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Replies to Best Track Change Committee - January 2009Replies to the Committee are indented.1921 #1: This proposed new system gives the appearance of a baroclinic low spinning down. The isothermal analysis also seems to support a baroclinic system. The system is very large, with little evidence of strong, or strengthening, winds near the center. The system is not accepted for inclusion in HURDAT. 1921/01 (proposed, now deleted): Agreed to not include the system into HURDAT. The cyclone is mentioned in the Additional Systems section. 1921 #2: Removal of positions on the 15th accepted. Note that TS Gamma, 2005, could serve as an analog for the developmental phase of this system. The 45 kt wind at Progresso suggests shifting the track northward. Also, the reduction in wind on the 20th is too severe. 65 kt would be more appropriate. Wind of 80 kt at the time of landfall is accepted. Given the MWR account, the 980 mb central pressure observation seems incontrovertible. Note that Schloemer (1954) states his equation is valid up to distances of 100 miles. While increasing distance may increase uncertainly in the estimate, Ho's application of this equation cannot be rejected on the grounds of distance alone, as stated in the metadata. Spelling: search for 'apprently', 'slight east', 'crops were damage' 1921/01 (was proposed 1921/02): Mention of the analog to TS Gamma now included in the metadata writeup. Track is shifted northward on the 18th to better account for 45 kt winds at Progresso. Winds reduced from 85 kt down to 65 kt as recommended on the 20th. Given that the distance from landfall to Houston is just about at the 100 nmi limit of the Schloemer equation, perhaps it is not surprising that the calculation is substantially off. As agreed, 980 mb for a central pressure is utilized. Spelling errors are corrected. 1921 #3: Although new positions are added on the 5th with 35 kt winds, comments for that day indicate no gale force winds observed. Given this, it would be more consistent to keep this system as a depression on the 5th. The pressure was probably lower than 992 mb at landfall, given the 996 mb ship observation (i.e. Connor's estimate was too high). A lower central pressure would also be more consistent with the 70 kt wind. 1921/02 (was proposed 1921/03): Agreed to reduce winds down to tropical depression intensity on the 5th. Agreed to estimate a lower (985 mb) central pressure at landfall in Mexico.
1921 #4: On the 10th, the 961 mb central pressure
around 1800 UTC supports a wind of 100 kt. It is reasonable to assume
that the hurricane continued to strengthen prior to hitting the eastern
Dominican Republic, and therefore winds of 110 kt are suggested for 0000
UTC Sept 11, and winds of 110 kt at 0600 UTC. Once north of the
Dominican Republic, the reduction in intensity does not seem justified.
On the 13th the 967 mb ship report was not a central pressure
(as noted) and supports the original intensity.
1921/03 (was proposed 1921/04): Agreed to boost intensity at landfall in Domincan Republic to 110 kt. Agreed to retain Category 3 status after the cyclone moved back over the Atlantic. The 959 mb ship report is now mentioned in the metadata writeup.
1921 #5: Note that the 70 kt ship report on 9/12 near 0Z
supports an intensity higher than 60 kt. 70 kt is suggested. In order
to blend in this increase, on 9/11 suggest 50 kt at 12Z and 60 kt at 18Z
Then, given 70 kt at 0Z on 9/12, increase to 75 kt at 6Z. Otherwise
accepted.
1921/04 (was proposed 1921/05): Agreed to changes to slight increases to intensity as suggested. Typos are also corrected. 1921 #6: The case is not well-made for the addition of this new system. The classification as tropical seems to hinge upon the dissipation of the frontal features on the 9th. The system was only non-frontal for one day before absorption or merger with another (possibly the same) front. Given this, can it be shown somewhat more conclusively that the frontal nature had transitioned? Given the uncertainty, one option might be to preserve the data and documentation given here and transfer the system to 'possible.' 1921/06 (proposed, now deleted): Agreed to not include the system into HURDAT. The cyclone is mentioned in the Additional Systems section. 1921 #7: Accepted as modified. 1921 #8: Given the west wind of 20 kt found in the HWM, it is suggested that the wind at 12Z on 10/20 be maintained at 35 kt. Please note that the observation cited in the metadata for 10/23 (27.5, 85.6) appears to be either for some other day, or the latitude is incorrect (21.5?). A major concern is the southward shift in the track at the time of Florida landfall. An extended calm is well-documented over Tarpon Springs, and the original track in fact passes directly over this area. However, the revised track is shifted considerably south of Tarpon Springs. This does not seem warranted. Further, the change in intensity to 110 kt at landfall may be a bit high. Given the fact that this was a large, late-season system that was filling as it made landfall, and given the relatively low environmental pressure, 105 kt is suggested. (post-meeting, Brian Jarvinen confirms (through Richard Pasch) that the area of landfall was Tarpon Springs, and that intensity was likely 105 kt.) Given the focus on the assignment of a Saffir/Simpson scale number, is there any evidence to suggest that southeast Florida should be included in this case? (a zoomed map is available) It was suggested that running a likely wind-swath along the track would at least trigger possibilities for consideration. 1921/08 (was proposed 1921/06): Agreed to maintain wind at 35 kt on the 20th. The observation mentioned in the metadata was indeed entered incorrectly, as the actual latitude was around 21.5N Agreed to retain original track with landfall over Tarpon Springs and to not utilize Ho et al.'s landfall point. Agreed to utilize a 105 kt wind at landfall, rather than 110 kt. After reconsideration of the RMW of the hurricane and the track just north of Cape Canaveral (the dividing point between southeast and northeast Florida), southeast Florida is also added in as being impacted by Category 1 conditions. Additional #1: Please note that the MWR indicates a possible system in the Gulf of Mexico during the period May 15th-17th of this year. It is no doubt a weak system, but it should be investigated. May 15-17 system: The Historical Weather Maps show a cold front that moves into the Gulf of Mexico on 14 May. The front becomes stationary by the 16th as a closed low formed along the front in the eastern Gulf of Mexico. The cyclone - which did not exhibit any gales during its duration - weakened on the 17th. It appears that the cyclone remained baroclinic throughout its lifetime, so it is not added into HURDAT. Additional #2: Do the data on the 8th and 9th rule out a closed circulation? Jul. 5-11 system: Yes, it is possible that this system had a closed circulation on the 8th and 9th. This is now mentioned explicitly in the metadata writeup.
Additional #6: There was considerable discussion about whether
this system was a tropical storm. The consensus was that this seems
like a good candidate that bears further investigation. Note that the
ship S.S. Mexican did not report a wind shift, and was therefore not in
the center. It is therefore not surprising that the pressure was not
lower, as stated. Also note the pressure deficit of 7 mb.
Nov. 19-25 system: After obtaining the COADS ship database for this system, several gale force winds were obtained in addition to finding gale force winds for Sand Key, FL on the 23rd. Given these additional observations, it is judged that this system was a tropical storm and has now been added into HURDAT as the 7th tropical storm in 1921.
1922 #1: Do not drop the positions on the 12th, but
rather make the system a depression with winds of 25 kt. (note spelling:
northwested) Some weakening over the Yucatan is shown, but 25 kt may be
more appropriate. Otherwise accepted.
1922/01: Agreed to keep positions on the 12th as a tropical depression. Agreed to weaken the cyclone to a 25 kt tropical depression over the Yucatan. 1922 #2: Committee agrees with starting this system as a depression. After some discussion, the increase in winds on the 16th and 17th appears to be justified. In fact, the system could easily have been stronger than 105 kt, but there may be no way to support this.
The reduction in winds over Bermuda on the 21st also appears
to be justified. Jack volunteered to contact Bermuda to see if there
could possibly be any further observations, but these may have been
destroyed in the office fire.
The committee was not clear on the meaning of 'sprant' in the metadata. Was this how it appeared in the original source? HWM did not handle this major system well, which again brings up the point of what other sources the analysts did or did not have. 1922/02: The 944 mb on the 25th does appear to be a valid observation, but it was accompanied with 50 kt of wind. Thus a 939 mb central pressure for the cyclone (extratropical at that time) is analyzed and included into HURDAT. The sea conditions encountered by the SS Aquitania have been included in the metadata writeup. It is agreed that the HWM analyses were too weak in the central pressure estimates and these were thus not seriously utilized in the reanalysis. 1922 #3: Based on re-examination of surface observations, do not remove positions on the 12th, but retain as a 25 kt depression. On the 13th, the frontal analysis in HWM does not appear to support the suggested change to extratropical. Depression status at landfall will change XING = 1 to XING = 0. (CJM will check on this point). 1922/03 (now 1922/04): Agreed to keep positions on the 12th as a tropical depression and the 13th as a tropical storm. Depression status at landfall in the U.S. does change XING=1 to XING=0. 1922 #4: While there is some question about the proximity of the initial positions for this system and #3, they do appear to be distinct. Of greater note, however, this system may have started earlier off the coast of Columbia. See p. 555 MWR 1922. In particular, see description of damage on Oct 10-11, from Magdalena, Columbia, and the comment that this was likely connected to the disturbance in the western Caribbean on the 12th.
Data appearing in HWM suggests the following 12Z positions: Also, on 10/16, the NW ship supports winds of 60 kt at 12Z, and 65 kt at 18Z. 1922/04 (now 1922/05): Agreed to begin the system on the 11th near Columbia. Winds adjusted on the 16th as requested.
1922 #5: There are several key questions concerning this new
system. 1) Much of the argument for tropical storm strength seems to
hinge on the 37 kt wind recorded at Pensacola. Does this need to be
adjusted for equipment, etc? This has frequently been done in the past.
2) the highest ship observation appears to be 25 kt. 3) The HWM series
seems to suggest that the center came from the south, not from the north.
1922/05 (originally proposed): The winds of 37 kt at Pensacola do indeed reduce to lower than gale force (31 kt) after adjusting for the high bias and 5 min-to-1 min conversions. As suggested, this system has been moved into the Additional Notes section and not included into HURDAT. Additional additional systems: 1) Please note the MWR discussion concerning conditions in the Gulf of Mexico during 5/25 - 6/1. Storm warnings were posted. 2) A possible 'Beryl' analog was moving near Nantucket 6/21- 22. It is possible that this was an extratropical system exiting the mainland, but it might have transitioned. 3) See MWR p. 443. A disturbance is noted in the Caribbean which may have crossed Central America. 4) See MWR p. 503. The discussion from the New Orleans Forecast District notes disturbed conditions off the Texas coast during 9/17- 9/20. Storm warnings were issued. During this period 13' of rain and 48 mph winds were reported from Corpus Christi. This may have been frontal, but it bears further investigation. 5) See MWR p. 596. An area of low pressure is noted in the West Indies from 11/13- 11/17. Concerning existing additional #7 . see MWR p. 495. The discussion on the Cuban ship S.S. Paloma on the 19th notes: 'wind increasing to almost hurricane force from SE. Lowest barometer reading 29.72" wind force 11.' The position of this ship is closer to the center of the low than the other reported observations Additional systems: All of the additional systems mentioned were looked at in detail. In particular, the late May and June ones remained extratropical during the lifetime. The August Caribbean disturbance was a tropical wave, that likely became a tropical storm in the Northeast Pacific after passing Central America. The September high winds/heavy rain in Corpus Christi were due to thunderstorms associated with a weak, stationary frontal boundary, with no closed low in the vicinity. The November West Indies low pressure did not have a closed circulation. None of these appear to have any significant chance of being an Atlantic basin tropical storm, so they are not added to the list of 10 suspect systems already that are detailed in the metadata writeup. Additional System #7 (now 1922/03): After re-consideration of the S.S. Paloma observations, other MWR ship and station data, the Historical Weather Map data, and COADS ship observations, the system is analyzed to be a minimal hurricane off of the U.S. coast. This has now been added into HURDAT and thoroughly documented. At the close of the meeting, Eric Blake presented a set of changes to the eastern Pacific track file in connection with the track book project. These changes should not be taken as a complete reanalysis, but rather as a quick attempt to fix major flaws. The committee will examine these changes and discuss them at the next meeting. The committee met to discuss 1923, and this year was completed. Many of the intensity changes for storms #2 and #4 are based on peripheral observations. Core observations provide a stronger argument, and should be emphasized in the text. Before discussing the Atlantic basin, it was agreed that Simone (1968) should be added to the eastern Pacific track file (specifics below provided by Blake). At this point it simply cannot be determined if this short-lived, but well-documented, system was deleted for some unknown reason, or was never included. In any event, it is now part of the database. Hopefully we are now in an era of better documentation. It was noted that Mike Chenoweth, with input from Cary Mock, had forwarded some suggested changes to storm #2 1857 and storm #8 1859. We will consider this at the next meeting. U.S. landfalls storm #6 1915 (LA4 becoming LA3) and storm #4 1916 (ATX3 becoming ATX4) will have to be submitted for outside review. There were a few questions concerning the 1915 landfall which have now been resolved. It was agreed that, in this case, the process would be best served by someone with knowledge of storm surge and historical reconstruction using the storm surge model. Hence, Brian Jarvinen will be asked to provide the review. He is still active professionally and his experience is unmatched in this area. Specific comments (eastern Pacific): 1968 #18 Simone (add)
10/18/1968 M=2 18 SNBR=199 SIMONE XING=1 10/18* 0 0 0 0* 0 0 0 0* 0 0 0 0* 135 915 45 0* 10/19* 138 918 45 0* 143 922 45 0* 147 926 35 0* 0 0 0 0* (The following submitted by Blake) Add landfall XING=1 because system crossed the coast as a TS. For whatever reason, Simone 1968 is not in the best track file despite its existence chronicled in many publications. The track of the system is based off the 1968 Navy Annual Tropical Cyclone Report, Annex A. No intensities are noted in the Navy report. However the 1968 MWR article says that winds of 40 to 45 kt were reported as the ship was (apparently) moving through the center. MWL mentions the same short-lived storm, though it has the ship reporting 40-50 kt maximum winds and a pressure of 1005.4 mb in the center. 45 kt is chosen as the maximum intensity, which better fits the relatively high pressure of 1005 mb reported than 50 kt. 45 kt is also a useful value because of the uncertainty involved since it is the value of generic tropical storms in the EPAC database. Specific comments (Atlantic):
1923 #1: (new) Although it has been noted previously, the
frequently used 'closed low of "at most" xxxx mb' is confusing. This
appears to refer to the innermost closed isobar. It would be preferable
to call it as such, or estimate the central pressure, or both.
Semantics: 'Oceanfall' is not a word. 1923/01 (new): Further examination of Penscola, Mobile, and New Orleans hourly observations from the Original Monthly Records provides data (from Pensacola) to support tropical storm intensity at landfall along the Gulf coast. Thus the system is now indicated to be a tropical storm both in the Gulf and again in the Atlantic. Wording of "oceanfall" changed.
1923 #2: The first part of the track (30th-31st)
is dropped in this revision. However, it should be noted that there are
multiple references to a possible late August origin for this system (MWR
p. 419, 477, and 481).
1923/02: Agreed. References are included in the metadata writeup about the possible late August origin for the system. Intensity from the 6th to the 8th now retained as that in original HURDAT due lack of inner core observations. 1923 #3: (new) It was noted that this new system appears to be a TS Florence (1964) or TS Debby (2006) analog. Time of occurrence is similar, and thus fits climatology. Is there any possibility of more detailed data from the Cape Verde islands? Can it be more clearly determined if the 1003 mb observation was a central pressure? Otherwise accepted. 1923/03 (new): The similarities to TS Florence (1964) and TS Debby (2006) in location, time of year, and intensity to this new tropical storm are now noted in the metadata writeup. Unfortunately, no additional observations are readily available from the Cape Verde Islands. The 1003 mb pressure value was unaccompanied by a wind observation from the source in COADS, so it is unknown if it was a central pressure. 1923/04: (new) See below in Additional Systems. 1923 #4: The genesis of this system appears to be OK. However, there are some concerns surrounding the large reduction in intensity on the 28th and 29th. Which observations near the center, if any, support this change? Further, the pressure seems too high. 'Numerous' observations are noted on the 30th, but which ones in particular? The 70 kt ships cited appear to be well-removed from the center. 1923/05 (was proposed 1923/04): Agreed to retain peak winds of 105 kt on the 29th as originally shown in HURDAT. Note that while the HWM pressures are noted in the metadata, these are not explicitly believed as accurate.
1923 #5: It is stated that 'a peripheral pressure of 1001 mb
suggests winds of 45 kt '85from the southern pressure-wind
relationship'8545 kt chosen for HURDAT (up from 35 kt) because of low
environmental pressures.' This reasoning seems to be backwards. Why
would the wind be increased with low environmental pressure?
In general, the revision seems to be going in the right direction with regard to the reduction in intensity, given a fast-moving system in a baroclinic environment, but the question is has it gone far enough? Is it possible that this system was below hurricane strength at the time of landfall, even with the 983-985 mb central pressure? A recent analog would be Isidore (2002) making landfall in Louisiana. Also note that the New Orleans office reports 2-3' of surge at Morgan City, and 8' at Biloxi, implying that this system did not have a tight core. There seems to have been some confusion about the nature of this system, even at the time. Were the maximum winds in Pensacola, 250 miles away (MWR p. 654)? Or was the system of uc0u8232 "small diameter, not of great intensity" (MWR p. 544)? There is only one ship report (74 mph). Where was this in relation to the center? Given that the pressure stayed the same at Morgan City (990 mb) for 1.5 hours, was this a central pressure? Also, can the data gap between Morgan City and Vicksburg be filled in? Finally, concerning the landfall designation, ul ifulnone the 68 kt at Pensacola is correct, should we then include AFL1? Also note that the track map indicates 985 mb, while the track file shows 983 mb at 06Z on the 16th. 1923/06 (was proposed 1923/05) : The metadata writeup was not clear about how the low environmental pressures were utilized. This is now stated as: "A peripheral pressure of 1001 mb on the 12th of October suggests winds of at least 45 kt from the southern pressure-wind relationship. A lower value of 40 kt is chosen for HURDAT because of the low environmental pressures, though this is an increase over the 35 shown originally." Agreed to reduce the intensity of the cyclone to tropical depression while over the Isthmus. It is agreed to even further delay the onset of hurricane intensity to 18 UTC on the 15th (originally 12 UTC on the 14th), based upon numerous observations indicating a slower intensification rate. The 68 kt wind was incorrectly listed. The 56 kt SE wind at 13 UTC was the highest observed sustained (5 min) wind at Pensacola, which reduces to 46 kt true after adjusting for the high bias and converting to 1 min. Thus it does not appear that including northwest Florida (AFL) as having a hurricane impact would be appropriate. This system certainly did have a large inner core. Given the 8' storm surge in Biloxi and the 7' in Gulfport (but no wind observations for the Mississippi coast), it is likely that Mississippi also received Category 1 hurricane force winds. Thus both Lousiana and Mississippi are indicated as having a Category 1 impact. The one ship that reported hurricane force winds just before landfall was likely about 75 nmi northwest of the cyclone's center around 01 UTC on the 16th. No other data are available between Morgan City and Vicksburg and it does appear that the 990 mb pressure reading in Morgan City was likely a central pressure reading or quite close to it (keep in mind the very large RMW of the cyclone, so that the city would have been in the "eye" for a substantial amount of time despite its quick motion). 1923 #6: Based on operational experience, It seems highly unlikely that the surface circulation survived the passage over this portion of the Mexican terrain. An argument could be made that if the circulation did not survive, then the eastern Pacific portion of the track should not be included here, but rather in the eastern Pacific track file itself. (However, in reality, given that this file contains no entries before 1949, this could cause some unnecessary confusion.) The crux of the matter is to more firmly establish whether a circulation center survived. A once-per-day snapshot may not be sufficient to determine this. Also note that on the 15th, the 35 kt wind at Salina Cruz is probably too far away to be relevant. This is probably part of a larger monsoonal flow rather than representative of the direct circulation of the remnants over the Mexican plateau. Concerning U.S. landfall, the 992 mb is accepted, but 55 kt seems too high. Suggest 50 kt instead. 1923/08 (was proposed 1923/06): Agreed that the system probably did not survive continuously across mainland Mexico as a tropical cyclone. Wording included in metadata to suggest that the Gulf cyclone may have been associated with remnants from the NE Pacific cyclone. Agree to reduce winds at landfall down to 50 kt. 1923 #7: Are there any observations from Bermuda? As far as the extratropical transition, there are no fronts on the surface map on the 19th. Did cold air penetrate to the center of the system? Note that this is a very unusual pattern for an extratropical system. Suggest holding the system at a peak of 55 kt. Semantics: on the 19th, it appears that the system moved inland ul southulnone of Boston. 1923/07: Unfortunately, there are no observations available from Bermuda for this system. After reinspection, it is concluded that tropical cyclone status should be retained, as cold air did not reach the center of this system and extratropical transition did not occur over the Atlantic. (The cyclone was absorbed by a large extratropical storm moving in from the west around 18 UTC on the 19th.) Agreed to keep the peak wind in this cyclone at 55 kt, due to its slow translational speed and low environmental pressure. Wording corrected on the 19th. 1923 #8: Can the case be strengthened for tropical storm status before merging with the front. The important point in this case is that the frontal analysis in HWM analysis is questionable, and should be reanalyzed. 1923/09 (was proposed 1923/08): Agreed that the HWM frontal analysis looks dubious on the 26th and this is so stated in the metadata writeup. No gales were observed before likely extratropical transition around 00 UTC on the 27th. The cyclone cannot be definitively confirmed as a tropical storm. But given the rather sparse data available, it is possible/likely that minimal tropical storm intensity did occur.
Additional systems: 3) This system has been further analyzed and it does appear to be a new, short-lived hurricane. A complete writeup and entry into HURDAT has been included, as storm 1923 #4.
Additional additional systems: The Oct. 8-9 system has been investigated and included in the Additional Systems section. No observations of gale force wind or low pressure were found, so this system does not meet the definition of being a tropical storm.
4) Removal of this system is provisionally accepted, but there are some
questions. Note MWR p. 535, the S.S. Hayo Maru reported 29.75 mb, heavy
SW winds near Jamaica- about 200 miles from center. (MWR notes 'too far
from center to experience wind shift.') The circulation may have been a
large envelope with well-defined core, somewhat analogous to TS Frances,
1998. Data from Central America, the Cayman Islands, Jamaica, and the
Bahamas would be extremely helpful in resolving the status of this system.
4) Unfortunately, no additional observations are readily available for this system. The maps that were provided by Ramon Perez are of sea level pressure with a contour interval of 1 mm with the leading value of "700" not included. Thus "60" is "760 mm" (1013 mb) and "55" is "755 mm" (1006 mb). The possibility that the system did have a well-defined core, somewhat analagous to TS Frances, 1998, is mentioned in the metadata writeup.
Minutes of the best-track change committee meeting, 06 February, 2008
The committee met to conclude discussion of the responses from Landsea for the period 1915-1920, and to discuss 1924 and 1925. 1924 #1: (original) The available surface observations do not rule out the existence of this system. This seems to be a minimal tropical storm that fits well with climatology. Please retain and use the few observations that are available to adjust the positions westward, as noted on the 19th. 1924 #1 (re-revised) Agreed to retain system as a minimal tropical storm and to adjust positions westward. 1924 #1 (new): Accepted. However, it would strengthen the case for this system if the ship-observed temperatures were plotted to better define the temperature gradient. That is, was the gradient weak enough? The phrase "not included in HURDAT" is repeated several times, and really only needs to be stated once. July 30: suggest rewording the phrase "stationary front approaching from the south." 1924 #2 (re-revised) The temperature gradients were quite weak on the 28th and 29th, with a value of ~5°F in 5 degree latitude diameter and nearly 0F in 5 degree longitude on the 28th and ~5F in 5 degree latitude and ~4F in 5 degree longitude on the 29th. The plots are included in the binder. The phrase is now only included once. Rewording made on the phrase. 1924 #2: The center did not cross the coast, therefore XING = 0. The analysed pressure field in HWM is impressive, and significant wind was observed along a large section of coastline, consistent with a major hurricane. It does not seem that the case has been well made for the large reduction in intensity. Is there a specific central pressure observation that supports this reduction? Lacking this, please retain major hurricane intensity. August 24th- note that the 972 mb ship in MWR (also in COADS) is of uncertain position with no wind stated. Also note that the 975 mb in Hatteras suggests a major hurricane, given the distance off the coast. #3 (re-revised) The XING is changed to "0". After reanalyzing the available data, a central pressure estimate can be made from the observations from the Harvester (MWR, page 401). This value does appear to support significant weakening of the hurricane from that originally contained in HURDAT. The 972 mb on the night of the 24th is added into the daily highlights. The 975 mb in Hatteras is interpreted to support a central pressure of 963 mb with a track of just offshore. 1924 # 3: On the 28th, the quote from MWR states that the 965 mb readings were from 'nearby barometers' but where were they? The southwestward shift of the track around the 1st seems justified, but the revised track now contains some unsupported detail (wiggles) that should be smoothed out. Sept 29: Is it sufficiently known that the 967 mb observation was a central pressure? 1924 #4 (re-revised) It is guessed that the MWR author meant on Monteserrat, but not specifically at Cudjoc Head. The track has been smoothed out on the 31st and 1st. The wording of the MWR implies that this 967 mb pressure was a central pressure value. 1924 #4: Although the track is accepted, it seems extremely unusual for a system moving northeast to intensify before making landfall along the Florida panhandle. Summary discussion wording: based on marine and Canadian observations. Also, the 986 mb observation from Appalachicola is mentioned in the summary, but not in the metadata for 9/15. Sept 13: The metadata states the available observations suggest a 45 kt tropical storm, but then "ship highlights: no gales or low pressure." Please resolve. 1924 #5 (re-revised) It is noted that an intensification after recurvature toward the northeast is rather unusual, but that is what the rather numerous data suggest. The 986 mb Appalachicola observation is now included in the metadata. The "suggest a 45 kt tropical storm" has been removed. 1924 #5: In the introductory comments the MWR is given as a source, however nothing was found in that volume. Please check. Also, the comment "HURDAT did not find this system in its database" need only be mentioned once. It seems very unlikely that this system would have become a tropical depression after the 30th at this point in its lifecycle (i.e. at the time of recurvature.) This level of detail does not seem to be supported by the available observations. Track is otherwise accepted. Metadata for 9/26 states that "available observations suggest 35 kt" however ship highlights are "no gales or low pressures." This seems inconsistent. In cases such as this, any ship near the center should be highlighted, regardless of intensity. 1924 #7 (re-revised) The MWR reference has been removed. The comments about the system not being in HURDAT is stated just once now. It is agreed that the cyclone retained tropical storm intensity on the 30th. "Available observations suggest 35 kt" on the 26th is removed. 1924 #5 becoming #6: The key question surrounding this system is the time of extratropical transition. The central pressure was probably below 1000 mb at 12Z on 9/29, and not yet extratropical. Suggest leaving the intensity at 50 kt as a tropical system, thereby delaying extratropical transition until 0Z on the 31st. Further, can we be sure that the system was extratropical before landfall? This hinges on what can be determined about the thermal structure. Also, on the 29th, the peripheral pressure is given as 1003 mb, but mentioned as 1002 mb in the summary. Please clarify. Is this the correct date or the 45 kt wind at New York? It seems more likely an observation from a day or two later, given the track. Finally, could the system have been stronger at Norfolk? Is the type of anemometer known? Also, it is suspected that this anemometer did not have marine exposure. 1924 #8 (re-revised) It is agreed to delay extratropical transition until 00 UTC on the 30th (there aren't 31 days in September). Landfall occurred around 21 UTC on the 29th, thus the system will be considered a tropical storm (but one that was undergoing extratropical transition). Both the 1003 and 1002 mb pressure observations for the 29th are mentioned in the daily summary. The 45 kt wind at New York is correct, but that wind was unrelated to this cyclone and thus that observation has been removed from the discussion. The 66 kt at Norfolk adjusts to 54 kt after accounting for instrument bias and the 5 min to 1 min correction. Higher winds- 71 kt- were observed in Atlantic City, which adjust to 58 kt true. The estimate in HURDAT at 18 UTC on the 30th is 65 kt- hurricane force extratropical impact. 1924 #6 becoming #7: There is some uncertainty concerning the contribution from the large-scale pressure gradient. Observations suggest starting the system a day earlier, on the 11th. This would also blend in better with the 40 kt at 0Z on the 12th. Please evaluate the 49 kt ship report on the 14th 'near' Tampico. A plausible scenario is that the system continued to move south and died over Mexico. Lending credence to this scenario is the possibility that the large hurricane forming south of Cuba at this time exerted a southward pull on this much weaker system. A similar interaction has been observed operationally. 1924 #9 (re-revised) It is agreed begin the system at 12 UTC on the 11th. Also, the alternative scenario of the storm continuing into Mexico has been utilized. The possible influence of storm #9 in the Caribbean on steering is also discussed in the metadata. Best Track Committee Comments from meeting on 6/24/2008
1924 Storm 7 becoming Storm 8: 1924 #10 (re-revised) Perez has been contacted to provide a clarification. He indicated that the value of 917 mb was obtained from a calibration of the instrument by Cuban meteorologists soon after the hurricane. This value is then utilized to estimate a central pressure of about 910 mb. The write-up for 16 October mentions a ship report with a 988 mb pressure at 13 UTC. The data tables show that a ship named the Nameria had a 983 mb pressure at 13 UTC and a 988 mb pressure at 12 UTC. Please clarify this. 983 mb is the correct value, which has been utilized to obtain the intensity on the 16th. Barnes mentions a pressure of 975 mb at Marco Island Florida on 20 October. Is there any other reference to this data, particularly if it was a central pressure or not? Barnes has been contacted to provide a clarification. He indicated that this observation was obtained from the _Climatological Data_ publication. Unfortunately, the reference is not clear as to whether this was a central or a peripheral pressure reading. As this value is very close to an estimate derived (977 mb) from a pressure-decay value obtained from the central pressure reading in Miami, it is assumed that the 975 mb is a central pressure reading at landfall in Marco Island. Typo in the 19 October write-up: "hurricane fore winds". Corrected.
1924 Storm 8 becoming Storm 9: 1924 #11 (re-revised) Yes, the winds at 12 and 18Z on the 9th and 00Z on the 10th have been adjusted downward from what was proposed. Can the forward speed in the track on 12 November be smoothed a little? The track has been adjusted on the 12th to provide a smoother, more realistic track. There needs to be better documentation that the cyclone was absorbed by the baroclinic zone, as the 14 November write-up makes no mention of extratropical transition. Could the low on the maps be the former TC? System is absorbed by a developing extratropical low around 00 UTC on the 15th (by the extratropical low that was near 42N 67W on the 14th and near 47N 45W on the 15th). This is now more clearly described. Typo in the summary paragraph: "showed displayed". Typo corrected.
1924 Additional Systems 1: Typo corrected.
1924 Additional Systems 2 former tropical storm: System was already covered in previous committee meeting's notes. Agreed to retain system as tropical storm.
1924 Additional Systems 3: 1924 Additional System 2 (re-revised)- Comment added about possibly being in connection with the monsoonal flow.
1924 Additional System 4: 1924/06 (re-revised) The first observation was with 10 kt SE winds, while the second had calm winds. The combination of the observed winds and pressures leads the committee to think this system was a tropical storm. Please present a more detailed analysis of it. Agreed. The system is now to be added into HURDAT.
1924 Additional System 5: Now is 1924 Additional System 3 (re-revised). General comment on the 1925 write-ups: There are too many repetitions of "HURDAT did not previously include this system in its database". Please remove them. Done.
1925 New Storm 1: The 50 kt at 12 Z on the 19th was based upon extrapolation back from the hurricane force intensity (and observations) from the subsequent day. Is the 994 mb pressure a central pressure, or was it coincident with the 70 kt winds? The wind and pressure measurements were coincident.
1925 New Storm 2: Done. There needs to be additional information on the system becoming tropical on 26 August, whether in the daily write-up or the summary. Added in the summary.
1925 Storm1 becoming Storm 3: Yes, hourly observations for temperature and winds from Brownsville are available in the Original Monthly Records, which are included in full in the binder. Can the Brownsville obs be included in the data table for this system? The highest wind and lowest pressure observations are included in the daily writeup and all relevant observations are included in the accompanying spreadsheet.
1925 Storm 2 becoming Storm 4: The criterion for two gale force winds is usually applied for adding a brand new tropical storm into HURDAT. In this case, there is a very well-defined circulation on the 27th in the northwestern Caribbean, which dictated that a tropical cyclone had formed. The highest observed wind- from both COADS and HWM- is 35 kt, which looks reasonably reliable. This observation is the reason for the 35 kt intensity estimate. 28-29 November: If the system was a tropical storm on 27 November, are the observations on 28-29 November in sufficient numbers and in good enough locations to be conclusive that the system weakened? There is a possibility the system was a 30 kt depression from 27-29 November. The observations are quite sparse on the 28th and 29th, so perhaps it would be best to continue the system as a minimal tropical storm for these dates. For the 29th, this would mean no changes to the intensity in HURDAT. 1 December write-up: Are there sufficient observations of the core to justify the downgrade? Particularly, what observations are available on the Florida west coast between Tampa and Naples that would conclusively rule out a landfalling hurricane? The committee noted that oak trees were blown down, apparently in the Tampa area. Could wind speeds be inferred from that kind of damage? Observations are sparse near the center of the cyclone in the Gulf of Mexico and at landfall in southwestern Florida. It is agreed to maintain this system as a minimal hurricane given the wind-caused damages that occurred in Tampa. The track passes close to Tampa. However, the minimum pressures in Key West (1002 mb) and Miami (1000 mb) were only slightly higher than the Tampa minimum pressure (999 mb). This suggests the track over Florida was south and east of what is currently depicted. Could data from local newspapers help refine the track? Note that a ship report off the Florida east coast at 09 UTC 1 December (60 kt and 996 mb) suggests a central pressure significantly lower than the Tampa, Miami, and Key West obs, possibly lower than the 993 mb landfall pressure stated in the summary write-up. Agreed. Track is shifted farther southeast. The ship report does indicate that the cyclone was of hurricane force before and at landfall as well as again once back over the Atlantic. Detailed analysis of the temperatures over Florida may help refine the time of extratropical transition. Agreed. This has now been provided and does indicate extratropical transition likely occurred shortly after landfall in Florida (~06 UTC on the 1st of December). The track map shows the cyclone becoming extratropical before landfall in Florida. Please correct this even if no other changes are made. Corrected. 5 December write-up: This states the system passed near the Azores on the b 9th as stated in the Monthly Weather Review. Did the system continue as an extratropical low all the way across the Atlantic? What was the basis for ending the track on 5 December? Despite the Monthly Weather Review stating that the cyclone continued eastward to near the Azores on the 9th, daily analysis including the Historical Weather Maps indicates that a second, extratropical system which formed east of Bermuda on the 4th was the system that moved toward the Azores.
1925 Additional System 1: A daily synoptic analysis was performed for this system and is available in the binder. This analysis does not suggest any changes need to be made from the original assessment.
1925 Additional System 2: Certainly, this is always an issue of whether the available observations are sampling the most intense portion of the cyclone. (Most of the time, they are not.) Because of this, it is not certain that this system did not reach tropical storm intensity. Thus it is mentioned in the writeup that this may "have been a minimal tropical storm from the 30th until the frontal merger on the 1st. . Does the track on 1 October need adjustment to better fit the obs? Agreed. It is adjusted northwestward to 36°N 55°W. There is a possibility that the Historical Weather Maps mis-analyzed the system and its environment on 1 October. If so, the system might have made ET at a later time by staying ahead of a second frontal low. Please examine this. It does appear that the cyclone's center is northwest of where the Historical Weather Maps indicate. However, the first observation of gale force winds were at 08 UTC on the 1st with temperatures of 63°F and at least a 10°F east-west temperature gradient across the cyclone's center. There are no indications that the system stayed in the warm sector of separate extratropical cyclone. Instead, the low indicated in the Historical Weather Map on the 1st is the cyclone that had been tracked for two days previously. The terms "barotropic phase" and "barotropic attributes" should be changed to "tropical characteristics". Done. |
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