In contrast to last weekend, where Sunday was the better half, the reverse will be true this weekend. Remnants of Tropical Depression Bill will be moving over us on Sunday, bringing the potential for extended periods of showers and heavy rain. It is hoped that this much needed rain will put a dent in the persistent moderate drought conditions in the region.
Rest of today – there is a small chance for thunderstorms up until around lunchtime today, after which skies should gradually clear. High temperatures are expected to top out in the upper-80s to near 90.
Saturday – high pressure will be shifting to the east, bringing in an onshore flow, keeping temperatures cooler in the upper-70s under partly sunny skies. Chances for rain will be increasing steadily through the evening such that by the overnight hours, periods of steady rain should be the norm.
Sunday – As referenced above, remnants of Tropical Depression Bill, still carrying tropical moisture, will be moving over the region. There is still some uncertainty as to whether the areas of heaviest rain will move further south and over the ocean, however, at this point it seems likely that Sunday will feature periods of steady rain, heavy at times. Rainfall probability and rainfall totals will drop precipitously from south to north, since the storm center is expected to track to our south. We could pick up as much as 1″-1.5″ of rain over Long Island, which would be a blessing since this area is still in the grip of moderate drought conditions. With clouds and rain, high temperatures should top out around 80.
Quantitative Precipitation Forecast for SundayNorth American Model high resolution output for Sunday at 11AM EDT Drought coverage in New York as of this week
Monday – conditions improve following the passage of the storm on Sunday, with high temperatures rebounding into the mid-upper 80s under mostly sunny skies.
Another splendid weekend is in store for us with warm temperatures in the upper-70s and near 80. Subtropical Storm Ana marks the first named storm of the 2015 Atlantic Hurricane Season. It is not expected to bring us any direct impacts, however, it could bring moisture our way that could supplement a storm system forecast to pass through early next week.
Rest of today – early fog has burned off, skies have cleared, and temperatures should top out near 80. We have been under the persistent influence of a high pressure center that has been responsible for pumping in this warm, moist air from the south.
Saturday – clouds and sun, with sunny breaks more likely to appear near the coast in the afternoon. High temperatures should be a bit cooler in the mid-70s with the influence of clouds, however, any sunny breaks could easily shoot temperatures up a few degrees.
Sunday – once again, Sunday comes through as the best day of the weekend, with mostly sunny skies and highs in the low-80s.
Monday – clouds for the most part as a frontal boundary approaches from our north and west. High temperatures will still be quite mild with the influence of high pressure bringing southerly winds, expecting a high again near 80. Some chance for afternoon thunderstorms to develop as that frontal boundary nears.
Tuesday – probably our best shot at getting measurable rainfall as the aforementioned front passes through. Some left over moisture from Ana could work its way into this setup. Ahead of the front, temperatures should still rise into the upper-70s. It’ll be noticeably cooler for the second half of the week.
Subtropical Storm Ana
We have our first named storm of the 2015 Atlantic Hurricane Season which doesn’t officially begin until June 1st. Subtropical Storm Ana developed out of a weak tropical disturbance off of Florida. This just goes to show, a tropical cyclone can form under the right conditions at any time of the year.
Visible satellite loop of Subtropical Storm Ana this morning – Geostationary Satellite Server
Subtropical Storm Ana fortunately does not have much time to organize and intensify before it makes landfall on the coast of the Carolinas. This should limit any serious damage, however, these areas will likely experience prolonged high winds, torrential rain, and coastal flooding.
Global Forecast System ensemble forecast tracks for Ana
A downright summer-like stretch of weather that started this week will get mirrored again towards the end of this week and going into next week. After clearing out clouds today, the remainder of this week should see dry and sunnier weather with highs in the mid-upper 70s. This weekend, we are looking at the possibility of temperatures near 80, nearly 15º above normal. We also have what could turn into the 2015 season’s first tropical depression/storm churning up off the coast of Florida now.
Rest of today – a very slow-moving, largely stationary front pushed through last night, but is still sitting in our vicinity. Along this front, remnants of more organized convective activity will be able to slide east during this afternoon and evening. While the chances are not high, there could still be an occasional shower during the latter half of today, high temperatures will be somewhat subdued around 70 with the clouds in place.
Thursday – clouds will clear out tomorrow and we should have a sunny day with temperatures in the mid-70s.
Friday – a repeat of Thursday, with mostly sunny skies and highs again in the mid-70s.
Saturday – increasing cloud cover, but should still be a pleasant day with temperatures in the upper 70s.
Sandwiched between rain to our south and to our west, but our weather should still remain dry this weekend.
Sunday – warm and pleasant with a high near 80.
Climate Prediction Center temperature outlook for next week – still looks like we’ll be getting warmer than normal temps
First Tropical System of the 2015 Atlantic Hurricane Season?
As I write this, a low pressure system is building up steadily off the east coast of Florida. The National Hurricane Center puts the odds of this system organizing sufficiently to become the first named tropical depression, subtropical, or tropical storm of the 2015 Atlantic Hurricane Season. Even if this storm does become the first named tropical system, it is unlikely to do much damage as it will have very little time over open water to gain strength before it is forecast to make landfall over the Carolinas later. The most noticeable impact from this storm would be the rain it generates.
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.
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.
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.
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.
Blue shaded areas = 1-3′ of storm surge Yellow areas = between 3-6′ of storm surge
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.
A quick update on TS Arthur, before a more substantial post later this afternoon. Based on the latest satellite imagery, it appears that Arthur is continuing to gather strength. You can see below that a central eye feature is beginning to form, and that spiral bands have now begun wrapping around the west side of the storm. While Arthur continues to struggle with dry air on its western side, it does seem that this is gradually being overcome. The inner core of the storm is displaying relatively symmetrical outflows, a sign that the storm is strengthening.
As of 11AM EDT, the National Hurricane Center analysis indicated that Arthur now has sustained winds of 60mph, and is moving north.
