Good news to report regarding Hurricane Joaquin – since yesterday, forecast models have arrived at a much clearer consensus regarding the track of Joaquin once it leaves the Bahamas – and the resulting forecast track takes it well east of the US East Coast.
This means we will luckily miss any severe impacts from a landfalling tropical cyclone. However, with Joaquin to the south and a ridge of high pressure to the north, continuous onshore northeasterly winds will still present moderate coastal flooding issues. Temperatures will likewise remain cool under the clouds and onshore flow, with rain expected to continue from today until Saturday. Lingering showers may persists on Sunday.
This week of damp, grey weather is leading up to a weekend when the uncertain future of Hurricane Joaquin may have an enormous impact on our weather. Since its formation earlier this week, Hurricane Joaquin has intensified steadily into a Category 3 storm currently spinning around the Bahamas. Joaquin’s future is still highly uncertain, and there’s been considerable spread between major forecast models as to where the storm will be at the end of the weekend. At this point, a landfall in the NYC region late this weekend is not out of the question.
Rest of today – cloudy and cool with high temperatures only in the mid-60s.
Friday – rain at times, windy and raw, with northeast winds in the 20-25mph range. It will feel like November with highs only in the mid-50s.
Saturday – similar to Friday in terms of sensible weather, with highs only in the upper-50s.
Sunday – this is where things get interesting depending on the track of Hurricane Joaquin. Depending on how closely Joaquin comes to hitting us, we could be looking at tropical storm conditions building through the day. If, on the other hand, it recurves out to sea, Sunday could be the best day of the weekend.
The Big Question: Where’s Joaquin Going?
Currently, Joaquin is a Category 3 storm over the Bahamas, with noticeable central eye, and symmetrical outflow in satellite images. Joaquin has been moving southwest along the edge of a subtropical ridge. Joaquin is an environment favorable for continued intensification, sitting over some very warm water with moderate wind shear.
Forecast Track
Over the last couple of days, forecast models have been set in basically two camps, one curving Joaquin northwest into North Carolina or Virginia. The other camp continues to point to a recurvature of Joaquin. Given the large spread between the models, National Hurricane Center forecasters have been emphatic about the degree of uncertainty with the track forecast up to this point.
Some major forecast models’ track forecasts for JoaquinOfficial NHC track forecast
Potential Impacts
Regardless of the landfall point for Joaquin, it will be contributing to a plume of tropical moisture leading to widespread heavy rainfall over a large portion of the east coast.
With the persistent northeast winds ahead of the northward advancing Joaquin, coastal flooding is also likely to take place in flood prone areas.
A slow moving cold front brings an unsettled start to the week. Ahead of this cold front, temperatures will rise along with humidity, leading to a late-summer feel. Once this frontal boundary passes, high pressure to the west will allow for a cooler, drier Canadian airmass to enter the region, leading to more seasonable temperatures along with sunny skies.
Rest of today – a mix of sun and clouds continues with a small chance of some rain, with temperatures topping out around average in the low-80s.
Monday – as a cold front approaches from the west, humidity and temperatures will rise along with a south wind. There is some small chance for thunderstorms, especially west of the Hudson. Otherwise, expect a mix of sun and clouds with temperatures in the mid-80s.
Tuesday – with the cold front lingering in our vicinity, a small chance for showers and thunderstorms continues, along with warm and humid temperatures in the mid-upper 80s.
Wednesday – the cold front finally pushes through Tuesday, and gives way to high pressure building in from the west on Wednesday. This will lead to comfortable temperatures in the low-80s with sunny skies.
Thursday – similar conditions to Wednesday, with sunny skies and a pleasant, comfortable high in the low-80s.
A Note on the Tropics
We’re about to enter the most active period of the Atlantic hurricane season, and things have definitely picked up in the tropics. A series of monsoonal tropical waves are moving off of the cost of West Africa, giving rise to the potential for a couple of Cape Verde type tropical cyclones. This conveyor belt of tropical waves has already spawned this season’s first hurricane, Danny, which peaked as a major hurricane with winds of 115mph (Category 3) at the end of last week. Danny has weakened considerably, but could still bring some much needed rain to Hispaniola and Puerto Rico in the next couple days. Meanwhile, another tropical wave following on Danny’s footsteps could become Tropical Storm Erika in the coming days. Neither of these storms poses any immediate threat to the United States for the time being.
A potent and massive typhoon is taking aim at the northern Philippines, in particular, Samar Island. Some of these areas were devastated by Category 5 Super Typhoon Haiyan less than one year ago, which broke the record for strongest landfalling tropical cyclone with wind speeds measured in Tacloban of 190mph. If you have friends or family in the Northern Philippines, Hagupit certainly bears keeping an eye on. Luckily for Tacloban, the current forecast track should take the center and northern semicircle (the stronger portion) of the storm north of the area, which should spare the area worst hit by Haiyan from another direct hit and the worst effects of a typhoon.
Infrared satellite imagery of Typhoon Hagupit – note the symmetrical appearance of the inner portion of the storm, along with a well-defined eye (classic signs of a very strong storm).
Forecast Track
From the image below, you’ll see that Hagupit is currently forecast to move slowly west-northwestwards over the next 48 hours. Due to the strength of the storm, and the uncertainty surrounding the steering mechanisms in place (a subtropical ridge – high pressure area to the north weakening, and a frontal boundary), there is a low degree of confidence over the overall track forecast. However, it does appear, even with the uncertainty factored in that the storm center will pass to the north of Leyte Island and Tacloban, which was devastated by Super Typhoon Haiyan. That’s good news, since this would mean the weaker, southern semicircle of Hagupit would pass over the Leyte Gulf area. This would significantly reduce the effect of a devastating storm surge, since the winds from the storm would not have the best fetch (distance over open water) to build up a storm surge. In effect, with the current track, the strongest winds would be deflected by the terrain of Samar Island, sparing Leyte Island.
It is worth noting, based on this current track, that Legazpi City in extreme southeastern Luzon Island would bear the worst of the storm, including what could be a devastating storm surge. The bay east of Legazpi could serve to funnel storm surge westward under the right conditions, amplifying the effect of the surge in a similar (though less intense) manner as Leyte Gulf and San Pedro and San Pablo Bay did for Tacloban in Haiyan.
For comparison, the track of Super Typhoon Haiyan in November 2013. Dots indicate position of the center of the storm every 6 hours, the colors indicate strength, with red indicating Category 5.
Intensity Forecast
Typhoon Hagupit has well-established outflow in the northern quadrant, as you can see from the satellite image above (white streaks fanning out from the center of the storm). It is being affected by easterly vertical wind shear, hence the absence of the same outflow bands in that sector of the storm. Hagupit has already weakened from a Category 5 Super Typhoon, but is still forecast to approach the Philippines as either a strong Category 3 or weak Category 4 storm, which would mean wind speeds likely in the range of 110-120mph. After landfall, Hagupit should weaken dramatically as interaction with the mountainous terrain of the Philippines disrupts the typhoon’s dynamics.
This week features a rather active pattern, with several chances for precipitation starting with today.
Tuesday – there is some small chance for scattered rain showers today associated with an area of low pressure that is currently located over North Carolina. However, this chance of rain will be primarily confined to areas south of the city. As the area of low pressure slowly moves offshore of the Mid-Atlantic states, the pressure gradient will strengthen, allowing for a persistent easterly wind to continue transporting cool, maritime air into the region. Temperatures will remain on the cool side, with highs similar to yesterday in the mid-70s.
Wednesday – conditions will improve somewhat as the aforementioned area of low pressure exits east over the Atlantic. We will still not be able to escape a cool, onshore wind from the northeast, so even though clouds will diminish, high temperatures will again struggle to reach 80.
Cold front approaches on Thursday
Thursday – the most substantial chance for rain this week will arrive with the passage of a cold front late in the day Thursday into the overnight hours. Warmer air from the southwest ahead of the cold front will translate to about average high temperatures in the low 80s under cloudy skies. As the cold front nears, showers and some thunderstorms will be possible. Current timing of the forecast models suggest that the bulk of the rain will not arrive until the evening hours.
Friday – conditions will improve Friday as high pressure builds in again in the wake of the cold front passing Thursday. Temperatures will drop back into the mid-70s with cooler, Canadian air filtering in from the north behind the front.
Tropical Storm Edouard?
Tropical wave off the coast of Western Africa
A vigorous tropical wave moved offshore of Western Africa earlier this week, and is being monitored for possibility of tropical storm formation later this week. Environmental conditions are forecast to remain favorable for development with low wind shear and warm sea surface temperatures. This storm may bring some impacts to the East Coast of the United States, but it is too early at this point to know the scope of that impact.
I haven’t been active on this blog the past couple of weeks as I’ve been in Costa Rica, however, the unfolding situation with Hurricane Iselle warrants a posting. I’ve observed Iselle as it formed from a tropical wave and then a tropical depression along the Inter-Tropical Convergence Zone off of the coast of Central America where I’m currently staying. Now, Iselle is closing in on the Hawaiian Islands and is set to make landfall on the Big Island this evening.
Despite the fact that the Hawaiian Islands lie near an active area for tropical cyclones, they are rarely impacted, in part due to the sheer vastness of open ocean versus the relatively small land area of the islands. During most years, a semi-permanent high pressure area that resides near the Islands also precludes the formation, strengthening, and penetration of cyclones into the region. This changes dramatically when El Nino conditions prevail, as they seem to be currently. Iselle will be the first landfalling hurricane to affect the Hawaiian Islands in 22 years since the devastating Hurricane Iniki of 1992. Fortunately, Iselle will be making landfall as a much weaker storm than Iniki, but regardless, it will still pack a serious punch.
Satellite image of Hurricane Iselle with Hurricane Julio following behind. To the far left, you can see Hurricane Genevieve.
Track Forecast
With less than 24 hours before landfall, the forecast track for Iselle is essentially zeroed in. The official track forecast cone has Iselle hitting the Big Island straight on. The center of the current forecast track envelope, should it hold up, has Iselle potentially making a direct hit on the eastern portion of the Big Island, with the eye of the storm skirting just south or perhaps directly over the Hilo area. I would hope for a northward deviation of this track, as this would spare the region from the strongest quadrant of the storm’s winds and waves (in the northern hemisphere, the strongest quadrant of a cyclonic storm is generally the northeastern quadrant). In the case of Iselle, due to its forecast west-northwest motion, the strongest quadrant should actually be the northwest, since the forward speed of the storm is added to the winds in that area.
After making landfall on the Big Island, Iselle is forecast to move to the south of the rest of the islands, passing closest to Maui. Because of uncertainty in the track forecast, it is entirely possible that Iselle could end up making multiple landfalls on different islands. However, I would anticipate these subsequent landfalls to be less serious in nature as Iselle should weaken substantially due to the influence of interaction with the mountainous terrain of the Big Island as well as increasing vertical wind shear from the north and west. There could still be some damaging storm surge and high winds in the other Hawaiian Islands, especially if the center of Iselle passes to the south of them.
Intensity Forecast
Iselle has been stubbornly persistent in maintaining minimal Category 1 status. Forecast models have been giving conflicting signals as to whether Iselle will be impacted by increased wind shear. Forecasters had not anticipated that Iselle would enter into a col between two high pressure centers, essentially an area of very low wind shear, think of it as a calm spot between two swirling eddies. Different forecast models are providing two divergent scenarios: (1) that Iselle continues to move in tandem with the col, allowing it to maintain current strength, or (2) Iselle leaves the col and experiences much higher wind shear.
No matter what, Iselle will be making landfall on the Big Island as either a minimal Category 1 hurricane or a very strong tropical storm. The real impacts of either scenario will be hardly discernible. Wind over the Big Island should pick up substantially this afternoon and evening first from the northeast, then north, and then switching to the south and southeast overnight. Sustained tropical storm force winds in the range of 50-65mph are expected depending on the specific locale. Wind gusts of up to 90mph are also possible in some locations. Offshore waves will build from 6 feet to as high as 31 feet closer to the center of the eye. I hope all people on the islands are making adequate preparations. Wind speeds as high as the ones forecast could easily shred even a decently well constructed roof. I’m not sure if the local government has issued evacuation orders, but if so, I hope all citizens of Hawaii will heed the call and take every necessary precaution to secure life and property. Let’s hope this Iselle weakens some more before it makes landfall.
Notes
In contrast to the Atlantic Hurricane Season thus far, this year’s Pacific Hurricane Season has been quite active, in part due to the influence of anomalously warm sea surface temperatures over the Eastern Pacific. These temperatures are indicative of what could be the start of an El Nino event. Hurricane Iniki also formed during a very strong El Nino event.
Hurricane Arthur is still being analyzed by National Hurricane Center as packing winds of 80mph. Although the inner core is still very symmetrical, you can see that the overall storm is beginning to lose some symmetry. In addition, central pressure has risen a couple millibar since earlier today, indicating the storm is continuing to weaken.
There’s still plenty of rain in store for Southeastern New England, though, as a couple bands of heavy rain are still moving their way onshore. The worst of the storm is yet to come, with the center of Arthur forecast to make its closest pass to this portion of the country in the next couple hours. Overnight, tropical storm conditions are likely over portions of Eastern Cape Cod.
Current satellite imagery of Tropical Storm Arthur shows a storm that is increasingly organized, with well established outflow in all quadrants, a symmetrical appearance, and spiral bands around the whole storm. An eye feature continues to grow more clear. The National Hurricane Center current analysis of Arthur indicates a storm with sustained winds of 70mph, just below the 75mph criteria for a Category 1 hurricane.
Intensity Forecast
Current forecast reasoning shows low wind shear conditions over the next 48 hours, which should allow Arthur to continuously strengthen. Max winds are currently forecast at 85mph.
Track Forecast
As of right now, it seems Arthur has taken a jog to the west, so model forecasts have been pushed west as well. As a result, portions of the Outer Banks in North Carolina have now been placed under a hurricane warning. This slightly more westerly route also means increased potential for impacts in southeastern New England late Friday into Friday night. For NYC, we’ll be looking at soaking rains from the tropical moisture brought up by this storm tomorrow as well as Friday, however, confidence is decreasing that Arthur will rain out our fireworks in NYC.
