Hurricane/Tropical Storm Irene

(Click on images to enlarge)


While it had been an active tropical season, it was not until we reached our ninth tropical system that one became a hurricane. That storm was Irene, which had been a well defined tropical wave and formed off of Cape Verde on August 15th. It became the season's first hurricane, ironically after making its first of many landfalls on Puerto Rico on August 22nd. After that, it began to turn north and battered much of the Bahama Islands, briefly spinning up to a major hurricane Category 3 as it moved perilously close to the east coast of Florida.


Irene actually weakened a notch as it tracked toward North Carolina, making its first U.S. landfall at Cape Lookout on August 27th as a high end Category 1 hurricane, with sustained winds up 85 mph. The storm then tracked northward around 15 mph. At that time, the eye became cloud filled and dry air began entraining into its southwest side, hopeful signs that the storm would weaken.


However, even after tracking over land for 80 miles, the storm maintained Category 1 hurricane strength, as it moved into the mouth of the Chesapeake very early on August 28th. Then it turned slightly northeast just off the Delmarva Peninsula and making its second U.S. landfall at Little Egg Inlet in southern New Jersey. It was the first hurricane to make direct landfall in New Jersey since 1903! As it churned up the Jersey coast it finally weakened to a high end tropical storm before making its third and final landfall in Coney Island in the Brooklyn Borough of New York City at 9:00 AM August 28th. It then tracked faster and more northeast through western Connecticut, the Connecticut River valley of western Massachusetts and Vermont, then hooking into Southern New Hampshire and Maine. The storm passed about 60 miles to the east of Albany at 200 PM Sunday. The barometric pressure fell to 28.89 inches, the lowest August barometer reading on record at Albany.


Heavy bands of rain showers well ahead of the main storm began falling in our southern zones early Saturday morning. Radar estimates and ground truth surface observations indicated up to two inches fell in Litchfield County with the first batch of showers, often falling at a torrential rate. These showers moved northward and begain impacting the portions of the Greater Capital region late Saturday afternoon and points northward with lesser amounts of rainfall.


These showers were slightly detached from the rain bands directly from Irene, but would likely NOT be considered a "PRE" due to the proximity being too close to Irene and these showers eventually merged with the outer rain bands of Irene Saturday evening (Aug 27). Also, the showers only produced localized higher amounts of around two inches, but most areas received less than an inch.


The rain shield directly assoicated with Irene overspread the region Saturday evening from south to north. Rainfall rates quickly increased to between half an inch to as much as an inch per hour at times by Sunday morning. The wind increased out of the north, mainly in the immediate Capital District, sustained around 25 mph, but gusting over 50 mph by mid morning.


The gusty winds, coupled with fully leaved trees and very wet ground, began producing a plethora of power outages, first in our southern regions, but quickly spreading north to include most areas by midday. Flooding and flash flooding commenced quickly, and a historic event unfolded.


A secondary dry slot working from the southeast sector of the storm began to shut the heavy rainfall down during the afternoon. However, a drizzly rain, falling from ice free clouds, persisted well into the afternoon and in some cases the evening. While this additional rainfall did not add much to the damage, it hampered rescue events.


The north wind relaxed a little, with gusts down to around 30 mph. However, as the storm pulled away into New England, rapid pressure rises and the wind backing to the northwest brought a resurgence of wind felt through much of the area. Wind gusts increased back into the 40s, to near 50 mph in many places. This wind knocked down more trees and power lines. By Sunday night, over a million people in our county warning area were in the dark.


However, the worst part of the storm was the flooding. Total rainfall, which fell mainly in under a 24 hour period, ranged from around 4 inches to well over a foot of rain! The heaviest rainfall was generally across the higher terrain to the west of the Hudson Valley. The 4.69 inches that fell at the Albany International Airport on August 28th, smashed the old record of 3.5 inches set in 1971, and was the second wettest day on record at Albany. The storm total was officially 4.83 inches at the airport. An astonishing 18-inch rainfall was reported unofficially by a weather observer in Maplecrest, Greene County! This report was supported by a doppler estimated total of over 16 inches in the same location.


Many of our rivers and streams in our area rose rapidly to major flooding, some with localities reaching flood of records. There was unbelievable devastation to many towns on the Schoharie and Catskill Creek. The Mohawk and Hudson flooded in all locations and brought significant damage to many places near its path. In Vermont, many towns were completely cut-off with roads washed away. These towns were not only without power, but gas, sewer and water.


Numerous Floods of Record were achieved from this historical event:


1. Gilboa Dam on the Schoharie Creek


2. Breakabeen on the Schoharie Creek


3. Burtonsville on the Schoharie Creek


4. Granville on the Mettawee River


5. Cold Brook (Mt. Tremper) on the Esopus


6. Rosendale on the Rondout Creek


7. Canajoharie on the Canajoharie Creek


8. Poughkeepsie on the Hudson River


9. Rockingham on the Williams River (VT)


10. Bennington on the Walloomsac River (VT)


11. Saxtons on the Saxtons River (VT)


12. Prattsville on Schoharie Creek (gage destroyed...likely a record...will get flow estimate from USGS)


13. Gilboa Bridge (gage issue...likely a record...will need estimate from USGS)


The same issues and concerns from the Spring 2011 floods arose once again with our River Forecast Points at several locations where automated gages do not exist. The only difference was that this time we received bad readings from the staff at several of these points. On Monday, August 29, 2011 at approximately 1100 UTC Lock 5 (SYLN6) gave us a reading of 90.2', when checking with the person the next day they apologized and told us the reading at that time should have been 95.1' (we had forecast 96', the difference between the correct reading and the inaccurate reading was 27000 cfs and two flood stage categories Major versus Minor). As bad as this data was, the data from MCVN6 was even worse. On Monday, August 29, 2011 at approximately 1100 UTC Lock 2 (MCVN6) gave us a reading of 58' and told us that the water was topping the wall. The reading of 58' corresponds to the major flood stage category with 167,000 cfs. This reading was totally suspect and was not used as the combined flow from SYLN6 (95.1', 48,651 cfs) and EAGN6 (34,000-44,000 cfs) resulted in a discrepancy of some 75,000 to 85,000 cfs. Until such time as automated gages are installed at these sites, we may want to consider discontinuing the issuance of any River Forecasts or River Flood Warnings for these locations.


Climate Information:


Irene gave Albany the 2nd wettest day on record since 1874...


Top 5 Wettest Calendar Days at Albany (based on ELH's 200 All-Time Wettest Dates Table)


1. 5.60" SEP 16 1999 (Floyd)


2. 4.69" AUG 28 2011 (Irene)


3. 4.08" AUG 31 1950


4. 3.50" AUG 28 1971 (Dora)


5. 3.49" JUL 13 1996 (Bertha)


***It should also be noted this storm for a 24-hr moving time period may have the 2nd greatest rainfall behind Floyds 6.0" from 16-17 SEP 1999.


Top Ten Storms with the Greatest Precipitation Amounts Impacting Albany


1. 6.28" September 18-21, 1938 Great New England Hurricane


2. 6.21" September 15-17, 1999 Remnants of Hurricane Floyd


3. 5.80" December 29, 1948-January 1, 1949 Nor'easter


4. 5.76" August 27-29, 1927 Heavy thunderstorms; Low Pressure moving up the Hudson Valley


5. 5.46" June 27-30, 1973 Showers and thunderstorms with a slow moving cold front


6. 4.96" August 31 - September 1950 Showers and thunderstorms; Moist air mass from TS over Southeast


7. 4.92" September 11-13, 1960 Hurricane Donna


8. 4.84" August 27-28, 1971 Tropical Storm Doria


9. 4.83" August 27-28, 2011 Hurricane/Tropical Storm Irene


10. 4.76" October 8-9, 1903 Slow moving coastal low pressure system


Link to the Post Storm Hurricane/Tropical Storm report




Above:  Hurricane model tracks initialized at 12Z 23 August (left), 00Z 24 August (middle) and 12Z 27 August (right).  Note the spread in all the forecast model tracks and how there was a noticeable shift in the forecasted tracks from 23 August to 24 August.  There was still notable spread in the model solutions on 27 August.



Above:  GFSEnsemble member predicted tracks for Irene, initialized 12Z 23 August.  Note these forecasts were similar to all the model forecasts initialized at 12Z 23 August.



Above:  Hurricane model intensity forecasts.  Notice the consensus that the hurricane intensity was predicted to decrease, but the large spread contributed to high uncertainty in the magnitude of the decrease in intensity.



Above:  GFSEnsemble probability for 4 inches in 48 hours initialized 12Z 23 August (left), and 00Z 27 August (right). 



Above:  Short Range Ensemble Forecast probability for 4 inches in 48 hours initialized 03Z 26 August (left), and 03Z 27 August (right). 




Above:  Soundings from 12Z 28 August for Albany, NY (left), Chatham, MA (center left), Portland, ME (center right), and 00Z 28 August from Upton, NY (far right).  Note the strong veering wind profiles and deep moisture.




Above:  Total precipitation estimated from the Berne, NY (KENX) radar, and stage 4 precipitation totals for the 24 hour period between 12Z 28 and 12Z 29 August.



Above:  Hourly precipitation from Tannersville, NY.  The storm total was 11.30 inches.


Click here for a link to a radar loop of Irene.




















Above:  Hydrographs from river gages across eastern NY and western New England, showing moderate to major flooding at most river points.










































Above:  Photos of flood damage from Prattsville and surrounding areas of Schoharie County, through Windham and surrounding areas of Greene County.