1-in-100 year rains cause extreme flooding in NY, PA; Nate, Maria, and Katia
An extreme rainfall event unprecedented in recorded history has hit the Binghamton, New York area, where 7.49" fell yesterday. This is the second year in a row Binghamton has recorded a 1-in-100 year rain event; their previous all-time record was set last September, when 4.68" fell on Sep 30 - Oct. 1, 2010. Records go back to 1890 in the city. The skies have now cleared in Binghamton, with this morning's rain bringing the city's total rainfall for the 40-hour event to 9.02". However, another large region of rain lies just to the south in Pennsylvania, and all of the rivers in the surrounding region are in major or record flood. The Susquehanna River at Binghamton is at 25.18', its highest level since records began in 1847, and is expected to overtop the flood walls protecting the city this afternoon. In Hershey, Pennsylvania, Swatara Creek is 18' over flood stage, and more than 8' above its record flood crest. Widespread flash flooding is occurring across the entire area, and over 125,000 people have been evacuated from their homes.
Figure 1. Radar-observed rainfall from the Binghamton, NY radar.
Figure 2. The Susquehanna River at Binghamton is at its highest flood height on record this morning (25 feet.) Records at this gauge go back to 1847. Image credit: NOAA/AHPS.
Figure 3. In Hershey, Pennsylvania, Swatara Creek is 18' over flood stage, and more than 8' above its record flood crest. Records at this gage go back to 1930. Image credit: NOAA/AHPS.
The extreme rains are due the the remains of Tropical Storm Lee interacting with a stationary front draped along the Eastern U.S. Adding to the potent moisture mix last night was a stream of tropical moisture associated with Hurricane Katia that collided with the stationary front. You don't often see a major city break its all-time 24-hour precipitation record by a 60% margin, according to wunderground's weather historian, Christopher C. Burt, and he can't recall ever seeing it happen before. It's worth noting that the Susquehanna River Binghamton stream gage, which has been in operation since 1847, is due to be shut off in 3 weeks due to budget cuts. Here's the note at the USGS web site:
NOTICE (03/23/2011)--Data collection at this streamgage may be discontinued after October 1, 2011 due to funding reductions from partner agencies. Although historic data will remain accessible, no new data will be collected unless one or more new funding partners are found. Users who are willing to contribute funding to continue operation of this streamgage should contact Rob Breault or Ward Freeman of the USGS New York Water Science Center at 518-285-5658 or email@example.com.
Tropical Storm Nate
Tropical Storm Nate formed in the southern Gulf of Mexico yesterday afternoon after the Hurricane Hunters found a well-defined surface circulation and 45 mph surface winds. Nate is the 14th named storm this year, and comes three days before the climatological half-way point of the Atlantic hurricane season, September 10. A typical hurricane season has just 10 - 11 named storms, so we've already had 35% more than a whole season's worth of storms before reaching the season's half-way point. At this rate, 2011 will see 28 named storms, equaling the all-time record set in 2005. Nate's formation date of September 7 puts 2011 in 2nd place for earliest date of arrival of the season's 14th storm. Only 2005 had an earlier formation date of the season's 14th named storm (September 6, when Hurricane Nate got named.) Third place is now held jointly by 1936 and 1933, which got their 14th storm of the season on September 10.
Latest visible satellite loops show that Nate's low-level center is exposed to view, due to northeasterly upper-level winds that are creating a moderate 10 knots of wind shear. This shear is keeping all of Nate's heavy thunderstorms pushed to the south side of the center. Sustained winds at Buoy 42055, about 100 miles to the northwest of the suspected center of Nate, were north at 31 mph at 6:50 am CDT this morning. We haven't had a hurricane hunter aircraft in the storm since yesterday afternoon, and the next plane is due to arrive near 2 pm this afternoon. Water vapor satellite loops show that here is a large area of very dry air from Texas to the north of Nate, and this dry air is probably interfering with the storm's development.
Up until last night's 8 pm EDT runs of the computer models, the models were in general agreement that Nate would meander in the Bay of Campeche for several days, until a ridge of high pressure built in to the north of the storm, forcing it westwards to a landfall in Mexico. However, the latest 2 am EDT run by the GFS model predicts that Nate may gain enough latitude to escape being forced westwards by the ridge, and instead move northwards to make a landfall along the U.S. Gulf Coast. The GFDL, which uses the GFS for its initial conditions, is also on board with this idea, as is the HWRF model, to a lesser degree. The 2 am EDT run of the NOGAPS model did not go along with this idea, though. We will have to wait until the NOAA jet makes its first mission to sample the steering currents in the Gulf of Mexico to get a better idea on how probable this northern path might be; their first flight will be tonight, and the data will make it into the 8 pm models runs that will be available first thing Friday morning. As far as intensity goes, the very dry air to Nate's north should begin being less of a problem for it by Friday, when the upper level winds shift more to blow from the southeast, and the shear drops to the low range, 5 - 10 knots. Since the storm is moving very slowly, it will upwell cooler waters from the depths that will slow intensification, though. The earliest Nate would become a hurricane is probably on Saturday.
Figure 2. GOES-13 image of Hurricane Katia, Tropical Storm Maria, and Tropical Storm Nate taken at 8 am EDT September 8, 2011. Image credit: NASA/GSFC.
Tropical Storm Maria
Tropical Storm Maria is midway between the Northern Lesser Antilles Islands the coast of Africa, and due to arrive in the Northern Lesser Antilles late Friday night or Saturday morning. Satellite loops show that Maria has been ripped up pretty badly by the 10 - 20 knots of wind shear affecting it, with the low-level center exposed to view, and a few disorganized clumps of heavy thunderstorms lying to the west and northeast of the center. Water vapor satellite images show that Maria is embedded in a very moist environment. Ocean temperatures are near 28.5°C, which is 2°C above the 26.5°C threshold usually needed to sustain a tropical storm. Maria passed just south of Buoy 41041 this morning, and top sustained winds during passage were 42 mph, gusting to 56 mph. Maria will pass close to buoy 41040 near 8pm EDT tonight.
With wind shear predicted to continue in the moderate range for the next five days, and the storm struggling to maintain its circulation, strengthening of Maria to a hurricane before it reaches the Lesser Antilles seems unlikely at this time. None of the intensity models are calling for Maria to reach hurricane strength until well after the storm passes Puerto Rico. However, Mike Ventrice, a meteorology Ph.D. student at the University of Albany, pointed out to me yesterday that a atmospheric disturbance known as a Convectively-Coupled Kelvin Wave (CCKW) is passing through the Lesser Antilles Islands today, and is headed eastwards towards Maria at 25 mph. Maria will encounter this CCKW Thursday night or Friday morning. There is a great deal of upward-moving air in the vicinity of a CCKW, and will help strengthen the updrafts in Maria's thunderstorms, potentially intensifying the storm. None of our models are detailed enough to "see" CCKWs", so we may see more intensification of the storm than the models are calling for. Given the disorganized state Maria is currently in, though, the extra boost in upward motion provided by the CCKW may not make of a difference to the storm.
The track forecasts for Maria from the various models agree that the storm will affect the Northern Lesser Antilles Islands, Virgin Islands, and Puerto Rico. After it passes the Lesser Antilles, Maria has the usual amount of high uncertainty in its 5 - 7 day track forecast. The models are split on how strong the steering influence a trough of low pressure along the U.S. East Coast will have. The UKMET model prefers a more southerly track for Maria through the Turk and Caicos Islands and the Bahamas towards the U.S. East Coast, while the other models predict a more northwesterly track, with a potential threat to Bermuda. Climatology favors a track that would miss the U.S., with Dr. Bob Hart's track history pages suggesting that Maria has a 14% chance of hitting Canada, 5% chance of hitting Bermuda, and an 18% chance of hitting North Carolina.
Hurricane Katia has brought a few rain showers and some gusty winds of 20 - 30 mph to Bermuda last night and this morning, but is not going to bring hazardous weather to the island as the storm makes it swing around Bermuda today and tomorrow. Latest satellite loops show that Katia is a shadow of its former Category 4 self, as dry air has eaten into the southwest side of the storm into the eye. Katia's outer rainbands should remain just offshore from North Carolina, New England, and the Canadian Maritime provinces at the point of closest approach. The main impact of Katia will be a multi-day period of high surf leading to beach erosion and dangerous rip currents.
I'll have an update this afternoon.
Fetters Mill 9-8-11 morning