shortly after its first advisory by the National Hurricane Center.
Tropical Depression 7 forms in the Northeast Caribbean. GOES Floater RGB imagery of the depression shortly after its first advisory by the National Hurricane Center. Note proximity to Puerto Rico where tropical storm warnings are in effect.

Two tropical waves interacting in the northeastern Caribbean have produced an area that organized just enough in low level wind structure for the National Hurricane Center to designate the area Tropical Depression 7 (TD7). This system is currently impacting Puerto Rico and the leeward islands with squally showers and potentially flooding rain. It could also spread towards the Dominican Republic as the depression exits the Caribbean. Tropical Storm watches and warnings are in effect for those mentioned islands and countries.

Meanwhile, a slow moving, weakening cold front to the west of Bermuda and a pre-frontal trough of low pressure will be a major steering influence on this system. Timing is everything as usual with tracking tropical cyclones – exactly when, if and how a front interacts with the tropical cyclone will determine where it tracks. The current forecast track from the National Hurricane Center shows TD7 passing to the east of Bermuda late on Monday as it moves in the southwesterly flow ahead of the front stalled near Bermuda. It is important to note that this is a very tentative initial prediction and will likely change.

First Official Track for Tropical Depression 7 as appears on the Bermuda Weather Service Tropicals page. Valid as of 6pm Bermuda time.
First Official Track for Tropical Depression 7 as appears on the Bermuda Weather Service Tropicals page. Valid as of 6pm September 4th Bermuda time.

This forecast is more uncertain than normal. For one reason, the front that is forecast to steer TD7 is already slow moving and might not make it as far east as forecast, or could push further east than forecast. But more importantly, TD7 formed during the interaction of two tropical waves. This left TD7 with an extension of low pressure to the northeast of its relatively poorly defined surface center – this is the remnants of the second tropical wave. As TD7 absorbs this wave, it will likely initially take a track more to the right of the official National Hurricane Center forecast track which seems to be based more on the general steering currents around the Bermuda-Azores High, ignoring a small scale feature like this. The merger between TD7 and the remnants of a tropical wave to its northeast may be a better defined storm with more spin and convergence available – but the process could slow initial strengthening because the storm is so fragile right now. Currently, the environment that TD7 is in appears somewhat favorable, at least enough for intensification into a tropical storm by tomorrow.

For Bermuda, expect some showers in the convergence ahead of this approaching frontal boundary and associated pre-frontal trough for today and tomorrow. But keep an eye on TD7 as it could be nearing Bermuda over the weekend. As the tropics can change quickly, it is important to stay tuned to the Bermuda Weather Service for the latest official advisory products and forecasts for Bermuda. The official forecast track for TD7 can be found at the National Hurricane Center, and a version with some Bermuda specific information can be found at the Tropicals section of the Bermuda Weather Service site.