CPAC: ANA - Post-Tropical

[Kingarabian]

Latest visible. The CPHC mentioned numerous times that there's an extraordinary amount of shear up to 50kts between Ana and the Hawaiian islands.

It's confusing how every single model shows Ana becoming a hurricane. Even the conservative Euro.

[Kingarabian]

Yeah, the winds have clearly dropped based upon Dvorak numbers.

SAB dropped to 3.0/4.0 before the 11Am update yet they still kept it at 60kts.

[Kingarabian]

[AFWeather]

The 18z models continue to shift to the left. GFS has this now staying far enough south of the big island to remain totally intact, and it then passes SW of the other islands. GFS doesn't have Ana ever becoming a hurricane either. A scenario that is becoming more likely as I look at everything. The latest HWRF has a 971 mb cane just off south point, then in 3 hours she completely vanishes.

Yea, I misspoke as GFS has a 66kt max on the 18z run. Still, lower than the intensity CPHC is forecating. And the model isn't accounting for the mid level shear.

[Kingarabian]

SAB is lower at 2.5/3.5.

All signs pointing to an intensity drop unless it somehow improves within the next 3 hours.

[Yellow Evan]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.2.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 15 OCT 2014 Time : 233000 UTC
Lat : 14:21:09 N Lon : 147:45:07 W


CI# /Pressure/ Vmax
3.6 / 995.8mb/ 57.0kt


Final T# Adj T# Raw T#
3.6 3.2 3.2

Center Temp : -61.6C Cloud Region Temp : -60.7C

Scene Type : UNIFORM CDO CLOUD REGION

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 50km
- Environmental MSLP : 1013mb

Satellite Name : GOES15
Satellite Viewing Angle : 22.4 degrees

[cycloneye]

00z Best Track goes down to 55kts.

CP, 02, 2014101600, , BEST, 0, 141N, 1480W, 55, 998, TS

[Steve820]

This could still be a major threat to the Hawaiian islands, I wouldn't be surprised if we got a retirement candidate from this after it's all said and done. And it should be a hurricane soon, hopefully tonight!

[Yellow Evan]

This could still be a major threat to the Hawaiian islands, I wouldn't be surprised if we got a retirement candidate from this after it's all said and done. And it should be a hurricane soon, hopefully tonight!

Look at the above post about it weakening. As for this storm in general, we need to wait and see. This seems like one of those bizarre storms.

[Kingarabian]

CCC showing signs of thinning out with warmer cloud tops. That needs to happen for it to have any chance to become a hurricane.

[Yellow Evan]

This is a very tricky forecast. No system that I have ever tracked had to deal with a CCC, so I have no clue how it's gonna react.

[TheStormExpert]

This is a very tricky forecast. No system that I have ever tracked had to deal with a CCC, so I have no clue how it's gonna react.

What is CCC?

[Kingarabian]

TheStormExpert

Yellow Evan

Here is my post from last night if you guys didn't see it in regards to CCC.

It appears that Ana has developed a CCC, which stands for a cold cloud cover. Basically we will have to wait until the CCC thins and warms. As soon as that happens, we may begin to finally see an eye.

Read this for more information:

During late July 1996 the tropical atmosphere of the western North Pacific was dominated by an active monsoon trough. On 23 July, three TCs were developing along the axis of this trough: Frankie (in the South China Sea), Gloria (in the Philippine Sea, east of Luzon), and Herb (northeast of Guam) (Fig. 1). Gloria had been developing as a monsoon depression, defined by the Joint Typhoon Warning Center (JTWC) as a large (but relatively weak) cyclone in the monsoon trough that is composed of an ensemble of mesoscale convective systems (MCSs) (JTWC 1993). During the evening hours of 23 July, a cluster of small cold-topped MCSs began to grow near the estimated center position of Gloria. During a 6-h period, this cluster of MCSs mushroomed into an enormous CCC. By local midnight, the average diameter of the area within which the cloud-top temperature was at or below −70°C was approximately 780 km (Fig. 2).

In relation to published statistics of convective cloud sizes, Gloria’s CCC is extraordinarily large. The area of that portion of Gloria’s CCC (see Fig. 2) that is colder than −70°C is nearly 500 000 km2. For ease of visualization, one sees from Fig. 3 that this is nearly as large as the state of Texas (which encompasses 692 402 km2). In a study of 43 mesoscale convective complexes (MCCs) occurring over the central United States during 1978, Maddox (1980) measured the areal extent of cloud-top temperatures at, or below, −52°C. Only one of these 43 MCCs possessed a cold cloud shield (at, or below, −52°C) that was bigger than the portion of Gloria’s CCC that was at, or below, −70°C. In a study of winter monsoon cloud clusters in the region of Borneo and surrounding seas, Williams and Houze (1987) found no cluster elements (i.e., an individual cloud mass) meeting the area and temperature thresholds of at least 50 000 km2 of contiguous cloud below −60°C with a size greater than 300 000 km2. Mapes and Houze (1993) examined maritime tropical cloud clusters as defined by the very cold threshold of −65°C (which matches the instantaneous precipitation area in radar-sampled mature MCSs fairly well). In their study, a cloud cluster was identified on geostationary IR imagery by an algorithm that searched for connected areas of cold cloudiness. This algorithm required horizontal (along the satellite scan line) connectivity as well as a columnar (not merely touching diagonally) connectivity. Less than 0.1% of all cloud clusters at the temperature threshold of −65°C had sizes greater than 500 000 km2.

Gloria’s CCC was not only large but also exceptionally cold. Roughly half of the area of Gloria’s CCC was colder than −90°C. The coldest IR pixel, with an equivalent blackbody temperature of −100°C, was located near the geometric center of the CCC. This is an extremely cold cloud-top temperature that is rarely seen. It is only 2°C shy of the record cold cloud-top temperature of −102°C reported by Ebert and Holland (1992) in the deep convection associated with a TC near Australia.

By the early daylight hours of 24 July, the periphery of the CCC began to warm on IR imagery, and a new smaller CCC mushroomed into the preexisting cold cirrus canopy. As the day progressed, the underlying structure of Gloria gradually emerged in VIS imagery as the supporting convection of the CCC ended and the large cirrus canopy of the CCC thinned. By midafternoon, the cold cirrus of the CCC became nearly transparent, and a ragged eye accompanied by some peripheral convective cloud bands of the intensifying Gloria was then seen.

That a CCC indicates arrested development is a finding by Dvorak. This is generally accepted as valid and is used in operational application of Dvorak’s techniques. While it is true that there were no in situ measurements of the intensity of Gloria before, during, or after it possessed a CCC, the satellite imagery does provide evidence that little intensification took place. The JTWC best track (largely dependent upon satellite intensity estimates) shows little intensification during this time period. Prior to the formation of Gloria’s CCC, satellite intensity estimates (supported by ship observations) indicated that Gloria’s peak winds had increased to approximately 55 kt. During the afternoon hours of the following day, as the dense cirrus of Gloria’s CCC thinned to allow a view of the underlying central cloud structure, a very poorly defined eye was observed on VIS imagery, indicating that Gloria had become a minimal typhoon. By the morning hours of the next day, Gloria acquired a well-defined CDO within which there was a small cloud-filled eye. Applications of Dvorak’s techniques to the satellite imagery indicated that Gloria had reached 90 kt (its peak estimated intensity), representing a rise of only 35 kt during the 36-h interval following the onset of its CCC—hardly a remarkable change considering the extreme changes in the cloud pattern. This is consistent with Dvorak’s findings that the appearance of a CCC signals arrested development that is renewed as the eye pattern of the T4 (minimal hurricane) emerges beneath the thinning cirrus. It is an irony that the most significant convective event that may be observed during the life of a TC has little immediate effect upon the intensity.

[Kingarabian]

Hope for Ana?

12hours ago 37ghz, lowerlevels:



Current:


12hours ago 85ghz upperlevels:


Current:

[gatorcane]

So it looks like the ECMWF is panning out somewhat from yesterday so far where folks were wonder why it was keeping it weak and south of the big island. Though there is a big change in the 12Z ECMWF which strengthens it to 991MB as it turns into Oahu from the south.

[Kingarabian]

So it looks like the ECMWF is panning out from yesterday somewhat so far where folks were wonder why it was keeping it weak and south of the big island. Though there is a big change in the 12Z ECMWF which strengthens it to 991MB as it turns into Oahu.

ECMWF has been the most consistent and it's best we follow it for now. Maybe it over did it today and should've stuck in keeping it weak?

[Yellow Evan]

So it looks like the ECMWF is panning out somewhat from yesterday so far where folks were wonder why it was keeping it weak and south of the big island. Though there is a big change in the 12Z ECMWF which strengthens it to 991MB as it turns into Oahu from the south.

Too soon to say for sure. It's a wait and see kind of game at this point.

[hurricanes1234]

It looks asymmetric tonight. I would personally estimate a peak of 80-85 mph if it can catch itself.

[Yellow Evan]

It looks asymmetric tonight. I would personally estimate a peak of 80-85 mph if it can catch itself.

Just wondering, why only that much? I think you're nowcasting a bit too much.

[Kingarabian]

It looks asymmetric tonight. I would personally estimate a peak of 80-85 mph if it can catch itself.

Just wondering, why only that much? I think you're nowcasting a bit too much.

Well to be fair, Ana was supposed to be a hurricane by now. Nowcasting is the right thing to do since we don't know what is causing it to weaken.