CSU leaves their hurricane forecast unchanged; 92L and Colin's remains worth watching
Tropical Storm Colin was ripped apart by wind shear yesterday, and the storm's remnants are passing just north of the northernmost Lesser Antilles Islands today. Most of the heaviest thunderstorms are passing north of the islands, as seen on Guadeloupe radar. Long range radar out of Puerto Rico also shows this. Colin's remains are in a rather unfavorable environment for re-development, since the disturbance is passing beneath an upper-level low pressure system with dry air and high wind shear. Wind shear is a high 20 - 25 knots over Colin's remains this morning. Recent satellite imagery shows that heavy thunderstorm activity has increased in intensity and areal coverage over the past few hours, though, and Colin's remnants will need to be monitored for re-development.
Forecast for Colin's remains
The latest SHIPS model forecast predicts that wind shear will drop from 15 - 25 knots today to a moderate 15 - 20 knots on Thursday. Wind shear will continue to decline over the weekend, and this relaxation of shear prompts most of the major models to predict re-development of Colin sometime in the next four days. NHC is giving Colin's remain a 20% chance of developing into a tropical depression by Friday morning. A major trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough will pull Colin to the northwest and cause it to slow down. By Friday, Colin will be moving at half of its current speed. All of the major forecast models are predicting that the trough of low pressure will be strong enough to fully recurve Colin out to sea early next week. Colin's remains may pass close to Bermuda on Saturday, with the latest 06Z (2am EDT) run of the GFDL model predicting that Bermuda will experience tropical storm force winds on Saturday as Colin passes to the west of the island. The Hurricane Hunters are scheduled to investigate Colin's remains at 8pm EDT tonight. It currently appears that Colin will only be a threat to Bermuda and Canada.
Figure 1. Morning satellite image of Colin's remains and Invest 92L.
92L
A tropical wave (Invest 92) in the south-central Caribbean is moving west at 15 - 20 mph. This wave is over warm water and is experiencing low wind shear of 5 - 10 knots, and could show some development over the next two days. However, the wave's rapid westward motion should bring it ashore over Nicaragua and Honduras on Friday, or the Yucatan Peninsula on Saturday, and 92L probably does not have enough time over water to develop into a tropical depression. NHC is giving a 20% chance of this disturbance developing into a tropical depression by Friday morning. This storm was being tagged as 98L yesterday; I'm not sure why it is being called 92L today.
CSU's forecast numbers for the coming hurricane season remain unchanged
A very active Atlantic hurricane season is on tap for 2010, according to the seasonal hurricane forecast issued today, August 4, by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team continues to call for 18 named storms, 10 hurricanes, 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) index 185% of average. These are the same numbers as their June 2 forecast. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast continues to call for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (50% chance, 31% chance is average) and the Gulf Coast (49% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 64% (42% is average.)
The forecasters cited four main reasons for an active season:
1) Moderate La Niña conditions should be present during the most active portion of this year's hurricane season (August - October). This should lead to reduced levels of vertical wind shear compared with what was witnessed in 2009.
2) Current SST anomalies are running at near-record warm levels. These very warm waters are associated with dynamic and thermodynamic factors that are very conducive for an active Atlantic hurricane season.
3) Very low sea level pressures prevailed during June and July over the tropical Atlantic. Weaker high pressure typically results in weaker trade winds that are commonly associated with more active hurricane seasons.
4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80 - 85 percent of normalized hurricane damage.
Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this summer. Those four years were 2005, the worst hurricane season of all time; 1998, which featured 3 major hurricanes, including Category 5 Hurricane Mitch; 1952, a relatively average year that featured just 7 named storms, but 3 major hurricanes; and 1958, a severe season with 5 major hurricanes. The mean activity for these five years was 17 named storms, 11 hurricanes, and 5 intense hurricanes, almost the same as the 2010 CSU forecast.
How accurate are the August forecasts?
The August forecasts by the CSU team over the past 12 years have had a skill 21% - 44% higher than a "no-skill" climatology forecast for number of named storms, hurricanes, intense hurricanes, and the ACE index (Figure 2). This is a good amount of skill for a seasonal forecast, and these August forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. This year's August forecast uses a new formula, so we don't have any history on how the technique has behaved in the past. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.61 to 0.65 for their previous August forecasts using different techniques, which is respectable.
Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. The British firm Tropical Storm Risk (TSR) will issue their outlook for the 2010 Atlantic hurricane season on June 4. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) is scheduled to release their August forecast later today. NOAA will also be issuing their August forecast sometime in the next week.
This season has had three named storms so far (Alex, Bonnie, and Colin.) It will be difficult to have a season with 19 or more named storms, since the four seasons that had at least 19 named storms all had at least five named storms by this point (August 4.) These four seasons were 1887, 1933, 1995, and 2005.
Next update
I'll have an update on Thursday morning.
Jeff Masters
Reader Comments
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Former #1 for several weeks.
Here's to all the Blue Collar workers braving the heat/humidity. A blues tune~
I live 120 miles east of Ivan's landfall. TS conditions here. I'm the 4th county over in the Florida panhandle....
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT THU AUG 5 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE REMNANT OF TROPICAL STORM COLIN...A LOW PRESSURE AREA...IS
LOCATED ABOUT 300 MILES NORTH OF THE VIRGIN ISLANDS. SATELLITE
IMAGERY INDICATES THIS SYSTEM HAS BECOME A LITTLE BETTER ORGANIZED
THIS MORNING. WHILE SURFACE OBSERVATIONS SUGGEST THAT IT LACKS A
WELL-DEFINED CIRCULATION...TROPICAL STORM FORCE WINDS ARE LIKELY
OCCURRING OVER WATER WELL TO THE NORTH OF THE VIRGIN ISLANDS. SLOW
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE DURING THE NEXT COUPLE OF
DAYS...AND IT HAS THE POTENTIAL TO REGAIN TROPICAL STORM STATUS
LATER TODAY OR ON FRIDAY AS IT MOVES NORTHWESTWARD AT NEAR 20 MPH.
AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE THE AREA LATER TODAY. THERE IS A MEDIUM CHANCE...50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.
A WESTWARD-MOVING TROPICAL WAVE OVER THE SOUTHWESTERN CARIBBEAN SEA
CONTINUES TO PRODUCE DISORGANIZED CLOUDINESS AND THUNDERSTORMS.
SOME DEVELOPMENT OF THIS DISTURBANCE IS POSSIBLE DURING THE NEXT
DAY OR TWO BEFORE IT MOVES OVER CENTRAL AMERICA. THERE IS A LOW
CHANCE...10 PERCENT... OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER BEVEN
ABNT20 KNHC 051141
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT THU AUG 5 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE REMNANT OF TROPICAL STORM COLIN...A LOW PRESSURE AREA...IS
LOCATED ABOUT 300 MILES NORTH OF THE VIRGIN ISLANDS. SATELLITE
IMAGERY INDICATES THIS SYSTEM HAS BECOME A LITTLE BETTER ORGANIZED
THIS MORNING. WHILE SURFACE OBSERVATIONS SUGGEST THAT IT LACKS A
WELL-DEFINED CIRCULATION...TROPICAL STORM FORCE WINDS ARE LIKELY
OCCURRING OVER WATER WELL TO THE NORTH OF THE VIRGIN ISLANDS. SLOW
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE DURING THE NEXT COUPLE OF
DAYS...AND IT HAS THE POTENTIAL TO REGAIN TROPICAL STORM STATUS
LATER TODAY OR ON FRIDAY AS IT MOVES NORTHWESTWARD AT NEAR 20 MPH.
AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE THE AREA LATER TODAY. THERE IS A MEDIUM CHANCE...50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.
A WESTWARD-MOVING TROPICAL WAVE OVER THE SOUTHWESTERN CARIBBEAN SEA
CONTINUES TO PRODUCE DISORGANIZED CLOUDINESS AND THUNDERSTORMS.
SOME DEVELOPMENT OF THIS DISTURBANCE IS POSSIBLE DURING THE NEXT
DAY OR TWO BEFORE IT MOVES OVER CENTRAL AMERICA. THERE IS A LOW
CHANCE...10 PERCENT... OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
$$
FORECASTER BEVEN
Ivan remains my favorite storm (fascination wise, before anyone reads too deeply into that) because of its eventual regeneration in the Gulf.
Earl?
I can imagine. Opal was horrific. That one, along with 2000's Gordon, should be decent reminders that just because tropical cyclones develop over the Yucatan Peninsula, does not mean that they will be destroyed and unable to intensify when they hit water.
The Yucatan isn't a very mountainous or rugged area.
SW Caribbean: 10%
Seems reasonable.
It said northwest.
I was on the west/NW side of it. The winds weren't that strong here. Maybe 35-45/50 mph.
My bad; need to put my reading glasses back on.... :)
Ah - great song, though I prefer McKuen's version of that great Jacques Brel piece
Well then i should of said a 6 yr old daughter instead of a 4x4. lol You getting any rain in your area over in orlando?
Link
That hit the October before I bought this house(spring of 1996). The house had been empty for a few months. I'm not making this up...there was a pile of limbs/branches...in the front yard about 10 feet wide and several feet tall from Opal's furry. This place was a total mess.
I've had branches down from Ivan and Dennis, but it wasn't that bad and it was tropical storm conditions. Opal was hurricane conditions.
I looked at CMC, GFS, NOGAPS and all show the bermuda high breaking down next week setting up for a 'fishy' track for any mid-august atlantic storms.
Not the expert on interpretation but does it develop that wave currently around 35-40 west? It certainly looks a little bit foreboding this morning but not yet mentioned by NHC in their TWO and no vorticity at the moment per the latest CIMSS charts..
Ike - we moved in here about 6 months post Isabel. Front yard was nice and tidy. Back yard was full of leaves - and UNDER the leaves were all the branches and debris. First time I walked down the hill I stepped into a mess of branches to mid thigh! Took us nearly a month of clean up and 3 city dumpsters to get it all taken away!
I have 3 daughters and dont think that will be the first pain I get from them... Mostly the broken Hearts I get for them..
Not enough rain... They keep on slipping over to the west.(Tampa) Im going to tampa next week so hopefully this weather pattern will hold up and I get some good lightning shots on the coast!!!
We burned ours off. It took awhile. Having a lot of trees in the yard can be nice, until....hurricane conditions.
If ex-Colin is worthy of monitoring, as Dr. Masters says it is, and its development is being modeled, then why aren't the models available on the severe weather T&H page?
I am no MET but I think it has to do with the Low pressure system of a tropical storm.. I believe however, they do forecast and model other storms. Frankly, all of the models I look at do predict all the weather that it expects to happen. I mean I see other types of systems being modeled while Im watching the Tropical weather on the model..
I live in zephyrhills and yes we have had a few great storms over here on the west side. Good luck with getting your pics.
I'll be a frequent visitor at Harry T's...
Love that Jetty Juice :)
Hope you have a great time.
Why thank you very much! I am excited! I am still void of pictures over the ocean where you can see the whole bolt.
Ha - can't burn here in VaBeach - city has to make it's money one way or the other,LOL. Actually - 7x13x6 dumpster was only 25 bucks back then - gone up to 35 now.
06z GFS still calls for Danielle to form within the next 3 days.
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