Tag Archives: tropical cyclone

NYC Labor Day Weekend Weather & Hurricane Dorian Update – Aug 30, 2019

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Labor Day weekend is shaping up to be a good one overall in terms of sensible weather. A dry cold front passage today sets the stage for high pressure to take control over the remainder of the weekend. The only wrinkle is a warm front forecast to pass Monday that could bring some rain. Looking ahead into next week, a warm up should precede another cold front mid-week. The big weather story this weekend will be much further south of us, as Hurricane Dorian takes aim at Florida as a dangerous Category 4 storm.

Rest of today – sunny with high temperatures in the mid-upper 80s. Overnight lows in the upper-60s.

Saturday – high pressure starts to build from the west, which will result in a cooler weather with northerly winds. High temperatures topping out in the low-80s with lots of sun and overnight lows in the mid-60s.

Sunday – high pressure will progress east, giving us another pleasant day with lots of sun and comfortable temperatures in the low-80s. Overnight lows warm up in the upper-60s with a warm front approaching from the southwest.

Monday (Labor Day) – chance for rain during the day as a warm front, then a weakening cold front approach. High temperatures in the low-80s with mostly cloudy skies. Overnight lows around 70ºF.

Hurricane Dorian Heading Towards Florida

Over the course of the last few days, Hurricane Dorian made a pass over the Northern Lesser Antilles, hitting the Virgin Islands, and Martinique, but sparing Puerto Rico. This was a blessing for an island still recovering from the devastation of Hurricane Maria. However, because Dorian avoided the disruptive influence of high terrain in Puerto Rico, it entered the open waters of the Western Atlantic north of the island ready for continued intensification. Unfortunately, various forecast models have been consistently depicting Dorian making landfall somewhere in Florida early next week as a dangerous Category 4 hurricane packing max sustained winds of 140 mph.

Latest GOES visible satellite imagery of Hurricane Dorian

Overnight going into today, Dorian’s been steadily strengthening and is now showing a markedly more symmetrical structure than before, along with an eye developing in visible satellite imagery. This suggests that the southerly shear and dry air that was afflicting the storm yesterday has abated somewhat. At this point, there is nothing really stopping Dorian from continuing to strengthen to a major hurricane.

National Hurricane Center official forecast for Dorian as of 11AM Friday

Forecasters continue to have high confidence that Dorian will make a turn towards a more westerly direction as high pressure builds over Bermuda and keeps building to the west. This will block Dorian from taking a northerly route away from Florida. Worryingly, forecast models have trended towards a slower and more southerly track overnight, then a turn north after landfall. On this current track, a large part of Florida would be affected by the storm for a considerable amount of time, increasing the risk of damaging storm surge and inland flooding from prolonged heavy rain.

NYC Weekend Weather – Hurricane Irma Update, Sep 8 2017

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We’ve got a wonderful stretch of below average but sunny, fall-like weather ahead of us over the weekend. The main weather story lies far to our south as Florida braces for Hurricane Irma over this same time period. Irma has weakened a bit but is still a large and dangerous Category 4 storm capable of wreaking havoc over the entire state of Florida.

Rest of today – our weather will be dictated by an area of high pressure anchored over the Great Lakes. This will give us mostly sunny skies with a cool high in the mid-70s.

High pressure firmly in control of the weather in our part of the world. You can see Hurricane Irma making its finally approach on Florida in the lower right.

Saturday – sunny with temperatures in the low-70s as the high pressure over the Great Lakes moves east a bit.

Sunday – more of the same as Saturday with sunny skies and high temperatures in the low-70s.

Monday – slightly warmer with high temperatures creeping back into the mid-70s with some more clouds.

 

Hurricane Irma a Major Threat to South Florida

Current Situation

Hurricane Irma has been weakening in the last 12 hours. It’s evident the storm is undergoing an eyewall replacement cycle, where the inner eye of the storm collapses and is replaced by a larger, outer eye. During these internal cycles, max wind speeds often decrease and fluctuate before the storm consolidates a new eye. It has been downgraded to a Category 4 storm with maximum sustained winds of 150 mph.

Headlines

  • Landfall somewhere in South Florida over the weekend is a near certainty. Outer bands from Irma are expected to reach South Florida overnight tonight. Life-threatening storm surge inundation and damage from winds of major hurricane force (115 mph) are a near-certainty for parts of South Florida.
  • Since midday yesterday, forecast models have trended slight back towards a westerly solution for the forecast track of the storm. This almost eliminates the risks to Georgia and South Carolina coastal areas from a direct hit from a major hurricane. However, the risk to these areas from storm surge and strong tropical storm force/marginal hurricane force winds still exists.
  • There is still a chance Irma could make landfall on Cuba. This would weaken the storm ahead of subsequent landfall on Florida.

Forecast Track

As mentioned above, the best performing forecast models have shifted back to a more westerly track for Hurricane Irma.

Several different forecast models take on Irma’s track.

Official National Hurricane Center forecast as of 8AM today.

Forecast Intensity

While Irma has weakened to a Category 4 storm due to an ongoing eyewall replacement cycle, it remains an extremely dangerous storm with an expanding wind field due to this cycle. Hurricane force winds extend 70 miles on each side of the eye and tropical storm force winds well beyond that. It remains possible that Irma can re-strengthen if it completes the eyewall replacement cycle before it interacts with land. Mid-level wind shear remains negligible and Irma will soon be passing over very warm seas with increasing depth. Both of these factors would suggest it maintaining Category 4 strength or possibly re-intensifying to Category 5.

Uncertainties

  • Any landfall on Cuba or interaction of the core of the storm with the high mountains of that island would disrupt the storm and cause weakening. This would be good news for Florida, at the expense of Cuba of course.
  • Should the core of the storm avoid Cuba and close off a new eye before too much time elapses, it would have the possibility of re-strengthening before landfall. A strong Category 4 or even a Category 5 storm making landfall on Florida is not out of the question.

NYC Labor Day Weekend Weather – TS Hermine – Sep 2, 2016

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I wrote that I would not be posting any updates while on vacation unless there were to be a special event that warranted it. Well, the likely approach of the remnants of Tropical Storm Hermine into the offshore waters in our region certainly warrants this special update. As of now, it appears that Labor Day itself will be the only day when we could see significant impacts from this storm, but this could change. I will likely have another update Sunday.

Rest of today – sunny, and pleasant with a high in the low-80s. This will be by far the best day of the long weekend.

Saturday – increasing clouds, high temperature around 80ºF.

Sunday – mostly cloudy, with chances for rain increasing in the afternoon. Cool, with highs only in the mid-upper 70s.

Labor Day (Monday) – tropical storm conditions possible, strong and gusty winds, and possible periods of heavy rain, especially in coastal areas. Dangerous rip currents at the beaches, as well as moderate to major coastal flooding. Mostly cloudy otherwise with high temperatures in the upper-70s.

Tropical Storm Hermine this morning
Tropical Storm Hermine this morning

Tuesday – with the remnants of Hermine currently forecast to linger off of the coast of the Northeast, we could see another day of possible tropical storm conditions. Warmer, with high temperatures in the low-80s.

Tropical Storm Hermine’s Forecast

Since the inception of Hermine as a tropical wave off the coast of West Africa, forecasters have had difficulty in accurately capturing the track and intensity of this storm. Its approach towards our region is no different. The forecast is complicated by the fact that Hermine will be completing a process of extratropical transition. A complex set of interactions between it and a frontal boundary adds a high degree of uncertainty towards the late period of this forecast.

Forecast Track

As of this morning, the National Hurricane Center’s official 5 day forecast called for Hermine to continue tracking rapidly northeast just inland of the Southeast coast as it initially interacts with a frontal boundary in its vicinity. During this period, it is expected to weaken, but by Saturday evening, it is expected to re-emerge over open water off the North Carolina Coast. At this point, Hermine is expected to have completed extratropical transition. It will begin another interaction with a baroclinic frontal zone, which is expected to significantly slow its forward progress down. This slowing will likely also lead to the storm erratically meandering off the Northeast coast, possibly doing a loop.

093924W5_NL_sm

at201609_model
Some major forecast model’s current output for Hermine

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GFS ensemble models (spaghetti models), white denotes the consensus track

Intensity Forecast

During the period that the storm is over land, it will weaken continuously. However, by Saturday evening, when it is expected to re-emerge over open water, and complete extratropical transition, it will gain in strength. The extratropical transition will impart energy from baroclinic forces (interactions between airmasses of differing pressures), and the storm is expected to re-intensify into a strong extratropical storm with sustained winds of 60-65mph.

Impacts

The intensity and location of these impacts will depend greatly on the eventual track for this storm.

Tropical storm watches are in effect for the entire New Jersey coast. Heavy rain in coastal areas. Strong sustained winds, winds gusting in excess of 50mph in some coastal areas. Beach erosion along with coastal flooding, possibly for an extended period of time. High surf and dangerous rip currents.

 

Hurricane Iselle – Tropical Update

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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.

Screen Shot 2014-08-07 at 1.14.13 PM
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.

Weekend Weather, Hurricane Arthur Update – Jul 4, 2014 @ 10AM EDT

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As of 9AM EDT, Hurricane Arthur has weakened somewhat from its peak intensity as a Category 2, and sustained winds have declined to 90mph. However, its eye is still clearly visible, and as you can see below, the storm is maintaining a symmetrical appearance with good outflow in all quadrants, meaning this is still quite a powerful storm. As Arthur continues moving northeast, it is expected to weaken rapidly upon entering much cooler waters and with increasing vertical shear from the codl front seen below.
Screen Shot 2014-07-04 at 9.41.32 AM
Track Forecast

Forecast models are in very close agreement about Arthur’s track over the next 12 hours or so. As you see below, they are tightly clustered around the 40N, 70W benchmark. Hence, forecast reasoning has not changed much since yesterday night. Arthur is expected to continue its northeast track and speed up under the influence of the cold front depicted above, moving offshore of New England and into the Canadian Maritimes as it makes extratropical transition.

Screen Shot 2014-07-04 at 9.38.44 AM

What This Means for Us

As expected, Arthur will be bringing multiple rounds of rain to the entire Northeast over the course of the day today. You can already see Arthur’s outer rain bands on our regional radar (you’d see it in the standard 124 nautical mile radar, but I’ve inserted an image of 248 nautical mile range radar image to see the storm better). As Arthur accelerates and makes its closest pass to this part of the country, we’ll see repeated bands of rain moving on shore. You can expect periods of heavy rain and thunderstorms, interspersed with some dry spells under cloudy skies.

Screen Shot 2014-07-04 at 9.39.27 AM

The Rest of the Weekend

Once Arthur and the cold front clear the Northeast, we will see a return to a spectacular weekend with high pressure building back in. Sunny skies, mild, and dry conditions will prevail across the entire region with high temperatures in the low-mid 80s on both Saturday and Sunday. As the high pressure moves to our southeast, we’ll see a return flow from the backside of the high pressure ushering in another warm, humid airmass for the beginning of next week.

 

Hurricane Arthur Update – Jul 3, 2014

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Hurricane Arthur has held steady with 90mph winds over the last 6 hours or so. The storm’s eye continues to grow more defined, with central pressure continuing to fall to 977mb. These signs point to further strengthening, and the National Hurricane Center is still forecasting Arthur to hit Category 2 strength as it makes its closest pass over North Carolina.

Screen Shot 2014-07-03 at 8.11.13 PM

Track Forecast

Over the course of the day, Arthur has moved further north than originally forecast, and is only slowly beginning to make its turn towards the northeast. As a result, most forecast models have been pushed a bit further to the west. Most of the models now have Arthur making landfall somewhere over coastal North Carolina, and then passing inside the 40N, 70W benchmark offshore of the Northeast. The bottom line is that the updated forecast track increases the likelihood of adverse impacts to coastal areas all along the East Coast. This includes high surf, beach erosion, and dangerous riptides even in areas that don’t see direct impacts. This new track also puts portions of Southeastern New England under risk of experiencing tropical storm conditions, and heavy rain bands from Arthur as it passes offshore.

Screen Shot 2014-07-03 at 8.10.11 PM

It’s a good thing that mandatory evacuations were placed for the Outer Banks and coastal North Carolina, as portions of these low-lying areas are forecast to experience storm surge inundation of greater than 3 feet during the peak of the storm.

Screen Shot 2014-07-03 at 8.16.20 PM
Blue shaded areas = 1-3′ of storm surge Yellow areas = between 3-6′ of storm surge