Colorado State’s inaugural two week hurricane forecast busting (spectacularly)

Back on August 5, Philip Klotzbach and William Gray issued their very first two week forecast of hurricane activity.which replaced their monthly forecasts from previous years.  So far, the forecast has not gone well, and may end up being a spectacular bust. Rather than trying to predict the number of storms, they chose to predict the Accumulated Cyclone Energy for the forecast period August 6-20.  Also, rather than predicting a particular number, they went categorical, stating that ACE would be at below average (less than 70% of climatological average), i.e. less than six. While the exact figure may vary slightly with how Ana and Claudette are ultimately recorded in the books, ACE for August 6-present is now higher than seven. Wouldn’t be that bad of an outcome for the forecast, except that there is still two days left in the forecast period and Bill is still out there just below major hurricane status.  Just by staying at 95 knots for the next two days, Bill would double the ACE for the period causing it to be around 15.  That puts it out of the ‘average’ level and into ‘above average’! It’s not clear if they are going to be doing verification (after-action reports) on their forecasts, but if they did, they may have a bone to pick with the forecast of the Madden-Julian Oscillation.  While the forecast was for a phase of the MJO that would be unfavorable for tropical cyclone formation in the Atlantic, last week’s MJO discussion from the Climate Prediction Center  featured the following statements:

Enhanced convection over the past week rapidly shifted eastward to the eastern Pacific and Atlantic Oceans, which is indicative of subseasonal variations…. Tropical cyclogenesis is favored across the eastern Pacific and east-central Atlantic.

And with that, bust went the CSU forecast.

The sun sets on the forecast buster

A sequence of events as Tropical Depression Four/Claudette formed

(all times Eastern Daylight)

11:48 AM Alan Sullivan posts:

At 11 AM EDT, NHC designated TD #3 as expected, far out in the Atlantic. But the tropical wave currently over South Florida may also be spawning a depression. I see rotation and banding on the radar. The rotation is associated with a knot of intense thunderstorms near and over Key West. Surface pressure has not yet begun to fall, but banding is seen in other echoes over South Florida and adjacent waters. I would not be surprised if we get a designation of TD #4 tonight or tomorrow over the Gulf, if this convective pattern can persist.

1:15 PM Flight Plan for the Hurricane Hunters posted, all flights scheduled pertain to Ana,  by forward positioned assets:

NOUS42 KNHC 151715
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0115 PM EDT SAT 15 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
         VALID 16/1100Z TO 17/1100Z AUGUST 2009
         TCPOD NUMBER.....09-079

I.  ATLANTIC REQUIREMENTS
    1. TROPICAL STORM ANA
       FLIGHT ONE -- TEAL 70
       A. 16/1800Z,17/0000Z
       B. AFXXX 0102A ANA
       C. 16/1530Z
       D. 15.6N 56.3W
       E. 16/1700Z TO 17/0000Z
       F. SFC TO 10,000 FT

       FLIGHT TWO -- TEAL 71
       A. 17/0600Z,17/1200Z
       B. AFXXX 0202A ANA
       C. 17/0330Z
       D. 16.7N 60.0W
       E. 17/0500Z TO 17/1200Z
       F. SFC TO 10,000 FT

    2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 6-HRLY FIXES.
       A G-IV SURVEILLANCE MISSION IS PLANNED FOR 18/0000Z
       WITH TAKEOFF AT 17/1730Z.  A FOLLOW-ON G-IV MISSION
       IS POSSIBLE FOR 18/1200Z WITH TAKEOFF AT 18/0530Z.

    3. REMARK: NOAA43 AND THE G-IV WILL FLY FOUR SUCCESSIVE
       RESEARCH MISSIONS INTO AND AROUND ANA DEPARTING FROM
       TBPB AT 15/2000Z, 16/0800Z, 16/2000Z, AND 17/0800Z.

II. PACIFIC REQUIREMENTS
    1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
    2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
                      SEF

1:39 PM Tropical Weather Outlook

THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL WAVE HAS BECOME
MORE CONCENTRATED TODAY OVER THE FLORIDA KEYS AND THE ADJACENT
SOUTHEASTERN GULF OF MEXICO.  PRESSURES REMAIN HIGH IN THIS AREA...
AND ANY ADDITIONAL DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR
AS THE SYSTEM MOVES NORTHWESTWARD OVER THE EASTERN GULF OF MEXICO.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

7:31 PM Tropical Weather Outlook

A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS OVER THE SOUTHEASTERN
GULF OF MEXICO IS PRIMARILY ASSOCIATED WITH A TROPICAL WAVE
INTERACTING WITH A MID- TO UPPER-LEVEL TROUGH. THIS ACTIVITY HAS
BECOME A LITTLE MORE CONCENTRATED OVER THE SOUTHEASTERN GULF OF
MEXICO WHERE SURFACE PRESSURES ARE BEGINNING TO FALL. THERE ARE NO
SIGNS OF A SURFACE CIRCULATION AT THIS TIME AND ANY ADDITIONAL
DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR.  THIS SYSTEM SHOULD
MOVES TOWARD THE NORTHWEST OVER THE EASTERN GULF OF MEXICO ON
SUNDAY. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.  

8:37 PM Area of distrubed weather is designated as Invest 91L. Satellite Analysis Branch gives intensity estimate as minimal tropical depression (assuming that there’s a surface circulation, which there was no evidence of at that time).

1:42 AM Tropical Weather Outlook

SATELLITE AND RADAR DATA INDICATE THAT A SMALL AREA OF LOW PRESSURE
IN THE EASTERN GULF OF MEXICO...CENTERED ABOUT 80 MILES SOUTHWEST
OF TAMPA...IS BECOMING BETTER ORGANIZED AND MAY BE DEVELOPING A
CLOSED SURFACE CIRCULATION.  ENVIRONMENTAL CONDITIONS ARE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AND THERE IS A HIGH CHANCE...GREATER
THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
SOMETIME TODAY.  THIS SYSTEM IS EXPECTED TO MOVE NORTHWESTWARD OR
NORTH-NORTHWESTWARD AT ABOUT 15 MPH TODAY.  INTERESTS ALONG THE GULF
COAST OF FLORIDA SHOULD CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.   

5:00  AM Advisories initiated on Tropical Depression Four with Tropical Storm Warnings issued.

9:45 AM Plan of the day released with a “resources permitting” flight scheduled, (which, IIRC, means that the Air Force Reserve squadron is not olbigated to fly). Note how they’ve lost track of which storm we’re on:

3. REMARKS: A RESOURCES PERMITTING TASKING ON TROPICAL
       DEPRESSION 2 IN THE GULF OF MEXICO WILL BE LAUNCHED
       TODAY AT 16/1500Z.

12:15 PM Tallahassee Doppler Radar shows tropical storm force winds, Claudette is born.

12:43 PM Recon find 54 knot flight level winds, which are adjusted to 45 knots (50 mph) at the surface.

And here we are this afternoon:

Tallahassee Radar

http://weather.cod.edu/analysis/paulradar.pl?TLH

Tropical Storm Claudette

http://www.ssd.noaa.gov/PS/TROP/float3.html

Residents of the Big Bend/eastern Panhandle are advised to consult the National Weather Service offices of Tallahassee for the latest on local effects from Claudette.

Bursts of tropical cyclone development in late starting seasons

While we wait for the next package of advisories from the National Hurricane Center, which will introduce Tropical Storm Bill, I would like to point out a similarity of the past couple of days to the first two storms of 1949.  It appears that like Ana and Bill, the first two storms of 1949 developed from consecutive tropical waves.  The Hovmuller diagram below shows the progression (as well as the development of Hurricane Guillermo in the Pacific):

Time-lapse imagery of the Atlantic and East Pacific. By starting at the bottom and looking up and to the left, one can see what the storms developed from.

The past couple of runs of the GFS model suggest that the streak is going to be three in a row as it forecasts development of this wave, currently exiting Africa.

Sunset in the east atlantic as another wave goes feet wet.

The late starting and fairly quiet 1987 season also featured consecutive wave development.  The fairly late starting but busier 1980 season had a three storm run, though the last tropical storm of the bunch came from the first wave.

Tropical Storm Ana forms in the Atlantic, Tropical Depression Three to become official at 11 AM.

After Wednesday’s near miss at becoming Ana, Tropical Depression Two weakened substantially, to the point that the National Hurricane Center stopped issuing advisories on it. However, it slowly recovered and advisories were re-initiated last night with this morning’s advisory introducing Tropical Storm Ana. This put’s 2009 as ninth on the list of seasons (1944-present) with late first tropical storms:

Year	Date of first tropical storm (Zulu/UTC)	Significant hurricane
1977	30 August	Anita
1967	30 August	Beulah
1962	26 August
1952	24 August	Fox
1949	21 August	Hurricane # 2
1984	19/29 August	Diana
1992	16 August	Andrew
1983	15 August	Alicia
2009	15 August	???
1950	12 August	Easy, Dog
1987	9 August	Emily
1988	7 August	Gilbert
2000	4 August	Keith
1980	2 August	Allen
1963	2 August	Flora
2004	1 August	Ivan

The current forecast does not strengthen Ana to a hurricane, but there is a considerable spread in model guidance.

Further to the east . the NHC will start advisories on Tropical Depression Three at 11 AM. This is likely to be a considerable threat to the Leeward Islands by Thursday. As always, check with the National Hurricane Center for the latest.

The Atlantic this morning, with soon to be Tropical Depression Three in the bottom right, with Ana slightly up and to the left from it.

And yes, Ana doesn’t look too impressive in that picture. Looking at a satellite loop, the storm’s appearance has degraded since the overnight hours.

Tropical Depression Two and why one shouldn’t name disturbances

Late last night, after a few hours of watching the satellite loop of Tropical Depression Two, I created this unfortunate post on FriendFeed:

Barring a dramatic reversal in the next couple of hours, we will officially have Tropical Storm Ana in the Atlantic come 5 AM tomorrow morning. Also, it is starting to appear likely that there will be a Tropical Storm Bill by the weekend. (Both forming in the eastern Atlantic, with the latter appearing to be more troubling).

In it, I comitted the cardinal sin of naming disturbances before they actually earn the name***.  It is a pet peeve of mine, but my discipline broke down as I was 90% convinced that we would see the National Hurricane Center upgrade the tropical depression to tropical storm status this morning.  This, despite considerable uncertainty in where the center of the storm was at (the position of the center of circulation is an essential element of information in estimating intensity from conventional satellite imagery).  A fair bit of my skepticism was washed away by this commentary in the evening discussion:

A RECENTLY-
RECEIVED ASCAT PASS FROM 0000 UTC SUPPORTS INCREASING THE INTENSITY
TO 30 KT.  EVEN MORE RECENTLY...LATEST SATELLITE IMAGERY SUGGESTS A
FURTHER INCREASE IN ORGANIZATION AND THE DEPRESSION MAY NOW BE
CLOSE TO TROPICAL STORM STRENGTH.
Tropical Depression Seven Discussion Number Four

In other words, the wind speed in the 11 PM advisory was based off 3 hour old information and the satellite imagery showed the storm becoming better organized since then.  As it turned out, the next round of intensity estimates did not warrant an upgrade to tropical storm status at 5 AM.  However, the subsequent round did, but microwave satellite imagery did not, so the cyclone remained a tropical depression at 11 AM.  When the next estimates came in, they once again indicated a tropical storm and the NHC was right about to upgrade accordingly, but

...SINCE ABOUT 18Z THE CONVECTION HAS
DECREASED SIGNIFICANTLY AND HAS MOVED FARTHER AWAY FROM THE EXPOSED
LOW-LEVEL CENTER.  BASED ON THIS...THE CYCLONE WILL REMAIN A 30 KT
DEPRESSION FOR THIS ADVISORY.
Tropical Depression Two Discussion Number Seven

The discussion goes on to cover the difficulties the cyclone is encountering, one of them being the disturbance to its east.  The disturbance does not have any nomenclature attached to it yet, but was described thusly this afternoon in the Tropical Weather Discussion and Tropical Weather Outlook, respectively:

TROPICAL WAVE IS INTRODUCED ALONG 18W S OF 17N MOVING W AT 15 KT.
SATELLITE IMAGERY AND SSMI TOTAL PRECIPITABLE WATER IMAGERY
SHOWED A WELL DEFINED WAVE OFF THE COAST OF WEST AFRICA. UPPER
AIR SOUNDINGS FROM DAKAR SENEGAL ALSO DEPICTED WAVE PASSAGE.
WIDELY SCATTERED MODERATE CONVECTION IS FROM 6N-16N BETWEEN
15W-25W.

A LARGE AREA OF SHOWERS AND THUNDERSTORMS BETWEEN THE CAPE VERDE
ISLANDS AND AFRICA IS ASSOCIATED WITH A VIGOROUS TROPICAL WAVE.
SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT FEW DAYS
AS IT MOVES TO THE WEST AT 10 TO 15 MPH.  THERE IS A MEDIUM
CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

Forecast models have been very agressive in developing this storm; far more so than they had been for now Tropical Depression Two. They are advertising a tropical storm by Saturday with significant development to follow. It may be overly pessimistic on TD Two’s chances to think that the disturbance to its east becomes a tropical storm (especially since the NHC continues to forecast TD 2 becoming a tropical storm in the next 12 hours), but it is more plausible than was the case yesterday.

*** 2005 had at least two good examples of the problems in doing this. The tropical depression that became Cindy existed a couple of days before the one that became Dennis, but it was a close run thing that the tropical storm upgrades actually occurred in order of formation. An actual “bust” happened later in the season when Tropical Depression Ten was presumed to become Jose. People looking for Jose in the Atlantic, east of the Antilles were a bit surprised to find him in the Bay of Campeche instead.

Continued quiet in the Atlantic

It was five years ago yesterday afternoon that Tropical Storm Alex formed and 29 years ago yesterday evening that Allen formed.  With that, the 2009 season moves up the list of  seasons late to have a tropical storm (year links point to the season’s Unisys page, hurricane links point to the storm’s Wikipedia page):

Year	Date of first tropical storm (Zulu/UTC)	Significant hurricane
1977	30 August	Anita
1967	30 August	Beulah
1962	26 August
1952	24 August	Fox
1949	21 August	Hurricane # 2
1984	19/29 August	Diana
1992	16 August	Andrew
1983	15 August	Alicia
1950	12 August	Easy, Dog
1987	9 August	Emily
1988	7 August	Gilbert
2000	4 August	Keith
2009	???	???
1980	2 August	Allen
1963	2 August	Flora
2004	1 August	Ivan

In compiling this list, I went back to 1944, the first year of airborne storm reconaissance and one of the starting points for a reliable storm climatology.  Out of season sub-tropical storms were not considered, but in-season ones were. This put 1992 on the list and keeps 1974 off (and affects the first storm date for 1984).  Any list extending back more than a few years is going to have its limitations due to the increased amount of remote sensing data available.

A key thing to note when reviewing these seasons, is that while a few of the overall quietest seasons on record are on the list, these were not seasons without noteworthy storms. In fact, 7 of the 15 seasons (47%) featured a category five storm, which is a bit higher than climatology for the period (32%).

Visible satellite view of the western Atlantic

As we look at the Atlantic this morning, we see the basin as about quiet as can be.  Some stray showers near Bermuda and that’s it.  In the southeast, we see dry air pushing down to the ITCZ.

Visible satellite view of the eastern Atlantic

Looking further east, we see the latest thunderstorms to roll off the African coast along with the dry air just north of it.  The GFS model has intermittently suggested a surface low forming from this over the next few days.  A somewhat dubious propsect, but it is the only prospect of tropical cyclone formation out there at the moment. Regardless of what happens with this, we should see this season advance past 2000 on the list. If nothing materializes, 1988 and 1987 are likely to be surpassed as well before anything else threatens to form.

In the meantime, on August 4. Colorado State and Tropical Storm Risk will publish their updated season forecasts and we will probably see an update from NOAA as well next week.

Activity in the East Pacific, continued quiet in the Atlantic.

Thursday saw the formation of the first tropical depression in the Eastern Pacific. The system did not strenthen much further before making landfall and dissipating in Mexico, yesterday.

Because of that, we have yet to see a tropical storm in either the Atlantic or eastern Pacific.  This is not unusual for the Atlantic, but is for the Pacific.  Normally we would already have a named storm in the books and be talking about the second one by the last week of June.

The answer to the  question of the latest forming first tropical storm in the North Pacific is somewhat muddled by the varying quality of the history book.  The records are nearly unaminously considered to be spotty prior to satellite coverage in 1966.  However, many use 1971 as the starting point for reliable records, due to the lack of consistent quality satellite images and intensity estimates that were rough guesses (note the number of “45 knot” tropical storms and “75 knot” hurricanes in 1968, for example).   If we uses 1971-present as the benchmark, then we are in record territory as the latest first storm during that period was 1994’s Aletta, which formed on June 18 (local time).  However, if we were to use 1966 as the starting point, then we are not close to the record, because the first named storm of 1969, Ava, did not form until July 2.

Record or not, it is still unusual to be this far into the season without a tropical storm in the Pacific, but there are existing opportunities for that drought to come to an end.  There’s a reasonable chance of a depression forming off the west coast of Mexico in the next day or two. If it were to do so, it would have more time, if not necessarily better conditions, to become a tropical storm than the first tropical depression did.   A more outside chance exists near the western edge of the basin where there is a broad area of low pressure with thunderstorm activity.  The most recent Tropical Weather Outlook assigns it a low chance of tropical cyclone formation (compared to medium for the other system).

First tropical storm of the season in the making?

No such prospects exists in the Atlantic at this time.  The scenario of  a tropical cyclone forming in the western Caribbean mentioned in my previous post failed to materialize.  There aren’t even any marginal possibilities for the next few days.

This quiet of course, is not atypical as the average date for the first Atlantic tropical storm falls in early July.  Looking over the 1944-2008 seasons, it is roughly a 50/50 as to whether we have a tropical storm before July 1st or after.  If we don’t have one by July 1st, it is again a 50/50 as to whether one forms by August 1st.

A relatively tranquil Atlantic

All quiet in the western hemisphere.

From a named storm standpoint, we’re off to the quietest start to the western hemisphere (North Atlantic + East Pacific) hurricane season since 1999. That year the first tropical storm was not named until June 12.

However, if we count tropical depressions, we are on par with 2004, which saw a system develop in the Pacific on May 22 with nothing else developing until 12 July.  Of course in that season, the quiet in the Atlantic was not at all indicative of what was to come as August and September brought nine hurricanes.

This year, however, relative quiet is expected to be the theme for the Atlantic.  Sea Surface Temperatures that are merely average combined with an expected  El Niño event yielded the lowest activity forecasts seen in this active hurricane cycle (1995-present).  Dr Masters has a fine round-up of NOAA’s, Colorado State’s and Tropical Storm Risks hurricane season projections.

At the moment the only area worth watching for signs of activity is the southwest Caribbean.  For the past day or two the GFS and NOGAPS models have been suggesting development like that of Arlene in 2005 (but with the storm heading to the northeast over Cuba instead of north into the Gulf of Mexico).   A tropical wave currently east of the Antilles may act as a catalyst when it passes through the western Caribbean in the middle of next week  However, during the time I’ve been drafting this, the most recent set of model runs have been generated and they are not as keen on this scenario as previously.

Between anomalously high wind shear throughout much of the basin and the lack of other catalysts, should the west Caribbean scenario fail to pan out, it seems probable that the Atlantic would continue to be quiet into mid-June.

Notes on the 2009 storm names

As usual, this morning’s Tropical Weather Outlook for the first day of hurricane season gives the names allocated for this season along with some pronunciations:

NAME          PRONUNCIATION     NAME          PRONUNCIATION
————————————————————–
ANA           AH- NAH                          LARRY
BILL                                                        MINDY
CLAUDETTE     CLAW DET-           NICHOLAS      NIK- O LAS
DANNY                                                 ODETTE        O DET-
ERIKA         ERR- REE KA               PETER
FRED                                                      ROSE
GRACE                                                   SAM
HENRI         AHN REE-                     TERESA        TE REE- SA
IDA                                                         VICTOR        VIC- TER
JOAQUIN  WAH KEEN-                   WANDA
KATE

Some notes:

• This the first of the six lists, whose use started in 1979.
• On the list for the first time are Fred, Ida, and Joaquin, which replaced Fabian, Isabel, and Juan.
• Ana and Claudette are the only names that have been used every time for this list’s turn in the rotation.
• Each of the five times there was a Tropical Storm Ana, it failed to become a hurricane.
• Rose, Sam,  Teresa, Victor, and Wanda have never been used.
• Larry, Minda, Nicholas, Odette, and Peter were used only once (in 2003).

Stacy Stewart is back from Iraq (and so am I)

After nearly 20 months of active duty, Commander Stacy Stewart has returned to his civilian job as a Senior Hurricane Specialist at NOAA’s National Hurricane Center in Miami.

His biggest adjustment is returning to South Florida traffic. “I was used to driving down the middle of the road in a 15,000 pound Hummer with a .50 caliber machine gun and avoiding any kind of debris,” he said.

A 35-year Navy reservist, Stewart was recalled to active duty in January 2007 to aid in the troop surge in Iraq. He was part of the Coalition Army Advisory Training Team, providing advice and mentorship to three Iraqi Army divisions at An Neumaniyah Military Base. That’s 20,000 Iraqi soldiers. He also assisted in the training of three Iraqi brigades.

NHC welcomes back Stacy Stewart

I’m still in a condition where rain is a novel sight.  Fay hasn’t changed that, yet.