Tag Archives: TS Debby

Jeff Masters on TS Debby & Continuing Record Heat

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Debby stalls, drenches Florida; 114° in Colorado ties state heat record
Posted by: Dr. Jeff Masters, 1:09 PM GMT on June 25, 2012 +32

Tropical storm warnings continue to fly from Alabama eastward to Suwannee, Florida, as Tropical Storm Debby sits motionless over the Gulf of Mexico. On Sunday, Debby spawned a multitude of severe thunderstorms over much of Florida, which brought torrential rains, damaging winds, and numerous tornadoes. NOAA’s Storm Prediction Center logged 20 preliminary tornado reports on Sunday, and a tornado in Venus, Florida killed one person. Venus is in Central Florida, between Port St. Lucie and Sarasota. Another person is missing in Alabama, swept away by rough surf. The heaviest rains of Debby affected the Tampa Bay region, where over ten inches were reported at several locations. The Tampa Bay airport picked up 7.11 inches on Sunday. It’s a good thing this isn’t the week of the Republican National Convention, which is scheduled for late August in Tampa! Minor to moderate flooding is occurring at three rivers near Tampa, and flooding has been limited by the fact the region is under moderate to severe drought.


Figure 1. Radar-estimated rainfall from Tropical Storm Debby has totaled over 6 inches (orange colors) along a swath from Tampa to Ocala.

Winds from Debby have fallen considerably since Sunday, thanks to a slug of dry air that wrapped into Debby’s core, disrupting the storm. Our Wundermap for the surrounding ocean areas shows that winds at almost all buoys and coastal stations along the Gulf Coast were below 30 mph at 8am EDT. The exception was a Personal Weather Station at Bald Point, near Apalachiacola, Florida, which reported sustained winds of 32 mph. An Air Force hurricane hunter aircraft flying through Debby has measured top surface winds of 43 mph as of 9 am EDT. Visible satellite loops show Debby has virtually no heavy thunderstorms near its center of circulation, which will severely limit its potential for intensification today. The heavy thunderstorms of Debby are mostly on the east and north sides. Upper-level winds out of the west creating a moderate 10 – 20 knots of wind shear that continues to drive dry air into Debby’s core. This dry air can be seen on Water vapor satellite loops. Ocean temperatures are about 27.5°C (81°F) in the Northern Gulf of Mexico, which is about 1°F above average, but these waters do not extend to great depth, which will limit how strong Debby can get.


Figure 2. True-color visible Aqua satellite image of Debby taken at 3 pm EDT Sunday June 24, 2012. At the time, Debby had top winds of 60 mph. Image credit: NASA.

Forecast for Debby
Debby’s slow motion will make rainfall the primary threat from the storm, though tornadoes will continue to be a threat over the next few days. NOAA’s Storm Prediction Center has placed most of Florida in its “Slight Risk” area for severe weather today. The slow motion of Debby will inhibit intensification of the storm by stirring up cooler waters from the depths to the surface. Debby’s close proximity to land places a portion of its circulation over land, which will also tend to slow down intensification. Wind shear is expected to remain in the moderate range through Wednesday. I expect Debby will begin to build heavy thunderstorms near its core today and Tuesday, with the winds increasing again to 60 mph by Wednesday morning. The latest SHIPS model forecast gives Debby just a 4% chance of undergoing rapid intensification–a 30 mph increase of winds in 24 hours. The 8 am EDT NHC wind probability forecast is giving Debby a 19% chance of becoming a hurricane by early Wednesday morning. Steering currents for Debby are very weak, a the storm should hang out in its current location for several more days. The models continue to have a large spread in where they thing Debby might eventual make landfall, and the official NHC forecast may have large errors for its positions at the 3 – 5 day range.

Colorado’s 114°: hottest temperature in state history
The remarkable heat wave that affected Colorado on Saturday and Sunday has tied the all-time heat record for the state. According to wunderground’s weather historian Christopher C. Burt, Saturday’s 114° reading in Las Animas tied for the hottest temperature ever measured in the state of Colorado. Two other 114° readings have occurred in Colorado history: in Las Animas on July 1, 1933, and in Sedgwick on July 11, 1954.

Colorado Springs tied its all-time record for warmest temperature ever measured on both Saturday and Sunday, with readings of 100°. The city has hit 100° four other times, most recently on July 24, 2003. The record heat in Colorado Springs exacerbated a wildfire that grew to more than 3 square miles on Sunday, driving 11,000 residents (2% of the city’s population) out of their homes.

In Fort Collins, the mercury hit 102° on Sunday, just 1° below the city’s all-time hottest temperature of 103° set on Jul 21, 2005. The heat did no favors for firefighters struggling to the contain the massive 81,000 acre High Park fire fifteen miles northwest of Fort Collins. The fire is the second largest and most destructive wildfire in Colorado’s history, and is 45% contained.

La Junta, CO hit 110° on Sunday, tying its all-time hottest temperature record, set on June 28, 1990.

The heat wave extended into neighboring Kansas, where Hill City hit 114°, tying its all-time warmest June temperature. Tribune, Kansas hit 109°, tying its all-time hottest temperature. Goodland, Kansas hit 109°, its hottest June temperature on record.

Two more days of exceptional heat are predicted for Colorado and Kansas, with the forecast for Denver calling for a high of 101 – 104° on Monday. The city hit 102° on Sunday, just 3° below the hottest temperature ever recorded in Denver, the 105° readings on July 20, 2005 and August 8, 1878.

Jeff Masters

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Well, Hello, TS Debby

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Dr. Jeff Masters’ WunderBlog
Tropical Storm Debby has formed in the Gulf of Mexico
Posted by: Angela Fritz, 9:18 PM GMT on June 23, 2012 +22
Tropical Storm Debby has been named by the National Hurricane Center this afternoon after hurricane hunters investigated Invest 96L and found a solid closed circulation, with maximum winds of 50mph and gusts up to 65mph. All interests along the Gulf of Mexico coast should pay attention to the progress of Debby. Debby is drifting north at 5mph. The storm has brought heavy rains to Western Cuba, South Florida, and Mexico’s Yucatan Peninsula over the past two days, but the disturbance’s heaviest rains are located well offshore over the Eastern Gulf of Mexico, where heavy thunderstorms are generating winds near tropical storm-force. A buoy 243 miles east of Naples, FL measured sustained winds of 31 mph, gusting to 38 mph, with 10-foot waves, at 8 am EDT Saturday morning. Our Wundermap for the surrounding ocean areas shows a large region of the northern and eastern Gulf of Mexico is experiencing winds of 20 – 30 mph.

Visible satellite loops show an unorganized tropical cyclone with an obvious surface circulation, though the thunderstorm activity is well displaced to the east. The heavy thunderstorm activity is slowly expanding and growing more intense. Upper-level winds out of the west continue to create moderate 10 – 20 knots of wind shear over the region, though that is expected to increase over the next few days. Water vapor satellite loops show a region of dry air over the central Gulf of Mexico, which will continue to interfere with Debby’s development and make it hard for the west side of the circulation to maintain heavy thunderstorms. Ocean temperatures are about 28.5°C (83°F) in the Central Gulf of Mexico, which is about 1°F above average.


Figure 1. Saturday afternoon satellite image of Tropical Storm Debby in the Gulf of Mexico.


Figure 2. Saturday afternoon forecast track for Tropical Storm Debby.

Forecast for Debby
The National Hurricane Center is forecasting Debby to remain a tropical cyclone over the next 5 days as it drifts north and then west toward Texas. The Hurricane Center is forecast a very slow progression of the storm, with a potential landfall not occurring until Friday of next week. However, most of the models that predict the turn to the west suggest landfall will happen before or around Wednesday. The models are still generally split on the forecast for Debby; by Monday, the majority of the reliable models, including the ECMWF, NOGAPS, HWRF, and UKMET, agree that a ridge of high pressure will build in over the Southern U.S., forcing Debby west across the Gulf of Mexico and into South Texas by Wednesday. However, the GFS model, which has been our 2nd most reliable track model over the past two years (behind the ECMWF), has consistently been predicting that a trough of low pressure pushing off of the U.S. East Coast will be capable of grabbing the disturbance and accelerating it to the northeast across Florida north of Tampa Bay on Monday. The GFDL model splits the difference between these extremes and takes Debby north to a landfall near the Alabama/Florida border on Tuesday. The predicted track west to Texas is still the most likely outcome, though it remains a low-confidence forecast. In terms of intensity, none of the models is predicting Debby will become a hurricane, nor is the Hurricane Center. Though sea surface temperature is warm (and around 1°F above average), the actual heat content of the Gulf is relatively low, and while wind shear is predicted to remain moderately strong through Sunday, but will increase to 30+ knots by Tuesday.

Debby’s place in history (by Jeff Masters)
Remarkably, Debby’s formation on June 23 comes a full two months ahead of the usual formation date of the season’s fourth storm in the Atlantic, August 23. Debby’s formation beats by twelve days the previous record for formation of the fourth named storm of the year in the Atlantic, set in 2005, when Hurricane Dennis was named on July 5. An early start to the Atlantic hurricane season has been increasingly common in recent years. In 2008, I blogged about the research of Dr. Jim Kossin of the University of Wisconsin, who published a 2008 paper in Geophysical Research Letters, titled “Is the North Atlantic hurricane season getting longer?” He concluded that yes, there is a “apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high”. Three out of four of this year’s early quartet of storms–Alberto, Beryl, and Debby–formed in ocean areas that were more than 1°F above average, which is an unusually high amount of warmth. We should expect to see more early-season Atlantic tropical storms as a consequence of global warming, since cool ocean temperatures are a key impediment to formation of such storms. However, this assumes that factors such as wind shear and atmospheric stability won’t grow more hostile for tropical cyclone formation during the early part of hurricane season, and this is uncertain. If we do end up seeing a substantial increase in early-season tropical storms as a consequence of global warming, this is not necessarily a bad thing. Early-season tropical storms are often more boon than bane, bringing much-needed drought-busting rains, like Tropical Storm Beryl did for North Florida last month. There is typically a lot of wind shear around in May, June, and July, making it difficult for early season storms to reach major hurricane status. According to Wunderground’s list of major early-season hurricanes, since record keeping began in 1851, there has been only one major hurricane in May, two in June, and nine in July. Three of these occurred in the past ten years, so there has not as yet been a large increase in early-season major hurricanes due to global warming.

References
Kossin, J., 2008, “Is the North Atlantic hurricane season getting longer?”, Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Angela and Jeff

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