E Pacific Tropical Action of 2014

[Yellow Evan]

First visible show an intensifying hurricane.

 

[Srain]

From Forecaster Berg with the 8:00 AM PDT Discussion:

 

An eye has been observed sporadically in infrared satellite imagery
during the past few hours, and recent microwave data has also
revealed a small pinhole eye in the 85-GHz channel and a 12-15 n mi
eye in TRMM radar data. Satellite classifications are still rising,
and Amanda is being initialized as a 65-kt hurricane based on Dvorak
estimates of T4.0 from SAB and the UW-CIMSS ADT.  Amanda is
intensifying rapidly, strengthening by 35 kt over the past 24 hours.

Amanda is located over very warm water and in an environment of
light vertical wind shear, and all indications are that this period
of rapid intensification is likely to continue.  The operational
SHIPS Rapid Intensification Index (RII) is indicating a 60 percent
chance of a 40-kt increase in intensity during the next 24 hours,
which is almost 15 times higher than normal.  An experimental Joint
Hurricane Testbed version of the RII product, which includes
additional environmental variables, is showing even higher chances
of rapid intensification.  Based on this guidance, Amanda is
forecast to continue strengthening rapidly, potentially reaching the
threshold for major hurricane in about 24-36 hours.  After 48
hours, southerly vertical shear is expected to increase, which is
likely to cause Amanda's low- and mid-level circulations to
decouple.  Therefore, fast weakening is indicated toward the end of
the forecast period.  The updated NHC forecast is higher than the
previous one during the first 48 hours to account for the high
likelihood of continued rapid intensification, but it is largely
unchanged thereafter.

Amanda continues on its slow west-northwestward trek, and the
initial motion is estimated to be 290/4 kt.  A mid-level ridge
centered over Mexico should begin weakening soon, which will cause
the hurricane's forward motion to slow even further during the next
24 hours.  In about 2 days, the mid-level ridge is forecast to
restrengthen over the western Gulf of Mexico while a mid-level
trough amplifies near 130W.  This pattern change should push Amanda
northward between days 3 and 5, but the speed is still likely to be
fairly slow.  The GFS and ECMWF models are located on the right side
of the guidance envelope on this forecast cycle, and the NHC
forecast has therefore been shifted a bit to the right as well,
especially beyond 36 hours.  This track is also to the right of the
model consensus TVCE.
 

[Ground Scouring]

Well if Amanda undergoes rapid intensification in the next 24 hours (something the SHIPS RI index has been indicating) then this forecast goes out the window. Shear the last day or so has been negligible (again the system is currently still south of the stronger westerlies which are located NW of the system). This will play a role later in the forecast, but for the next 24-36 hours things are favorable for intensification, and I think the NHC's forecast at 11pm is very much in line with this possibility. Given the small inner core developing, there is an outside chance we could see a major hurricane out of this (but has to be in the next 24-36 hours). 

The significant tightening of the inner core probably helped the MLC and the LLC to align, thereby reducing the impacts of mid-level dry air and resulting in greater intensification than I had expected. (Currently the system is a true micro-hurricane, with hurricane-force winds extending 25 mi from the center.) I'm still skeptical, however, that Amanda will reach major-hurricane intensity, given its closer proximity to the more stable air mass N and W of the small circulation. A peak intensity of 85-90 kt seems most reasonable to me at this time.

[Yellow Evan]

The significant tightening of the inner core probably helped the MLC and the LLC to align, thereby reducing the impacts of mid-level dry air and resulting in greater intensification than I had expected. (Currently the system is a true micro-hurricane, with hurricane-force winds extending 25 mi from the center.) I'm still skeptical, however, that Amanda will reach major-hurricane intensity, given its closer proximity to the more stable air mass N and W of the small circulation. A peak intensity of 85-90 kt seems most reasonable to me at this time.

 

How is the stable air mass gonna affect the system if there's little shear? I agree it's a Microcane though.

[phil882]

How is the stable air mass gonna affect the system if there's little shear? I agree it's a Microcane though.

 

The answer is it won't until the shear increases. This thing is going to become a major hurricane given the very low shear and very warm SSTs (several ^oC warmer than typical for this time of the year). Amanda is still only around 11 degrees north and the system has barely moved the last 36 hours. This lack of motion has certainly helped keep Amanda in a favorable environment rather than it running face first into some pretty strong southwesterly flow. Now that the system is stronger though, its more likely to be picked up by the upper level westerlies, as most of the models are suggesting now. 

[Yellow Evan]

Amanda may have entered a little unarrested development due to dry air, but this Amanda could bomb out when its eve clears out. ATCF brings it 70 knots.

[Yellow Evan]

Amanda is looking very impressive for a Cat 1. Hard to believe, a little over 24 hours ago, this was a weak TS. I'd go with 85 knts. I think this could be a major by early tomorrow. T-number raw have it at 6.3 while the other data seems to suggest an intensity of 75-80 knts.

[Yellow Evan]

Amanda looks even more impressive than when I left. This is remarkable. It looks like 95-100 knts to me. Dare I say it, it is EI'ing.

[thewxmann]

Looking increasingly impressive, should be a Cat 2 in the upcoming advisory. 

[Ground Scouring]

...AMANDA NOW A MAJOR HURRICANE...
...ADDITIONAL STRENGTHENING EXPECTED...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...11.6N 110.7W
ABOUT 665 MI...1070 KM SW OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...966 MB...28.53 INCHES

 

The operational intensity estimate of Amanda at 00Z was less than
100 kt. Therefore, this makes Amanda the second earliest major
hurricane on record in the eastern North Pacific basin, behind only
Hurricane Bud of 2012.

[Yellow Evan]

...AMANDA NOW A MAJOR HURRICANE...

...ADDITIONAL STRENGTHENING EXPECTED...

SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION

----------------------------------------------

LOCATION...11.6N 110.7W

ABOUT 665 MI...1070 KM SW OF MANZANILLO MEXICO

MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H

PRESENT MOVEMENT...WNW OR 295 DEGREES AT 5 MPH...7 KM/H

MINIMUM CENTRAL PRESSURE...966 MB...28.53 INCHES

 

Well, if you count CPHC AOR, it's the 3rd earliest major.

[Yellow Evan]

Amanda's arguably the second fastest I've seen a storm deepen. After Jimena 09. It even rivals Rick 09, Celia 10, and Felicia 09's EI. WOW. This is shocking for May 24!!! That's the most impressive thing. I'd be shocking anytime of year, but given how early it is and how El Ninos tend to be late activity starters. WOW!! I am speechless, so much I can't type right now 

[TropicalAnalystwx13]

Gotta love rapid intensification. I think most of us knew it was likely to do so at some point this weekend, but I wasn't expecting it to intensify at the rate that it did. To think it was declared a tropical storm at 11am EDT yesterday.

 

And the strengthening trend continues. The eye is warming and -80C convection is attempting to wrap around the center. Raw T# from CIMSS is up to T6.9.

 

[Srain]

Amanda is now the earliest forming Major passing Bud 2!012.

[TropicalAnalystwx13]

Amanda is now the earliest forming Major passing Bud 2!012.

Bud was declared 100kt at 0z May 25, while Amanda was declared at 3z May 25. It'll ultimately come down to what post-season analysis says, though I don't think Amanda was quite organized enough to be declared a Cat. 3 at 0z.

[Yellow Evan]

Amanda is now the earliest forming Major passing Bud 2!012.

 

Nope, it was 3 hours short. It probs wasn't a major by 0z.

[Yellow Evan]

Raw T is now up to 7.0. Still don't think this will become a 5, but I don't think until last night, anyone expect this to become a major, so at this point, who knows.

[thewxmann]

Amanda is now up to Cat 4 as of the 2 AM advisory. Second strongest May EPAC storm behind Adolph in 2001.

[Yellow Evan]

EP, 01, 2014052512, , BEST, 0, 117N, 1111W, 135, 932, HU

 

ATCF brings it to 135 knots!!!!!

 

HOLY CRAP!!!!! WOW!!!!!!!!

I can not believe this. This is stunning. WOW!!!! Never though in my wildest dreams this would happen. 135 KNOTS in may!!!

[phil882]

We are very likely near peak intensity... ERC may already be ongoing per the last few satellite frames with the eye shrinking and also starting to undergo trochoidal wobbles.. Looks like Amanda might finish shy of a cat 5 (although it wouldn't be impossible to see NHC upgrade after the 15z satellite fixes). 

 

Again all the ingredients were there for a rapid intensification episode. Small inner core, low shear, very high SSTs. Sure the magnitude was unexpected, but the moment it got that inner core, the writing was on the wall that things were about to go off. 

[Superstorm93]

[Srain]

 

HURRICANE AMANDA FORECAST/ADVISORY NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP012014
1500 UTC SUN MAY 25 2014

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

HURRICANE CENTER LOCATED NEAR 11.8N 111.1W AT 25/1500Z
POSITION ACCURATE WITHIN  10 NM

PRESENT MOVEMENT TOWARD THE NORTH OR 360 DEGREES AT   2 KT

ESTIMATED MINIMUM CENTRAL PRESSURE  932 MB
EYE DIAMETER  15 NM
MAX SUSTAINED WINDS 135 KT WITH GUSTS TO 165 KT.
64 KT....... 25NE  20SE  15SW  20NW.
50 KT....... 40NE  40SE  30SW  30NW.
34 KT....... 70NE  70SE  60SW  70NW.
12 FT SEAS..150NE 120SE 180SW 210NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT.  RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
 

[Yellow Evan]

Amanada is sure epic. Best RI'ing storm since Wilma.

[Windspeed]

ERC or not, I don't think Amanda could maintain this intensity very long due to its slow rate of movement. Plenty of juiced OHC is near the surface in that location of the EPac for Amanda to experience RI and even reach a maximum intensity of category 5; however, the very slow rate of movement results in SSTs dropping faster near the surface, under the immediate center, due to upwelling. Such upwelling is occurring faster than Amanda's center can move away from it. Perhaps Amanda will gain a faster forward motion to the north and the outter eyewall will get away from the upwelled cooler isotherm. Either way I think Amanda has already passed peak intensity for its life cycle.

 

Amanda is quite a beautiful cyclone and an exciting kickoff to the El Nino enhanced EPac season!

[Yellow Evan]

I agree that Amanda has passed its peak.  Cold SST's is less of an issue IMO due to the El Nino though IMO.

[Windspeed]

I agree that Amanda has passed its peak.  Cold SST's is less of an issue IMO due to the El Nino though IMO.

 

I think you misunderstood me. The isotherm of 26º is plenty deep and enhanced by El Nino, sure; however, it takes higher than 26º to maintain a 135kt hurricane. That OHC drops pretty quickly when the eyewall is virtually stationary for a day or more, upwelling water from the cooler isotherm layers. That results in 28-30º temps at the immediate surface dropping down to 26º and even lower. The heat potential under the center will decrease below what will support Cat 4 or 5 intensity if the cyclone's core isn't moving away from its own upwelling fast enough.

[Yellow Evan]

ATCF brings it down to 130 knts.

 

 

EP, 01, 2014052518, , BEST, 0, 121N, 1112W, 130, 935, HU

[phil882]

I think you misunderstood me. The isotherm of 26º is plenty deep and enhanced by El Nino, sure; however, it takes higher than 26º to maintain a 135kt hurricane. That OHC drops pretty quickly when the eyewall is virtually stationary for a day or more, upwelling water from the cooler isotherm layers. That results in 28-30º temps at the immediate surface dropping down to 26º and even lower. The heat potential under the center will decrease below what will support Cat 4 or 5 intensity if the cyclone's core isn't moving away from its own upwelling fast enough.

Completely agree here. The smaller a storm is though, the slower it can move and not be significantly impacted by upwelled waters (due to smaller wind radii). But if the storm stalls (like Amanda has here) we could see it deteriate very quickly.

[Yellow Evan]

Amanda is #weakening.

[Windspeed]

Amanda is maintaining itself now if not rebounding a bit. If there was an ERC, it may have completed: Notice some warming just outside the pinhole and the CDO around that warming is expanding and cooling again. Perhaps Amanda will have a larger cleared-out eye during daylight hours on Monday. Also, looks like forward motion has finally picked up to the north overnight, so perhaps it can maintain itself and we can get some nice visible shots during the daylight hours before shear gets in the way.