Tropical weather analysis - October 28, 2013

By: KoritheMan , 7:09 AM GMT on October 28, 2013


Hurricane Raymond continues moving across the open eastern Pacific with no consequence to land. As of the 0300Z NHC advisory, the following information was available on the hurricane:

Wind: 105 mph, with higher gusts
Location: 15.3°N 116.8°W
Movement: NNW at 9 mph
Pressure: 972 mb
Category: 2 (Saffir-Simpson Hurricane Wind Scale)

Satellite estimates have not changed, with the latest TAFB and SAB estimate (6z) coming in at 5.0, or 90 kt. While the convective pattern of Raymond has begun to deteriorate as southwesterly shear increases, recent microwave data does not show that this shear has penetrated the core of the hurricane just yet. However, there is some indication from satellite imagery that the mid-level eye could be exhibiting a bit of a northeastward displacement from the low-level one due to the increasing shear. Oddly enough, a 0444Z AMSU pass indicated that the heaviest rains and convection are occurring in the western eyewall, which is a little puzzling given the shear is coming from that direction.

Figure 1. Latest infrared satellite image of Hurricane Raymond. Image credit: NOAA's Satellite Services Division (SSD).

Raymond had a good run, becoming the first major hurricane to form in the Western Hemisphere during 2013 and all, but its legacy is coming to an end. The SHIPS/GFS show the shear increasing to at least 30 kt over the next 24 hours and remaining that way for a few days; in fact, water vapor animations suggest it could get even stronger. A drier airmass and gradually cooling sea surface temperatures await the hurricane farther north during its recurvature as well, and my forecast follows this reasoning by taking the projected intensity just a shade lower than the National Hurricane Center. Raymond is forecast to become a remnant low in about 72 hours, although there is a chance it could occur.

Raymond still appears to be moving north-northwestward, but with the center still under the convection and the lack of any comparable microwave passes other than the AMSU one makes this estimate somewhat difficult to be sure of. Regardless, water vapor imagery shows a large upper-level trough amplifying over the western United States digging southward. Mid-level southwesterly flow radiates quite far south from the axis of this feature, and this is shunting the ridge to the north of the hurricane steadily eastward. This pattern should result in Raymond turning northward very soon, followed by a sharp recurvature around the western periphery of the ridge. A few days ago Raymond would not have gained as much latitude, but its abrupt intensification episode over the last 24 hours makes recurvature prior to dissipation a viable scenario. The guidance continues to be in good agreement that Raymond's low-level vortex will shear apart and stall as the cyclone becomes devoid of convection, with the primary difference being a matter of latitude. The GFS continues to be farther north than the ECMWF, but that model has a historical tendency to overamplify troughs and tropical cyclones' response to them, so I tend to side with the latter.

Intensity forecast and positions

INITIAL 10/28 0600Z 15.8°N 117.1°W 90 KT 105 MPH
12 hour 10/28 1800Z 16.6°N 117.2°W 80 KT 90 MPH
24 hour 10/29 0600Z 17.4°N 117.1°W 55 KT 65 MPH
36 hour 10/29 1800Z 17.8°N 117.0°W 40 KT 45 MPH
48 hour 10/30 0600Z 18.2°N 116.7°W 30 KT 35 MPH
72 hour 10/31 0600Z 18.5°N 116.6°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
96 hour 11/01 0600Z 18.7°N 116.4°W 20 KT 25 MPH...POST-TROPICAL/REMNAN LOW
120 hour 11/02 0600Z...DISSIPATED

Track forecast

Figure 2. My forecast track for Raymond.


Elsewhere in the tropics, the GFS and ECMWF hint that a broad area of low pressure could form off the coast of southern Mexico during the next few days. Upper-level winds appear diffluent enough for some development of this low if it manifests, although the amount of growth will rest strongly on how close the system parallels the coast of Mexico.

This system is expected to move west-northwest to northwestward, and may threaten southern Baja in a week or so.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Basement-dwelling pseudo-otaku with a thrill for forecasting on the side.

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