Based on a 1970-2016 time period, the 1979 Pacific Typhoon Season currently stands as near average to marginally below average Pacific Typhoon Season. Per JTWC data, the 22 tropical storms is four below that average of 26, 14 typhoons below the 16.8 average, and 8 category 3+ typhoons near the 8.8 average. Beyond storm count, ACE and PDI (278.0175 and 255.981375, respectively) also fall a little below the averages for my time period (294.4839 and 268.450441, again respectively). A set of tables with different types of storm data for the 1979 Pacific Typhoon Season is provided below. For a full context a full breakdown of the 1970-2016 data is provided here.
As mentioned in my previous entry, a few tropical cyclones had winds considerably lower than what would be expected for their recon measured pressures even using the Atkinson & Holliday pressure/wind relationship (AH77). The three biggest offenders are Typhoons Hope, Judy, and Owen. Hope and Judy were each rated as category 4 typhoons despite pressures measured at 898 mb and 887 mb, respectively. In a similar vein, Owen was rated as a category 3 typhoon despite a 918 mb pressure. Straight AH77 outputs for these three in order would be 142 kt, 151 kt, and 125 kt. It is systems like these that were largely the spur for my efforts at reanalysis. Pressures for these three typhoons and the rest of the 1979 Pacific Typhoon Season were lifted from the 1979 JTWC Annual Tropical Cyclone Report. An outline in the main methodology for the reanalysis is provided in the introductory post. With that said, the results of my 1979 Pacific Typhoon Season reanalysis begin now.
By just about every metric available, reanalysis data jumps the 1979 Pacific Typhoon Season to an above average season. Storm count rises to 27 tropical storms, 18 typhoons, 11 category 3+, and 5 category 5s (four of which with an intensity of 155 kt or greater). Changes resulted in ACE substantially increasing to 354.31 and PDI to 353.63975. Common themes across the majority of reanalyzed systems include earlier initial classification, quicker intensification, and higher/earlier peak intensities with respect to best track data. 10 classified systems came up 20 kt or higher maximum wind velocities in reanalysis. 10 systems also had an ACE and PDI total over 3 higher than best track. In contrast, only four systems went down in maximum wind velocity in any way, only three lost ACE, and only four lost PDI. Additionally, one system not in best track was added (X1W). A brief numerical summary of changes in reanalysis (in the same table format above) can be seen here. Some of the more interesting individual systems will now be discussed in more detail.
01W Alice: Vmax = 135 kt (C4), ACE = 42.16, PDI = 42.368
The 1979 Pacific Typhoon Season began exceptionally early with Alice. In fact, Alice technically could be a 1978 system, gaining sufficient organization to become a tropical depression by 12Z December 31, 1978. However, I do not believe that Alice became a tropical storm until 00Z January 1, 1979, and while I would argue that systems the occur prior to the annual Western Pacific tropical cyclone minimum in early to middle February are more closely associated with the previous season than the calendar year season, I have kept Alice here with the 1979 storms. Regardless, Alice was already a fairly intense tropical storm (I estimate 60 kt) by the time recon first investigated the system at 0115Z January 2 and found a 986 mb pressure. My graphical pressure trace for Alice can be found here.
Despite forming from a very large and convectively blessed disturbance likely enhanced by an upward pulse of Madden Julian, Alice matured into a smaller than average system. Alice featured two separate peaks of category 4 intensity. The first, and overall peak intensity (pictured above), occurred late on January 7 with a pressure of 928 mb. Using the 928 mb pressure, 14 kt forward speed, 98 nm average TS wind extent, 12.2ºN latitude, and 1006 mb outermost closed isobar, KZC actually output 137 kt, which does technically meet category 5 criteria. However, intensification was halted at this point by the onset of southwesterly shear and the eye had already begun to cool on IR imagery. Because of this, I erred on the conservative side with a 135 kt intensity, which would make Alice a top-end category 4. This is still considerably higher than the 110 kt best track intensity.
Secondary peak intensity was preceded by a period where Alice’s pressure rose all the way up to 974 mb by January 9, which I analyzed as an 80 kt category 1. However, Alice reintensified back down to 938 mb by January 11th as a borderline midget tropical cyclone. My reanalysis yields an intensity of 125 kt for this peak, much higher than the 100 kt listed in best track at this time. Alice quickly weakened after this secondary peak however, becoming a remnant low by January 14.
05W Unnamed: Vmax = 65 kt (C1), ACE = 2.2325, PDI = 1.237375
05W was a slightly more tricky system to reanalyze since it did not have any recon data. However, it is clear based on satellite imagery that it was more intense than JTWC’s 30 kt, which is apparently based on AH77 output from a 998 mb ship report near the system from an unspecified time and location in the JTWC report. Peak DTs were 4.5 for an off-white eye embedded in medium grey. Constraints came into play some due to the rapidly emerging banding eye feature as the system accelerated to the northeast through the Luzon Strait and into the subtropics, but I did estimate a peak intensity of 65 kt at 06Z, May 23. KZC output a 983 mb pressure at that time, which appears reasonable enough to me.
09W Hope: Vmax = 155 kt (C5/T7.5), ACE = 25.33, PDI = 30.56275
Hope is one of three systems from 1979 that deepened to below 900 mb. Despite this, JTWC’s best track only lists a peak intensity of 130 kt. I found a more intense system. Between July 29 and July 31, Hope is a system that can be characterized by rapid deepening, as seen in the pressure trace. The deepening was particularly extreme prior to 12Z on July 31 and featured a 14 mb drop from 912 mb to 898 mb in 2 hours 22 minutes between 0648Z and 0910Z. KZC outputs for the 898 mb pressure, 15 kt forward speed, 222 nm average TS wind radius, 19.4ºN latitude, and 1003 mb outermost closed isobar a 151 kt intensity. Based on the rapid intensification taking place at the time and warming of the eye on IR imagery up to 12Z, I estimated a peak intensity of 155 kt at 12Z, July 31. At that time, KZC output an 894 mb pressure, which appears reasonable to me.
12W Irving: Vmax = 80 kt (C1), ACE = 11.9325, PDI = 7.850875
Irving is one of the few systems that I found to be less intense than best track. The system is characterized by steady gradual deepening. Based on satellite imagery, Irving frequently appeared to be sporting multiple incomplete eyewall structures, resulting in a sloppy, sprawling structure. When coupled with very low background pressures around 1000 mb, KZC estimates actually undercut the standard AH77 estimates and ran almost identically to a variable environmental pressure version of AH77 that I run on occasion [6.6 * (oci + 2 – p) ** 0.65]. The deepest pressure of 954 mb measured by recon yielded an 81 kt intensity (which I rounded to 80 kt) when coupled with a 7 kt forward speed, 222 nm average TS wind radius, 24.6ºN latitude, and 999 mb outermost closed isobar. This is about 10 kt lower than the 90 kt in best track.
X1W Unclassified: Vmax = 45 kt (TS), ACE = 1.135, PDI = 0.4335
As mentioned previously, I added one additional system not in JTWC’s best track. I originally spotted this little system in the subtropics off the Japan coast while looking at satellite imagery for Typhoon Irving. In fact, the only agency that has this system classified is the China Meteorological Agency. Because of this though, it has thankfully been included in IBTrACS as 1979224N32143, meaning that archived imagery of the system is available through HURSAT. Based on my own use of the Dvorak Technique, I estimate that this system, which I have personally classified as X1W (essentially extra one), achieved a peak intensity of 45 kt at 06Z, August 15. This is near the time of the image above. No wind radii data was available, so I somewhat spitballed a 40 nm average TS wind radius estimate to use KZC with. The 988 mb pressure that ended up resulting from the use of KZC looks a little low to me, but without much to go on, that is the pressure I stuck with.
13W Judy: Vmax = 165 kt (C5/T7.5), ACE = 37.6575, PDI = 44.769375
It’s hard to find a more classic pinhole eye tropical cyclone than Super Typhoon Judy. Not long after initially developing, Judy dropped about 100 mb in 48 hours, reaching a minimum pressure of 887 mb. Judy also possesses the warmest 700 mb temperature recorded in a tropical cyclone of which I am aware, a 34ºC temperature from the 1931Z center pass on August 19. Despite this, JTWC only listed a 135 kt maximum intensity in best track. Why? Well, I really can’t say. Regardless, the 887 mb pressure resulted in a 165 kt intensity estimate when put into KZC, and that’s even with an average TS wind radius derived from JMA data that looks like it could possibly be too big (186 nm). I did leave it alone since Judy did appear to be embedded in a surge of the southwest monsoon, which did give the system a rather striking monsoon tail at the time of peak intensity, but it wouldn’t surprise me if Judy were perhaps a few knot even more intense than my reanalysis indicates.
19W Owen: Vmax = 140 kt (C5), ACE = 26.0975, PDI = 26.639875
Typhoon Owen is another system that received a generous intensity bump. Based on a measured pressure of 918 mb, KZC returned a 138 kt intensity with a 6 kt forward speed, average TS wind radius of 149 nm, 23.1ºN latitude, and 1007 mb outermost closed isobar. I rounded this up to 140 kt, a 30 kt increase over the 110 kt category 3 maximum intensity in best track. As is often the case with intense systems, Owen was yet another rapid intensifier. The recorded pressures did oscillate near the time of peak intensity, so I tried to smooth it out as best as I could.
23W Tip: Vmax = 175 kt (C5/T8.0), ACE = 60.7375, PDI = 76.782875
A system that needs little introduction, Super Typhoon Tip is the world’s deepest recorded tropical cyclone, with an 870 mb pressure recorded at 0350Z, October 12. Unlike many of the most intense tropical cyclones however, Tip did not rapidly intensify early in its lifetime. Tip developed well to the southeast of Guam in early October, east of an exceptionally messy monsoon trough/gyre/slop setup that involved Tropical Storm Roger. Because of this it took Tip several days before any significant intensification could take place. However, on October 9, Tip began to strengthen appreciably, and at about 12Z, October 10, Tip began its first ~12 hour bout of explosive intensification. At the end of this bout, I analyzed Tip to have achieved a 155 kt based on the measured 900 mb pressure and KZC. Tip weakened slightly after this episode, but then began a second round of explosive intensification around 12Z October 11. By the time recon arrived back to the system early on October 12, Tip had intensified to an 870 mb system. Using KZC, an 870 mb pressure, 8 kt forward speed, average TS radius of 204 nm, 16.7ºN, and outermost closed isobar of 1005 mb yields a 175 kt maximum sustained wind estimate on the nose. As far as comparisons to other studies is concerned, this is in close agreement to the 173 kt/873 mb ADT estimate from Veldon et al.
Following peak intensity, Tip remained a rather deep system (although nowhere as deep as near peak), but grew to become an absolute behemoth with poor core structure. Much like with Irving, KZC estimated wind values sank down to and even occasionally below those from both versions of AH77 I ran for the system. Because of this, I tugged down a few post-peak intensities from the best track values, but usually only by 5 kt or so here or there.
24W Vera: Vmax = 160 kt (C5/T7.5), ACE = 23.85, PDI = 30.27075
Vera is the system where I departed from my methodology the most. The first involved the TS wind radii. I ended up determining that they were too large for the small typhoon. For peak intensity at 12Z, November 4 (image above), the average wind radii I was deriving was 149 nm, which is an average to slightly above average size. When using the minor axis of 30 kt winds from JMA rather than the average, I ended up with a 113 nm average for the same time, which is similar in size to Hurricane Patricia from 2015. Deciding that this was a much more reasonable estimate, I ended up using this methodology for estimating the average extent of TS winds for Vera’s lifetime.
The second revolved around a recorded flight level wind of 170 kt slightly before peak intensity at 0507Z, November 4. When using a fairly standard 90% reduction from 700 mb, a 155 kt wind velocity could then be derived. This is in spite of the extrapolated pressure of 921 mb at the time, which would only result in an estimate of about 145 kt using KZC. Keeping this in mind, the minimum pressure of 915 mb at 12Z, October 4 would usually result in a 150 kt intensity from KZC. However, when adjusted with the ratio of flight level wind reduction from the previous fix, maximum winds are estimated at a higher 160 kt. Because of the 170 kt flight level wind, reanalyzed winds are a little above the KZC estimates near peak intensity.