Current: Hurricane Irene is a category two storm – sustained winds at 100mph. It’s eyewall is not well-defined – likely a result of strong wind shear. This could inhibit any future significant intensification.
Short-term Forecast: Irene is on a track mostly north to north-northeast. The Outer Banks are still expected to experience landfall Saturday afternoon. Intensification over the next 24 hours will be limited – could slightly with the warm ocean temperatures – but could also weaken slightly with the wind shear and lack of an eyewall. Most likely, intensification will change little prior to landfall tomorrow.
Timing/Track: Timing is slightly faster than yesterday’s forecast (as mentioned in this morning’s update). Early-afternoon Saturday landfall over NC. Early Sunday morning, the center of Irene should be very near Cape May, NJ. By late-morning (9AM-noon), it should be on a latitude equal to that of Philadelphia. The Jersey Shore continues to be the most likely to experience direct landfall – and it will move north along the entire shoreline. Sunday afternoon brings Irene to NYC/Long Island/CT/RI region.
Track/Intensity: As mentioned in the opening statement in red, at the top, the intensity of Irene has a good chance of being limited moving forward. It will likely be a category 1 or 2 as it makes landfall in NC tomorrow – and likely less than a category two with the second landfall Sunday in the NJ/DE/MD region (could be a category one or strong tropical storm – only slight chance of category two). Regardless of the intensity, Irene is still a massive hurricane (compare its size with the state of Pennsylvania, on the map above). This hurricane will still impact a large section of the Northeast this weekend.
Impacts/Precipitation: Model projections of precipitation totals are generally not as much as yesterday’s forecast. This may be under-forecasting it a bit – as the storm is still massive (regardless of the slight weakening). There have been tropical storms that produced more rain than the GFS model prediction, as seen on the image below. The weakening intensity (or lack to strengthening further) is more of a concern with reduced winds than reduced rainfall. I still believe you’ll find 10+” (maybe not widespread) over NJ – and high tide will add to the flooding issues. 8-10” will be common over NJ. Philadelphia will fall in the 6-9” range – as will coastal MD and the Delaware Beaches. Western PHL suburbs will experience 3-6” commonly – with some 4-8” totals possible. 4-8” over Newcastle County, DE. The Susquehanna Basin will record mostly 1-4” totals. Lancaster County and surrounding regions, 2-5”.
Precipitation projection (lighter blue – over South Jersey is 6-8”, dark blue – over PHL is 4-6”):
The Hydrometeorological Prediction Center is a bit more bullish (8-10” in yellow – including Philadelphia).
Impacts/Wind: Peak sustained winds of 100mph at this time. Not expected to increase significantly (but not completely ruled out) this weekend. May weaken more after it crosses NC tomorrow. National Hurricane Center wind forecast is between 85 and 100mph sustained as it moves into the PA/NJ/DE/MD region Sunday AM (closer to 85mph). Strongest winds along the coast – but mostly between 60-80mph sustained – max gust potential 100mph, but mostly 80-90mph tops. Inland, winds will be more commonly in the 40-60mph range sustained east (gusts to 75) and 25-40mph range west (gusts to 60).
Impacts/Storm Surge: Storm surge will be a tremendous concern – especially north and east. Remember, this event will be occurring during high tide. That adds several feet of water to the potential storm surge ahead of Irene (generally north and east of the center). NJ up toward Manhattan, Long Island, Rhode Island all will likely have some serious concerns with potential inundation of high levels of water Sunday. Waves of 10-15ft in some places are possible.
Additional Thoughts: There are stronger winds (125mph) reported aloft within the hurricane. However, these winds have been unable to mix downward (again, a factor of the wind shear). This does suggest there still may be some potential – even if small – for further intensification. But for the most part, I’m downplaying this idea. True, the winds may be more limited in strength as a result; but flooding rains will likely still be a major factor Sunday. The flooding issues/concerns are the same. It’s been a record-breaking month for rain. The ground is saturated. Coastal concerns come with the fact that it’s also high tide. Rainfall amounts will likely average 4-8” across the region with some higher amounts. Storm surge -- with a storm this big (some characteristics more common with a major hurricane than a category one or two) will still be an issue – but mainly well north (NYC, Long Island, Rhode Island). It’s likely best not to overreact to this reduced intensity. There still is time for minor adjustments to this forecast – but in some cases, an inch or two of rain… 10-15mph… or 50 miles can be significant.
