Dr. Jeff Masters' WunderBlog

Irene slightly weaker, but still very dangerous

Posted by: Dr. Jeff Masters, 20:59 GMT le 25 août 2011

+28

An Air Force Reserve hurricane hunter aircraft investigating Irene has found a slightly weaker storm. As of 4pm EDT, the strongest surface winds seen by the aircraft with their SFMR instrument were 91 mph in the storm's northeast eyewall. Highest winds measured at their flight level of 10,000 feet were 114 mph. Assuming the aircraft missed sampling the strongest winds of the hurricane, it's a good guess that Irene has fallen to Category 2 strength with 100 - 105 mph winds, even though the official advisory is higher. The aircraft noted that the eyewall was missing a large chunk on it southwest side, but the central pressure was about the same as early this morning, 950 mb. Satellite imagery from late this morning and early this afternoon showed a distinctly lopsided appearance to Irene's cloud pattern, with not much heavy thunderstorm activity on the southwest side. This was due to moderate wind shear of 10 - 20 knots due to upper-level winds out of the southwest. This shear was able to disrupt Irene's circulation while it was attempting to complete an eyewall replacement cycle, resulting in dry air getting wrapped into the core, which can be seen as a streak of darker clouds in this morning's MODIS satellite image (Figure 1.) satellite loops show that Irene is beginning to recover from this adversity, with a respectable amount of heavy thunderstorms beginning to wrap around to the southwest side from the north. An upper-level wind analysis from the University of Wisconsin CIMSS site shows that Irene's upper-level outflow is much more restricted than was the case 24 hours ago. An upper-level outflow channel that was open to the south is gone, and has been replaced by shearing winds from the west and southwest that are ripping into the hurricane. I think it is 30% likely that Irene will have trouble recovering from this setback, and will not reach the peak intensity of 120 mph winds it had earlier. However, it is more likely that the hurricane will be able to re-establish its upper-level outflow and overcome the shear, based on the latest satellite loops, plus forecasts from the various hurricane models such as the GFDL, HWRF, and ECMWF, which all show Irene at Category 3 strength as it approaches North Carolina on Saturday afternoon.

Figure 1. MODIS satellite image of Hurricane Irene taken at 11:50 am EDT Thursday August 25, when Irene was a Category 3 hurricane with 115 mph winds. The eye of the storm was just off the coast of Abaco Island in the Bahamas. Note the rather squashed appearance of the hurricane, with less heavy thunderstorms on its southwest side. Upper level winds of 10 - 20 knots out of the southwest were eating away at the clouds on this side, and you can see that this shear helped drive some dry air into the hurricane, which can be seen as a darker strip of cloud spiraling into the center from the south, around the east side, then into the center along the northwest side of the storm. Image credit: a href=http://rapidfire.sci.gsfc.nasa.gov/gallery/ NASA.

Irene likely to bring destructive fresh water flooding
In this morning's post, I highlighted the threat from storm surge flooding, but flash flooding and river flooding from Irene's torrential rains are also a huge threat. The hurricane is expected to bring rains in excess of 12" to 100-mile swath from Eastern North Carolina northwards along the coast, through New York City. The danger of fresh water flooding is greatest in northern New Jersey, Southeast Pennsylvania, and Southeast New York, where the soils are saturated from heavy August rains that were among the heaviest on record. At Philadelphia, rainfall so far this August has been 13 inches, not far from the record for rainiest month of all-time, the 15.82" that fell in August 1867. This record will almost certainly be broken when Irene's rains arrive. In general, the heaviest rains will fall along the west side of the hurricane's track, and the greatest wind damage will occur on the east side. Right now, it does not appear that tornadoes will be a major concern, but there will probably be a few weak tornadoes. Hurricane Bob of 1991, the last hurricane to affect New England, spawned six tornadoes, most of them weak F-0 and F-1 twisters.

Figure 2. Predicted rainfall for the 5-day period ending at 8 am EDT Tuesday August 30, as issued by NOAA/HPC.

Latest forecast for Irene
The latest set of model runs don't show any major changes to Irene's track or intensity. Irene will bring damaging winds, torrential rains, and an extremely dangerous storm surge to the coast, affecting a huge area of the mid-Atlantic and New England. Take this storm seriously! Expect widespread disruptions to electric power, transportation, and water systems. Be prepared for many days without power, as utility crews will be overwhelmed with the damage. Irene is capable of inundating portions of the coast under 10 - 15 feet of water, to the highest storm surge depths ever recorded. I strongly recommend that all residents of the mid-Atlantic and New England coast familiarize themselves with their storm surge risk. The best source of that information is the National Hurricane Center's Interactive Storm Surge Risk Map, which allows one to pick a particular Category hurricane and zoom in to see the height above ground level a worst-case storm surge may go. If you prefer static images, use wunderground's Storm Surge Inundation Maps. If these tools indicate you may be at risk, consult your local or state emergency management office to determine if you are in a hurricane evacuation zone. Mass evacuations of low-lying areas along the entire coast of New Jersey, Delaware, Maryland, and Virginia are at least 50% likely to be ordered by Saturday. The threat to the coasts of New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, and Maine is less certain, but evacuations may be ordered in those states, as well. Irene is a very dangerous storm for an area that has no experience with hurricanes, and I strongly urge you to evacuate from the coast if an evacuation is ordered by local officials. My area of greatest concern is the coast from Ocean City, Maryland, to Atlantic City, New Jersey. It is possible that this stretch of coast will receive a direct hit from a slow-moving Category 2 hurricane hitting during the highest tide of the month, bringing a 10 - 15 foot storm surge.

Links
For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Wunderblogger Mike Theiss is in Nassau, documenting the storm's impact on the Bahamas.

Jeff Masters

Irene Rainband from downtown Ft. Lauderdale (pho)

8/25/11 0910 local time.

HurricaneIreneIsOutThere! (trigirl)

Early at the beach to snap the waves from Hurricane Irene east of our coast, the wind was unreal with thunderclouds rolling in with lots of rain for the day.

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2101. sunlinepr 04:47 GMT le 26 août 2011
Hope it ends up in the sea.. Member Since: 2 août 2010 Posts: 19 Comments: 8435

2103. HadesGodWyvern 04:48 GMT le 26 août 2011
Quoting bigwes6844: WOW and is that the new tropical storm onto the right of the screen ya, that is Severe Tropical Storm Talas (50 knots) Member Since: 24 mai 2006 Posts: 43 Comments: 36682

2104. AllStar17 04:48 GMT le 26 août 2011
Quoting bigwes6844: OHHHHH okay so thats why wake up with Al is on there in the morning. I see what u mean. Do you know who had them before? Landmark Communications Member Since: 29 juin 2009 Posts: 13 Comments: 5135

2105. trHUrrIXC5MMX 04:49 GMT le 26 août 2011
Quoting WatchingThisOne: I know of just one flight that had instrumentation problems for at least part of the mission very early this morning. I don't think anything else is suspect. The current recon is heading back to the eye Member Since: 23 avril 2011 Posts: 32 Comments: 7872

2106. j2008 04:49 GMT le 26 août 2011
Quoting victoriahurricane: You'd rather go with satellite estimates then real time data? Ok, suit yourself. No I meant that I didnt go by anything alone, I like to put them all together and when one doesnt fit I through it out. Member Since: 19 décembre 2008 Posts: 1 Comments: 201

2107. stormtopz1 04:49 GMT le 26 août 2011
how wide is the eye? does anyone know? Member Since: 27 juillet 2011 Posts: 0 Comments: 61

2109. HadesGodWyvern 04:50 GMT le 26 août 2011
Quoting BrockBerlin: Lol Hades I was really confused for a second thought it magically teleported. LOL Member Since: 24 mai 2006 Posts: 43 Comments: 36682

2110. bigwes6844 04:50 GMT le 26 août 2011
Quoting HadesGodWyvern: ya, that is Severe Tropical Storm Talas (50 knots) SEVERE?? Member Since: 25 juillet 2010 Posts: 0 Comments: 1340

2111. nigel20 04:50 GMT le 26 août 2011
Quoting HadesGodWyvern: ya, that is Severe Tropical Storm Talas (50 knots) It's huge! Member Since: 6 novembre 2010 Posts: 2 Comments: 4510

2112. Xyrus2000 04:51 GMT le 26 août 2011
Quoting Levi32: The abrupt shift to a N to NNE movement a bit sooner than expected likely means the NHC track will have to shift a tad east tomorrow. Assuming it isn't doing the the unbalanced washing machine bit again. Guess we'll see. Member Since: 31 octobre 2009 Posts: 0 Comments: 1016

2113. atmosweather 04:51 GMT le 26 août 2011
Quoting stormtopz1: how wide is the eye? does anyone know? 30 nautical miles from last RECON vortex. L. OPEN SW M. C30 Member Since: 24 septembre 2005 Posts: 33 Comments: 9255

2114. sunlinepr 04:51 GMT le 26 août 2011
Member Since: 2 août 2010 Posts: 19 Comments: 8435

2115. victoriahurricane 04:51 GMT le 26 août 2011
Quoting j2008: Its been a long day, give me a break LOL. I'm still not on board with a Cat 2 though, pinhole eye ,940 pressure, and the fact that she was a Cat 3....I'll believe shes a cat 2 when the update says so. ARGHHHH Ok, I give up, you win. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

2116. bigwes6844 04:52 GMT le 26 août 2011
Quoting AllStar17: Landmark Communications oh okay. Well i guess the good old days of TWC will always be remembered on youtube. R.I.P. the good days at TWC Storm Alert Member Since: 25 juillet 2010 Posts: 0 Comments: 1340

2117. AllStar17 04:52 GMT le 26 août 2011
Center of Irene appears that it will cross back to the east of 77W. The NHC 11pm track took Irene all the way to 77.8W before turning. Member Since: 29 juin 2009 Posts: 13 Comments: 5135

2119. j2008 04:53 GMT le 26 août 2011
Quoting atmosweather: Not a pinhole eye...for the last time. 000 URNT12 KNHC 260334 VORTEX DATA MESSAGE AL092011 A. 26/03:20:00Z B. 28 deg 04 min N 077 deg 20 min W C. 700 mb 2588 m D. 66 kt E. 264 deg 8 nm F. 359 deg 83 kt G. 272 deg 11 nm H. 942 mb I. 13 C / 3047 m J. 18 C / 3047 m K. 14 C / NA L. OPEN SW M. C30 N. 12345 / 7 O. 0.02 / 0.05 nm P. AF304 2409A IRENE OB 06 MAX OUTBOUND AND MAX FL WIND 107 KT SE QUAD 03:25:40Z I havnt been here all day, give me a break. Good to see its not pinhole, thats a little bit more of a relief. Well goodnight for real, hope I wasnt to much of a pain. Im grouchy when I'm tierd. Tell Irene to go to sleep, shes torchering all the people on the East Coast. Member Since: 19 décembre 2008 Posts: 1 Comments: 201

2120. JLPR2 04:53 GMT le 26 août 2011
... Member Since: 4 septembre 2007 Posts: 7 Comments: 7482

2121. victoriahurricane 04:54 GMT le 26 août 2011
Upper level winds have finally responded to the drop in pressure. 04:49:30Z 29.083N 76.650W 696.8 mb (~ 20.58 inHg) 2,955 meters (~ 9,695 feet) - - From 146° at 98 knots (From between the SE and SSE at ~ 112.7 mph) 7.6°C* (~ 45.7°F) - 100 knots (~ 115.0 mph) 70 knots (~ 80.5 mph) Now will it translate to the surface? Only time will tell. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

2122. AllStar17 04:54 GMT le 26 août 2011
Quoting bigwes6844: oh okay. Well i guess the good old days of TWC will always be remembered on youtube. R.I.P. the good days at TWC Storm Alert Yep. They may do Storm Alert - maybe not. But NBC always looks for ratings, etc. The downward spiral began when they let a bunch of well-known mets. go. That also prompted Dr. Steve Lyons to leave....likely due to him noticing the situation Member Since: 29 juin 2009 Posts: 13 Comments: 5135

2123. sunlinepr 04:54 GMT le 26 août 2011
In 13 hours it regenerated that defined eye... Member Since: 2 août 2010 Posts: 19 Comments: 8435

2124. HadesGodWyvern 04:55 GMT le 26 août 2011
Quoting bigwes6844: SEVERE?? ya the west pacific has different three categories for cyclone classification Tropical Storm Severe Tropical Storm Typhoon other Asian counties also has Severe Typhoon and Super Typhoon Member Since: 24 mai 2006 Posts: 43 Comments: 36682

2125. Levi32 04:55 GMT le 26 août 2011
Quoting atmosweather: Interaction between the ULL and the digging trough is also producing covergence on the western flank of the storm. Yeah that's why dry air has been west of the storm for so long. Member Since: 24 novembre 2005 Posts: 586 Comments: 25439

2126. wolftribe2009 04:55 GMT le 26 août 2011
I am not claiming to be psychic but something odd happened today. Out of all the mass amount of "Structures that could possibly have popped up in my mind" that could be in danger from this hurricane were the New Jersey Tunnel (Holland Tunnel I think it is called) and Fenway Park in Boston. Now why not think of all the other sports arenas and so I looked it up. The Charles River Basin goes right by the stadium and also the canal going through Fenway Victory Garden. I dont know how close those waterways are but perhaps the boston redsoxs might have to relocate like the New Orleans Saints did. I just wanted to hear what you all think of the threat to these two big structures? Member Since: 22 juillet 2010 Posts: 6 Comments: 752

2127. nola70119 04:55 GMT le 26 août 2011
Looks like a wobble East to me......see ya' in the AM. Member Since: 16 juin 2006 Posts: 0 Comments: 1535

2128. NOVArules 04:56 GMT le 26 août 2011
Quoting JLPR2: ... Loop de loop! Member Since: 26 août 2009 Posts: 0 Comments: 178

2130. AllStar17 04:56 GMT le 26 août 2011
This has been mentioned several times.....wobbles like this one can have a significant affect on where an eventual landfall could be....especially in this instance due to the shape and angle of the coastline. Member Since: 29 juin 2009 Posts: 13 Comments: 5135

2131. Levi32 04:56 GMT le 26 août 2011
We might be about to see some real Cat 3 winds this time in the northeast eyewall. Let's see what the next set of recon obs find. There's an insanely long stretch of near-100kt flight-level winds northeast of the eye. Member Since: 24 novembre 2005 Posts: 586 Comments: 25439

2132. atmosweather 04:57 GMT le 26 août 2011
Quoting victoriahurricane: Upper level winds have finally responded to the drop in pressure. 04:49:30Z 29.083N 76.650W 696.8 mb (~ 20.58 inHg) 2,955 meters (~ 9,695 feet) - - From 146° at 98 knots (From between the SE and SSE at ~ 112.7 mph) 7.6°C* (~ 45.7°F) - 100 knots (~ 115.0 mph) 70 knots (~ 80.5 mph) Now will it translate to the surface? Only time will tell. Those winds have been present at 700 mb all day. Nothing has changed there. She cannot bring those winds down to the surface unless her eyewall closes up and protects her core from the dry air and the effects of SW-erly shear. Member Since: 24 septembre 2005 Posts: 33 Comments: 9255

2133. trHUrrIXC5MMX 04:57 GMT le 26 août 2011
Quoting bigwes6844: oh okay. Well i guess the good old days of TWC will always be remembered on youtube. R.I.P. the good days at TWC Storm Alert well maybe not for this hurricane but i'm sure there will be more this active year.. chances are still there,, i hope because i want to hear the song again... Member Since: 23 avril 2011 Posts: 32 Comments: 7872

2134. PrivateIdaho 04:57 GMT le 26 août 2011
Quoting JLPR2: ... Wow!! or maybe woe. Member Since: 29 août 2010 Posts: 0 Comments: 5211

2135. dewfree 04:58 GMT le 26 août 2011
liquid motion takes alittle time to accumilate .i agree with the assesment that the storm will take alittle time to catch up with it's suface pressure .i also agree with the cat 3 winds after about 6 to 12 hours of time if the storm can continue to support that kind of pressure . Member Since: 27 août 2006 Posts: 7 Comments: 589

2136. AllStar17 04:58 GMT le 26 août 2011
Quoting trHUrrIXC5MMX: well maybe not for this hurricane but i'm sure there will be more this active year.. chances are still there,, i hope because i want to hear the song again... If there was ever a hurricane in which to do Storm Alert.....this would be one. Member Since: 29 juin 2009 Posts: 13 Comments: 5135

2137. bigwes6844 04:58 GMT le 26 août 2011
Quoting AllStar17: Yep. They may do Storm Alert - maybe not. But NBC always looks for ratings, etc. The downward spiral began when they let a bunch of well-known mets. go. That also prompted Dr. Steve Lyons to leave....likely due to him noticing the situation oh yeah i forgot about him. I remember that guy help me watch Katrina more than anyone. Im surprised Jim is still there. But what ever happen to mike schwartz the kool man who used to remind me of Uconn's Women coach. Now he was really kool when he did the weather. Member Since: 25 juillet 2010 Posts: 0 Comments: 1340

2138. nigel20 04:59 GMT le 26 août 2011
Quoting sunlinepr: Super typhoon Nammadol may make a run for cat 5 status. Member Since: 6 novembre 2010 Posts: 2 Comments: 4510

2139. atmosweather 04:59 GMT le 26 août 2011
Quoting Levi32: We might be about to see some real Cat 3 winds this time in the northeast eyewall. Let's see what the next set of recon obs find. There's an insanely long stretch of near-100kt flight-level winds northeast of the eye. Interesting that in all the passes today, the SFMR instrument is consistently showing surface winds 60-70% of flight level winds, not the 80-90% that is generally observed. Either the SFMR isn't quite accurate, or her core energy is so sprawled out that it is actually what the 700-900 mb winds are translating to down at the surface. Member Since: 24 septembre 2005 Posts: 33 Comments: 9255

2140. victoriahurricane 04:59 GMT le 26 août 2011
Quoting atmosweather: Those winds have been present at 700 mb all day. Nothing has changed there. She cannot bring those winds down to the surface unless her eyewall closes up and protects her core from the dry air and the effects of SW-erly shear. Yes, but they've been sporadic. In the turn RECON has done I've seen a very long stretch of high flight level winds whereas most of today there's been a few here or a few there. Member Since: 16 octobre 2008 Posts: 0 Comments: 544

2141. PrivateIdaho 04:59 GMT le 26 août 2011
Quoting sunlinepr: Hope it ends up in the sea.. You and me both....When do Puerto Ricans sleep? :^) Member Since: 29 août 2010 Posts: 0 Comments: 5211

2142. sunlinepr 05:00 GMT le 26 août 2011
Member Since: 2 août 2010 Posts: 19 Comments: 8435

2143. bigwes6844 05:00 GMT le 26 août 2011
Quoting HadesGodWyvern: ya the west pacific has different three categories for cyclone classification Tropical Storm Severe Tropical Storm Typhoon other Asian counties also has Severe Typhoon and Super Typhoon oh okay did not know that.Thanks but that thing is moving at 2mph???? WOW!! Member Since: 25 juillet 2010 Posts: 0 Comments: 1340

2145. HadesGodWyvern 05:02 GMT le 26 août 2011
Quoting bigwes6844: oh okay did not know that.Thanks but that thing is moving at 2mph???? WOW!! yup, last few advisories the cyclone has been not moving much. Member Since: 24 mai 2006 Posts: 43 Comments: 36682

2146. AllStar17 05:02 GMT le 26 août 2011
Quoting bigwes6844: oh yeah i forgot about him. I remember that guy help me watch Katrina more than anyone. Im surprised Jim is still there. But what ever happen to mike schwartz the kool man who used to remind me of Uconn's Women coach. Now he was really kool when he did the weather. Schwartz left. So didn't Jennifer Lopez, Cheryl Lemke, Nicole Mitchell, Betty Davis, Kristina Abernathy, Kristin Dodd, Rich Johnson, Mark Mancuso, Sharon Resultan, Alexandra Steele, etc., etc. More info (I didn't remember all these, LOL): Link Member Since: 29 juin 2009 Posts: 13 Comments: 5135

2147. atmosweather 05:04 GMT le 26 août 2011
Now some Category 2 winds per the SFMR: 050000 2841N 07706W 6977 02725 //// +091 //// 125092 094 083 032 01 Member Since: 24 septembre 2005 Posts: 33 Comments: 9255

2148. trHUrrIXC5MMX 05:04 GMT le 26 août 2011
Quoting bigwes6844: oh yeah i forgot about him. I remember that guy help me watch Katrina more than anyone. Im surprised Jim is still there. But what ever happen to mike schwartz the kool man who used to remind me of Uconn's Women coach. Now he was really kool when he did the weather. i loved Schwartz, he was the funniest one. Does he work somewhere else.? I do remember this from a live report... Schwartz sells shirts.. lol Member Since: 23 avril 2011 Posts: 32 Comments: 7872

2149. sunlinepr 05:04 GMT le 26 août 2011
Quoting PrivateIdaho: You and me both....When do Puerto Ricans sleep? :^) When Rip arrives??? No, joking, maybe now that there is no electric power... Member Since: 2 août 2010 Posts: 19 Comments: 8435

2150. bigwes6844 05:04 GMT le 26 août 2011
Quoting BrockBerlin: Off topic but btw Steve Lyons is now the MIC (meteorologist in charge) at the NWS in San Angelo. oh okay thats good he was a good meter. to my opinion but not better than the great John Hope Member Since: 25 juillet 2010 Posts: 0 Comments: 1340

2151. beell 05:04 GMT le 26 août 2011
00Z Charleston, SC (KCHS) 00Z Morehead City, NC (KMHX) Member Since: 11 septembre 2007 Posts: 124 Comments: 12807

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